SIM918 - Measurement SRS - Free user manual and instructions

Product Type	Precision Current Amplifier
Model	SIM918
Brand	SRS (Stanford Research Systems)
Bandwidth	DC to 1 MHz
Gain Range	10^6 to 10^9 V/A
Input Offset Current	<1 pA
Input Bias Current	<10 fA
Input Noise	<1 fA/√Hz
Output Voltage Range	±10 V
Input Impedance	1 MΩ // 20 pF
Power Supply	±15 V DC, 100 mA
Dimensions (H x W x D)	3.5 x 1.5 x 1.5 inches (approx.)
Weight	0.5 kg (approx.)
Operating Temperature	0°C to 40°C
Storage Temperature	-20°C to 70°C
Input/Output Connectors	BNC (female)
Features	Low noise, high gain, adjustable offset, overload protection
Accessories Included	Power cable, user manual
Safety Precautions	Use proper grounding; do not exceed input voltage limits
Maintenance	Keep clean and dry; avoid dust and moisture
Repairability	Contact SRS authorized service center

Frequently Asked Questions - SIM918 SRS

How to connect the SIM918 to a circuit?

Use BNC cables for input and output. Connect the input to the current source and the output to a voltmeter or ADC. Ensure proper grounding to avoid noise.

What is the maximum input current the SIM918 can handle?

The SIM918 can handle input currents up to ±1 mA without damage. Exceeding this may cause overload or damage.

How to calibrate the offset voltage?

Use the offset adjustment pot on the front panel. With no input, adjust until output reads zero volts. For fine adjustments, use a multimeter.

What is the output voltage range of the SIM918?

The output voltage range is ±10 V for a full-scale input current at the selected gain. For example, at 10^6 V/A gain, 10 μA input gives 10 V output.

Can the SIM918 measure AC currents?

Yes, it measures AC and DC currents. Its bandwidth extends to 1 MHz, allowing measurement of fast signals.

What power supply is required for the SIM918?

It requires ±15 V DC at 100 mA. A suitable power supply is the SRS SIM900 mainframe or a benchtop supply with BNC connectors.

How to reduce noise in measurements?

Use shielded cables, keep the device away from magnetic fields, and ensure stable power. The SIM918 has low noise (<1 fA/√Hz) but proper shielding is essential.

How to clean the SIM918?

Disconnect power. Wipe the exterior with a dry or slightly damp cloth. Do not use solvents or cleaners. Keep connectors dust-free.

Where can I download the user manual for the SIM918?

Visit the SRS website or notice-facile.com. The manual is available in PDF format and contains detailed specifications and usage instructions.

What is the warranty period for the SIM918?

SRS typically provides a one-year warranty against defects in materials and workmanship. Contact SRS support for details and warranty claims.

USER MANUAL SIM918 SRS

PrecisionCurrentPreamplifier

SIM918

Stanford Research Systems

Certification

StanfordResearchSystemscertifiesthatthisproductmetitspublishedspecificationsatthetime ofshipment.

Warranty

ThisStanfordResearchSystemsproductiswarrantedagainstdefectsinmaterialsandworkmanshipforaperiodofone(1)yearfromthedateofshipment.

Service

Forwarrantyserviceorrepair, thisproductmustbereturnedtoaStanfordResearchSystems authorizedservicefacility.ContactStanfordResearchSystemsoranauthorizedrepresentative beforereturningthisproductforrepair.

Informationinthisdocumentissubjecttochangewithoutnotice.

Copyright © StanfordResearchSystems, Inc., 2017. Allrightsreserved.

StanfordResearchSystems, Inc.

1290-DReamwoodAvenue

Sunnyvale, CA94089 USA

Phone:[phone]• Fax:[phone]

www.thinkSRS.com• e-mail:[e-mail]

PrintedinU.S.A.Documentnumber9-01592-903

Contents

GeneralInformationiii

SafetyandPreparationforUse......iii

Symbols......vi

Notation......vii

Specifications......vii

1GettingStarted1-1

1.1 Introduction to the Instrument......1-2

1.2Front-PanelOperation....1-5

1.3Connections....1-8

1.4 Power-On 1-9

1.5RestoringtheDefaultConfiguration...... 1-9

1.6SIMInterface....1-10

2DescriptionofOperation

2-1

2.1 About Transimpedance Amplifiers 2-2

2.2BiasandGround....2-4

2.3Output....2-5

2.4 Autozero Trim 2-5

2.5 Phase-Locked Loop 2-6

2.6 Autocalibration 2-6

2.7 Clock Stopping 2-7

2.8 Quiescent Operation 2-8

3RemoteOperation

3-1

3.1IndexofCommonCommands.... 3-2

3.2 Alphabetic List of Commands 3-4

3.3 Introduction 3-6

3.4 Commands 3-7

3.5 Status Model 3-24

4CircuitDescription

4-1

4.1SchematicDiagrams 4-2

A Index

A-1

GeneralInformation

TheSIM918PrecisionCurrentPreamplifier, part of Stanford Research Systems' Small Instrumentation Modules family, converts an input electric current into a proportional voltage output while maintaining zero potential difference between the input terminal and bias terminal.

Themainamplifierstagepresentsatransimpedance R_F, equalto thecurrentgainofthepreamplifier,toaninputcurrenti in. Thebias voltage V_bias isubtractedfromtheoutputofthestage,sothatthe voltageattheoutputoftheinstrumentis

$$ V _ {\text { out }} = (V _ {\text { bias }} - \text { in } i \times \text { R } - V _ {\text { bias }} = - i _ {\text { in }} \times \text { R } $$

SafetyandPreparationforUse

Connections

Nodangerousvoltagesaregeneratedbythemodule. However, theoutershieldofthefront-panelInputcoaxial(BNC)connector intheSIM918canbeswitchedtotherear-panelPrograminput. If adangerousvoltageisappliedtotheProgramterminal, itmaybe presentontheoutershelloftheInputconnector, and may cause injuryordeath.

WARNING

Do not exceed ±60 volts to the Earth at the center terminal of the rear-panel ShieldProgramVoltageBNCconnector.

CAUTION

Do not exceed ±15 volts to the Earth at the center terminal of the front-panel Input and Bias BNC connectors, or at the center terminal of therear-panel RefClock Sync BNC connector.

Biomedical applications

WARNING

Undercertainconditions,theSIM918mayprovetobeunsafefor applicationsinvolvinghumansubjects.Incorrectgrounding,componentfailure,andexcessivecommon-modeinputvoltagesareexamplesofconditionsinwhichtheinstrumentmayexposethesubject

tolargeinputcurrents.Therefore,StanfordResearchSystemsdoes notrecommendtheSIM918forsuchapplications.

Cautionregardingusewithphotomultipliers

CAUTION

Thefront-endamplifierofthisinstrumentiseasilydamagedifa photomultiplierisusedimproperlywiththepreamplifier.Whenleft completelyunterminated,acableconnectedtoaPMTcancharge toseveralhundredvoltsinarelativelyshorttime.Ifthiscableis connectedtothecurentinputoftheSIM918,thestoredchargemay damagethefront-endJFET.Toavoidthisproblem,providealeakage pathofabout100kΩtogroundinsidethebaseofthePMTtoprevent chargeaccumulation.

Service

Do not install substitute parts or perform unauthorized modifications to this instrument.

Preparationforuse

TheSIM918isasingle-widemoduledesignedtobeusedinsidethe SIM900Mainframe. Donotturnonthepowertothemainframeor applyvoltageorcurrentinputstothemoduleuntilthemoduleis completelyinsertedintothemainframeandlockedinplace.

SymbolsyoumayFindonSRSProducts

Symbol Description
	Alternating current
	Caution - risk of electric shock
	Frame or chassis terminal
	Caution - refer to accompanying documents
	Earth (ground) terminal
	Battery
	Fuse
	On (supply)
	Off (supply)

Notation

WARNING

CAUTION

The following notation will be used throughout this manual:

A warning mean that injury or death is possible if the instructions are not obeyed.

Acautionmeansthatdamagetotheinstrumentorotherequipment is possible.

Typesetting conventions used in this manual are:

• Front-panelbuttonsaresetas[GAIN]; [GAIN]isshorthandfor"[GAIN]&[GAIN]".
  • Front-panelindicatorsaresetasOVLD.
  • Signalnamesaresetas-STATUS.
  • SignallevelsaresetasHIGH.
• Remotecommandnamesaresetas*IDN?
• Literaltextotherthancommandnamesissetas0FF.
  • SpecialASCII charactersaresetas⟨CR⟩.

Remotecommandexampleswillallbesetinmonospacedfont. In these examples, datasentbythehostcomputertotheSIM918areset asstraightteletypefont, whileresponsesreceivedbythehost computerfromtheSIM918aresetasslantedteletypefont.

Specifications

Performancecharacteristics

GainSelection10		MinTypMaxUnits
		^6, 10^7, 10^8			V/A
CurrentinputSelection	Accuracy, 10^6 V/A± 10^7 V/A± 10^8 V/A± 10^6 V/A± 10^7 V/A± 10^8 V/A± 10^6 V/A± 10^7 V/A± 10^8 V/A± 10^6 V/A± 10^7 V/A± 10^8 V/A± ± 100		0.1%
			0.1%
			2%
	Stability, 10^6 V/A± 10^7 V/A± 10^8 V/A± 10^6 V/A± 10^7 V/A± 10^8 V/A± 10^6 V/A± 10^7 V/A± 10^8 V/A ± 10^6 V/A± 10^7 V/A± 10^8 V/A± 10^6 V/A± 10^7 V/A± 10^8 V/A± 10^6 V/A± 10^7 V/A± 10^8 V/A±		10ppm/		°C
			50ppm/		°C
			100	ppm/	°C
	On,open
	Offset voltage [1-3]			±10	μV
	Resistance			1	Ω
	Capacitance		18		pF
	Bias current, DC [3,4]AC[1,4,5]		1.0	3.0	pA
			3.5pArms
	Currentnoiseat100 Hz[6], 10^-6 V/A		130		fA/
	10^7 V/A		42		fA/
	10^8 V/A		15		fA/
	Voltage noise [1,5]		25		μV rms
	-3 dBbandwidth[6], 10^-6 V/A		22		kHz
	10^7 V/A		12		kHz
	10^8 V/A		4		kHz
	Terminals		IsolatedBNC[7]
	BNCshieldGround,bias,program/open
BiasinputSelection	On,ground
	Voltage [8]	-5.0		+5.0	V
	Resistance		10		MΩ
	-3 dBbandwidth		0.2Hz
	Terminals	IsolatedBNC[7]
	BNCshield	Ground,float
Program input	Voltage	-60		+60	V
	Resistance	3			GΩ
	Terminals	GroundedBNC[9],rear
ReferenceclocksyncSelection	Input,output
	Interface	RearBNC[9],TTL[10]
	Inputfrequency[11]	0.90		1.10	Hz
	Outputfrequency		1.0Hz

AutozeroSelectionOn,hold		MinTypMaxUnits
Output	SourceInternal,externalreferenceclock
	Switchingfrequency0.50Hz
	Voltage [8]	-10.0		+10.0	V
	Maximumcurrent±100mA
	ShortcircuitdurationIndefinite
	Resistance		100		Ω
	Offset voltage [2]			±50	μV
	Common-moderejection,DC	80			dB
	Terminals	GroundedBNC[7]
Operating	Temperature[12]	0		40	°C
	Power	+5, ±15			V DC
	Supply current, +5 V ±15 V		100		mA
			150		mA

Conditions:

[1] With autozero on.
[2] Following an autocalibration at (23± 5)^ within24 hours.
[3] 100s average.
[4] At 23°C. Doubles every6 °C to10 °C.
[5] 0.1 Hz to 10 Hz.
[6] For a 100 pF source capacitance and an infinite source resistance. Higher values of source capacitance or a finite source resistance will degrade thesespecifications.
[7] Amphenol 31–10–4052 or similar.
[8] An overload will be detected and the instrument is not guaranteed to perform properly if these limits are exceeded, or if |V_bias - i_in × R_F| exceeds the limits. Continuous application of a bias voltage V_bias in excess of ± 15V will damage the instrument.
[9] Tyco 227169–4 or similar.
[10] Rising-edge sensitive.
[11] External reference clock capture range. The instrument is not guaranteed to perform properly if these limits are exceeded.
[12] Non-condensing.

General characteristics

Interface	Serial(RS-232)throughSIMinterface
Connectors	BNC(3front[7],2rear [9]);DB-15(male)SIMinterface
Weight	1.7 lbs
Dimensions	1.5 " W × 3.6" H × 7.0" D

1GettingStarted

Thischaptergivesyouthenecessaryinformationtogetstarted quicklywithyourSIM918PrecisionCurrentPreamplifier.

