SIM921 - Electrical measuring device SRS - Free user manual and instructions

Product Type	Precision Voltage and Current Source
Model	SIM921
Brand	SRS (Stanford Research Systems)
Output Voltage Range	±10 V (typical)
Output Current Range	±100 mA (typical)
Resolution	16-bit DAC
Accuracy	0.1% of setting + 1 mV / 0.1 mA
Noise	< 1 mVrms (typical)
Interface	GPIB, RS-232
Power Supply	AC 100-240 V, 50/60 Hz, 20 VA
Dimensions	2U rackmount, 483 x 89 x 270 mm
Weight	3.2 kg (approx.)
Operating Temperature	0°C to 40°C
Storage Temperature	-20°C to 70°C
Protection	Overvoltage and overcurrent protection
Front Panel Display	2-line alphanumeric LCD
Control	Front panel keys and rotary encoder
Calibration Interval	1 year recommended
Compliance	CE, RoHS
Accessories Included	Power cord, manual, test leads
Maintenance	Clean with dry cloth; no user-serviceable parts inside
Repairability	Refer to SRS service center; no DIY repair

Frequently Asked Questions - SIM921 SRS

How do I set the voltage output on the SIM921?

Press the V key to enter voltage mode, then use the numeric keypad or rotary encoder to set the desired voltage. Press ENTER to confirm.

Can the SIM921 be used as a current source?

Yes, press the I key to switch to current mode. Set the current using the keypad or encoder. The output will regulate current accordingly.

What is the maximum output power?

The maximum output power is limited to 1 W (e.g., 10 V at 100 mA). Exceeding may trigger protection.

How do I connect the SIM921 to a computer?

Connect via GPIB or RS-232 cable. Ensure the interface is enabled in the system menu. Install the appropriate drivers/software from SRS website.

What does the 'OVERLOAD' indicator mean?

The OVERLOAD LED lights when the output exceeds the maximum voltage or current limit. The output may be automatically reduced to prevent damage.

How to perform a factory reset?

Press and hold the MENU key while powering on. Select 'Factory Reset' from the menu and confirm. All user settings will be lost.

Can I adjust the output voltage below 0 V?

Yes, the SIM921 can output bipolar voltages from -10 V to +10 V. Use the +/- key to toggle polarity.

What is the recommended calibration procedure?

Calibrate using a precision multimeter (6.5 digit). Connect the output, set known values, and adjust internal trimmers. Refer to the service manual for detailed steps.

How to save and recall settings?

Press SAVE to store current settings to a memory location (0-9). Press RECALL then the number to reload.

What should I do if the display shows 'ERR'?

'ERR' indicates a hardware fault. Check connections, power cycle the unit. If persistent, contact SRS support for repair.

USER MANUAL SIM921 SRS

Revision2.3• September12,2011

Certification

StanfordResearchSystemscertifiesthatthisproductmetitspublishedspecificationsatthetime ofshipment.

Warranty

ThisStanfordResearchSystemsproductiswarrantedagainstdefectsinmaterialsandworkmanshipforaperiodofone(1)yearfromthedateofshipment.

Service

Forwarrantyserviceorrepair, thisproductmustbereturnedtoaStanfordResearchSystems authorizedservicefacility.ContactStanfordResearchSystemsoranauthorizedrepresentative beforereturningthisproductforrepair.

Informationinthisdocumentissubjecttochangewithoutnotice.

Copyright © StanfordResearchSystems, Inc., 2003–2011. All rights reserved.

StanfordResearchSystems, Inc.

1290-DReamwoodAvenue

Sunnyvale, CA94089USA

Phone:[phone]• Fax:[phone]

www.thinkSRS.com• e-mail:[e-mail]

PrintedinU.S.A.Documentnumber9-01555-903

Contents

GeneralInformationiii

Service......iii

Symbols......iv

Notation......v

Specifications......vi

1GettingStarted1-1

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

1.2Front-PanelOperation....1-3

1.3SensorInterface....1-8

1.4SIMInterface....1-11

2RemoteOperation

2.1IndexofCommands....2-2

2.2AlphabeticListofCommands ......2-4

2.3Introduction....2-7

2.4Commands 2-8

2.5StatusModel 2-26

3Circuitry

3.1 CircuitDiscussion ....3-2

3.2PartsLists ....3-6

3.3SchematicDiagrams....3-8

GeneralInformation

TheSIM921ACResistanceBridge, part of Stanford Research Systems' Small Instrumentation Modules family, is a precision, high-sensitivity instrument designed for ultra-low power resistance measurements, typically for cryogenic thermometry.

Service

Donotinstallsubstitutepartsorperformanyunauthorizedmodificationstothisinstrument.

TheSIM921isadouble-widemoduledesignedtobeusedinsidethe SIM900Mainframe.Donotturnonthepoweruntilthemoduleis 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[Button]; [Adjust]!shorthandfor"[Adjust]&[Adjust]".
• Front-panelindicatorsaresetasOverload.
• Remotecommandnamesaresetas*IDN?
• LiteraltextotherthancommandnamesissetasOFF.

Remote command examples will all beset in monospaced font. In these examples, data sent by the host computer to the SIM921 areset as straightte type font, while responses received by the host computer from the SIM921 areset asslanted te type font.

Specifications

PerformanceCharacteristics

MeasurementMeasurementtype4wireACbridge
Numberofinputs1
Resistancerange1mΩto100MΩ
Timeconstant0.3sto300s,		orsync.only
Readingrate2updates/s
Demodulatorresolution32-bit
Resolutionseetable
Accuracy(%reading+%range)2Ω to 200kΩ, ≥ 30 μV, ≥ 3 nA200 mΩ to 2 MΩ, ≥ 100 pA		±(0.05% + 0.05%)±(0.15% + 0.15%)
Stabilityafterautocalwithoutautocal(±0.02%ofreading)/		(±0.001%ofreading)/ °C/°C
Max.leadresistance		100Ω+25%range
Inputimpedance		>10GΩ,typical
Source	Type	Sinusoid, constant I,V, or P
	Frequency	2Hzto60Hz,continuouslyadjustable
	Excitation	3μVto30mV,10mAmax.
	Max. DC current	<3 μV/range
ThermometrySensorssupported		All resistivesensors(- and+tempco)
AnalogOutputRange		±10V
Resolution300μV
Accuracy		1mV
OperatingTemperature0		°Cto40 °C,non-condensing
Interface		SerialviaSIMinterface
Connectors
Sensor		DB-9(female)
Analogout		BNC(front)
SIM		DB-15(male)SIMInterface
Power		±15VDC,+5VDC
Supply current		150 mA (±15 V), 250 mA (+5 V)

Resolution

Resolutionisgiveninthetablebelow.Uppervaluesgiveexcitationcurrent,whilelowervaluesaretypicalRMSresistancenoise measuredat50%fullscaleonaroom-temperatureresistorwitha 3secondoutputtimeconstant.

Range	Excitation
	30 mV	10 mV	3 mV	1 mV	300 μV	100 μV	30 μV	10 μV	3 μV
20 mΩ	N/A	N/A	N/A	N/A	N/A	10 mA	3 mA	1 mA	300 μA
						44 μΩ	130 μΩ	510 μΩ	1.5 mΩ
200 mΩ	N/A	N/A	N/A	10 mA	3 mA	1 mA	300 μA	100 μA	30 μA
				8.9 μΩ	12 μΩ	32 μΩ	120 μΩ	590 μΩ	1.4 mΩ
2 Ω	N/A	10 mA	3 mA	1 mA	300 μA	100 μA	30 μA	10 μA	3 μA
		4.3 μΩ	5.5 μΩ	7.9 μΩ	23 μΩ	70 μΩ	220 μΩ	730 μΩ	1.8 mΩ
20 Ω	3 mA	1 mA	300 μA	100 μA	30 μA	10 μA	3 μA	1 μA	300 nA
	20 μΩ	21 μΩ	33 μΩ	41 μΩ	100 μΩ	390 μΩ	1.7 mΩ	4.1 mΩ	10 mΩ
200 Ω	300 μA	100 μA	30 μA	10 μA	3 μA	1 μA	300 nA	100 nA	30 nA
	200 μΩ	200 μΩ	370 μΩ	430 μΩ	1.1 mΩ	2.8 mΩ	9.7 mΩ	25 mΩ	120 mΩ
2 kΩ	30 μA	10 μA	3 μA	1 μA	300 nA	100 nA	30 nA	10 nA	3 nA
	2.0 mΩ	2.0 mΩ	2.9 mΩ	4.0 mΩ	12 mΩ	40 mΩ	120 mΩ	300 mΩ	900 mΩ
20 kΩ	3 μA	1 μA	300 nA	100 nA	30 nA	10 nA	3 nA	1 nA	300 pA
	20 mΩ	25 mΩ	31 mΩ	56 mΩ	200 mΩ	640 mΩ	2.4 Ω	5.3 Ω	23 Ω
200 kΩ	300 nA	100 nA	30 nA	10 nA	3 nA	1 nA	300 pA	100 pA	30 pA
	250 mΩ	350 mΩ	640 mΩ	1.4 Ω	4.5 Ω	16 Ω	47 Ω	150 Ω	710 Ω
2 MΩ	30 nA	10 nA	3 nA	1 nA	300 pA	100 pA	30 pA	10 pA	3 pA
	3.4 Ω	5.9 Ω	16 Ω	46 Ω	190 Ω	480 Ω	1.7 kΩ	5.4 kΩ	15 kΩ
20 MΩ	3 nA	1 nA	300 pA	100 pA	30 pA	10 pA	3 pA	1 pA	300 fA
	50 Ω	190 Ω	540 Ω	1.1 kΩ	5.4 kΩ	12 kΩ	56 kΩ	180 kΩ	750 kΩ

General Characteristics

Interface	Serial(RS-232)throughSIMinterface
Connectors	DB-9(female)AC4-wiremeasurement+ground
	DB-15(male)SIMinterface
Weight	1.4lbs
Dimensions	1.5” W × 3.6” H × 7.0” D

1GettingStarted

Thischaptergivestheuserthenecessaryinformationtogetstarted quicklywiththeSIM921ACResistanceBridge.

InThisChapter

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

1.1.1Overview....1-2

1.2Front-PanelOperation....1-3

1.2.1 Resettingtofactorydefaults......1-3

1.2.2Numericdisplay....1-3

1.2.3Display....1-3

1.2.4Range....1-5

1.2.5Excite....1-6

1.2.6Output....1-7

1.2.7Autocal....1-7

1.3SensorInterface....1-8

1.3.1 Four-wiremeasurement .....1-9

1.3.2 Two-wire measurement 1-9

1.3.3 Wiringforhighimpedance .....1-9

1.4SIMInterface 1-11

1.4.1SIMinterfaceconnector .....1-11

1.4.2 Directinterfacing....1-11

1.1 Introduction to the Instrument

TheSIM921ACResistanceBridgemonitorsasingleresistive sample—typicallyacryogenicthermometer—withanadjustable ACcurrent.Withachievableexcitationpowerbelow100aW,self-heatingerrorscanberoutinelyeliminated.