InThisChapter

1.1 Introduction to the Instrument......1-2

1.1.1 Currentamplifiersandautozero......1-2
1.1.2Clocks....1-2
1.1.3Cablingandgrounding......1-3
1.1.4Autocalibration....1-3
1.1.5Remoteinterfaceandstatus......1-3
1.1.6Blockdiagram....1-4
1.1.7Frontandrearpanels....1-5

1.2Front-PanelOperation .....1-5

1.2.1Gain....1-5
1.2.2 Autozero....1-5
1.2.3Input 1-7
1.2.4Bias ....1-7
1.2.5Outputoverload 1-8

1.3Connections....1-8

1.4Power-On....1-9

1.5RestoringtheDefaultConfiguration......1-9

1.6SIMInterface 1-10

1.6.1SIMinterfaceconnector......1–10
1.6.2 Directinterfacing......1-10

1.1 Introduction to the Instrument

1.1.1 Currentamplifiersandautozero

offset voltage

Acurrent,ortransimpedance,amplifierconvertselectriccurrentinto aproportionaloutputvoltage.Unlikeasimpleresistor,theamplifierpresentsalow-impedanceterminaltotheinputcurrent.In theSIM918PrecisionCurrentPreamplifier,theelectricpotentialof theinputterminal, V_in ,isaccuratelymadeequaltotheuser-provided potentialatthebiasterminal, V_bias , or to ground. The absolute magnitudeoftheresultinginputoffsetvoltageisnearlyzero:

$$ V _ {\mathrm{ofs}} = V _ {\mathrm{in}} - V _ {\mathrm{bias}}, \quad | V _ {\mathrm{ofs}} | < 1 0 \mu \mathrm{V}. $$

virtual ground

In all transimpedance amplifiers, the input potential is kept near that of the biasthrough the action of negative feedback. When the bias voltage is at ground, the input terminal is softensaid to present a virtual ground, or a virtual null. Without autozeroing, this virtual ground drifts, insome cases by manymillivolts. This error in the electric potential of the input terminal may be unacceptable in precision measurements.

In the SIM918, an autozero circuit measures V_ofs every2 seconds and maketheadjustmentnecessarytokeeptheoffsetvoltageatzero. Theautozerofeaturecanbeengagedorinhibitedremotelyorfrom thefrontpanel,givingtheuserflexibilityinsensitiveapplications. Withautozeroinhibited, thepreamplifierretainsmicrovoltinput accuracyformanyhours. When engaged,ittakestheautozeroonly a few cycles of a reference clock to restore the offset to within its specifiedlimits.

The gain, or transimpedance, of the preamplifier can be set to R_F=10^6,10^7 , or 10^-8 V/A, remotely and from the front panel. Along with voltage accuracy, the SIM918 offers low input bias current and acurrent noisethatisclosetothelower limit imposed by the Johnsonnoise of the transimpedance.

1.1.2Clocks

reference clock one pps

The autozero circuit switches between measuring the input offset voltage, and the offset voltage of the zeroing amplifier itself, at one half the frequency of an internal or external reference clock. The internal clock signal (typically 1.0 pulse per second, pps, i.e. 1.0 Hz) can be selected, remotely or from the front panel, to be output on

arear-panelconnector. Alternatively, the same connector can be used to input a clock signal at (1.0 ± 10%) pps (i.e. 1.10 Hz–0.90 Hz), synchronizing the switching to an external source.

ThereferenceclockintheSIM918operatesindependentlyoftheoscillatorusedtoclockthedigitalcontrolcircuitry. Thelatterisdesigned withaspecialclock-stoppingarchitecture. Themicrocontrolleris turnedononlyinthefollowingcases: whenthesettingsarebeing changed;autozeroisturnedonoroff;andduringautocalibration,remotecommunications,orwhenanoverloadconditionoranexternal reference clock event occurs. This guarantees that no digital noise contaminateslow-levelanalogsignals.

Withautozerooffandintheabsenseofanexternalclockinput, thepreamplifierentersa completelyquiescentstate: noreference clocktransitionsarepresentthatcandisturbthemeasurementofa low-levelelectriccurrent.

1.1.3Cablingandgrounding

TheSIM918providesmaximumflexibilityforcablingandgrounding. Theinputconnectioncanbeopened,andthebiasvoltagecan beconnectedtosignalground.

TheshieldoftheInputBNCcanbeswitchedbetweensignalground, thebiasvoltage,ortherear-panelPrograminput(whichcanbeleft floating,ifdesired).WiththePrograminput,ausercansupply anexcitationpotentialtoanexperimentviatheshieldconductor of the input cable, while the excited current flows through the center conductortotheSIM918. TheshieldoftheBias BNCcanbeindependentlygroundedorfloated.

Theinputandbiasselections, and thoseoftheirshields, canbemade viathepushofafront-panelbuttonorremotely.

1.1.4Autocalibration

Auser-commandedautocalibrationprocedureallowsonetoeliminatetheeffectsofthermaldriftsintheautozerocircuit,andtoreduce outputoffsetvoltage.

1.1.5Remoteinterfaceandstatus

remote interface A remote computer can access the module through the SIM900 Mainframe, usingRS-232orGPIB. Allinstrumentsettingscanbequered via the remote interface. The SIM918 can be operated outside the SIM900MainframebypoweringitwithitsrequiredDCvoltages.

Ifthemaximumbiasvoltageisexceeded,orthechosengainsetting causestheoutputvoltagetoexceeditsmaximum,theappropriate overloadLEDturnson.Ifthemodulecannotlocktoanexternal referenceclocksignal,anLEDindicatesan unlockedstate.Ifarmed, themodulealsogeneratesastatussignalaltoalerttheuserofthe overloadorunlockedcondition.

1.1.6Blockdiagram

The output of the main amplifier (transimpedance stage) is referenced to the bias voltage. Adifference amplifiers subtract the bias voltage, so the output of the instrument is directly proportional to the input current in and the gain R F:

$$ V _ {\text {out}} = \left(V _ {\text {bias}} - \text {in} i \times \text {R} - V _ {\text {bias}} = - i \text {in} \times \text {R} (1. 1) \right. $$

AblockdiagramofthepreamplifierisshownbelowinFigure1.1.

graph TD
    A["INPUT"] --> B["BIAS"]
    B --> C["0.5 Hz"]
    C --> D["Zeroing amp"]
    D --> E["(±1)"]
    E --> F["LPF"]
    F --> G["Difference amp"]
    G --> H["OUTPUT"]
    I["R_F"] --> J["Main amp"]
    J --> K["offset adj"]
    K --> L["+"]
    L --> M["OUT"]
    N["Ground"] --> D

Figure1.1:TheSIM918blockdiagram.

1.1.7Frontandrearpanels

VSRS SIM918 Precision Current Preamp GAIN 1 10 100 V/µA AUTOZERO ON External Unlocked Output 1 pps/Hz INPUT Shield Prog Bias Open BIAS ±5 V max 10 MΩ GND OVIDL Shield Float OUTPUT OVIDL ±10 V

SIM918 Precision Current Preamp Shield Program Input Clock Sync (1 pps) S/N SRS MADE IN U.S.A.

Figure1.2:TheSIM918frontandrearpanels.

1.2Front-PanelOperation

1.2.1Gain

Thegain R_F of the preamplifier, in voltspermicroampere, is indicated on the front panel of the instrument via a green annunciator LED. ^2 Press one of the [GAIN] button stochangethe gain. If [GAIN] is pressed when R_F = 1 ~V / A , the press has no effect. If [GAIN] is pressed when R_F = 100 ~V / A , the press has no effect.

Asimultaneous press of [GAIN] has a special meaning. This press initiates autocalibration (Section 2.6).

1.2.2 Autozero

1.2.2.1 Engagingtheautozerocircuit

The autozero circuit is turned ON by the press of a front-panel button. There will be a pause of up to 3.3 seconds (a wait for a positive-going edge of the reference clock). At the end of the pause, the green

annunciatorLEDwillturnonandthezeroingcircuitwillbecome active.

Thesamebuttonturnsautozeroingoff. Therewillbealessthan1s pauseinorderforthepresentcontroloutputoftheautozerocircuit tobesampledandstored. Attheendofthepause, theLEDindicator willturnoffandallswitchinginsidetheSIM918willcease. Thesampledcontroloutput(trim)willremainappliedtothetransimpedance-stageamplifier, zeroingittothebestofprecisionavailableatthetime theautozerocircuitryisinhibited.

1.2.2.2 Reference clock detection

lockacquisitiontime

Theautozerocircuitswitchesatonehalfthefrequencyofaninternalorexternalreferenceclock.IfaperiodicTTL-levelsignalisappliedtotherear-panelRefClockSyncconnector,andtheconnectorisnotselectedforoutput(seethenextsection),thepreamplifierwillrecognizetheexternalclockandattempttolocktothesignal.ThegreenExternalLEDwillilluminateforthedurationoftheexternalclockinput.Ifthefrequencyoftheexternalclockisstableandisbetween0.90Hzcapturerangeand1.10Hz,themodulewillsuccessfullylocktothesignal.Ittypically takes 250s (just over 4 minutes) to acquire a lock. The yellowUnlockedLEDisilluminatedwhenevertheSIM918isnotinalockedstate.Forfurtherdiscussionoflocking,seeChapter2.5.Forthedurationofanunlockedstate,theswitchesintheautozerocircuitarenotguaranteedtohavecorrectdutycycles.Therefore,thespecifiedinputoffsetaccuracyisnotguaranteedwhileUnlocked.Theinternalreferenceclockis usedwhenanexternalclocksignalis not present. In this state, neither the External LED nor the Un-lockedLEDisilluminated.

1.2.2.3 Output1 ppssync

Therear-panelRefClockSyncconnectorcanbeusedtooutputthe internalreferenceclock. ThesignalattheoutputisTTL, typically at1.0Hz(1.0pps).The[Output1ppssync]buttontogglesthedirectionofthesignalattherear-panelconnector.Theoutputdirectionis indicatedbyagreenLED.AninactiveOutput1ppssync indicates thattheconnectormaybeusedtoinputanexternalclock.

If[Output1ppssync]ispressedwhileanexternalreferenceclock signalispresentattheconnector,clockoutputwillfailandaDevice-DependentError(Section3.5.3)willbeissued.Ifanexternalsignalis appliedtotheRefClockSyncterminalwhiletheconnectorisselected foroutput,theexternalsignalwillnotberecognized.

1.2.3 Input

The[INPUTOpen]buttonopensandclosesarelayinthepathofthe inputcurrent.AgreenLEDindicatesadisconnectedinputterminal. TheinputcapacitanceoftheSIM918isatitslowestwithinputopen, andisspecifiedinthetableonPageviii.

1.2.3.1 Inputshield

Successivepressesofthe[INPUTShield]buttonconnecttheouter shelloftheInputBNCtotherear-panelShieldProgramVoltage terminal,abufferedcopyofthebiasvoltage,andtosignalground. Thestateoftheinputshieldconnectionisindicatedbyoneofthree LEDs:theyellowINPUTShieldProg,theyellowINPUTShieldBias,orthegreenINPUTShieldGND.

TofloattheshieldoftheInputconnector,leavetheShieldProgramVoltageBNCopenandselectINPUTShieldProg.

1.2.4Bias

The[BIASGND]buttontogglesthesourceofthebiasbetween thevoltageatthecenterterminaloftheBiasBNCandthesignal groundoftheinstrument. Ifthebiassourceissettoground,the greenBIASGNDlightison.

With Biasgrounded, the difference amplifier (Figure 1.1) is switched out and the output of the instrumentistakendirectly from the trans-impedance stage. With this configuration, there is no common-mode error and the output-offset errors reduced.

WhenBiasisconnectedtoauservoltage,thevoltageisbuffered internallybeforebeingdistributedtootherpartsofthepreamplifier. The offset error of the bias buffer is included in the input offset accuracyspecificationsinthetableonPageviii.

1.2.4.1 Biasoverload

AnoverloadconditionisrecognizedandtheBIASOVLD LEDis activatediftheabsolutevalueofthevoltageappliedtotheBias bias overload limits input exceeds certain limits. These limits are typically ±5.0 V, and arebetween

$$ - 5. 2 \mathrm{V} \leq V _ {\min} \leq - 4. 9 \mathrm{V}, \quad 4. 9 \mathrm{V} \leq V _ {\max} \leq 5. 2 \mathrm{V}. $$

The overloadLEDstaysonforaminimumof50 ms; after thistimeit turn soffif the overload condition has ceased.

1.2.4.2 Biasshield

Successivepressesofthe[BIASShield]buttonfloattheouter shelloftheBiasBNCandconnectittoground. Thestateofthe biasshieldconnectionisindicatedbyoneoftwoLEDs:theyellowBIASShieldFloatorthegreenBIASShieldGND.

NotethatitistheelectricpotentialattheBiasterminal,notthepotentialdifferenceacrosstheBiasconnector,thattheautozerocircuit usesasthereferencefortheinputvoltage.

1.2.5 Outputoverload

AnoverloadconditionisrecognizedandtheOUTPUTOVLDLED isactivatediftheabsolutevalue |i_in× R_F| exceedscertainlimits. These output overload limits limits are typically ±10.0 V, and are between

$$ - 1 0. 4 \mathrm{V} \leq V _ {\min} \leq - 9. 9 \mathrm{V}, \quad 9. 9 \mathrm{V} \leq V _ {\max} \leq 1 0. 4 \mathrm{V}. $$

The overloaded state is also recognized, and OUTPUT OVLD activated, if the raw output of the transimpedance stage, |V_bias - i_in × R_F| , exceedstheselimits. Todistinguishbetweenthetwooutputoverload possibilities, use the OVLD? query. The overload LED stays on foraminimumof50ms;afterthistimeitturnsoffitheoverload conditionhasceased.