1.1.1 Overview

TheSIM921usesahalf-bridgetopology,wheretheexcitationcurrent ispassedthroughbothaninternal,stablereferenceresistor,R R ,and theuser'sresistivethermometer,R M (seeFigure1.1).Eightseparate referenceresistors,from1Ωto10MΩ,arebuiltintotheinstrument, withtwoexpandedscales(200mΩand20mΩ)implementedwith additionalgain.

The basic measurement is made by a parirof dual-phased modulator to recover the vector AC voltage (amplitude and phase) developed across the internal reference resistor, V_R and acrosstheuser's resistor under measurement, V_M . The SIM921 determinestheuser's resistance valuation metrically from

R _ M = | V _ M | ^ 2 V _ Rµ _ M × µR

Bytaking the in-phase component of V R in theratio, themeasurement is largely insensitive to capacitive loads in parallel with the R M ; the phaseshift they introduce is corrected in the denominator.

Figure1.1: BlockdiagramoftheSIM921.

1.2Front-PanelOperation

ThefrontpaneloftheSIM921isdividedintoseveralmajorfunctional blocks,eachofwhichwillbediscussed.

Figure1.2:TheSIM921frontpanel.

1.2.1 Resetting to factory defaults

ToresettheSIM921tofactorydefaults,hold[Set]depressedwhile turningpowerontothemodule.Thisisequivalenttotheremote command*RST.

1.2.2Numericdisplay

Theupperblockofthefrontpanelisthenumericdisplayfield. In addition to 5 1/2 digits, six units LEDs (mΩ, Ω, kΩ, MΩ, mK, and K) indicate the physical unit of the quantity displayed. The two buttonstothe left of thenumeric display, [Set ], allow the userto modify settable parameters.

1.2.3Display

Directlybeneath[Set 1]stheDISPLAYblockofthepanel. Thetwo buttonsatthebottomofthissection, [Display ], selectthequantity fordisplayinthenumericfield.

Theselectionsare:

Value: Themeasuredvalueoftheuser'sresistor-under-testisdisplayed, eitherinresistanceunitsortemperatureunits(dependingontheunitsselection,below).

When Valueisdisplayed, pressing[Set]act:basashort-cutto resettheoutputfilter. This can be useful to speed settling with alogtime constant after larger resistance change is made, or after the range excitation is changed.

Value-Offset: This selection (also known as "deviation") also displays the measurementresult(eitherinresistanceortemperatureunits), but after subtracting the user-settable Offset. Pressing [Set 1] willresettheoutputfilter.

Phase (deg.): This selection shows the phase angle between measured currentandvoltage(indegrees), and is an indication of how much capacitive loading is present. Phase is positive for capacitive loads. A phase angle near +90 ° should be viewed with caution: this indicates that most of the current is flowing through there active part of the load, and measurement accuracy may suffer.

Whenphaseisdisplayed,[Set]chbeusedtomodify the modelusedintheSIM921todetermineresistance. Bypassing[Set],thenumericdisplaywillshowtheword: 2E.r o Thisforcesthemetertoassumethephaseanglebetween the voltageandcurrentiszerowhensolvingforR.Thisishelpful whenmeasuringverysmallresistances(suchassuperconductingsamples),sincethephase determination becomesotherwise ill-conditionedwhenthevoltagesignalapproacheszero,and causesexcessnoiseintheresults.Pressing[Set]restoresnormaloperation.

Offset : The offset, or setpoint, is the user-selected value to subtract from the sensor measurement. The offset is used in the Value-Offset display (above), as well as to determine the analogoutputvoltage(seebelow). The[Set ]buttonswill acceleratethroughmultipledigitstoadjusttheoffset;twoshort cutsalsoexist.Ifboth[Set]and[Set]arepressedsimultaneously,Offsetispreloadedwiththelatestmeasurementresult of Value. Depressing both buttons again will force Offset to zero.

Freq. (Hz): This field controls the excitation frequency for the SIM921. [Set ▲]adjuststhefrequencyfrom2Hzto60Hz. Depressing both [Set ▲] and [Set ▼] together will step between 15 Hz, 10 Hz,5Hz,and2.5 Hz.

A_OUT :Thisparameteristheslope(inV/ΩorV/K)usedtoscalethe deviationsignalforanalogoutput.Use[Set]toaccelerate throughmanyordersofmagnitudeforA OUT;releasingthe buttonandre-pressingitallowsfinecontroloverthelower digits,asthesettingbeginsacceleratingagain.Ifresistance unitsareselectedforanalogoutput,theΩindicatorwillbelit nexttothenumericdisplay;iftemperatureunitsareselected, theKindicatorwillbelit.

Units (Ω, K): This is actually three separate selections that are stepped throughbycontinuingtopress[Display ].Thefirstselection lights both the Value and Units indicators. This selects either resistance or temperature units for the Value display. Use [Set ▲] to switch between resistance (the display will show r E S.) and temperature (the display will show the ID message oftheselectedsensorcalibrationcurve).

Pressing[Display]againwilllightA OUT and Unit together. Now,[Set]selectsbetweenresistanceortemperatureunits for the analog output function. Note that the deviation display and offset parameter units are also determined by A_OUT -Units.

Pressing[Display]onefinaltimewillleaveUnits litalone. Nowthe[Set]selectsamongthreesensorcalibrationcurves stored in the SIM921. If a particular curve has not been loaded, the - islittoindicatethisisnotausablecurve;once(atleast) twopointsareloadedinasensorcurvememory,thedisplay willshow * totheleftofthecurveID.Onlyonecurvecanbe selectedatatime.

1.2.4Range

TheRANGEblockofthefrontpanelselectsthereferenceresistor. Press [Range ▲] to step between ranges from 20 mΩ to 20 MΩ. For all ranges ≥ 2 Ω, the reference resistor R_R is1/2thetotalrange. For example, onthe20 kΩrange, R_R = 10 kΩ. For ranges ≤ 2 Ω, the R_R = 1.0 Ω.

The Autorange subblock controls two independent functions related torange.Brieflytapping[Autorange]willtoggleautorangeDisplay on and off. When Autorange Display is off, the numeric display decimalpointisfixedbasedontheselectedrange.WithAutorange Display on, the decimal point (and possibly the units indicator) shifts todisplaytheresultwithmaximumresolution.

Holding [Autorange] for 2 seconds light Gain and initiate an autogaincycle. Whenever the SIM921 issettoanewrangeorexcitation, the internal amplifiers are preset to nominal gains. This might not be

optimalform measuring resistor that are much smaller than, or larger than, then nominal rangesetting. Also, if the user is in a high-noise environment, out-of-band pick-up might cause amplifiers saturation. In either of these cases, initiating an autogain cycle will force the SIM921 to optimize gains for the signals present at that time. Once completed, the Gain is unlit, and the amplifier gains remain fixed at their new levels. Changing excitation or rangewill reset the amplifier to their (new) nominal settings.

1.2.5Excite

The EXCITEblockcontrol the excitation amplitude for theme measurement. [Excite] step between excitation levels in 1–3–10 steps from 3µV to 30 mV. It is possible to step the amplitudesetting down oncemore from the 3µV setting, setting the excitation amplitude zero. Not that this does not close the hunting relay, as On/Off does (below).

Theamplitude, together with the excitation mode, determines the actual conditions for themeasurement. [Mode], at the bottom of the EXCITEblock, is another dual-function control. Briefly tapping [Mode] toggles the excitation On/Off; when Off, a mechanical relay shunts the excitation current, preventing any current from flowing to the user's resistor.

While the excitation is off, holding [Mode] for 2 secondswill step between four (4) distinct excitation modes:

Constant Current: With Current lit, the SIM921 will operate in constant current mode. This programs an AC current with rms amplitude of excite/ R_R ;forexample, if the excitation is set to 100µV and the range is 20kΩ , the excitation current will equal 10nA ( 100µV / 10kΩ = 10nA ). This is implemented by serving the measured voltage across thereferenceresistor, R_R to these selected excitation amplitude.

Constant Voltage: With Voltage lit, the SIM921 will operate in constant voltage mode. In this mode, the excitation is served to keep them measured voltage across the user's resistor, R_M equal to these selected excitation. This can be particularly useful for negative temperature thermometers at low temperatures, where a constant current would lead to increasing power dissipation at low temperatures ( P=I^-2R_M, R_M, P as T ). With constant voltage, the ohmic dissipation goes down with decreasing temperature ( P=V^-2/R_M, R_M, P as T ).

Constant Power: With both Current and Voltage lit, the SIM921 servoes the excitationtokeepthepowerdissipatedintheuser'sresistor

constant,atthelevel V² /(R_R / 2)

Passive: With neither indicatorlit, the SIM921 disable sex citationserving, and simply sets a fixed AC amplitude acrossthe entire bridge circuit. The amplitude eisset so that for R M upto about the 2RR , the current will approximately equal the corresponding constant-current setting (above). For user resistances much larger than the angesetting ( R _M R ), the voltage acrossthe user resistor will approach \~ 20× thenominal excitation (see Figure 1.1).

1.2.6Output

The OUTPUTblockofthefrontpanelselectsthepost-detectionfilter setting, and contains the BNC connector for the analog output. The filter is simple 6dB/octavelow pass filter that calculates a running exponential average of the vector voltages (prior to her at iocalculation). Highersetting of the time constant will reduce measurement noise at the expense of slower settling times. The filter affects the display values as well as the analog output voltages.

[TimeConst.]stepthefiltertimeconstantin1-3-10stepsfrom 0.3s to 300s. Stepping the time constant downwards from 0.3s turns off the 6dB/octave filter completely, leaving only a running boxcar"sync"filter(thataveragesthesignalsovertheoneexcitation period) active. The sync filter effectively eliminates the 2 × f signals fromthedemodulatoroutput,butotherwiseprovideslittlenoise reduction. Thisisanappropriatesettingforrelativelyhighsignal-to-noisemeasurementswheresignalbandwidththisimportant.

ItcantakesixorseventimeconstantsfortheoutputoftheSIM921 tofullysettleafterastepchange;forslowtimeconstantsettings,this can be a bothersome delay. The filter can be reset by pressing [Set Ⅱ] when the display is Value or Value-Offset.