1.3Connections

TherearefiveBNCconnectorsintheSIM918,threeonthefrontpanel andtwoattherear.

PanelBNC		TerminalSignal	Direction
Front	Input	Center	Input current	Input
		Shield	Shield programvoltage,bias voltage, signal ground	Output
	Bias	Center	Bias voltage	Input
		Shield	Float, power ground
	Output	Center	Output voltage	Output
		Shield	Signal ground	Output
Rear	Shield Program Voltage	Center	Shield program voltage	Input
		Shield	Chassis ground
	Ref Clock Sync	Center	Reference clock	Input, output
		Shield	Chassis ground	Input, output

Table1.1:BNC connectionsintheSIM918.

For further discussion of grounding, see Section 2.2.1. The SIM interface connector is discussed in Section 1.6.1.

1.4Power-On

Theinstrumentretainsthefollowingsettingsinnon-volatilememory:

1. The powerline frequency (FPLC): 60 Hz or 50 Hz.

2.Thegain.

1. Autozeroon/off.

4.Inputselection(on,open).

5.Inputshieldselection(program,bias,ground.)

6.Biasselection(on,ground).

7.Biasshieldselection(float,ground.)

1. Whetherornotthephaselockedloop (Section2.5) staysactive whenautozeroisoff.

9.Calibrationvalues.

The power-on configuration of theremote interface is detailed in Section 3.3.1.

1.5RestoringtheDefaultConfiguration

ThedefaultconfigurationoftheSIM918is:

1. Gain 10^6 V/A.

2. Autozeroon.

3.Inputconnected.

4.Inputshieldatground.

5.Biasatground.

6.Biasshieldatground.

1. Reference clock direction is input.

2. The phase-locked loop (Section 2.5) is in active when auto zero is off.

Toresetthemoduleintothisconfiguration,turntheSIM900Mainframepoweronwhileholdingafront-panelbuttonoftheSIM918 foratleast2.0seconds.Thesameconfigurationcanalsobereached fromtheremoteinterfacebyissuingthe*RSTcommand.

1.6SIMInterface

The primary connection to the SIM918 Precision Current Preamplifier is therear-panel DB-15 SIM interface connector. Typically, the SIM918 is mated to a SIM900 Mainframe viathis connection, either through one of the internal mainframes slots or theremotecable interface.

ItisalsopossibletooperatetheSIM918directly, without using the SIM900Mainframe. Thissectionprovidesdetailsontheinterface.

1.6.1 SIMinterfaceconnector

TheDB-15SIMinterfaceconnectorcarriesallthepowerandcommunicationlinestotheinstrument.Theconnectorsignalsarespecified inTable1.2.

Pin	SignalSrc	DestDescription	Direction
1	S	IGNALGNDMF	SIM Signalground
2	STATUS	SIM MF	Status/service request (GND = asserted, +5 V= idle)
3	RTS	MF SIM	HW handshake (unused in SIM918)
4	CTS	SIM MF	HW handshake (unused in SIM918)
5	REF_10MHZ	MF SIM	10 MHz reference (no connection in SIM918)
6	-5V	MF SIM	Power supply (no connection in SIM918)
7	-15V	MF SIM	Power supply
8	PSRTN	MF SIM Powerground
9	CHASSISGND	Chassisground
10	TXD	MF SIM	Async data (start bit = “0”= +5 V; “1”= GND)
11	RXD	SIM MF	Async data (start bit = “0”= +5 V; “1”= GND)
12	REF_10MHZ	MF SIM	10 MHz reference (no connection in SIM918)
13	+5V	MF SIM	Power supply
14	+15V	MF SIM	Power supply
15	+24V	MF SIM	Power supply (no connection in SIM918)

Table1.2:SIMinterfaceconnectorpinassignments,DB-15.

1.6.2 Directinterfacing

TheSIM918isintendedforoperationintheSIM900Mainframe, but usersmaywishtodirectlyinterfacethemoduletotheirownsystems withouttheuseofadditionalhardware.

ThematingconnectorneededisastandardDB-15receptacle,such asTycopartnumber747909-2(orequivalent). Clean,well-regulated supply voltages of ± 15.0V DC, +5.0V DC must be provided, following the pinout specified in Table 1.2 and the minimum currents in thetableonPageix.GroundmustbeprovidedonPins1and8,with chassis ground on Pin 9. The STATUS signal may be monitored

CAUTION

onPin2foralow-goingTTL-compatibleoutputindicatingastatus message.SeeSection3.5forthedescriptionofstatusmessages.

The SIM918 has no internal protection against reverse polarity, missing supply, or overvoltage on the +5 V and the ±15 V power-supply pins. Supply voltages above 5.5 V on Pin 13, above +16 V on Pin 14, or below -16 V on Pin7 are likely to damagethe instrument. SRS recommends using the SIM918 together with the SIM900 Mainframe form most applications.

1.6.2.1 Directinterfacecabling

If the user intend stodirectly wire the SIM918 independent of the SIM900 Mainframe, communication is usually possible by directly connecting the appropriate interfacelines from the SIM918 DB-15 plug to the RS-232 serial port of a personal computer. ^4 Connect RXD from the SIM918 directly to Rx Don the PC, TX D directly to TxD. In other words, anull-modem-style cable is not needed.

TointerfacedirectlytotheDB-9male(DTE)RS-232porttypically foundoncontemporarypersonalcomputers,acablemustbemade withafemaleDB-15sockettomatewiththeSIM918,andafemale DB-9sockettomatewiththePC'sserialport.Separateleadsfrom theDB-15needtogotothepowersupply,makingwhatissometimes knowasa"hydra"cable.ThepinconnectionsaregiveninTable1.3.

DB-15/FtoSIM918Name

	DB-9/F
10←→	3	TxD
11←→	2	RxD
	5	ComputerGround
	toPowerSupply
7←→	-15VDC
13←→	+5 V DC
14←→	+15 V DC
1←→	Signal Ground (separate wire to Ground)
8←→	Power Ground (separate wire to Ground)
9←→	Chassis Ground (separate wire to Ground)

Table1.3:SIM918directinterfacecablepinassignments.

note about grounds The distinct Signal Ground and Power Ground, and the chassis ground, are not directly connected within the SIM918. The power

groundcarriesthereturncurrentsofdigitalcontrolsignals,power-intensiveanalogamplifiers,andthepowersupplies,whereasthe outputvoltagereferencestoastablesignalground(Section2.2.1). WhenoperatingintheSIM900,thethreegroundsaretiedtogether intheSIM900Mainframe.SignalGroundandPowerGroundare connectedthroughback-to-backSchottkydiodes,sotheycannotbe more than ±0.35 V apart. The three ground lines should be separatelywiredtoasingle,low-impedancegroundsourceatthepower supply.

1.6.2.2 Serialsettings

The initial serial port settings at power-on are: baud rate 9600, 8 bits, no parity, 1 stop bit, and no flow control. The baud rate of the SIM 918 cannot be changed. Flow control is not implemented in the SIM 918. The parity may be changed with the PARl command.

2DescriptionofOperation

Thischapterprovidesanumberofadditionaldetailsoftheoperation oftheSIM918.

InThisChapter

2.1 About Transimpedance Amplifiers.....2-2

2.1.1 Input capacitance and stability......2-2

2.1.2 Choosingtherightgain......2-3

2.2BiasandGround....2-4

2.2.1 Grounds....2-4

2.2.2Bias 2-4

2.3Output 2-5

2.4AutozeroTrim....2-5

2.5Phase-LockedLoop....2-6

2.6Autocalibration....2-6

2.7ClockStopping......2-7

2.8QuiescentOperation 2-8

2.1 About Transimpedance Amplifiers

transimpedance amplifier A transimpedance amplifier is an operational amplifier with a resistor inthefeedbackpath.Moregenerally,thefeedbackimpedanceZ F al- wayshasaresistiveandareactivecomponent.Thetwoinputstothe operationalamplifierhaveaveryhighimpedance;andthefeedback intheamplifieractstokeepthetwoinputsatthesameeelectricpoten- tial.Therefore,theinputcurrenti in isforcedthroughthefeedback impedance,andtheamplifierproducesanoutputvoltage

$$ V _ {\text { out,TA }} = V _ {\text { bias }} - \mathrm{in} i \times \mathrm{EZ} $$

Theamplifieractstotranslatetheinputcurrentintoaproportional outputvoltage,withthefeedbackimpedancebeingthecoefficientof proportionality.Hencethetermtransimpedance.

ThemainamplifieroftheSIM918PrecisionCurrentPreamplifierisa transimpedanceamplifierbasedonacomposite, JFET-inputdesign.

2.1.1 Input capacitance and stability

The input impedance of JFET devices is extremely large. However, the impedance experienced, as a whole, by a current input to the feedback amplifier (i.e. the change in the input voltage ^1 divided by the input current) has two other, much more significant contributions in parallel. The first one is the effect of the output on the input via feedback duetofinite open-loop voltage gain of the operational amplifier, and these second one is input capacitance.

Input BNC i_in C_in Z^(F)_in Bias C_F R_F Op-amp V_out, TA Bias

Figure2.1: A transimpedance amplifier.

The first term equal the feedback impeded divided by the open-loop gain of the operational amplifier ^2 :

$$ Z _ {\text {in}} ^ {(F)} = Z _ {F} / A _ {O L} \tag {2.1} $$

andisbelow1ΩatDC. Theopen-loopgainisveryhighatDC, and typicallydecreasesasinversefrequencywithacorresponding90 phaselag:

$$ A _ {\mathrm{OL}} = - j f \quad \tau / f $$

wheref isthegain-bandwidthproductoftheoperationalamplifier ( 10MHz intheSIM918).SubstitutingintoEquation(2.1),observe

$$ Z _ {\mathrm{in}} ^ {(\mathrm{F})} = j \frac {Z _ {\mathrm{F}}}{f _ {\mathrm{T}}} f. $$

If the feedback element is purely resistive, the term dueto Z _F behaves exactly as if a large inductor were connected between the input and the biasterminals. This contribution to the input impedance increases linearly with frequency, with corresponding 90° phase lead. ^3

The input terminal always hassome amount of parasitic capacitance to the biasterminal, and to ground. The input capacitances specification in the table on Page iii applies for nonable connected to the Input BNC. A coaxial cable adds \~ 100 pF/m of capacitance. Even onemeter of coaxial dramatically increase the input capacitance.

Theinputcapacitance,inparallelwiththeeffectiveinductance,can formaresonanttankcircuitifthecapacitanceislargeenoughthat theresultingresonantfrequencylieswithinthebandwidthofthe transimpedanceamplifier. TheSIM918hasadequatecompensation (feedbackcapacitance)topreventoscillationforupto100pFofadditionalinputcapacitance. ^4 Toavoidafefeedbackoscillation,follow thesesteps:

1. Placethepreamplifierascloseaspossibletothesignalbeing measured, andusetheshortestcablelengthnecessarytoconnectthem.
2. Reduceallstraycapacitancetobiasorgroundattheoutput of theexperimentundermeasurement.
3. Use a lower gain setting, which reduces the effective input inductance.

Other detrimentaleffectsofexcessinputcapacitanceincludereduced currentbandwidth,poorstepresponse(overshootandringing),and increasedoutputnoise.

2.1.2 Choosingtherightgain

It is important to consider the output resistance (ingeneral, impedance) of the current source being measured. The transimpedance

^3 Theinputvoltageleadstheinputcurrent.
^4 Longercablelengthsaretoleratedatlowergainsettings.

stageamplifiesitsinputvoltagenoisebythefactor ^5 of (1+R_F/R_source) , where R_source isthesourceresistance. This noiseaddsinquadrature with the current noise of the stage. Toprevent the voltageoiseterm from dominating the overall output noise, set the current gainto

$$ R _ {\mathrm{F}} \lesssim R _ {\text { source }}. $$

2.2 BiasandGround

2.2.1 Grounds

The output of the SIM918 is referenced to ground. To maintain the DC accuracy of the instrument, there are two separate ground references. Power Ground (Pin 8 of the SIM interface connector) provides a current return path for digital control signals, power-intensive analog amplifiers, and the powersupplies. Signal Ground (Pin 1 of the interface connector) serves as the reference point for analog voltages. The outer shell of the Output BNC connector is tied to Signal Ground. The output current of the preamplifier returns to the powersupply through Signal Ground. When INPUTShield GND is selected, the shell of the Input BNC is also tied to Signal Ground.

The outer shells of the rear-panel Shield Program Voltage and RefClockSyncBNCsareconnectedtochassisground,Pin9ofthe DB-15 SIM interface connector. The separate power, signal, and chassisgroundsarenotdirectlyconnectedwithinthepreamplifier. When operating in the SIM900 Mainframe, the three grounds are tied together inside the mainframe, and through the mainframe totheEarth. Thesignalandpowergroundsareconnectedinside theSIM918through back-to-backSchottkydiodes,sotheycannotbe morethan\~±0.35Vapart.

2.2.2Bias

Thebiaspotentialisreceivedbyanultralow-offsetvoltagebuffer.It isthisbufferedvoltagethatappearsontheshieldoftheInputBNC whenINPUTShieldBiasisselected.

The shield of the Bias connector is not used as a reference for the bias voltage. When Bias Shield GND is selected, the shield is at SignalGround. ThelimitsonthebiasvoltageinSection1.2.4.1 are relativetothisground. Avoltageexceedingthese limitsby more than 1 V will be clamped, through diodes, to ±5.5 V relative to PowerGround. The10MΩinputresistorisconnectedbetweenBias andSignalGround.

ToreduceoutputnoiseoftheSIM918,theBiasinputislimitedtoa bandwidthspecifiedinthetableonPageviii.Beyondthisfrequency, thetransimpedancestagecannotfollowvariationsinthebiasvoltage, buttheoutputdifferenceamplifier(discussedinthenextsection) does.Hencethecommon-moderejectionoftheinstrumentisgreatly reducedatfrequenciesaboveDC.

Thebiassensingcircuitryisalwaysactive, and will signal BIAS OVLD when the applied input exceeds the voltage limits in Section 1.2.4.1, even if Biasissetto GND.

2.3Output

When Biasisswitched to GND, the output of the instrument is taken directly from the transimpedance stage; otherwise, from a difference amplifier (Figure 1.1) that subtract the bias voltage from the output of the transimpedance stage. Both output should equal drive capacity.

The output impedance of the SIM918 Precision Current Preamplifier is 100 . The preamplifier can drive load impedances from to 0 for the full ± 10 V range of output voltage. When driving a 50 load, the gain will be onethird of that displayed on the front panel.

The output signal is filtered by a passive LRC, with f_-3dB = 25kHz . The filter eliminates broad-spectrum noise, while adding an negligible amount of overshoot in the step response. The R in the filter contributes to the output resistance.

The output difference amplifier, when engaged (Biasnotat[GND]), introduces an offset error that can be greater than the maximum input of offset error of the preamplifier. The errors reduced by autocalibration (Section 2.6). The output offset can also be trimmed from the remote interface by using the command OFST1.

2.4 Autozero Trim

Theautozerocontrolloopisfullyanalog. ^6 Itssettlingtime,to withinthemaximuminputoffsetvoltagespecificationinthetableon Pageviii,is40s.Twoadjustmentscanbemadetoloopparameters via the remote command OFST. The first one to consider, OFST 3, adjuststhezeropointoftheloopitself,i.e.thevoltagetowhichthe controlloopdrivestheinputoffsetwhenautozeroisON.

The command OFST 2 sets the code in a digital-to-analog converter, the outputofwhichaddstogetherwiththeoutput oftheloopto form the overall control output of the autozero circuit. When autozeroisengaged,thecontrolloopwillcompensateforchangesmade

via OFST 2, driving the input offset voltage back to a value determined by OFST 3. With autozero off, OFST 3 has no effect and OFST2changestheinputoffsetdirectly.

ThebestvalueforOFST2isreadjustedeachtimeautozeroisturned fromontooff.Ifthepreamplifieristobeoperatedunderconditionsthattolerateabsolutelynoclocktransitions,therecommended courseofactionistoturnautozeroon,letthecontrolloopdrivethe outputtozeroandsettle,andturnautozerooffforthedurationof theexperiment(Section2.8).

The value for OFST 3 is reestablished by autocalibration (Section 2.6).

2.5Phase-LockedLoop

Theswitchesintheautozerocircuitreceiveaclocksignalfroman internalphase-lockedloop. Ifanexternalreferenceclockisavailable attherear-panelRefClockSyncconnector, autozeroison, and the connectorisnotselectedforoutput, thePLLwillattempttolockto theclocksignal. Thesynchronizationwillbesuccessfulforexternal clockfrequenciesbetween0.90Hzand1.10Hz.

In the internal reference clock mode, the PLLoscillator runs freely, generating a 1.0 Hz square wave with rising edges at the beginning of each auto zero half-cycle. The voltage-controlled oscillator in the loop operates at 240 Hz for 60 Hz power line frequency (FPLC), and at 200 Hz for FPLC = 50 Hz.

ThePLLcanbeautomaticallyinhibited, and the voltage-controlled oscillator turned off, when the reference clock is External and autozero is off. The behavior is set by the remote command APLL. With APLL OFF, the oscillator turns off. In this mode, under external reference clock, the instrument will undergo the full capture and lock transient after autozero is switched on. To avoid the 4 minute capture delay, set APLL ON. The module restores the last known APLL mode upon power-on.

When autozero is on, the PLL oscillator is always running, regardless of thereferenceclocksource. If thereferenceclockisinternaland autozero is off, the PLL oscillator is off. There is no capture delay underinternalclock.

2.6Autocalibration

To ensure the specified offset accuracy, the preamplifier must be self-calibrated within the 24 hours preceding a measurement. A valid autocalibrationmusttakeplaceat(23 ± 5) °Cwiththemodulewarmed up for at least 2 hours at (23 ± 5) °C. If the module is being used inside

theSIM900Mainframe, theautocalibration must also be inside the mainframe. Otherwise, perform the autocalibration with the same connection to an independent supply as you use for the operation.

DisconnectallinputsandoutputstotheSIM918whileperformingthe autocalibration.ConnectthecenterandshieldterminalsoftheBiasBNC togetherexternally,e.g.withagroundingcap.Tocalibrate,issuethecommandACAL,orpressboth[GAIN]atthesametime.Depending onthefirmwarerevision,thecalibrationmaytakeupto20minutesto complete.Duringtheautocalibration,allLEDsarelit.Attheendof thecalibration,themodulereturnstoitspre-ACALsettings,except thereferenceclockdirectionisresettoinput.

If autocalibration is unsuccessful,forexamplebecauseanexternal currentisappliedtoInput,thecalibrationconstantsreverttotheir originalvaluesandthecommandLDDE?willreturnCode2.Ifan externalreferenceclockisdetected,theautocalibrationterminates immediatelywithLDDE?2.

Autocalibrationdoesnotaffectgainaccuracy.

2.7 ClockStopping

ThemicroprocessorclockoftheSIM918stopsifthemoduleisidle, "freezing"thedigitalcircuitry.Thefollowingactions"wakeup"the clock:

1. Apower-on.
2. Apressofafront-panelbutton.
   3.Activity(sendorreceive)attheremoteinterface.
3. Anoverload.

4. LossofPLLlock.

5. A change in external reference clock status: several rising edges at therear-panel connector while in internal clock mode, or cessation of clocking while in external mode.

The clock runs for as long as is necessary to complete a change of settingsrequestedfromthefrontpanel, ortocommunicatethe outputofaquerythroughtheremoteinterface. However,theclock will remain active for as long as the overload or unlocked condition exists,andforthefulldurationofanautocalibration.

This default behavior can be modified with the remote command AWAK. Setting AWAK ON will prevent the clock from stopping. The module returns to AWAK OFF upon power-on.

NotethatheoperationofthePLLoscillatoriscompletelyindependentofthemicroprocessorclock.

2.8 Quiescent Operation

Follow these stepst ooperat the SIM918 Precision Current Preamplifier insensitivemeasurement sthatcantolerate absolutelynomodule clock transitions:

1. Resetthepreamplifier(Section1.5).
   2.SetInputtoOpen.
2. Waitforatleast40s.
3. Turnautozerooff.
4. Select the desired gain.
   6.Closetheinput.
5. Perform themeasurement.

Afterthissequenceiscomplete, thecontroloutputoftheautozero circuitholdsatavaluethatinitiallydrivestheinputoffsetwithinits specification. Withoutactiveautozeroing, theinputoffsetmaydrift astimeprogresses, soSteps1–6mayneedtoberepeated.

3RemoteOperation

ThischapterdescribesoperatingtheSIM918overtheserialinterface.

InThisChapter

3.1IndexofCommonCommands......3-2
3.2AlphabeticListofCommands....3-4
3.3Introduction....3-6

3.3.1 Power-onconfiguration....3-6
3.3.2Buffers....3-6
3.3.3DeviceClear....3-7

3.4Commands....3-7

3.4.1 Commandsyntax....3-7
3.4.2 Notation....3-9
3.4.3Examples 3-9
3.4.4 General commands....3-10
3.4.5Configurationcommands......3-11
3.4.6 Calibration commands .....3-14
3.4.7Statuscommands....3-16
3.4.8Interfacecommands....3-19
3.4.9 Serialcommunicationcommands......3-22

3.5StatusModel 3-24

3.5.1StatusByte(SB)....3-25
3.5.2ServiceRequestEnable(SRE)......3-25
3.5.3 StandardEventStatus(ESR) .....3-26
3.5.4 StandardEventStatusEnable(ESE).....3-26
3.5.5CommunicationErrorStatus(CESR) .....3-26
3.5.6CommunicationErrorStatusEnable(CESE) .3-27
3.5.7OverloadStatus(OLSR)......3-27
3.5.8OverloadStatusEnable(OLSE) .....3-28
3.5.9 ReferenceClockStatus(RCSR) ......3-28
3.5.10 ReferenceClockStatusEnable(RCSE) .....3-29

3.1 IndexofCommonCommands

SymbolDefinition

iBitnumber(0-7)

jUnsignedinteger(0-65535)

mUnsignedinteger(1-3)

y,zLiteraltoken

(?)Requiredforqueries;illegalforsetcommands

varParameteralwaysrequired

{var} Requiredparameterforsetcommands;illegalforqueries

[var]Optionalparameterforbothsetandqueryforms

General

HELP(?)3-10InstrumentHelp

AWAK(?) {z} 3-11 Keep Clock Awake

Configuration

FPLC(?) {j} 3-12 Power Line Cycle Frequency

GAIN(?) {m} 3-12 Gain

INPT(?) {z} 3-12 Input

BIAS(?) {z} 3-12 Bias

SHLD(?) y {, z} 3-13 Shield

CHOP(?) {z} 3-13 Autozero

SYNC(?) {z} 3-13 Reference Clock Direction

FREQ? 3-13ReferenceClockFrequency

PHAS? 3-14AutozeroPhase

APLL(?) {z} 3-14 Keep PLL Active

Calibration

ACAL 3-14Autocalibration

READ?m 3-15ReadMicrovoltmeter

OFST(?) m,j 3-15 Offset Trim

Status

*CLS 3-16ClearStatus

*STB? [i] 3-16 Status Byte

*SRE(?) [i,] {j} 3-16 Service Request Enable

*ESR? [i] 3-16 Standard Event Status

*ESE(?) [i,] {j} 3-16 Standard Event Status Enable

CESR? [i] 3-17 Communication Error Status

CESE(?) [i,] {j} 3-17 Communication Error Status Enable

OLSR? [i] 3-17 Overload Status

OLSE(?) [i,] {j} 3-17 Overload Status Enable

RCSR?[i]3-17ReferenceClockStatus

RCSE(?) [i,] {j} 3-17 Reference Clock Status Enable

PSTA(?) {z} 3-18 Pulse STATUS Mode

LBTN?3-18LastButton

OVLD?3-18Overload

RCLK?3-19ReferenceClockState

Interface

*RST3-19Reset

*IDN?3-20Identify

*TST? 3-20SelfTest

*OPC(?) 3-20OperationComplete

CONS(?) {z} 3-20 Console Mode

LEXE?3-21ExecutionError

LCME? 3-21CommandError

LDDE?3-22DeviceError

TOKN(?) {z} 3-22 Token Mode

TERM(?) {z} 3-22 Response Termination

SerialCommunications

PARI(?) {z} 3-23 Parity

3.2AlphabeticListofCommands

★

*CLS3-16ClearStatus
*ESE(?) [i,] {j} 3-16 Standard Event Status Enable
*ESR?[i]3-16StandardEventStatus
*IDN?3-20Identify
*OPC(?)3-20OperationComplete
*RST3-19Reset
*SRE(?) [i,] {j} 3-16 Service Request Enable
*STB?[i]3-16StatusByte
*TST?3-20SelfTest

A

ACAL 3-14Autocalibration

APLL(?) {z} 3-14 Keep PLL Active

AWAK(?) {z} 3-11 Keep Clock Awake

B

BIAS(?) {z} 3-12 Bias

C

CESE(?) [i,] {j} 3-17 Communication Error Status Enable
CESR?[i] 3-17CommunicationErrorStatus
CHOP(?) {z} 3-13 Autozero
CONS(?) {z} 3-20 Console Mode

F

FPLC(?) {j} 3-12 Power Line Cycle Frequency
FREQ? 3-13ReferenceClockFrequency

G

GAIN(?) {m} 3-12 Gain

H

HELP(?) 3-10InstrumentHelp

|

INPT(?) {z} 3-12 Input

L

LBTN? 3-18LastButton
LCME? 3-21CommandError

LDDE?3-22DeviceError LEXE?3-21ExecutionError

0

OFST(?) m {,j} 3-15 Offset Trim OLSE(?) [i,] {j} 3-17 Overload Status Enable OLSR?[i]3-17OverloadStatus OVLD?3-18Overload

P

PARI(?) {z} 3-23 Parity PHAS? 3-14 AutozeroPhase PSTA(?) {z} 3-18 Pulse STATUS Mode

R

RCLK?3-19ReferenceClockState RCSE(?) [i,] {j} 3-17 Reference Clock Status Enable RCSR?[i] 3-17ReferenceClockStatus READ?m 3-15ReadMicrovoltmeter

S

SHLD(?) y {, z} 3 - 13 Shield SYNC(?) {z} 3 - 13 Reference Clock Direction

T

TERM(?) {z} 3-22 Response Termination TOKN(?) {z} 3-22 Token Mode

3.3 Introduction

RemoteoperationoftheSIM918istroughasimplecommandlanguagedocumentedinthischapter.Bothsetandqueryformsofmost commandsaresupported,allowingtheusercompletecontrolofthe amplifierfromaremotecomputer,eitherthroughtheSIM900MainframeordirectlyviaRS-232(seeSection1.6.2.1).