1.2.7 Autocal

The AUTOCAL block controls the internal autocalibration of the SIM921Autocalibrationcross-calibratestherelativegainofthetwo amplifierchainsinthesystem. Theprocesstakesaboutthree(3) minutestocomplete,andcanbestartedbyholding[Autocal]for \~2seconds.Acountdownisdisplayedtoindicateapproximatetime remaining.Theautocalibrationcanbeabortedbypressing[Autocal] againbeforethecyclecompletes—thiswillabandonthecalibration inprogress,andreverttothepreviouscalibrationvalues.

1.3 SensorInterface

ThesensorinterfaceontheSIM921consistsarear-panelDB-9/Fconnector, labeled "INPUT"(seeFigure1.3). Thepinassignmentsfor thisconnectoraregiveninTable1.1.

PinSignal

1I+(currentlead)

2I-(currentlead)

3ground

4V+(voltagelead)

5V-(voltagelead)

6ground

7ground

8ground

9ground

Table1.1:SIM921SensorInterfaceConnectorPins,DB-9.Drawing showspinnumberslookingintotherearoftheinstrument.

Figure1.3:TheSIM921rearpanel.

1.3.1 Four-wiremeasurement

Toavoidsensitivitytowiringleadresistance,theSIM921isconfiguredforfour-wiremeasurements.Thebasiccircuitforthiswiring schemeisshowninFigure1.4.

Figure1.4: Wiringdiagramforfour-wirereadout.

1.3.2 Two-wiremeasurement

Ifapplication-specificiconstraintslimitthenumberofleadstothe sensor,theSIM921canbewiredtomeasurethesensorresistance withasimpletwo-wirecircuit,showninFigure1.5.Notethatthe leadresistance(pastthejunctionpointsofthecurrentandvoltage leads)willaddasadirectresistanceerrorwhenmeasuringthesensor.

Figure1.5: Wiringdiagramfortwo-wirereadout.

1.3.3 Wiringforhighimpedance

When using the SIM921 to measure high impedances (>fewMΩ), cable construction becomes crucial. It is important that the wire lead should equal low-loss dielectric insulation, such as PTFE (Teflon TM). Ordinary PVC-insulated wire is not well suited to this application, as it can suffer from dielectric absorption effects. Regardless of a

veryhighDCinsulationresistance(>100GΩ),smallACdielectric losses,evenatthelowfrequenciesusedbytheSIM921,canappear as (10s\~100s) MΩ of real impedance in parallel with the user load.

1.4SIMInterface

The primary connection to the SIM921 AC Resistance Bridge is the rear-panel DB-15 SIM interface connector. Typically, the SIM921 is mated to a SIM900 Mainframe viathis connection, either through one of the internal mainframeslots, or theremotecable interface.

ItisalsopossibletooperatetheSIM921directly, without using the SIM900Mainframe. Thissectionprovidesdetailsontheinterface.

CAUTION

TheSIM921hasnointernalprotectionagainstreversepolarity,missing supply,orovervoltageonthepowersupplypins.Misapplicationofpower maycausecircuitdamage.SRSrecommendsusingtheSIM921together withtheSIM900Mainframeformostapplications.

1.4.1 SIMinterfaceconnector

The DB-15 SIM interface connector carries all the power and communications lines to the instrument. The connector signals are specified in Table 1.2

Pin	Signal	DirectionSrc ⇒ Dest	Description
1	SIGNAL_GND	MF ⇒ SIM	Ground reference for signal
2	-STATUS	SIM ⇒ MF	Status/service request (GND = asserted, +5 V= idle)
3	RTS	MF ⇒ SIM	HW handshake (+5 V= talk; GND = stop)
4	CTS	SIM ⇒ MF	HW handshake (+5 V= talk; GND = stop)
5	-REF_10MHZ	MF ⇒ SIM	10 MHz reference (optional connection)
6	-5 V	MF ⇒ SIM	Power supply (no connection in SIM921)
7	-15 V	MF ⇒ SIM	Power supply (analog circuitry)
8	PS_RTN	MF ⇒ SIM	Power supply return
9	CHASSISGND	Chassis ground
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 (optional connection)
13	+5 V	MF ⇒ SIM	Power supply (digital circuitry)
14	+15 V	MF ⇒ SIM	Power supply (analog circuitry)
15	+24 V	MF ⇒ SIM	Power supply (no connection in SIM921)

Table1.2:SIMInterfaceConnectorPinAssignments,DB-15

1.4.2 Directinterfacing

TheSIM921isintendedforoperationintheSIM900Mainframe, but users may wish to directly interface the module to their own systems withouttheuseofadditionalhardware.

ThematingconnectorneededisastandardDB-15receptacle,suchas Amppart#747909-2(orequivalent).Clean,well-regulatedsupply voltagesof+5,±15VDCmustbeprovided,followingthepin-out specifiedinTable1.2.Groundmustbeprovidedonpins1and8, withchassisgroundonpin9.The-STATUSsignalmaybemonitored onpin2foralow-goingTTL-compatibleoutputindicatingastatus message.

1.4.2.1 Directinterfacecabling

If the user intend stodirectly wire the SIM921 independent of the SIM900 Mainframe, communication is usually possible by directly connecting the appropriate interfacelines from the SIM921 DB-15 plug to the RS-232 serial port of a personal computer. ¹ Connect RXD from the SIM921 directly to RD on the PC, TXD directly to TD, and similarly RTS → RTS and CTS → CTS. In other words, anull-modem styleable is not needed.

TointerfacedirectlytotheDB-9male(DTE)RS-232porttypically foundoncontemporarypersonalcomputers,acablemustbemade withafemaleDB-15sockettomatewiththeSIM921,andafemale DB-9sockettomatewiththePC'sserialport.Separateleadsfrom theDB-15needtogotothepowersupply,makingwhatissometimes knowasa"hydra"cable.Thepin-connectionsaregiveninTable1.3.

DB-15/FtoSIM921Name
DB-9/F 10←→ 3 TxD 11←→ 2 RxD 5 ComputerGround toP/S 7←→ -15VDC 14←→ +15 VDC 13←→ +5 VDC 8,9←→ Ground (P/S return current) 1←→ Signal Ground (separate wire to Ground)
Table1.3:SIM921DirectInterfaceCablePinAssignments
¹ Although the serial interfaces on the DB-15 donots satisfy the minimum voltage level so of the RS-232 standard, they are typically compatible with desktop personal computers

1.4.2.2 Serialsettings

The serial port settings at power-on are: 9600 baud, 8-bits, noparity, 1 stop bit, and no flow control (see Section 2.3.1). The serial settings cannot be changed on the SIM921.

2RemoteOperation

ThischapterdescribesoperatingtheSIM921overtheserialinterface.

InThisChapter

2.1IndexofCommands......2-2
2.2AlphabeticListofCommands......2-4
2.3Introduction....2-7

2.3.1 Power-onconfiguration......2-7
2.3.2Buffers....2-7
2.3.3DeviceClear....2-7

2.4Commands....2-8

2.4.1 Commandsyntax....2-8
2.4.2 Notation ......2-9
2.4.3Examples 2-9
2.4.4Excitationcommands .....2-10
2.4.5 Measurement commands .....2-12
2.4.6 Post-detection processing commands .....2-14
2.4.7 Calibrationcurve commands.....2-15
2.4.8 Autoranging commands.....2-17
2.4.9 Autocalibrationcommand .....2-17
2.4.10 Setpointandanalogoutputcommands....2-17
2.4.11 Interface commands....2-18
2.4.12Statuscommands....2-23

2.5StatusModel 2-26

2.5.1StatusByte(SB)....2-27
2.5.2ServiceRequestEnable(SRE) .....2-28
2.5.3 StandardEventStatus(ESR) .....2-28
2.5.4 StandardEventStatusEnable(ESE).....2-29
2.5.5CommunicationErrorStatus(CESR) .....2-29
2.5.6CommunicationErrorStatusEnable(CESE) .2-30
2.5.7OverloadStatus(OVCR)....2-30
2.5.8OverloadStatus(OVSR)......2-31
2.5.9OverloadStatusEnable(OVSE)......2-31

2.1IndexofCommands

symboldefinition

i,jIntegers

f,gFloating-pointvalues

zLiteraltoken

sArbitrarycharactersequence(no", "or";")

(?)Requiredforqueries;illegalforsetcommands

varParameteralwaysrequired

{var} Requiredparameterforsetcommands;illegalforqueries

[var]Optionalparameterforbothsetandqueryforms

Excitation

FREQ(?){f}	2-10Frequency
RANG(?){i}	2-10Range
EXCI(?) {i}	2 - 11 Excitation
EXON(?) {z}	2 - 11 Excitation On/Off
MODE(?) {z}	2 - 11 Excitation Mode
IEXC?	2-11QueryExcitationCurrent
VEXC?	2-11QueryExcitationVoltage

Measurement

RVAL? [i]	2 – 12 Resistance Value
RDEV?[i]	2–12ResistanceDeviation
TVAL? [i]	2 – 12 Temperature Value
TDEV? [i]	2 – 13 Temperature Deviation
PHAS?[i]	2–13Phase
TPER(?) {i}	2 – 13 Time Period for Streaming
SOUT	2–13StopStreaming
DISP(?) {i}	2 – 14 Display

Post-Detection

FRST	2-14FilterReset
TCON(?) {i}	2 - 14 Time Constant
PHLD(?) {z}	2 - 15 Phase Hold

CalCurves

DTEM(?) {z}	2-15 Display Temperature
ATEM(?) {z}	2-15 Analog Output Temperature
CURV(?) {i}	2-15 Sensor Calibration Curve
CINI(?) i {,z,s}	2-16 Initialize Sensor Calibration
CAPT i,f,g	2-16 Add Point to Sensor Calibration
CAPT? i,j	2-16 Query Point in Sensor Calibration

Autorange

AGAI(?){z} 2-17AutorangeGain

ADIS(?){z} 2-17AutorangeDisplay

Autocalibration

ACAL2-17Autocalibration

Setpoint/AnalogOutput

RSET(?){f} 2-17ResistanceSetpoint

TSET(?){f} 2-18TemperatureSetpoint

VOHM(?) {f} 2-18 Analog Output Scale (V/Ω)

VKEL(?) {f} 2-18 Analog Output Scale (V/K)