SeeTable1.2forthespecificationoftheDB-15SIMInterfaceConnector.

3.3.1 Power-onconfiguration

The initial settings for theremote interface are 9600 baud with no parity and no flow control, and with locale chodisabled (CONSOFF).

The following values are retained in non-volatile memory:

1. The powerline frequency (FPLC).
2. Thegain.
3. Autozeroon/off.
   4.Inputselection(on,open).
   5.Inputshieldselection(program,bias,ground.)
   6.Biasselection(on,ground).
4. Biashieldselection(float, ground.)
5. Whetherornotthephase-lockedloopstaysactivewhenautozeroisoff.
6. Calibration values.

Uponpower-on, thoseettingsarerestored to their values before the power wasturned off.

Whereappropriate, thedefaultorpower-onvalueforparametersis listedinboldfaceinthecommanddescriptions.

3.3.2Buffers

TheSIM918storesincomingbytesfromthehostinterfaceina64-byteinputbuffer.Charactersaccumulateintheinputbufferuntil a command terminator (either CR or LF ) is received, at which pointthemessageis parsed and executed.Queryresponsesfrom theSIM918arebufferedina64-byteoutputqueue.

If the input buffer overflows, then all data in both the input buffer and the output queue are discarded, and an error is recorded in the CESRandESRstatus registers.

3.3.3DeviceClear

TheSIM918hostinterfacecanbeasynchronouslyresettoitspower-onconfigurationbysendinganRS-232-style(break)signal.Fromthe SIM900Mainframe,thisisaccomplishedwiththeSRSTcommand; ifdirectlyinterfacingviaRS-232,thenuseaserialbreaksignal.After receivingtheDeviceClear,theCONSmodeisturned0FF.Notethat thisonlyresetsthecommunicationinterface;thebasicfunctionof theSIM918isleftunchanged;toresetthepreamplifier,use*RST.

TheDeviceClearsignalwillalsoterminatetheoutputoftheHELP?commandfromtheSIM918.

3.4 Commands

Thissectionprovidessyntaxandoperationaldescriptionsforremote commands.

3.4.1 Commandsyntax

The four letter mnemonic (shown in CAPS) in each command sequence specifies the command. Therest of these sequence consists of parameters.

Commandsmaytakeeithersetorqueryform,dependingonwhether the“?”characterfollowsthemnemonic.Setonlycommandsare listed without the “?”, query only commands show the “?” after the mnemonic,andoptionallyquerycommandsaremarkedwitha“(?)”.

Parametersshownin{ } and[]arenotalwaysrequired.Parameters in{ } arerequiredtosetavalue,andshouldbeomittedforqueries.Parametersin[]areoptionalinbothsetandquerycommands.Parameterslistedwithoutsurroundingcharactersarealwaysrequired.

Donotsend()or{ } or[]aspartofthecommand.

Multipleparametersareseparatedbycommas.Multiplecommands maybesentononecommandlinebyseparatingthemwithsemicolons(;)solongastheinputbufferdoesnotoverflow.Commands are terminated by either CR or LF characters. Null commands andwhitespacesareignored. Executionofthecommanddoesnot beginuntilthecommandterminatorisreceived.

tokens Token parameters (generically shown as y and z in the command descriptions) can be specified either as a keyword or a integer

value.Commanddescriptionslistthevalidkeywordoptions,with eachkeywordfollowedbyitscorrespondingintegervalue.Forex-ample, to set the response termination sequence to CR+ LF , the followingtwocommandsareeequivalent:

TERM CRLF—or—TERM3

Forqueriesthatreturntokenvalues,thereturnformat(keywordor integer)isspecifiedwiththeTOKNcommand.

3.4.2 Notation

The following tables summarize the notation used in the command descriptions:

SymbolDefinition

iBitnumber(0-7)

jUnsignedinteger(0-65535)

mUnsignedinteger(1-3)

y,zLiteraltoken

(?)Requiredforqueries;illegalforsetcommands

varParameteralwaysrequired

{var} Requiredparameterforsetcommands;illegalforqueries

[var]Optionalparameterforbothsetandqueryforms

3.4.3Examples

Each command is provided with a simple example illustrating its usage. In these examples, all data sent by the host computer to the SIM918 are set as straight teletype font, while responses received by the host computer from the SIM918 are set as slanted teletype font.

The usage examples vary with respect to query, optional parameters, and token formats. These examples are not exhaustive, and are intended to provide a convenient starting point for user programming.

3.4.4 General commands

InstrumentHelpHELP(?)

OutputsacondensedversionofSection3.4totheremoteinterface.

HELPmaybeusedwithorwithoutthequerysign,withthesame effects.

HELP?Example:

Notation:

iisbitnumber(0..7);

jisa16-bitunsignedinteger(0..65535);

misasmallunsignedinteger(1..3);

y,zaretokens

(?)questionrequiredforqueries,illegalforsetcommands;

[]=parameterisoptionalforbothsetandqueryforms;

{}=parameterisrequiredtoset,illegalforqueries;

parameterwithoutbracketsisalwaysrequired;

thebracketsthemselvesshouldnotbesent.

General commands:

HELP?-Sendthistext.

AWAK(?) {z}-Keepthemoduleclockawake.

Configurationcommands:

FPLC(?){j}-Powerlinerejectionfrequency(50,60).

GAIN(?) {m}-Set/querygain.

INPT(?) {z}-Input (OPEN, CLOSE).

BIAS(?){z}-Bias(GND,ON).

SHLD(?)y{,z}-Shield(INPUT,BIAS)

(GND, BIAS, FLOAT, PROG).

CHOP(?){z}-AutozeroOFF/ON.

SYNC(?){z}-ReferenceclockIN/OUT.

FREQ?-Referenceclockfrequency(Hz).

PHAS?-Switchposition(ZeroAmp, ZeroZero).

APLL(?){z}-KeepPLLactivewhenautozeroisoff.

Calibrationcommands:

ACAL-One-timeautocalibration.

READ?m-Checkintermediate/outputvoltage(uV).

OFST(?)m{,j}-Set/queryoffsettrim.

Statuscommands:

*CLS-ClearStatus.

*STB?[i]-QuerytheStatusByte.

*SRE(?) [i, ] {j}-ServiceRequestEnable.

*ESR?[i]-QueryStandardEventStatusregister.
*ESE(?) [i,]{j}-StandardEventStatusEnable.
CESR?[i]-QuerytheCommunicationsErrorStatus.
CESE(?) [i,]{j}-CommunicationsErrorStatusEnable.
OLSR?[i]-QueryOverloadStatusregister.
OLSE(?) [i,]{j}-OverloadStatusEnable.
RCSR?[i]-QueryReferenceClockStatusregister.
RCSE(?) [i,]{j}-ReferenceClockStatusEnable.
PSTA(?) {z}-PulseStatusorchangeitslevel.
LBTN?-Whichbuttonlastpressed?
OVLD?-Bias, intermediate, oroutputoverloaded?
RCLK?-Referenceclockint./ext., locked? 

Interfacecommands:
*RST-Resettoknownstate.
*IDN?-Identify.
*TST?-Doesnothing.
*OPC(?)-Operationcomplete.
CONS(?){z}-ConsoleOFF/ON.
LEXE?-LastExecutionError.
LCME?-LastCommunicationsError.
LDDE?-LastDeviceError.
TOKN(?){z}-TurntokenmodeOFF/ON.
TERM(?){z}-Cmdlineend(NONE, CR, LF, CRLF, LFCR). 

Serialinterfacecommand(baudrateisalways9600): PARI(?){z}-Parity(NONE, EVEN, ODD, MARK, SPACE). 

KeepClockAwakeAWAK(?){z}

Set (query) the SIM918 keep-awake mode {to z = (OFF 0, ON 1) }.

Ordinarily, the clock oscillator for the SIM918 microcontroller is held in a stopped state, and only enabled during processing of events (Section 2.7). Setting AWAK ON forces the clock to stay running, and isusefulonlyfordiagnosticpurposes.

Example: AWAKON

3.4.5 Configuration commands

	PowerLineCycleFrequencyFPLC(?){j}
	Set (query) the power-line rejection frequency {to j = (50, 60)}, in Hz.
	TheFPLCvalueisretainedinnon-volatilememory,andisnotmod-ifiedbyapower-onreset.
	FPLC60Example:
	GainGAIN(?){m}
	Set(query)thepreamplifiergain{tom}.
	ValueGain,V/A
	02.0×104
	11.000×106
	21.000×107
	31.00×108
	A special case m = 0 connects the input terminal to the output of the transimpedancestagethroughR F=20kΩ. This state is indicated by all GAIN LEDs switched off. With BIAS GND, the configuration reproducestheinputoffsetvoltageattheoutputoftheinstrument. ThisvoltagemaybemeasuredwithREAD?3.
	The configuration m = 0 is volatile, and is reset to m = 1 upon power-on.
Example:	GAIN?
	2
INPT(?){z}	Input
	Set (query) the preamplifier input connection {to z = (OPEN 0, CLOSE1)}.
Example:	INPTCLOSE
BIAS(?){z}	Bias
	Set (query) the preamplifier bias connection {to z = (GND 0, ON 1)}.
Example:	BIAS?
	ON
SHLD(?) y {,z}	ShieldSet (query) the preamplifier BNC shield connection for y = (INPUT 0,BIAS 1) {to z = (GND 0,BIAS 1,FLOAT 2,PROG 3)}.Thefollowingcombinationsarevalid:
	BNCyShieldz
	INPUTGNDBIASPROG
	BIASGNDFLOAT
	SHLDINPUT,BIASExample:SHLDBIAS,FLOAT
	AutozeroCHOP(?){z}Set (query) the preamplifier autozero selection {to z = (OFF 0,ON 1)}.There will be a wait before the chosen regime takes effect (Section1.2.2.1).
Example:	CHOP?ON
SYNC(?) {z}	Reference Clock DirectionSet(query)thedirectionofthesignalattheSIM918rear-panelRef Clock Sync connector {to z = (IN 0,OUT 1)}. The direction is resettoINuponpower-on.
Example:	SYNC1
FREQ?	ReferenceClockFrequencyQuery the reference clock frequency of the preamplifier, in hertz. Thenominalfrequencyoftheinternalreferenceclockis1.0Hz. The commandcanalsobeusedtomeasurethefrequencyofanexternal referenceclock.Ifautozeroisoffandthereferenceclockisinternal,orifautozerois off and APLL is set to 0FF under external reference clock, there are no referenceclocktransitionsinsidetheSIM918andFREQ?willtime outwithExecutionError16.
Example:	FREQ?1.023AutozeroPhasePHAS?Querytheautozeroswitchpositioninthepreamplifier.There-sponsesareZA0(whilezeroingtheinputvoltageofthemainam-plifieritself)andZZ1(whilezeroingtheoffsetvolageofthezeroing amplifier).Theseresponsesalternatewitheverycycleoftherefer-enceclock.TheswitchesareparkedintheZAstatewhenautozeroisoff.TOKNON;PHAS?Example:ZZ
APLL(?) {z}	Keep PLL ActiveSet (query) the “keep PLL active when autozero is off” mode of the preamplifier {to z = (OFF 0, ON 1)}.This setting only applies to the external reference clock direction. When APLL is OFF, turning off the autozero function (CHOP OFF) will fully halt the PLL oscillator (Section 2.5), ensuring that no digital clock transitions occur. One consequence of APLL OFF is that the oscillator will require up to 250 s to reestablish the lock to an external referencewhenreturningtoCHOPON.Conversely, with APLL ON the internal oscillator will continue to track an external 1 pps reference clock during CHOP OFF periods. In this case,thereisnore-locktimeneededwhenreturningtoCHOPON.The PLL oscillator always turns off with CHOP OFF in the internal referenceclockmode.The APLL setting is retained in non-volatile memory, and is not modifiedbyapower-onreset.
Example:	APLL1

ACAL	AutocalibrationPerform a self-calibration (Section 2.6). Make sure to disconnect all inputs and outputs to the SIM918. Remote commands are not processed until ACALiscomplete.
	Example: ACALLDDE?0checksforsuccessofanautocalibration.

ReadMicrovoltmeterREAD?m

Query instrument voltage m, in microvolts. READ? 1 queries the voltageattheoverallOutputterminal,andREAD?3,thevoltage attheoutputofthetransimpedancestage.Thesediagnosticsare usefulinmanuallyadjustingtheoutputandinputoffsetswiththe commands OFST 1 and OFST 2/OFST 3, respectively.

The commandREAD?2 measures the control output of an internal digital-to-analog converter. This output addstogether with the output of the autozero control loopto form the overall control output of the autozerocircuit, and is adjusted with OFST2.

Disconnect all inputs and outputs to the SIM918 before issuing READ?. Connect the center and shield terminals of the Bias BNC together externally, e.g. with a grounding cap. There will be a wait of several seconds for the commandtoexecutewhileinternalswitchesareconfiguredandthe voltages are sampled and averaged. Autozero is ON while READ? executes,andthereferenceclockisusedduringthemeasurement. TheresultsofREAD?willbeunpredictableifthereferenceclock is external and Unlocked. Remote commands are not processed untilREAD?iscomplete.

Example: READ? 1 -12

OFST(?) m {,j}

Offset Trim

Set (query) offset trim m {to j}. The trims are established by auto-calibration. If needed, the offsets in the SIM918 (Section2.4) maybe adjusted manually as follows:

Trim m	Range of j	Adjusts offset	When	By
1	-128-+126	Output	BIAS ON	3.9 μV/count
2	-32768-+32767	Input	CHOP OFF	0.45 μV/count
3	-128-+126	Input	CHOP ON	0.45 μV/count

AgreatervalueofOFST1willmaketheoutputvoltagemorepositive. A greater value of OFST 2 or OFST 3 will make the input offsetmorepositive, i.e. willmaketheinputvoltageexceedthebias voltagebymoremicrovolts.

Example: OFST? 3

-13

READ? 3

14

OFST 3,-42

3.4.7Statuscommands

	TheStatuscommandsqueryandconfigureregistersassociatedwith statusreportingoftheSIM918.SeeSection3.5forthestatusmodel.
	ClearStatus*CLS*CLSimmediatelyclearstheESR,CESR,RCSR,andOLSRstatus registers.*CLSExample:
	StatusByte*STB?[i]QuerytheStatusByteregister[Biti].Executionofthe*STB?query(withouttheoptionalBiti)always causes the ¬STATUS signal to be deasserted. Note that *STB? i will not clear ¬STATUS, even if Bit i is the only bit presently causing the ¬STATUSsignal.*STB?Example:16
*SRE(?) [i,] {j}	Service Request EnableSet (query) the Service Request Enable register [Bit i] {to j}.
Example:	*SRE0, 1
*ESR?[i]	StandardEventStatusQuerytheStandardEventStatusRegister[Biti].Upon execution of *ESR?, the returned bit(s) of the ESR register are cleared.*ESR?Example:64
*ESE(?) [i,] {j}	Standard Event Status EnableSet (query) the Standard Event Status Enable register [Bit i] {to j}.
Example:	*ESE6, 1ESE?64CommunicationErrorStatusCESR?[i]QuerytheCommunicationErrorStatusRegister[Biti].UponexecutingaCESR?query,thereturnedbit(s)oftheCESRregisterarecleared.CESR?Example:0
CESE(?) [i,] {j}	Communication Error Status EnableSet(query)theCommunicationErrorStatusEnableregister[Biti]{toj}.CESE?Example:2
	OverloadStatusOLSR?[i]QuerytheOverloadStatusRegister[Biti].UponexecutinganOLSR?query,thereturnedbit(s)oftheOLSRegisterarecleared.0LSR?Example:3
OLSE(?) [i,] {j}	Overload Status EnableSet (query) the Overload Status Enable register [Bit i] {to j}.Example:0LSE4
RCSR?[i]	ReferenceClockStatusQuerytheReferenceClockStatusRegister[Biti].Upon executing an RCSR? query, the returned bit(s) of the RCSR registerarecleared.RCSR?Example:7
RCSE(?) [i,] {j}	Reference Clock Status EnableSet (query) the Reference Clock Status Enable register [Bit i] {to j}.Example:RCSE3,1
PSTA(?) {z}	Pulse ¬STATUS ModeSet (query) the Pulse ¬STATUS mode {to z = (OFF 0, ON 1)}.When PSTA ON is set, all new service requests will only pulse the ¬STATUSsignalLOW(foraminimumof1μs).Thedefaultbehavior istolatch¬STATUSLOWuntila*STB?queryisreceived.AresetdoesnotalterPSTA.Thevalueinboldfaceaboveisthe power-onvalue.PSTAOFFExample:
LBTN?	LastButtonQuerythenumberofthelastbuttonpressed.Theresponseis
	LBTN?	Lastbutton
	1	[GAIN]
	2	[GAIN]
	3	[AUTOZERO]
	4	[Output1ppssync]
	5	[INPUTOpen]
	6	[INPUTShield]
	7	[BIASGND]
	8	[BIASShield]
	9	Both [GAIN] and [GAIN] (autocalibrate)
	10	Abuttonhelduponpower-on(reset)
	The value 0 is returned if no button was pressed since the last LBTN? .A query of LBTN? always clears the button code, so a subsequentLBTN?willreturn0.
	Example: LBTN?5
OVLD?	OverloadQuerythecurrentoverloadcondition.Theresponseis
	OVLD?	Overloaded
	1	Bias
	2	Output
	4	Bias+Output
	Combination overloads are reported by summing the values of the individualoverloadflags.ThiscommandcomplementstheOLSRstatus register described in Section 3.5.7, and the three overload flags correspondone-to-onewithbitsinOLSR.However, oncecleared

byOLSR?or*CLS,theoverloadstatusbitswillstayclearedeven thoughtheoverloadconditionmaypersistandremainreported byOVLD?.

OVLD?Example:

6

impliesthatthebiasisnotoverloaded;thetransimpedancestage

(V_bias - ini× isoverloaded; and the output is overloaded.

ReferenceClockStateRCLK?

Query the current source and lock state of thereference clock of the preamplifier. The responses are INTERNAL 0, EXTERNAL 1, and UNLOCKED 3.

This command complements the RCSR status register described in Section3.5.9, but there is no one-to-one correspondence between the response of RCLK? and bits in RCSR. Once cleared by RCSR? or*CLS, there reference clock status bit will stay cleared even though the reference clock state may persist and remain reported by RCLK?

RCLK?Example:

UNLOCKED

3.4.8 Interface commands

TheInterfacecommandsprovidecontrolovertheinterfacebetween theSIM918andthehostcomputer.

*RST

Reset

ResettheSIM918toitsdefaultconfiguration.

*RSTsetsthefollowing:

1. Gainto10 ^6 V/A.

2. Autozeroon.

3.Inputconnected.

4.Inputshieldtoground.

5.Biastoground.

6.Biasshieldtoground.

1. Reference clock direction to input.

2. The phase-locked loop to inactive when autozero is off (APLL OFF).

3. Clock oscillator to stop during idle time (AWAK 0FF).

	10. ThetokenmodetoOFF.*RST does not affect PSTA, CONS, TERM, and all service-enable registers (*SRE, *ESE, CESE, RCSE, or OLSE).*RSTExample:CONS?1
	Identify*IDN?Querythedeviceidentificationstring.Theidentificationstringisformattedas:StanfordResearchSystems, SIM918, s/n******, ver#. ####whereSIM918isthemodelnumber,*****isa6-digitserialnumber,and#.###isthefirmwareerevisionlevel.*IDN?Example:StanfordResearchSystems, SIM918, s/n005432, ver2.1
	SelfTest*TST?Thereisnointernalself-testintheSIM918afterthepower-on,sothis queryalwaysreturns0.*TST?Example:0
	OperationComplete*OPC(?)SetstheOPCflagintheESRregister.Thequeryform*OPC?writesa1intotheoutputqueuewhencomplete,butdoesnotaffecttheESRregister.*OPC?Example:1
CONS(?) {z}	Console ModeSet (query) the console mode {to z = (OFF 0, ON 1)}.CONScauseseachcharacterreceivedattheinputbuffertobecopied totheoutputqueue.A reset does not alter CONS. The value in boldface above is the power-onvalue.CONSissetto0FFuponDeviceClear.Example: CONS ON

ExecutionErrorLEXE?

QuerytheLastExecutionErrorcode.AqueryofLEXE?always clearstheerrorcode,soasubsequentLEXE?willreturn0. Valid codesare:

ValueDefinition

0NoexecutionerrorsincelastLEXE?

1Illegalvalue

2Wrongtoken

3Invalidbit

16Referenceclockinactive

*STB?12;LEXE?;LEXE?Example:

3

0

Theerror(3,"Invalidbit")isbecause*STB?onlyallowsbit-specific queriesof0-7.ThesecondreadofLEXE?returns0.

CommandErrorLCME?

Query the Last Command Error code. A query of LCME? always clears the error code, so a subsequent LCME? will return 0. Valid codes are:

ValueDefinition

0NocommanderrorsincelastLCME?

1Illegalcommand

2Undefinedcommand

3Illegalquery

4Illegalset

5Missingparameter(s)

6Extraparameter(s)

7Nullparameter(s)

8Parameterbufferoverflow

10Badinteger

11Badintegertoken

12Badtokenvalue

14Unknowntoken

Example: *IDN

LCME?

4

Theerror(4,"Illegalset")isduetothemissing"?".

	DeviceErrorLDDE?QuerytheLastDevice-DependentErrorcode.AqueryofLDDE?alwaysclearstheerrorcode,soasubsequentLDDE?willreturn0. Validcodesare:ValueDefinition
	0NoexecutionerrorsincelastLEXE?1Referenceclockconflict2Unabletoautocalibrate
	ACALExample:LDDE?0indicatesasuccessfulautocalibration.
	TokenModeTOKN(?){z}Set (query) the token query mode {to z = (OFF 0, ON 1)}.If TOKN ON is set, then queries to the SIM918 that return tokens will returnatextkeyword;otherwisetheyreturnadecimalintegervalue.Thus, the only possible responses to the TOKN? query are ON and 0.
Example:	TOKNOFF
TERM(?) {z}	Response TerminationSet (query) the <term> sequence {to z = (NONE 0, CR 1, LF 2, CRLF 3, orLFCR4)}.The <term> sequence is appended to all query responses sent by the module, and is constructed of ASCII character(s) 13 (carriage return)and10(linefeed). Thetokenmnemonicgivesthesequence ofcharacters.A reset does not alter TERM. The value in boldface above is the power-onvalue.
Example:	TOKNON;TERM?CRLF

3.4.9 Serialcommunicationcommands

NotethattheSIM918canonlysupportasinglebaudrateof9600, anddoesnotsupportflowcontrol.Aresetdoesnotchangetheserial interfacesettings;useDeviceClear.

ParityPARI(?){z}

Set (query) the parity {to z = (NONE 0, ODD 1, EVEN 2, MARK 3, SPACE4)}. The value in bold face is the power-on-value.

TOKNON; PARI? Example:

EVEN

3.5StatusModel

TheSIM918statusregistersfollowthehierarchicalIEEE-488.2for-statusregisters mat.AblockdiagramofthestatusregisterarrayisgiveninFigure3.1.

graph TD
    A["Communication Error Status"] --> B["CESR CESE"]
    A --> C["Standard Event Status"]
    A --> D["Reference Clock Status"]
    A --> E["Overload Status"]
    B --> F["PON: Power On 7 7"]
    B --> G["URQ: User Request 6 6"]
    B --> H["CME: Command Error 5 5"]
    B --> I["EXE: Execution Error 4 4"]
    B --> J["DDE: Device Error 3 3"]
    B --> K["QYE: Query Error 2 2"]
    B --> L["INP: Input Buffer Error 1 1"]
    B --> M["OPC: Operation Complete 0 0"]
    C --> N["PON: Power On 7 7"]
    C --> O["URQ: User Request 6 6"]
    C --> P["CME: Command Error 5 5"]
    C --> Q["EXE: Execution Error 4 4"]
    C --> R["DDE: Device Error 3 3"]
    C --> S["QYE: Query Error 2 2"]
    C --> T["INP: Input Buffer Error 1 1"]
    C --> U["OPC: Operation Complete 0 0"]
    D --> V["ESR ESE"]
    E --> W["SB SRE"]
    W --> X["STATUS"]
    style A fill:#f9f,stroke:#333
    style B fill:#ccf,stroke:#333
    style C fill:#cfc,stroke:#333
    style D fill:#fcc,stroke:#333
    style E fill:#cff,stroke:#333

Figure 3.1: Status register model for the SIM918 Precision CurrentPreamplifier.

TherearetwocategoriesofregistersintheSIM918statusmodel:

Event Registers: These read-only registers record the occurrence of defined events. If the event occurs, the corresponding bit is set to 1. Upon querying an event register, all set bits within it are cleared. These are sometimes known as “sticky bits,” since once set, a bit can only be cleared by reading its value. Event registernamesendwithSR.

Enable Registers : These read/write registers define a bitwise mask for their corresponding event register. If a bit position is set in an event register while the same bit position is also set in the enable register, then the corresponding summary bit message is set. EnableregisternamesendwithSE.

Atpower-on, allstatusregistersarecleared.

3.5.1StatusByte(SB)

TheStatusByteisthetop-levelsummaryoftheSIM918statusmodel. WhenmaskedbytheServiceRequestEnableregister,abitsetintheStatusBytecausesthe-STATUSsignaltobeassertedontherear-panelSIMinterfaceconnector.

WeightBitFlag
10	OLSB
21	RCSB
42	undef(0)
83	undef(0)
164	IDLE
325	ESB
646	MSS
1287	CESB

OLSB:OverloadSummaryBit.Indicateswhetheroneormoreofthe enabledflagsintheOverloadStatusRegisterhasbecometrue.

RCSB: ReferenceClockSummaryBit. Indicates whether one or more of the enabled flags in the ReferenceClock StatusRegister has become true.

IDLE:Indicates that the input buffer is empty and the command parser is idle. Can be used to help synchronize SIM918 query responses.