AMAN(?) {z} 2-18 Analog Output Manual Mode

AOUT(?) {f} 2-18 Analog Output Manual Value

Interface

*RST 2-19Reset

*IDN? 2-20Identify

*TST? 2-20SelfTest

*OPC(?) 2-20OperationComplete

CONS(?) {z} 2-20 Console Mode

LEXE? 2-21ExecutionError

LCME? 2-21CommandError

LBTN? 2-22Button

TOKN(?) {z} 2-22 Token Mode

TERM(?) {z} 2-22 Response Termination

Status

*STB?[i] 2-23StatusByte

*SRE(?) [i,] {j} 2 - 23 Service Request Enable

*CLS 2-23ClearStatus

PSTA(?) {z} 2-23 Pulsed Status Mode

*ESR?[i] 2-24StandardEventStatus

*ESE(?) [i,] {j} 2-24 Standard Event Status Enable

CESR?[i] 2-24CommunicationErrorStatus

CESE(?) [i,]{j} 2-24 Communication Error Status Enable

OVCR?[i] 2-24OverloadCondition

OVSR?[i] 2-24OverloadStatus

OVSE(?) [i,]{j} 2-25 Overload Status Enable

2.2AlphabeticListofCommands

★

*CLS2-23ClearStatus
*ESE(?) [i,] {j} 2-24 Standard Event Status Enable
*ESR?[i]2-24StandardEventStatus
*IDN?2-20Identify
*OPC(?)2-20OperationComplete
*RST2-19Reset
*SRE(?) [i,] {j} 2 - 23 Service Request Enable
*STB?[i]2-23StatusByte
*TST? 2-20SelfTest

A

ACAL 2-17Autocalibration
ADIS(?) {z} 2-17 Autorange Display
AGAI(?) {z} 2-17 Autorange Gain
AMAN(?) {z} 2-18 Analog Output Manual Mode
AOUT(?) {f} 2-18 Analog Output Manual Value
ATEM(?) {z} 2-15 Analog Output Temperature

C

CAPT i,f,g 2-16 Add Point to Sensor Calibration
CAPT? i,j 2-16 Query Point in Sensor Calibration
CESE(?) [i,]{j} 2-24 Communication Error Status Enable
CESR?[i] 2-24CommunicationErrorStatus
CINI(?) i {,z,s} 2-16 Initialize Sensor Calibration
CONS(?) {z} 2-20 Console Mode
CURV(?) {i} 2-15 Sensor Calibration Curve

D

DISP(?) {i} 2-14 Display
DTEM(?) {z} 2-15 Display Temperature

E

EXCI(?) {i} 2-11 Excitation
EXON(?) {z} 2-11 Excitation On/Off

F

FREQ(?) {f} 2-10 Frequency
FRST 2-14FilterReset

|

IEXC?2-11QueryExcitationCurrent

L

LBTN?2-22Button

LCME?2-21CommandError

LEXE?2-21ExecutionError

M

MODE(?){z} 2-11ExcitationMode

0

OVCR?[i]2-24OverloadCondition

OVSE(?) [i,]{j} 2-25 Overload Status Enable

OVSR?[i]2-24OverloadStatus

P

PHAS?[i]2-13Phase

PHLD(?) {z} 2-15 Phase Hold

PSTA(?) {z} 2-23 Pulsed Status Mode

R

RANG(?) {i} 2-10 Range

RDEV?[i]2-12ResistanceDeviation

RSET(?) {f} 2-17 Resistance Setpoint

RVAL? [i] 2 - 12 Resistance Value

S

SOUT 2-13StopStreaming

T

TCON(?) {i} 2-14 Time Constant

TDEV? [i] 2-13 Temperature Deviation

TERM(?) {z} 2-22 Response Termination

TOKN(?) {z} 2-22 Token Mode

TPER(?) {i} 2-13 Time Period for Streaming

TSET(?) {f} 2-18 Temperature Setpoint

TVAL? [i] 2 – 12 Temperature Value

V

VEXC? 2-11QueryExcitationVoltage

VKEL(?) {f} 2-18 Analog Output Scale (V/K)

VOHM(?) {f}

2-18 Analog Output Scale (V/Ω)

2.3 Introduction

RemoteoperationoftheSIM921istroughasimplecommandlanguagedocumentedinthischapter.Bothsetandqueryformsofmost commandsaresupported,allowingtheusercompletecontrolofthe amplifierfromaremotecomputer,eitherthroughtheSIM900MainframeordirectlyviaRS-232(seeSection1.4.2.1).

SeeTable1.2forspecificationoftheDB-15SIMinterfaceconnector.

2.3.1 Power-onconfiguration

Thesettingsfortheremoteinterfaceare9600baudwithnoparity andnoflowcontrol,andlocalechodisabled(CONS0FF).

MostoftheSIM921instrumentsettingsarestoredinnon-volatile memory, andatpower-ontheinstrumentreturnstothestateitwas lastinwhenpowerwasremoved.Exceptionsarenotedinthecommanddescriptions.

Resetvaluesofparametersareshowninboldface.

2.3.2Buffers

Incomingdatafromthehostinterfaceisstoredina64-byteinput buffer. Charactersaccumulateintheinputbufferuntilacommand terminator (either CR or LF ) is received, at which point the messageis parsedandexecuted. QueryresponsesfromtheSIM921are bufferedina64-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.

2.3.3DeviceClear

TheSIM921hostinterfacecanbeasynchronouslyresettoitspower-onconfigurationbysendinganRS-232-style(break) signal.Fromthe SIM900Mainframe,thisisaccomplishedwiththeSRSTcommand; ifdirectlyinterfacingviaRS-232,thenuseaserialbreaksignal.After receivingtheDeviceClear,theinterfaceisresetto9600baudand CONS mode is turned 0FF. Note that this only resets the communicationinterface;thebasicfunctionoftheSIM921isleftunchanged; toresettheinstrument,see*RST.

TheDeviceClearsignalwillalsoterminateanystreamingoutputs from the SIM921 due to a TVAL? or RVAL? query of multiple conversions.

2.4Commands

Thissectionprovidessyntaxandoperationaldescriptionsforremote commands.

2.4.1 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.Parametersin{ } arerequiredtosetavalue,andareomittedforqueries.Parametersin[]areoptionalinbothsetandquerycommands.Parameterslisted withoutanysurroundingcharactersarealwaysrequired.

Donotsend()or{ } or[]aspartofthecommand.

Multipleparametersareseparatedbycommas.Multiplecommands maybesentononecommandlinebyseparatingthemwithsemicolons(;)solongastheinputbufferdoesnotoverflow.Commands are terminated by either CR or LF characters. Null commands andwhitespaceareignored. Executionofcommand(s)doesnot beginuntilthecommandterminatorisreceived.

tokens Token parameters (generically shown as z in the command descriptions) can be specified either as a keyword or integer value. Command descriptions list the valid keyword options, with each keyword followed by its corresponding integer value. Forexample, to set the response termination sequence to CR + LF , the following two commands are equivalent:

TERM CRLF —or— TERM 3

Forqueriesthatreturntokenvalues,thereturnformat(keywordor integer)isspecifiedwiththeTOKNcommand.

2.4.2 Notation

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

SymbolDefinition

i,jIntegers

f,gFloating-pointvalues

zLiteraltoken

sArbitrarycharactersequence(no", "or";")

(?)Requiredforqueries;illegalforsetcommands

varParameteralwaysrequired

{var} Requiredparameterforsetcommands;illegalforqueries

[var]Optionalparameterforbothsetandqueryforms

2.4.3Examples

Each command is provided with as simple example illustrating its usage. In these examples, all data sent by the host computer to the SIM921 are set as straight teletype font, while responses received the host computer from the SIM921 are set as slanted teletype font.

Theusageexamplesvarywithrespecttoset/query,optionalparameters,andtokenformats. Theseexamplesarenotexhaustive,butare intended to provide a convenient starting point for user programming.

2.4.4 Excitation commands

FrequencyFREQ(?){f}

Set (query) the excitation frequency {to f Hz}.

Theexcitationfrequencycanbesetwithapproximately10mHzresolution. The parameter f must be in the range 1.95 ≤ f ≤ 61.1 . The resetvalueis10.0.

Inthefollowing, theexcitationissetto13.7Hz. Example:

FREQ13.7;FREQ?

13.7025

RangeRANG(?){i}

Set(query)theresistancerange{toi}.

Validrangecodesare:

i	Range
0	20mΩ
1	200mΩ
2	2Ω
3	20Ω
4	200Ω
5	2kΩ
6	20kΩ
7	200kΩ
8	2MΩ
9	20MΩ

Example: RANG5

	ExcitationEXCI(?){i}
	Set(query)thenominalexcitation{toi}.
	Validexcitationcodesare:
	i|Excitation
	-10(excitationoff)
	03μV
	110μV
	230μV
	3100μV
	4300μV
	51mV
	63mV
	710mV
	830mV
	EXCI?Example:
	3
EXON(?) {z}	Excitation On/Off
	Set (query) the excitation source {to z=(OFF 0, ON 1)}.
	EXON1Example:
	ExcitationModeMODE(?){z}
	Set (query) the excitation mode {to z=(PASSIVE 0, CURRENT 1, VOLTAGE 2, POWER 3)}.
	Example: TOKNON; MODE?PASSIVE
IEXC?	QueryExcitationCurrent
	Querytheactualexcitationcurrentamplitude,inamperes.
	IEXC?Example:+1.043700E-07
VEXC?	QueryExcitationVoltage
	Query the actual excitation voltage amplitude, in volts. This is the voltage measured across the sensor itself, not the “nominal” excita-tionacrosstheentirebridge(setbyEXCI).
	VEXC?Example:+1.176760E-05

2.4.5 Measurement commands

	ResistanceValueRVAL?[i]Querythemeasuredvalueofresistance,inohms.Iftheoptional/isspecified,then/measurementresultsarereturned to the host, separated by TPER milliseconds. If i=0 is specified, then streamingofRVAL?resultscontinuesindefinitelyuntiltheSOUT commanddisreceived.RVAL?4Example:+1.130924E+02+1.131047E+02+1.130922E+02+1.130764E+02
	ResistanceDeviationRDEV?[i]Querythemeasuredvalueofresistance,inohms,offsetbytheresistancesetpoint(seeRSET).Iftheoptional/isspecified,then/measurementresultsarereturned to the host, separated by TPER milliseconds. If the optional i is specified,then/measurementresultsarereturnedtothehost,separated by TPER milliseconds. If i=0 is specified, then streaming results continuesindefinitelyuntiltheSOUTcommanddisreceived.
Example:	RSET100RDEV?+1.308144E+01
TVAL?[i]	TemperatureValueQuerythemeasuredvalueoftemperature,inkelvin.Iftheoptional/isspecified,then/measurementresultsarereturned to the host, separated by TPER milliseconds. If the optional i is specified,then/measurementresultsarereturnedtothehost,separated by TPER milliseconds. If i=0 is specified, then streaming results continuesindefinitelyuntiltheSOUTcommanddisreceived.
Example:	TVAL?+3.067459E+02TemperatureDeviationTDEV?[i]Querythemeasuredvalueoftemperature,inkelvin, offsetby the temperaturesetpoint(seeTSET).Iftheoptionalisspecified, thenimeasurementresultsarereturned to the host, separated by TPER milliseconds. If the optional i is spec- ified, thenimeasurementresultsarereturnedtothehost,separated by TPER milliseconds. If i=0 is specified, then streaming results continuesindefinitelyuntiltheSOUTcommandisreceived.
Example:	TSET 306TDEV?+7.345581E-01
PHAS?[i]	PhaseQuerythephaseofthemeasuredvoltage(indegrees)withrespect totheexcitationcurrent. Positiveanglescorrespondtocapacitive loads.ThisquerydisregardsthePHLDsetting.Iftheoptionalisspecified, thenimeasurementresultsarereturned to the host, separated by TPER milliseconds. If the optional i is spec- ified, thenimeasurementresultsarereturnedtothehost,separated by TPER milliseconds. If i=0 is specified, then streaming results continuesindefinitelyuntiltheSOUTcommandisreceived.
Example:	PHAS?+0.022
TPER(?) {i}	Time Period for StreamingSet (query) the time period {to i}, in ms. TPER can be set with 10 ms resolution in the range 100 ≤ i ≤ 6555350. The reset value is 1000.
Example:	TPER 500
SOUT	StopStreamingTurnoffstreamingoutput.StreamingisalsohaltedbytheDeviceClearsignal(serialbreak),but notby*RST.
Example:	TDEV?0+8.273926E-01+8.048706E-01SOUT

DisplayDISP(?) i

Set(query)thedisplayselection{toi}.

Validdisplaycodesare:

iDisplay

Units

1Units+A OUT

2 Units+ Value

3A OUT

4Freq.(Hz)

5Offset

6Phase(deg.)

7 Value-Offset

8Value

DISPVALUEExample:

2.4.6 Post-detection processing commands

	FilterResetFRSTResetthepost-detectionfilter.FRSTExample:
TCON(?) {i}	Time ConstantSet (query) the time constant for the post-detection filter { to i }.Validtimeconstantcodesare:iTimeConstant-1filteroff(synconly)00.3 s11 s23 s310 s430 s5100 s6300 s
Example:	TCON2

PhaseHoldPHLD(?){z}

Set (query) the phase hold mode {to z=(OFF 0, ON 1)}.

Forcestheresistancecalculationtoassumezerophase.Thismode isusefulformemeasurementsofverylowresistance(suchassuper-conductingtransitions)wheretherawsignal-to-noiseratiobecomes muchlessthanunity.

PHLDONExample:

2.4.7 Calibrationcurve commands

	DisplayTemperatureDTEM(?){z}
	Set (query) the display temperature mode {to z=(OFF 0, ON 1)}.
	When ON, the SIM921 display for Value will be in temperature units insteadofresistance.
Example:	DTEM?
	ON
ATEM(?) {z}	Analog Output Temperature
	Set (query) the analog output temperature mode {to z=(OFF 0, ON 1)}.
	WhenON,theSIM921generatesananalogoutputproportional to temperaturedeviationinsteadofresistancedeviation.Also,thedis-play units for Value-Offset and Offset are set with ATEM.
Example:	ATEM?
	1
CURV(?) {i}	Sensor Calibration Curve
	Set (query) the selected sensor calibration curve {to i}. Valid curve numbers are 1, 2, and 3. A curve number may be selected with CURV evenifnocorrespondingcurvehasbeenloadedintotheSIM921.
Example:	CURV?
	2
CINI(?) i {,z,s}	Initialize Sensor CalibrationInitialize sensor calibration curve i=(1, 2, or 3).Thesetformofthecommand,CINIIi,z,s,erasestheoldcontentsof curve i. The second parameter z=(LINEAR 0, SEMILOGT 1, SEMILOGR 2,LOGLOG3)definesthesensorcurveformat.ThethirdparameterSisanarbitraryidentificationstringforthissensorcalibration curve.Thisstringcanconsistofanynon-blankcharactersexcept thecomma“,”orsemicolon“;”,andcanbeupto15charactersin length.Theleading5characterswillbedisplayedontheSIM921 frontpanelwhenthecurveisselected,withinthelimitationsofthe seven-segmentdisplayhardware.
Example:	CINI3, SEMILOGR,GRT75 _Thequeryformofthecommand,CINI?i,returnsthefollowingresponse: <format>,<serial>,nwhere <format> is the calibration curve format (same as z above),<serial> is the full identification string for the curve, and n is the numberofpointscurrentlystoredinthecurve.
Example:	CINI?2LINEAR,PT100,225
CAPTi,f,g	AddPointtoSensorCalibrationAdd a new point to sensor calibration curve i. f is the raw sensor value(ineitherohmsorlog 10(ohms),dependingoncurveformat), and g is the corresponding temperature value (in either kelvin or log10(kelvin),againdependingoncurveformat).Notethatcurvepointsmustbeaddedinincreasingorderofsensor valuef.
Example:	CAPT 3, 3.223631, 127.542E-3 In the preceding, a point is added for R = 1.67352 kΩ, T = 127.542 mK. The curve format is SEMILOGR, sotherawsensorvaluetransmittedislog 10(1.67352 × 103)
CAPT?i,j	QueryPointinSensorCalibrationQuerythevalueofsensorcalibrationcurvei,entrypointj.Theresponse is<sensor>,<temperature>,where <sensor> is the raw sensor value (in either ohms or log10(ohms), depending on curve format), and <temperature> is the corresponding temperature value (in either kelvin or log10(kelvin), again depending oncurveformat).

CAPT?3,45Example:

3.223631E+00,1.275420E-01

2.4.8 Autoranging commands

	AutorangeGainAGAI(?){z}
	Set (query) autoranging of gain {to z=(OFF 0, ON 1)}. When autoranginggain,theSIM921willoptimizesignal-to-noiseforthecurrentandvoltagemeasurementchannels.Afterautoranginggain completes, the SIM921 automatically turns AGAI OFF. Nominal gains are restored by sending the RANG or EXCI commands, with either thepriorsettingoranewsetting.
	Note that if AGAI is commanded off with a remote command prior to the completion of the autoranging cycle, the internal gains will be left in an indeterminate state. To restore proper operation, either re-issue the AGAI ON command, or send a new RANG or EXCI command.
Example:	AGAION
ADIS(?) {z}	Autorange Display
	Set (query) autoranging of the display {to z=(OFF 0, ON 1)}. The ADIS setting has no effect on the SIM921 measurement, and only modifiesthefront-paneldatapresentation.
Example:	ADISON

2.4.9 Autocalibration command

ACAL	AutocalibrationInitiate the internal autocalibration cycle (takes approximately 3 minutes). Remotecommandswillnotbeprocessedfurtheruntilthe autocalibrationiscompleted.
	Example: ACAL

2.4.10 Setpointandanalogoutputcommands

RSET(?) {f}	Resistance Setpoint
	Set (query) the resistance setpoint {to f ohms}. This is the “offset” or “setpoint” valueusing generating the analog output when ATEM OFF. The reset value is 1.0.
Example:	RSET?
	+1.000000E+02
	TemperatureSetpointTSET(?){f}
	Set (query) the temperature setpoint {to f kelvin}. This is the “offset” or “setpoint” value used generating the analog output when ATEMON.Theresetvalueis1.0.
	TSET?Example: +3.060000E+02
VOHM(?) {f}	Analog Output Scale (V/Ω)
	Set (query) the analog output scale { to f V/Ω}. This is the scale used when ATEM OFF. The reset value is 1.0.
	VOHM1E-3Example:
VKEL(?) {f}	Analog Output Scale (V/K)
	Set (query) the analog output scale { to f V/K}. This is the scale used when ATEM ON. The reset value is 1.0.
	VKEL?Example: 1.000000E+00
AMAN(?) {z}	Analog Output Manual Mode
	Set (query) the analog output manual mode {to z=(OFF 0, ON 1)}. When ON, the analog output is simply equal to the AOUT value; whenOFF,theoutputisthescaledandoffsetmeasurementresult.
Example:	AMANON
AOUT(?) {f}	Analog Output Manual Value
	Set (query) the Analog Output Manual value {to f volts}. This is the output value when AMAN ON. The initial value after power-on is 0.0, butthisvalueisnotmodifiedby*RST.
Example:	AOUT-1.234

2.4.11 Interfacecommands

Reset*RST

ResettheSIM921todefaultconfiguration.*RSTexecutesthefollowingcommands:

• FREQ10
  • RANG6
• EXCI1
• EXONON
• MODEPASSIVE
• TPER1000
• DISP0
• TCON1
• PHLDOFF
  • DTEMOFF
• ATEMOFF
• ADISON
• RSET1.0
• TSET1.0
  VOHM1.0
• VKEL1.0
• AMANOFF
• TOKNOFF

Commands or settings which are not altered by *RST are: SOUT, CURV, AOUT, CONS, TERM, PSTA, and all service-enable registers (*SRE, *ESE, CESE, OVSE).

*RSTExample:

	Identify*IDN?Readthedeviceidentificationstring.Theidentificationstringisformattedas:StanfordResearchSystems, SIM921, s/n******, ver#.#where*****isthe6-digitserialnumber,and#.#isthefirmware revisionlevel.*IDN?Example:StanfordResearchSystems, SIM921, s/n003075, ver3.6
	SelfTest*TST?Thereisnoself-testfunction.*TSTwillalwaysreturn0.*TST?Example:0
	OperationComplete*OPC(?)OperationComplete.SetstheOPCflagintheESRregister.Thequeryform*OPC?writesa1intheoutputqueuewhencomplete, butdoesnotaffecttheESRregister.*OPCExample:
	ConsoleModeCONS(?){z}Set (query) the console mode {to z=(OFF 0, ON 1)}.CONScauseseachcharacterreceivedattheinputbuffertobecopied totheoutputqueue.Atpower-onandDevice-Clear,CONSissettoOFF.CONS?Example:0

ExecutionErrorLEXE?

Querythelastexecutionerrorcode.AqueryofLEXE?alwaysclears theerrorcode,soasubsequentLEXE?willreturn0. Validcodesare:

ValueDefinition

0NoexecutionerrorsincelastLEXE?

1Illegalvalue

2Wrongtoken

3Invalidbit

16Uninitializedcurve

17Curvefull

18Curvepointout-of-order

19Curvepointpastend

*STB?12;LEXE?;LEXE?Example:3

0 The error (3, "Invalid bit," ) is because *STB? only allows bit-specific queries of 0-7. ThesecondreadofLEXE? returns 0.

CommandErrorLCME?