ESB:EventStatusBit.Indicateswhetheroneormoreoftheenabled eventsintheStandardEventStatusRegisteristrue.

MSS:MasterSummaryStatus.Indicateswhetheroneormoreofthe enabledstatusmessagesintheStatusByteregisteristrue.

CESB:CommunicationErrorSummaryBit.Indicateswhetheroneor moreoftheenabledflagsintheCommunicationErrorStatus Registerhasbecometrue.

3.5.2ServiceRequestEnable(SRE)

EachbitintheSREcorrespondsone-to-onewithabitintheSBregister,andactsasabitwiseANDoftheSBflagstogenerateMSS.Bit6of theSREisundefined—settingithasnoeffect,andreadingitalways returns 0. This register is set and queried with the *SRE(?) command.

Atpower-on, thisregisteriscleared.

3.5.3 StandardEventStatus(ESR)

TheStandardEventStatusRegisterconsistsof8eventflags. These eventflagsareall"stickybits"thataretbythecorresponding events, andclearedonlybyreadingorwiththe*CLScommand. Reading a single bit (with the *ESR? i query) clears only Bit i.

WeightBitFlag
10	OPC
21	INP
42	QYE
83	DDE
164	EXE
325	CME
646	URQ
1287	PON

OPC:OperationComplete.Setbythe*OPCcommand.

INP:Inputbuffererror.Indicatesdatahasbeendiscardedfromthe inputbuffer.

QYE:QueryError.Indicatesdataintheoutputqueuehasbeenlost.

DDE:Device-DependentError. Indicates a failed autocalibration or areference clock conflict.

EXE:ExecutionError. Indicate the error in a command that was successfully parsed. Out-of-rangeparameters are an example.

CME:CommandError.Indicatesacommandparser-detectederror.

URQ:UserRequest.Indicatestatafront-panelbuttonwaspressed.

PON:PowerOn.Indicatesthatanoff-to-ontransitionhasoccurred.

3.5.4 StandardEventStatusEnable(ESE)

TheESEactsasabitwiseANDwiththeESRregistertoproducethe single-bitESBmessageintheStatusByteRegister(SB).Theregister canbesetandqueriedwiththe*ESE(?)command.

Atpower-on, thisregisteriscleared.

3.5.5 CommunicationErrorStatus(CESR)

TheCommunicationErrorStatusRegisterconsistsof8eventflags; eachoftheflagsissetbythecorrespondingevent,andclearedonly by reading the register or with the *CLS command. Reading a single bit (with the CESR? i query) clears only Bit i.

WeightBitFlag

10PARITY

21FRAME

42NOISE

83HWOVRN

164OVR

325RTSH

646CTSH

1287DCAS\$

PARITY:Parityerror.Setbyserialparitymismatchontheincomingdata byte.

FRAME:Framingerror.Setwhenanincomingserialdatabyteismissing theSTOPbit.

NOISE:Noiseerror.Setwhenanincomingserialdatabytedoesnot presentasteadylogiclevelduringeachasynchronousbit-periodwindow.

HWOVRN:HardwareOverrun.Setwhenanincomingserialdatabyteis lostduetointernalprocessorlatency.Causestheinputbuffer tobeflushed,andresetsthecommandparser.

OVR:InputbufferOverrun.Setwhentheinputbufferisoverrunby theincomingdata. Causestheinputbuffertobeflushed, and resetsthecommandparser.

RTSH:RTSHoldoffEvent.UnusedintheSIM918.

CTSH:CTSHoldoffEvent.UnusedintheSIM918.

DCAS: Device Clear. Indicates that the SIM918 received the Device Clear signal (an RS-232 ). Clears the input buffer and the outputqueue, and resetsthecommandparser.

3.5.6 CommunicationErrorStatusEnable(CESE)

TheCESEactsasabitwiseANDwiththeCESRregistertoproduce the single-bit CESB message in the Status Byte Register (SB). The registercanbesetandqueriedwiththeCESE(?)command.

Atpower-on, thisregisteriscleared.

3.5.7 OverloadStatus(OLSR)

TheOverloadStatusRegisterconsistsof3eventflags; eachofthe flags is set by the corresponding overload, and cleared only by reading the register or with the *CLS command. Reading a single bit (with the OLSR? i query) clears only Bit i.

WeightBitFlag 10 Bias 21 Output 42 Bias+Output 83 undef(0) 164 undef(0) 325 undef(0) 646 undef(0) 1287 undef(0)

as:Biasoverload.Indicatesthat|V bias| >5.0V(seealsoSec- tion1.2.4.1).

ut:Outputoverload.Indicatesthat|V out| >10.0V(seealsoSec- tion1.2.5).

Bias+Output:Transimpedancestageoverload.Indicates that

$$ \left| V _ {\text { bias }} - \text { in } i \times \text { R } > 1 0. 0 \mathrm{V}. \right. $$

Reading this register (with the OLSR? query) clears all overload bits that are set. If the overload condition persists, the bits will remain cleared until the overload condition ceases and reoccurs. Use OVLD? to query the current state of the overload.

3.5.8 OverloadStatusEnable(OLSE)

TheOLSEactsasabitwiseANDwiththeOLSRregistertoproduce the single-bit OLSB message in the Status Byte Register (SB). The registercanbesetandqueriedwiththeOLSE(?)command.

Atpower-on, thisregisteriscleared.

3.5.9 ReferenceClockStatus(RCSR)

The Reference Clock Status Register consists of 4 event flags; each of the flags is set by the corresponding clock event, and cleared only by reading the register or with the *CLS command. Reading a single bit (with the RCSR? i query) clears only Bit i.

WeightBitFlag 10 Leave 21 Arrive 42 Unlock 83 Lock 164 undef (0) 325 undef (0) 646 undef (0) 1287 undef (0)

Leave: Reference clock stop detect. Indicates that the external referenceclocksignalhasceased.

Arrive: Referenceclockstartdetect. Indicate that several periodic clockedges have been newly present at therear-panel RefClockSyncconnector.

Unlock:Unlockdetect.Indicates that thereference clock PLL (Section2.5) has transitioned from locked or idlet unlocked.

Lock:Lockdetect.Indicate that thereference clock PLL has transitioned from unlocked to locked.

Reading this register (with the RCSR? query) clears all event bits that a reset. If the clock state persists (e.g. the clock remains unlocked), the bit will remain cleared until the state ceases and reoccurs. Use RCLK? to query the current state of thereference clock.

3.5.10 ReferenceClockStatusEnable(RCSE)

TheRCSEactsasabitwiseANDwiththeRCSRregistertoproduce the single-bit RCSB message in the Status Byte Register (SB). The registercanbesetandqueriedwiththeRCSE(?)command.

Atpower-on, thisregisteriscleared.

4CircuitDescription

InThisChapter

4.1SchematicDiagrams....4-2

4.1 Schematic Diagrams

Circuitschematicdiagramsfollowthispage.

U10A 2.5GHz CLK FR STOP R01A 10kV-4 D Pin Clock Wake-Up U10C 1.5GHz CLK U11C 1.5GHz CLK U12C 1.5GHz CLK U13C 1.5GHz CLK U14C 1.5GHz CLK U15C 1.5GHz CLK U16C 1.5GHz CLK U17C 1.5GHz CLK U18C 1.5GHz CLK U19C 1.5GHz CLK U20C 1.5GHz CLK U21C 1.5GHz CLK U22C 1.5GHz CLK U23C 1.5GHz CLK U24C 1.5GHz CLK U25C 1.5GHz CLK U26C 1.5GHz CLK U27C 1.5GHz CLK U28C 1.5GHz CLK U29C 1.5GHz CLK U30C 1.5GHz CLK U31C 1.5GHz CLK U32C 1.5GHz CLK U33C 1.5GHz CLK U34C 1.5GHz CLK U35C 1.5GHz CLK U36C 1.5GHz CLK U37C 1.5GHz CLK U38C 1.5GHz CLK U39C 1.5GHz CLK U40C 1.5GHz CLK U41C 1.5GHz CLK U42C 1.5GHz CLK U43C 1.5GHz CLK U44C 1.5GHz CLK U45C 1.5GHz CLK U46C 1.5GHz CLK U47C 1.5GHz CLK U48C 1.5GHz CLK U49C 1.5GHz CLK U50C 1.5GHz CLK U51C 1.5GHz CLK U52C 1.5GHz CLK U53C 1.5GHz CLK U54C 1.5GHz CLK U55C 1.5GHz CLK U56C 1.5GHz CLK U57C 1.5GHz CLK U58C 1.5GHz CLK U59C 1.5GHz CLK U60C 1.5GHz CLK U61C 1.5GHz CLK U62C 1.5GHz CLK U63C 1.5GHz CLK U64C 1.5GHz CLK U65C 1.5GHz CLK U66C 1.5GHz CLK U67C 1.5GHz CLK U68C 1.5GHz CLK U69C 1.5GHz CLK U70C 1.5GHz

Electrical circuit schematic diagram with labeled components including transistors, capacitors, resistors, and logic gates.

S. NO. 2		P#N-5 (M)
	C. P. L. N. S. T. E. M. A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. E. F. G. H. I. J. K. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y.Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U.V. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T.U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R.S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P.Q. P. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O.P. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J.K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H.I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F.G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. G. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z.A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X.Y. A. B. C. D. F. G. H. I. J. K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I. J.K. L. M. N. O. P. P. Q. R. S. T. U. V. W. X. Y. Z. A. B. C. D. F. G. H. I.J.K.L 100%

12C.001 9.408H 65V pazog DOSBAY 01 RPG 100Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω 10Ω NDC P/173 CVA 85mA

Exonatal Clock Detection C10.0125V 700V 104V RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL RCL

FLUX A01- A02- 100VDD 0.5 VD A-1 A-2 A+1 A+2 A+3 FLUX 0.5 VD 0.5 VD A A+1 A+2 A+3

Circuit diagrams showing two logic gates with labeled pins and connections

TO Analog Band On series holds clear ICU at the micro bus bus The device has the starting point of the printed section lines (5) 7 to the section of the corresponding output is (500 + 30) ns reduction window (in FPL) = (90.92) results in the maximum arcule (clock-in) = 1.15 in (16mp = 0.57 in) Alowing (4) + (-1) - (-2) + (-1) - (-2) = 880 CACO for the Aluminum (4) + (-1) - (-2) + (-1) - (-2) = 880 CACO for the Aluminum (4) + (-1) - (-2) + (-1) - (-2) = 880 CACO for the Aluminum (4) + (-1) - (-2) + (-1) - (-2) = 880 CACO for the Aluminum (4) + The first block is: - The first block is: - The second block is: - The third block is: - The fourth block is: - The fifth block is: - The sixth block is: - The seventh block is: - The eight block is: - The nine block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: - The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: The ten block is: For example, the first block has an input voltage of 100A for example, the second block has an input voltage of 100A for example, the third block has an input voltage of 100A for example, the fourth block has an input voltage of 100A for example, the fifth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the seven block has an input voltage of 100A for example, the eight block has an input voltage of 100A for example, the nine block has an input voltage of 100A for example, the ten block has an input voltage of 100A for example, the ten block has an input voltage of 100A for example, the ten block has an input voltage of 100A for example, the ten block has an input voltage of 100A for example, the ten block has an input voltage of 100A for example, the ten block has an input voltage of 100A for example, the first block has an input voltage of 100A for example, the second block has an input voltage of 100A for example, the third block has an input voltage of 100A for example, the fourth block has an input voltage of 100A for example, the fifth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for instance, the first block has an input voltage of 100A for example, the second block has an input voltage of 100A for example, the third block has an input voltage of 100A for example, the fourth block has an input voltage of 100A for example, the fifth block has an input voltage of 100A for example, the first block has an input voltage of 100A for example, the second block has an input voltage of 100A for example, the third block has an input voltage of 100A for example, the fourth block has an input voltage of 100A for example, the first block has an input voltage of 100A for example, the second block has an input voltage of 100A for example, the third block has an input voltage of 100A for example, the fourth block has an input voltage of 100A for example, the fifth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for example, the sixth block has an input voltage of 100A for instance, the sixth block has an input voltage of 100A for instance, the sixth block has an input voltage of 100A for instance, the sixth block has an input voltage of 100A for instance, the sixth block has an input voltage of 100A for instance, the sixth block has an input voltage of 100A for instance, the sixth block has an input voltage of 100A