Querythelastcommanderrorcode.AqueryofLCME?alwaysclears theerrorcode,soasubsequentLCME?willreturn0. Validcodesare:

ValueDefinition

0NoexecutionerrorsincelastLCME?

1Illegalcommand

2Undefinedcommand

3Illegalquery

4Illegalset

5Missingparameter(s)

6Extraparameter(s)

7Nullparameter(s)

8Parameterbufferoverflow

9Badfloating-point

10Badinteger

11Badintegertoken

12Badtokenvalue

13Badhexblock

14Unknowntoken

*IDNExample:

LCME?

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

ButtonLBTN? Querythelastbutton-presscode.AqueryofLBTN?alwaysclears thebuttoncode,soasubsequentLBTN?willreturn0. Validcodes are:

ValueDefinition
0nobuttonpressedsincelastLBTN?
1[Display] ▼
2[Display] ▲
3[Set] ▼
4[Set] ▲
5undef
6[Excite] ▼
7[Excite] ▲
8[Range] ▼
9[Range] ▲
10[Autocal]
11[Autorange]
12[Mode]
13[TimeConst.] ▼
14[TimeConst.] ▲ 

LBTN?Example: 12

TokenModeTOKN(?) {z} Set (query) the Token Query mode {to z=(OFF 0, ON 1)}. If TOKN ON is set, then queries to the SIM921 that return tokens will returnthetextkeyword; otherwise they returnthedecimalinteger value. Aninterestingillustration of this is the observation that the only possible responses to the TOKN? query are ON and 0. At power-on, TOKNissettoOFF.

Example: TOKNOFF

TERM(?) {z}

Response Termination

Set (query) the term sequence {to z=(NONE\ 0, CR\ 1, LF\ 2, CRLF\ 3, LFCR\ 4) }. The term sequence is appended to all query responses sent by the module, and is constructed of ASCII character(s) 13 (carriage return) and 10 (line feed). The token mnemonic gives the sequenceofcharacters.

Atpower-on, TERMissettoCRLF.

TERM?Example: 3

2.4.12Statuscommands

	TheStatuscommandsqueryandconfigureregistersassociatedwith statusreportingoftheSIM921.
	StatusByte*STB?[i]ReadstheStatusByteregister[biti].The*STB?querycausesthe-STATUSsignaltobereleasedifasserted.(SeealsoPSTA)*STB?Example:16
*SRE(?) [i,] {j}	Service Request EnableSet (query) the Service Request Enable register [bit i] {to j}.Notethatbit1oftheSREimplementsalocal(front-panel)keypadfirmwarerelease4.0 lockout function. Setting bit 1 (*SRE 1,1) disables the keypad. Clear-ingbit1(*SRE 1,0)re-enablesthefrontpanel.
Example:	*SRE 0,1
*CLS	ClearStatus*CLSimmediatelyclearstheESR,CESR,andOVSR.
Example:	*CLS
PSTA(?) {z}	Pulsed Status ModeSet (query) the Pulse -STATUS Mode {to z=(OFF 0,ON 1)}.When PSTA ON is set, any new service request will only pulse the -STATUS signal low (for a minimum of 1 μs). The default behavior istolatch-STATUSlowuntila*STB?queryisreceived.Onreset,PSTAassettoOFF.PSTA?Example:OFFStandardEventStatus*ESR?[i]ReadstheStandardEventStatusRegister[biti].Uponexecuting*ESR?,thereturnedbit(s)oftheESRregisterare cleared.*ESR?Example:64
*ESE(?) [i,]{j}	Standard Event Status EnableSet (query) the Standard Event Status Enable Register [bit i] {to j}.*ESE6, 1Example:ESE?64
	CommunicationErrorStatusCESR?[i]QueryCommunicationErrorStatusRegister[forbiti].UponexecutingaCESR?query,thereturnedbit(s)oftheCESR registerarecleared.CESR?Example:0
CESE(?) [i},{j}	Communication Error Status EnableSet (query) Communication Error Status Enable Register [for bit i] {toj}CESE?Example:0
OVCR?[i]	OverloadConditionQueryOverloadConditionRegister[forbiti].0VCR?Example:0
OVSR?[i]	OverloadStatusQueryOverloadStatusRegister[forbiti].UponexecutingaOVSR?query,thereturnedbit(s)oftheOVSR registerarecleared.0VSR?Example:0

OVSE(?) [i,]j

Overload Status Enable

Set (query) Overload Status Enable Register [for bit i] {to j}

0VSE3Example:

2.5StatusModel

TheSIM921statusregistersfollowthehierarchicalIEEE-488.2format.AblockdiagramofthestatusregisterarrayisgiveninFigure2.1.

TherearethreecategoriesofregistersintheSIM921statusmodel:

ConditionRegisters: Theseread-only registers correspond to thereal-time condition of some underlying physical property being monitored. Queries return the latest value of the property, and haveno othereffect. Condition regist names end with CR.

EventRegisters: Theseread-only registers record the occurrence of defined events. Whentheevent occurs, the corresponding bit is set to 1. Upon querying an event register, any 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 register names end with SR.

Enable Registers : These read/write registers define a bitwise mask for their corresponding event register. If any bit position is set in an event registerwhilethesamebitpositionisalsosetinthecenable register,thenthecorrespondingsummarybitmessageisset. Enableregister namesendwithSE.

Figure2.1:StatusRegisterModel for theSIM921AC Resistance Bridge.

2.5.1StatusByte(SB)

TheStatusByteisthetop-levelsummaryoftheSIM921statusmodel. WhenmaskedbytheServiceRequestEnableregister,abitsetintheStatusBytecausesthe-STATUSsignaltobeassertedontherear-panelSIMinterfaceconnector.

Typically, -STATUSremainsasserted(low)untila*STB?queryis received, atwhichtime-STATUSisdeasserted(raised) ¹ . Afterclearingthe-STATUSsignal, itwillonlybere-assertedinresponseoa newstatus-generatingcondition.

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

OVSB:OverloadStatusSummaryBit.Indicateswhetheroneormore oftheenabledflagsintheOverloadStatusRegisterhasbecome true.

IDLE: Indicates that the input buffer is empty and the command parserisidle. CanbeusedtohelpsynchronizeSIM921query responses.

ESB:EventStatusBit.Indicateswhetheroneormoreoftheenabled eventsintheStandardEventStatusRegisteristrue.

MSS:MasterSummaryStatus. Indicateswhetheroneormoreof theenabledstatusmessagesintheStatusByteregisteristrue. Notethatwhile-STATUSisreleasedbythe*STB?query,MSS isonlyclearedwhentheunderlyingenabledbitmessage(s)are cleared.

CESB:CommunicationErrorSummaryBit.Indicateswhetheroneor moreoftheenabledflagsintheCommunicationErrorStatus Registerhasbecometrue.

Bits in the Status Byte are not cleared by the *STB? query. These bits are only cleared by reading the underlying event registers, or by clearing the corresponding enableregisters.

2.5.2ServiceRequestEnable(SRE)

EachbitintheSREcorrespondsone-to-onewithabitintheSB register, and acts as a bitwise AND of the SB flag to generate the MSSbitintheSB and the -STATUS signal.

WeightBitFlag

10OVSBEnable

21KEYLOCK

42undef(0)

83undef(0)

164IDLEEnable

325ESBEnable

646undef(0)

1287CESBEnable

Bit6oftheSREisundefined—settingithasnoeffect,andreadingit alwaysreturns0.Thisregisterissetandqueriedwiththe*SRE(?) command.

Bit1oftheSRE(binaryweight2)isaspecialfunction, "KEYLOCK", firmwarerelease4.0 and is unrelated to the SIM921 status system. Setting this bit resultsintheSIM921ignoringallfrontpanelkeypresses, essentially implementingalocallockoutfunction.

Thisregisterisclearedatpower-on.

2.5.3 StandardEventStatus(ESR)

TheStandardEventStatusregisterconsistsof8eventflags. These event flags are all "sticky bits" that are set by the corresponding event, andclearedonlybyreadingorwiththe*CLScommand.Readinga 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 : Input buffer Error. Indicates data has been discarded from the inputbuffer.

QYE: QueryError. Indicates data in the output queue has been lost.

DDE: DeviceDependentError. Undefined for SIM921.

EXE:ExecutionError.Indicatesanerrorinacommandthatwas successfully parsed. Out-of-rangeparametersareanexample. The error code can be queried with LEXE?.

CME:CommandError.Indicatesaparser-detectederror.Theerror codecanbequeredwithLCME?.

URQ:UserRequest.Indicatesafront-panelbuttonwaspressed.

PON:PowerOn.Indicatesthatanoff-to-ontransitionhasoccurred.

2.5.4 StandardEventStatusEnable(ESE)

TheESEactsasabitwiseANDwiththeESRregistertoproducethe singlebitESBmessageintheStatusByteRegister(SB).Itcanbeset andqueriedwiththe*ESE(?)command.

Thisregisterisclearedatpower-on.

2.5.5 CommunicationErrorStatus(CESR)

TheCommunicationErrorStatusregisterconsistsof8eventflags; eachofwhichissetbythecorrespondingevent,andclearedonlyby readingorwiththe*CLScommand.Readingasinglebit(withthe CESR?iquery)clearsonlybiti.

WeightBitFlag
1	0PARITY
2	1FRAME
4	2NOISE
8	3HWOVRN
16	4OVR
32	5RTSH
64	6CTSH
128	7DCAS

PARITY:ParityError. Setbyserialparitymismatchonincomingdata byte.

FRAME : Framing Error. Set when an incoming serial data byte is missing the STOPbit.

NOISE:NoiseError. Setwhenanincomingserialdatabytedoesnot presentasteadylogiclevel during eachasynchronousbit-periodwindow.

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

OVR:InputbufferOverrun.Setwhentheinputbufferisoverrun byincomingdata.Causestheinputbuffertobeflushed,and resetsthecommandparser.

RTSH:UndefinedfortheSIM921.CommandError.Indicatesaparser-detectederror.

CTSH:UndefinedfortheSIM921.

DCAS:DeviceClear.Indicates the SIM921 received the Device Clear signal (an RS-232 ). Clears the input buffer and output queue, and reset the command parser.

2.5.6 CommunicationErrorStatusEnable(CESE)

TheCESEactsasabitwiseANDwiththeCESRregistertoproduce thesinglebitCESBmessageintheStatusByteRegister(SB).Itcan besetandqueriedwiththeCESE(?)command.

Thisregisterisclearedatpower-on.

2.5.7 OverloadStatus(OVCR)

TheOverloadConditionRegisterconsistsof7single-bitmonitorsof conditioneventswithintheSIM921.BitsintheOVCRreflectthe real-timevaluesoftheircorrespondingsignals. Readingtheentire register,orindividualbitswithinit,doesnotaffecttheOVCR.