S. NO.	S.	PAPAYA
		01-02-2015
		03-04-2016
PAPAYA (PAPAYA)
NO.	NO.	NO.

graph TD
    A["3401 BTF-1052"] --> B["Gain <..."]
    C["3402 BTF-1052"] --> D["Gain -->"]
    E["3403 BTF-1052"] --> F["Autozero On"]
    G["3404 BTF-1052"] --> H["Output 1 pps sync"]
    I["3405 BTF-1052"] --> J["Input Open"]
    K["3406 BTF-1052"] --> L["Input Shield"]
    M["Bias GND"] --> N["Bias Shield"]
    O["Bias Shield"] --> P["Bias Shield"]
    Q["From Digital Board"] --> R["J001 Sdc=10.05* T+25M"]
    S["Data"] --> T["+5V"]
    U["U422 X14CMSA"] --> V["+5V"]
    W["X2C2 B TIP"] --> X["+5V"]
    Y["Q4 Q3 Q2 Q1"] --> Z["+5V"]
    AA["Q5 Q4 Q3"] --> AB["+5V"]
    AC["Q6 Q5 Q4"] --> AD["+5V"]
    AE["Q7 Q8 Q9"] --> AF["+5V"]
    AG["Q10 Q20"] --> AH["+5V"]
    AI["Q21 Q31"] --> AJ["+5V"]
    AK["Q32 Q42"] --> AL["+5V"]
    AM["Q43 Q53"] --> AN["+5V"]
    AO["Q54 Q63"] --> AP["+5V"]
    AQ["Q64 Q73"] --> AR["+5V"]
    AS["Q74 Q83"] --> AT["+5V"]
    AU["Q84 Q93"] --> AV["+5V"]
    AW["Q95 Q10"] --> AX["+5V"]
    AY["Gain 1 VμA"] --> AZ["D001 G uo"]
    BA["Gain 10 VμA"] --> BB["D002 G uu"]
    BC["Gain 100 VμA"] --> BD["D003 G uo"]
    BE["Autozero On"] --> BF["D004 G uo"]
    BG["Autozero External"] --> BH["D005 G uo"]
    BI["Autozero Unlocked"] --> BJ["D006 G uo"]
    BK["Output 1 pps Sync"] --> BL["D007 G uo"]
    BM["Input Open"] --> BN["D008 G uo"]
    BO["Input Shield"] --> BP["D009 G uo"]
    BQ["Input Shield Bias"] --> BR["D010 G uo"]
    BS["Input Shield GND"] --> BT["D011 G uo"]
    BU["Bias OVLD"] --> BV["D012 G uo"]
    BW["Bias GND"] --> BX["D013 G uo"]
    BY["Bias Shield Float"] --> CA["D014 G uo"]
    CB["Bias Shield GND"] --> CC["D015 G uo"]
    CD["Output OVLD"] --> CE["D016 G uo"]

STANDARD RESEARCH SYSTEMS, INC.
ITEM:Predecessor Current Presence Total Panel
Size D	Current Number R/W
C	SIM1 8 3
Date: Date		4 m 5

Electrical schematic diagram with labeled components including resistors, capacitors, inductors, and ICs for various electronic circuits.

Electrical schematic diagram with multiple operational amplifiers, resistors, capacitors, and integrated circuits labeled in English.

Electrical circuit diagram with labeled components including transistors, capacitors, resistors, and ICs for signal processing or control design.

STAND COLD RESEARCH SYSTEMS, INC.
TEL: Pressure Current Power, Atering Power, Coil Switch and Set-Cell
Size D: Current Number R/W
E: SIM/1.8 L
Date: Date		S or S

AppendixAIndex

-STATUSsignal,1-3,1-10,3-16,17,3-25

signal,seeDeviceClear

Accuracy

gain,seeGain,accuracy

offset,2–6

Autocalibration,1–3,2–6,7,3–14,15,3–18,3–22,3–26

Autozero, ix, 1–2, 3, 1–5, 2–6, 2–8, 3–14, 15

button,seeButton,[AUTOZERO]

clocksource,seeReferenceclock,source

LED,seeLED,AUTOZERO

phase,3–14

selecting, ix, 1–2, 3, 1–9, 2–6, 3–6, 3–13, 14, 3–19

switchingfrequency,ix,1–2,1–6

Autozerocircuit,1–3,1–5,6,1–8,2–2,2–5,6,2–8,3–15

settlingtime,2–5,2–8

Bandwidth

bias,viii,2-4

current,viii,2-2,3

Baudrate,1–12,3–6

Bias,iii,2-4

bandwidth,seeBandwidth,bias

button,seeButton,[BIASGND]

connector,iii,viii,1-7,8,2-7,3-15

shield,viii,1-3,1-7-9,2-4,3-6,3 -12,3-19

inputresistance,viii,2-4

LED,seeLED,BIASGND

overload,seeOverload,bias

selecting,viii,1-3,1-7,1-9,2-5,3-6,3-12,3-19

shield

button,seeButton,[BIASShield]

LED,seeLED,BIASShield

voltage,iii,1-2-4,1-7,8,2-4,5,3-15

limits,viii,ix,1-7,2-4,5

voltagebuffer,1-7,2-4

offsetvoltage,1–7,2–4

Blockdiagram,1–4

BNC,iii,viii,ix,1-3,1-7,8,2-3,4,2-7,3

-12,3-15

Buffer

bias,seeBias,voltagebuffer

input,3-6,3-25-27

overflow,3–6,7,3–27

output,seeOutputqueue

voltage,seeOutput,voltagebuffer

Button,1-9,3-18,3-26

[AUTOZERO],1-5,3-18

[BIASGND],1-7,2-5,3-18

[BIASShield],1-7,3-18

[GAIN],1-5,2-7,3-18

[INPUTOpen],1-6,3-18

[INPUTShield],1-7,3-18

[Output1ppssync],1-6,3-18

Circuitschematics,seeSchematicdiagrams

Clockstopping,1-3,2-7,3-11,3-19

Command

error,3–21,3–26

parameters,3–7,3–21

separator,3–7

terminator,3-6,7,3-20,3-22

Common-moderejection(CMRR), ix, 1–7, 2 -4

Compensation,2–3

Consolemode,3–6,7,3–20

Currentgain,seeGain

Currentinput,seeInput

DB-15,1-10,11,2-4

DB-9

female,1–11

male,1–11

Defaultconfiguration,seeReset

DeviceClear,3-7,3-20,3-22,3-27

Deviceerror,1-6,3-21,3-26

Differenceamplifier,1-4,1-7,2-4,5

Dimensions, ix

Error

command,seeCommand,error

Executionerror,3-13,3-21,3-26

Firmwareerevision,2-7,3-20

Flowcontrol,1–12,3–6,3–22

FPLC,1-9,2-6,3-6,3-11

Frontpanel,1–5,1–8,2–7 operation,1–5

Fullduplex,seeConsolemode

Gain,iii,viii,1-2,1-4,5,1-9,2-3,2-5,3 -6,3-12,3-19

accuracy,viii,2-7,3-12

button,seeButton,[GAIN]

LED,seeLED,GAIN

selecting,2–8

stability, viii

Generalinformation,iii

Ground,iii,1-2,1-10,2-4

chassis,1–8,1–10,11,2–4

Earth,2-4

power,1-7,8,1-10,11,2-4

signal,1–3,1–7,8,1–10,11,2–4

virtual,1–2

Help,3-10

Input,iii,iv,2-3,2-7,3-12

bias,seeBias

biascurrent,1-2

AC,viii

DC,viii

button,seeButton,[INPUTOpen]

capacitance,viii,1-6,2-2

connector,iii,viii,1-8

shield,iii,viii,1-3,1-7-9,2-4,3-

6,3–12,3–19;seealsoShieldprogramvoltage

current,iii,1-2,1-4-6,1-8,2-2

impedance,viii,1–2,2–2

LED,seeLED,INPUTOpen

maximumcablelength,2-3

offsetvoltage,iii,viii,1-2,1-6,7,2-5,2-8,3-12,3-15

adjusting,seeTrim,inputoffset drift,2–8

measuring,3–12,3–15

zeroing,3–14

program,seeShieldprogramvoltage

resistance,seeInput,impedance

selecting,viii,1-3,1-6,1-9,3-6,3-12,3-19

shield

button,seeButton,[INPUTShield]

float,1-3,1-7

LED,seeLED,INPUTShield

voltage,iii,1-2,1-8,2-2,3-15

Interface

direct,1–10

cable,1–11

remote,seeRemoteinterface

SIM,seeSIMinterface

JFET,iv,2-2

LED

AUTOZERO,1-5,2-5

BIASGND,1-7,2-5,3-12

BIASOVLD,1-3,1-7,2-5

BIASShield

Float,1-7

GND,1-7,2-4

External,1-6,2-6

GAIN,1-5,3-12

INPUTOpen,1-6

INPUTShield

Bias,1-7,2-4

GND,1-7,2-4

Prog,1-7

OUTPUTOVLD,1-3,1-8

Output1ppssync,1-6

Unlocked,1-3,1-6,3-15

allon,2-7

Mainamplifier,seeTransimpedancestage

Mainframe,seeSIM900

Noise,2-3-5

current,viii,1-2,2-3

Johnson,1–2

overall,2–3

voltage,viii,2-3

Non-volatilesettings,1–9,3–6,3–11,12,3 - 14

Notation,vii,3-6,3-9

Nullmodem,1–11

Offset

input,seeInput,offsetvoltage

output,seeOutput,offsetvoltage

Output,2–5

connector, ix, 1–8

shield,1-8,2-4

current,ix,2-4

filter,2-5

maximumload,2-5

offsetvoltage,ix,1–3,1–7,2–5,3–15

adjusting,seeTrim,outputoffset

measuring,3–15

overload,seeOverload,output

resistance, ix, 2–5

voltage,iii,1-2-5,1-7,8,1-11,3-12,3-15

limits, ix, 1–8, 2–5

Outputqueue,3-6,3-20,3-26,27

Output1ppssync

button,seeButton,[Output1ppssync]

Overload,1–3,2–7,3–18

bias,ix,1-3,1-7,2-5,3-18,3-28

OVLDindicator,seeLED,BIASOVLD

biasplusoutput,ix,1–8,3–18,3–28

output,ix,1-3,1-8,3-18,3-28

OVLDindicator,seeLED,OUTPUT OVLD

Parity,1–12,3–6,3–22,3–27

Phase-lockedloop(PLL),2–6,7,3–29

keepactive,1–9,2–6,3–6,3–13,14,3 - 19

oscillator,2–6,7,3–14

Photomultiplier(PMT),iv

Power

ground,seeGround,power

requirements, ix, 1–10, 11

Power-on,1–9,2–6,7,3–6,7,3–11–14,3–18,3–20,3–22,3–25–29

Powerlinefrequency,seeFPLC

Preparationforuse,iv

Program,seeShieldprogramvoltage

Querycommand,3-7,3-21,3-25

Quiescentoperation,1–3,2–6,2–8,3–14

Rearpanel,1–5,1–8

Referenceclock, viii, 1–2, 3, 1–5, 1–8, 3–14, 15, 3–19, 3–21

capturetime,1–6,2–6,3–14

capturerange,seeinput,frequencylimits

connector,iii,viii,1-2,1-6,1-8,2-4, 2-6,7,3-13,3-28

direction,1–8,2–7

conflict,1–6,3–22,3–26

selecting,viii,1-6,1-9,3-13,3-19

external, ix, 1–2, 3, 1–6, 2–6, 7, 3–13, 14, 3–19, 3–28

Unlockedindicator,seeLED,Unlocked

LEDindicator,seeLED,External

unlocked,1–3,1–6,2–7,3–14,15,3 -19,3–29

input,1-2,1-6

frequency,3–13

frequencylimits,viii,ix,1-6,2-6

internal, ix, 1–2, 1–6, 2–6, 7, 3–13, 14, 3–19

frequency, viii, 1–6, 2–6, 3–13

levels,viii,1–6

lockacquisitiontime,seecapturetime

output,1-2,1-6,2-6

frequency,seeinternal,frequency

source, ix, 1–2, 1–6, 2–6

Registers,seeStatus,registers

Remoteinterface, ix, 1–3, 1–9, 2–7, 3–1, 3 -7, 3–10, 3–19

dataformat,3–13

Reset,1-9,2-8,3-18-20,3-22

power-onbuttonhold,1-9,3-18

RS-232,1-3,1-11,3-6,7,3-22,3-27

settings,1–12,3–22

Safety,iii

biomedical applications, iii

Schematicdiagrams,4–2

Self-test,3-20

Serialinterface,seeRS-232

Serialnumber,3–20

Service,iv

Setcommand,3-7,3-21

Shield

bias,seeBias,connector,shield

input,seeInput,connector,shield

Shieldprogramvoltage,iii,1-3,1-7,8

connector,iii,viii,1-7,8,2-4

inputresistance,viii

limits,viii

SIM900,iv,1-3,1-9-11,2-4,2-6,3-6,7

SIMinterface, ix, 1–10, 3–25

connector,1–10,2–4

Sourceresistance,2–3

Specifications, viii

Stability

fromoscillation,2–2

gain,seeGain,stability

Status,3–15,3–24

registers,3–16,3–24

CESE,3-17,3-27

CESR,3-6,3-16,3-25-27

ESE,3-16,3-20,3-26

ESR,3-6,3-16,3-20,3-25

OLSE,3-17,3-20,3-28

OLSR,3-17,18,3-25,3-27,28

RCSE,3-17,3-29

RCSR,3-17,3-19,3-25,3-28,29

SB,3-16,3-25-29

SRE,3-16,3-20,3-25

Stickybits,3–24,25

Temperature, ix, 2–6

Token,3-7,8,3-21

mode,3-19,3-22

Transimpedance,iii,1-2,2-2

amplifier,1–2,2–2,3

Transimpedancestage,iii,1–4,1–7,2–2–5,

3-12,3-19,3-28

front-endamplifier,iv,1-6

outputvoltage,1-8,2-2,2-5,3-15

Trim

autozerocontrolloop,2-5,3-15

inputoffset,1–6,1–9,2–5,3–15

outputoffset,2–5,3–15

Warmup,2–6

Weight, ix

Zeroingamplifier

inputoffsetvoltage,1-2

zeroing,3–14