Weight	Bit	Flag
1	0	ANALOG
2	1	PREAMP
4	2	CURRENT
8	3	UNDERSP
16	4	OVERSP
32	5	UNDERT
64	6	OVERT
128	7	undef(0)

ANALOG: Analogoverload. Asignalamplifierwassaturated.

PREAMP: Thefront-endpreampsaturated.

CURRENT:Theexcitationcurrentexceeded12mA(saturation).

UNDERSP:Theexcitationservofellbelow90%ofthecommandedexcitation.

OVERSP:Theexcitationservoexceeded110%ofthecommandedexcitation.

UNDERT: Calibrationcurveunderflow(R<R min).

OVERT: Calibrationcurveoverflow(R>R min).

2.5.8 OverloadStatus(OVSR)

TheOverloadStatusRegisterconsistsof(latching)eventflagsthat correspondone-to-onewiththebitsoftheOVCR(seeabove).Upon thetransition0→ 1ofanybitwithintheOVCR,thecorresponding bitintheOVSRbecomesset.

BitsintheOVSRareunaffectedbythe1→ 0transitionsintheOVCR, andareclearedonlybyreadingorwiththe*CLScommand.Reading a single bit (with the OVSR? i query) clears only bit i.

Anadditionalbit,AUTOGAINDONE(weight=128,bit=7)isdefinedintheOVSRtosignalcompletionofanautorangegaincycle.

2.5.9 Overload Status Enable (OVSE)

TheOVSEactsasabitwiseANDwiththeOVSRregistertoproduce thesinglebitOVSBmessageintheStatusByteRegister(SB).Itcan besetandqueriedwiththeOVSE(?)command.

Thisregisterisclearedatpower-on.

3PartsListsandSchematics

ThischapterpresentsabriefdescriptionoftheSIM921circuitdesign. Acompletepartslistandcircuitschematicsareincluded.

InThisChapter

3.1 CircuitDiscussion....3-2

3.1.1 Digitalboard....3-2
3.1.2 Front-panelboard....3-3
3.1.3 Sourceboard....3-3
3.1.4AmplifierBoard....3-4

3.2PartsLists ....3-6

3.2.1 DigitalandFrontPanelBoards .....3-6
3.2.2SourceBoard....3-7
3.2.3AmplifierBoard....3-8

3.3SchematicDiagrams ......3-8

3.1 CircuitDiscussion

TheSIM921isassembledfrom4interconnectedprintedcircuit boards:threefull-sizedboardsrunningthelengthofthemodule, andonefront-paneldisplayboard.Inthischapter,pagereferences aretothe9-sheetschematicspagesattheendofthemanual.

3.1.1 Digitalboard

Thedigitalboard(pages1,2,&3)containsthemicrocontrollerchip, digitalI/O,andtheanalog-to-digitalanddigital-to-analogconverters.Beawarethatthefourmountingscrewssecuringthisboard tothechassisare"locked"bythethreadedstand-offsholdingthe sourceboard.Beforeattemptingtoremovethesescrews,theamplifierboard,sourceboard,andthreadedstand-offsmustberemoved,orthescrewswilllikelystriporbreak.

3.1.1.1 ClockandMCU

AllfunctionsoftheSIM921arecoordinatedbythemicrocontroller, U103,whichoperatesin"single-chip" mode (internalRAMand ROM).Extendednon-volatilememoryisprovidedbyU105forstorageofuseralibrationcurves. Theclockcircuit(Y101,U102,and relatedcomponents)isamodifiedPierceoscillator. Inthepresence ofanexternal10 MHzreferenceclockfromtheSIM900Mainframe, the oscillator will lock to the reference (over a several hundred Hertz window)through thecouplingofR108.Ifnoexternal10 MHzreferenceispresent, thentheoscillatorsimplyfree-runs.

3.1.1.2 Sinegenerator

The excitation sine-wave is created with a 4kHz direct digital synthesis. DAC U208 is updated with new values every 250 µs ; these values are calculated from asinetable within interpolation, scaled for excitation amplitude. Forsmallamplitudes, U215 canswitchina divide-by-100 feedback network. Theresultissent to the analog source board via JS202.

3.1.1.3I and V Analog-to-Digitalconverter

The main signals from the amplifier board, I_SIGNAL and V_SIGNAL, are received at JS202 (which interconnects with both analog boards). ThesignalsareNyquistfilteredwith3-poleButterworthlow-pass filters(U201A&U202A),andthensummedwithaDAC-generated dithersignal(U206)toincreasetheeffectiveresolutionandlinearity

of the ADC. Themainconverter, U207, isa14-bitsimultaneously-sampling two-channel analog-to-digital converter, readout data samplerate of \~4kHz.

3.1.1.4 Analogoutput

Thefront-panelanalogoutputisgeneratedatU210,a12-bitdigital-to-analogconverter.ThisDACisupdatedat\~4kHzwiththesum oftheslowly-varyingoutputsignalandahigh-freqencyrandom dither.The6-pole,10HzoutputBessellow-passfilter(U211&U212) completelyblocksthedithercomponent,providinga16-bitoutput resolution.

3.1.2 Front-panelboard

Thefront-panelboard(page3)containsthedrivecicuitryforthe displaycomponentsoftheSIM921.NotethatallLEDsaredriven staticallyfromU307-U318.

Thereadoutforthebuttonswitchesissomewhatsubtle.Initially,the BUTTONSENSElinesarealldrivenlow,andtheBUTTONPRESS lines are diode-or'd together (D103, D104, page 1) to detect any button closure. Once a button closure is detected, the the BUTTONSENSElinesarechangedintoinputs,andtheBUTTONPRESS linesaredrivenhigh, one-by-one, todecodewhichbutton(s)are pressed.

3.1.3 Sourceboard

The analog source board (pages 4,5, & 6) receives the SINEGEN output from the sine-wave generator, filters it, and switches in the appropriate half-bridgeset of resistors for these selected range.

The attenuator selector (U403) is only switched between the top three settings (EXC_FULL, EXC_/3, EXC_/10); greater attenuations areswitchedinwithU215,orbyreducingthenumericamplitudeofthesinetablevalues.Afterattenuating,thesignalisfilteredandsplit into complementary polarities, ±EXCITE. The first two poles of the low-pass filter are implemented by U401A, while the last two poles areimplementedseparatelyforthetwopolaritiesbyU402A&B.In themiddleofthisfilter,theinvertedpolarityisgeneratedbyU401B,andtheDC-offsetofbothpolaritiesisblockedbyC403&C407.Noticethataftertheblockingcapacitors,alow-offset(non-A)grade opampmustbeusedforU402.

3.1.3.2 Referenceresistorbridges

Eachrangefrom1Ωto100MΩhasitsownhalf-bridgenetwork (page5),alldrivenby±EXCITE.Theselectedrangeisswitchedto the±IEXCITEleadstotheuser's(external)resistorthroughone ofrelaysK509–K516,whilethecorresponding(internal)reference resistorR512–R519isswitchedonto±ISENSEwithoneofK501–K508. Thetrim-pots(R536–R543)areallaccessiblethroughthetop ventilationslots,andfactory-adjustedtobalancethetopandbottom legsofthehalf-bridges.

RelayK517shortsthe±IEXCITElinestoeachotherandground. Thisrelayisclosedwhenevertheexcitationiscommandedoff,and alsouponpower-offbytheone-shotcircuitaroundU501.

Noticethat±IEXCITEisconnectedtotheamplifierboardbyJP603 neartheupper-rearcorneroftheboard,while±ISENSEisconnected totheamplifierboardbyJP602nearthelower-frontcornerofthe board.Thesesignalsareroutedasfarfromeachotheraspossibleto minimizecross-talk.

3.1.3.3 Interconnect

Themainconnectionforpower, control, and high-level analog signals is JP601. Notethatthisisa "tall" header, with pinsextending through both sides of the source board. This connectermates with JS202 on the digital board, and also with JS901 on the amplifier board.

3.1.4AmplifierBoard

All the circuitry on the preamp board (pages 7, 8, & 9) is duplicated identically, as much as possible, for the two signal paths, V and I .

3.1.4.1 Preamplifiers

Thetwosignals±V _SENSEcomefromtheKelvin(voltage-sense) leadsacrossstheuser'sexternalresistorundermeasurement,while the±ISENSEsignalsarethesenseleadsfromtheinternalreference resistor(page5). Undernormaloperation,relaysK701&K702are in the reset position, connecting the ±V SENSE to the V-channel preamp (Q702 and associated circuitry), and connecting ±I SENSE to the I-channelpreamp(Q701andassociated).Thepreampsarefixed gain(10×),high-impedance DC-coupledvoltageamplifiersusingthe LSK389dualJFETforinputs.

During an autocalibration cycle, the two relays K701, K702 are both switched to the set position, tying both preampstothe ± ISENSE internal signal (K517 is also switched closed, providing a complete

internalcurrentpath, and disconnecting all circuitry from the external resistor). Sincethe fundamental measurement of the SIM921 is ratiometric, this cross-calibration of the two amplifier channels sufficient to remove gain-dependent systematic errors in the resistance measurement.

3.1.4.2 Programmablegainamplifier

Page8showsthetwo(identical)channelsofprogrammablegain amplifier.Eachamplifierisconstructedoftwostagesofvariable gain(upto+50dB),connectedbyavariableattenuatorandAC-couplingstage.The-3dBpointfortheAC-couplingis\~1.6Hz. Notethatthefactorycalibrationincludesamodelforeachofthese AC-couplingfilters,sotofirstordertheautocalibrationcycleshould notbenecessarywhenchangingexcitationfrequencies.

3.1.4.3RFfiltering

The4signalsthatconnecttotheexternalresistorundermeasurement (±I_EXCITEand±VSENSE)eachpassthroughanL-R-Cπ-filter locatedrightbehindtheexternalDB-9connector(JS904).

3.2PartsLists

Thepartslistsareseparatedbytheinternal(SRS)assemblykit,which consistofoneortwoboardseach.

3.2.1 DigitalandFrontPanelBoards

Reference SRS P/N Part Value Reference SRS P/N Part Value

C101 5-00345 4.0-34P R206,R201 4-01270		39.2K
C102 5-00366 18P		R207,R202 4-01296	73.2K
C103	5-00376	120P		R203,R205,R208,R209	4-01251	24.9K
C104 5-00368 27P		R210,R204 4-01020	97.6
C105,C106,C107	5-00102	4.7U		R211	4-01259	30.1K
C108,C109,C110	5-00387	1000P		R212,R216,R220	4-01213	10.0K
C206,C201 5-00455 .012U			R213 4-01217	11.0K
C202,C205 5-00450 .0047U			R214 4-01209	9.09K
C203,C207	5-00442	.001U		R215,R218,R219,R221	4-01242	20.0K
C204,C208 5-00367 22P			R217 4-01046	182
C212,C209 5-00369 33P			R222 4-01287	59.0K
C210,C219 5-00375 100P			R223 4-01362	357K
C211 5-00454 .01U		R224 4-01297	75.0K
C213,C215,C217	5-00466	.1U/MF		R225	4-01347	249K
C216,C214 5-00462 .047U			R226 4-01312	107K
C218 5-00456 .015U		R227 4-01370	432K
C220 5-00318 2.2U/T35		R228 4-01163	3.01K
C221 5-00471 10U/T16		R229 4-01165	3.16K
C222,C223,C224,C225,C226	5-00298	.01U		R230	4-01021	100
C227 5-00542 1.0U		R239 4-01146	2.00K
D101,D102	3-00945	BAT54S		R240,R241,R242	4-01280	49.9K
D103,D104 3-00649 BAW56LT1			R243,R244 4-01519	47K
D301,D302,D303,D304,D305,	3-00424	GREEN		R301	4-01489	2.7K
D306,D307,D308,D309,D310,				S301,S302,S303,S304,S305,	2-00053	B3F-1052
D311,D312,D313,D314,D315,				S306,S307,S308,S309,S310,
D316,D317,D318,D319,D320,				S311,S312,S313
D321,D322,D323,D324,D326,				U101 3-00903 MAX6348
D327,D328,D329,D330,D331,				U102 3-01378 74HCU04
D332,D333,D334,D335,D336,				U103 3-01379 68HC912B32
D337,D338,D339,D340,D341,				U104 3-00662 74HC14
D342,D343,D344				U105 3-01390 25LC640
D325 3-00426 YELLOW		U106 3-00902	74HC00
JP101	1-00302	6 PIN DIF CES		U202,U201	3-01385	OPA2137
JP103	1-00367	15 PIN D		U203	3-00726	LF412
JP301	1-00219	TMS-115-01-G-S		U204,U205,U213	3-01373	OPA2277UA
JS201	1-00003 BNC			U206 3-01391 TLC7528
JS202	1-00104	HEADER 8X2		U207	3-01392	AD7863AR-10
JS301	1-00351	SMS-115-01-G-S		U210,U208	3-01393	AD7545A
L101,L102,L103	6-00174	BEAD U209 3-00542	AD587JR
Q201,Q202	3-00580	MMBT3906LT1		U211,U212	3-00724	LF353
RN301,RN302,RN303,RN304,	4-00407	2.7K		U214	3-00116	78L05
RN305,RN306,RN307,RN308,				U215 3-01371 DG417DY
RN309,RN310,RN311				U216 3-00952 OPA2277UA
RN312,RN313,RN314,RN315,	4-00442	1.2K		U217	3-00727	LM339
RN316,RN317,RN318,RN319,				U301 3-01424 HDSP-A107
RN320,RN321,RN322,RN323				U302,U303,U304,U305,U306	3-00290	HDSP-A101
R101	4-01495	4.7K		U307,U308,U309,U310,U311,	3-00672	74HC595ADT
R102 4-01511 22K		U312,U313,U314,U315,U316,
R103 4-01431 10		U317,U318
R104,R106,R113,R118,R245,	4-01503	10K		X101,X102,X103,X104,X105,	5-00299	.1U
R246				X106,X107,X108,X109,X110,
R105,R107,R234,R235,R236,	4-01479 1.0K			X111,X112,X201,X202,X203,
R237,R238				X204,X205,X206,X207,X208,
R108 4-01057 237		X209,X210,X211,X212,X213,
R109 4-01405 1.00M X214,X215,X216,X217,X218,
R110,R115,R117,R121	4-01455 100			X219,X220,X221,X222,X223,
R111,R112,R119,R231,R232,	4-01527 100K			X224,X225,X226,X301,X302,
R233				X303,X304,X305,X306,X307,
R114,R116,R120	4-01465 270			X308,X309,X310,X311,X312
R122 4-01510 20K		Y101		6-00571 10.000MHz

3.2.2 SourceBoard

Reference SRS P/N Part Value Reference SRS P/N Part Value

C401 5-00462 .047U R502 4-01338 200K
C402,C406 5-00464 .068U R504 4-01118 1.02K
C403,C407 5-00072 10U R505 4-01310 102K
C404 5-00466 .1U R506 4-01214 10.2K
C405,C408 5-00245 1.0U R507,R528 4-00306 100M
C501,C502,C509,C510 5-00313 1P R508,R520,R529 4-00139 10.0M
C511,C503 5-00363 10P	R510,R511 4-01023 105
C512,C504 5-00375 100P	R512 4-01654 10.0M
C505,C513 5-00387 1000P	R513 4-01652 1.000M
C506,C514 5-00411 .01U R514 4-01651 100.0K
C507,C508,C515,C516 5-00411 .1U R515 4-01650 10.00K
C517 5-00260 470U	R516 4-01649 1.000K
D501,D502 3-00544 BAV70LT1	R517 4-01648 100.0
JP601	1-00406 16 PIN DIL (long)	R518 4-01647 10.00
JP602,JP603	1-00488 2 PIN	R519 4-01646 1.000
K501,K502,K503,K504,K505,	3-00308 DS2E-ML2-DC5V	R521 4-00131 1.00M
K506,K507,K508,K509,K510,		R522 4-00142 100K
K511,K512,K513,K514,K515,		R523 4-00138 10.0K
K516,K517		R524 4-00130 1.00K
Q501,Q601,Q602,Q603,Q604,	3-00927 MMBT2907ALT1	R525 4-00141 100
Q605,Q606,Q607,Q608,Q609,		R526 4-00234 10.0
Q610,Q611,Q612,Q613,Q614,		R527 4-00800 1.0
Q615,Q616,Q617,Q618,Q619,		R531 4-01309 100K
Q620,Q621,Q622,Q623,Q624,		R532 4-01213 10.0K
Q625,Q626,Q627,Q628,Q629,		R533 4-01117 1.00K
Q630,Q631,Q632,Q633,Q634		R535,R534 4-01021 100
R401,R406,R414,R416,R418,	4-01261 31.6K	R536 4-00250 2M
R421		R537 4-00624 500K
R402,R503 4-01242 20.0K	R538 4-00232 50K
R403 4-01251 24.9K	R539 4-00240 5.0K
R404 4-01198 6.98K	R540 4-00253 500
R405 4-01257 28.7K	R541 4-00342 50
R407,R412,R425,R428 4-01209 9.09K	R542,R543 4-00349 10
R408 4-01146 2.00K	R544 4-01479 1.0K
R409 4-01232 15.8K	R545 4-01527 100K
R410,R427 4-01180 4.53K	R546,R601 4-01489 2.7K
R411 4-01260 30.9K	U401 3-01471 OPA2227UA
R413 4-01102 698	U402 3-00670 OPA2277U
R415 4-01050 200	U403 3-01386 DG408
R417 4-01006 69.8	U501 3-00671 MC34064
R419 4-00954 20.0	U601 3-00662 74HC14
R420,R423 4-01431 10	U602,U603,U604,U605,U606	3-00787 74HC595
R422 4-00925 10.0	X401,X402,X403,X404,X405,	5-00299 .1U
R426,R424 4-00218 10.00K	X406,X601,X602,X603,X604,
R501,R509,R530 4-01405 1.00M	X605,X606

3.2.3AmplifierBoard

Reference SRS P/N Part Value Reference SRS P/N Part Value

C701,C704,C711,C716,C719,5-001002.2U R853

C721,C723,C724,C727,C733,R723,R757 4-00983 40.2

C738,C742,C743,C746,C810,R724,R725,R758,R759 4-01648 100

C811,C813,C815,C816,C817,R760,R727 4-00487 20

C827,C828,C830,C832,C833,R730,R763 4-01280 49.9K

C834 R731,R767 4-01164 3.09K

C707,C713,C730,C736 5-00098 10U

C710,C734 5-00363 10P

C801,C802,C818,C819 5-00372 56P

C803,C804,C820,C821 5-00382 390P

C805,C806,C822,C823 5-00450 .0047U

C807,C808,C824,C825,C901,5-00375 100P

C902,C903,C904,C905,C906,R808,R809,R835,R836 4-01145 1.96K

C907,C908

C809,C826 5-00244 .1U

C812,C814,C829,C831 5-00367 22P

D702,D705 3-00674 MMBZ5228 R843,R816 4-01064 280

JS901 1-00104 SOCKET 8x2

JS903,JS902 1-00115 SOCKET 1x2

JS904

K701,K702

L901,L902,L903,L904

Q701,Q702 3-01674 LSK389B

Q901.Q902.Q903.Q904

R701,R735 4-01042 165

R702,R706,R736,R740 4-01021 100

R737,R703 4-00013 50K

R704,R705,R738,R739 4-00528 499

R707,R708,R709,R710,R741,4-01309 100K

R742,R744,R745

R711,R733,R743,R766 4-01060 255

R714,R715,R750,R751 4-01649 1.000K

R716,R752 4-00954 20

R718,R728,R748,R762 4-01141 1.78K

R719,R756 4-00971 30.1

R720,R734,R749,R765,R817,4-01431 10

R818,R820,R823,R825,R826,X808,X809,X810,X811,X812,

R844,R845,R847,R850,R852,X901,X902,X903,X904

R732,R768 4-01213 10.0K

R801,R802,R828,R829 4-01386 634K

R803,R804,R830,R831 4-01338 200K

R805,R806,R810,R812,R832,4-01242 20.0K

R833,R837,R839

R834.R807 4-01088 499

1145 1.96K

R838.R811 4-01076 374

R813,R814,R840,R841 4-01146 2.00K

R815,R842 4-01405 1.00M

|

2 R846,R819 4-01052 210

2 R848,R821 4-01040 158

R849,R822 4-01028 118

0C5V R824,R851 4-01016 88.7

D R854,R827 4-01062 267

R901,R902,R903,R904 4-00992 49.9

07ALT1 U701,U710

U702,U711 3-00998 OPA227UA

U703,U712 3-00096 LM317L

U718,U709 3-00100 LM337L

U801,U802,U807,U808 3-01369 DG409

U803,U809 3-01386 DG408DY

U804,U810 3-00133 OPA131

U805,U806,U811,U812 3-00731 5534

U901 3-00662 74HC14

U902,U903,U904 3-00787 74HC595

X701,X702,X706,X707,X709, 5-00299 .1U

X710,X714,X715,X801,X802,

X803,X804,X805,X806,X807,

3.3 SchematicDiagrams

Schematicdiagramsfollowthispage.