1. Manuals
  2. Brands
  3. SRS Labs Manuals
  4. Network Hardware
  5. SIM921
  6. Operation and service manual

SRS Labs SIM921 Operation And Service Manual

Ac resistance bridge
Hide thumbs
Table of Contents

Advertisement

Quick Links

Download this manual
Operation and Service Manual
AC Resistance Bridge
SIM921
Stanford Research Systems
Revision 2.3
September 12, 2011

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the SIM921 and is the answer not in the manual?

Questions and answers

Subscribe to Our Youtube Channel

Summary of Contents for SRS Labs SIM921

  • Page 1 Operation and Service Manual AC Resistance Bridge SIM921 Stanford Research Systems Revision 2.3 September 12, 2011...
  • Page 2 Copyright c Stanford Research Systems, Inc., 2003 – 2011. All rights reserved. Stanford Research Systems, Inc. 1290–D Reamwood Avenue Sunnyvale, CA 94089 USA Phone: (408) 744-9040 Fax: (408) 744-9049 www.thinkSRS.com e-mail: info@thinkSRS.com Printed in U.S.A. Document number 9-01555-903 SIM921 AC Resistance Bridge...

  • Page 3: Table Of Contents

    Contents General Information Service ......Symbols ......Notation .
  • Page 4 Contents SIM921 AC Resistance Bridge...

  • Page 5: General Information

    Do not install substitute parts or perform any unauthorized modifi- cations to this instrument. The SIM921 is a double-wide module designed to be used inside the SIM900 Mainframe. Do not turn on the power until the module is completely inserted into the mainframe and locked in place.

  • Page 6: Symbols

    Symbols you may Find on SRS Products 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) SIM921 AC Resistance Bridge...

  • Page 7: Notation

    Literal text other than command names is set as OFF. Remote command examples will all be set in monospaced font. In these examples, data sent by the host computer to the SIM921 are set as straight teletype font, while responses received by the host computer from the SIM921 are set as slanted teletype font.

  • Page 8: Specifications

    0 C to 40 C, non-condensing Interface Serial via SIM interface Connectors Sensor DB–9 (female) Analog out BNC (front) DB–15 (male) SIM Interface Power 15 VDC, 5 VDC Supply current 150 mA ( 15 V), 250 mA ( 5 V) SIM921 AC Resistance Bridge...
  • Page 9 180 k 750 k General Characteristics Interface Serial (RS-232) through SIM interface Connectors DB–9 (female) AC 4–wire measurement ground DB–15 (male) SIM interface Weight 1.4 lbs Dimensions 1 5 W 3 6 H 7 0 D SIM921 AC Resistance Bridge...
  • Page 10 General Information SIM921 AC Resistance Bridge...

  • Page 11: Getting Started

    1 Getting Started This chapter gives the user the necessary information to get started quickly with the SIM921 AC Resistance Bridge. In This Chapter 1.1 Introduction to the Instrument ... . . 1 – 2 1.1.1...

  • Page 12: Introduction To The Instrument

    AC current. With achievable excitation power below 100 aW, self- heating errors can be routinely eliminated. 1.1.1 Overview The SIM921 uses a half-bridge topology, where the excitation current is passed through both an internal, stable reference resistor, R , and the user’s resistive thermometer, R...

  • Page 13: Front-Panel Operation

    1.2 Front-Panel Operation 1 – 3 1.2 Front-Panel Operation The front panel of the SIM921 is divided into several major functional blocks, each of which will be discussed. Figure 1.2: The SIM921 front panel. 1.2.1 Resetting to factory defaults To reset the SIM921 to factory defaults, hold [Set ] depressed while turning power on to the module.
  • Page 14 O set is preloaded with the latest measurement result of Value. Depressing both buttons again will force O set to zero. Freq. (Hz) : This field controls the excitation frequency for the SIM921. [Set ] adjusts the frequency from 2 Hz to 60 Hz. Depress- ing both [Set ] and [Set ] together will step between 15 Hz, 10 Hz, 5 Hz, and 2.5 Hz.

  • Page 15: Range

    Holding [Autorange] for 2 seconds light Gain and initiate an auto- gain cycle. Whenever the SIM921 is set to a new range or excitation, the internal amplifiers are preset to nominal gains. This might not be...

  • Page 16: Excite

    While the excitation is o , holding [Mode] for 2 seconds will 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 ;...

  • Page 17: Output

    This is an appropriate setting for relatively high signal- to-noise measurements where signal bandwidth is important. It can take six or seven time constants for the output of the SIM921 to fully settle after a step change; for slow time constant settings, this can be a bothersome delay.

  • Page 18: Sensor Interface

    1 – 8 Getting Started 1.3 Sensor Interface The sensor interface on the SIM921 consists a rear-panel DB–9 F con- nector, labeled “INPUT” (see Figure 1.3). The pin assignments for this connector are given in Table 1.1. Signal I (current lead)

  • Page 19: Four-Wire Measurement

    Figure 1.5: Wiring diagram for two-wire readout. 1.3.3 Wiring for high impedance When using the SIM921 to measure high impedances ( few M ), cable construction becomes crucial. It is important that the wire leads have a low-loss dielectric insulation, such as PTFE (Teflon Ordinary PVC-insulated wire is not well suited to this application, as it can su er from dielectric absorption e ects.
  • Page 20 1 – 10 Getting Started very high DC insulation resistance ( 100 G ), small AC dielectric losses, even at the low frequencies used by the SIM921, can appear as (10s 100s) M of real impedance in parallel with the user load.

  • Page 21: Sim Interface

    SIM900 Mainframe via this connection, either through one of the internal mainframe slots, or the remote cable interface. It is also possible to operate the SIM921 directly, without using the SIM900 Mainframe. This section provides details on the interface.
  • Page 22 RS-232 serial port of a personal computer. 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, a null-modem style cable is not needed.
  • Page 23 1 – 13 1.4.2.2 Serial settings The serial port settings at power-on are: 9600 baud, 8–bits, no parity, 1 stop bit, and no flow control (see Section 2.3.1). The serial settings cannot be changed on the SIM921. SIM921 AC Resistance Bridge...
  • Page 24 1 – 14 Getting Started SIM921 AC Resistance Bridge...

  • Page 25: Remote Operation

    2 Remote Operation This chapter describes operating the SIM921 over the serial interface. In This Chapter 2.1 Index of Commands ....2 – 2 Alphabetic List of Commands .

  • Page 26: Index Of Commands

    CURV(?) i 2 – 15 Sensor Calibration Curve 2 – 16 Initialize Sensor Calibration CINI(?) i ,z,s CAPT i,f,g 2 – 16 Add Point to Sensor Calibration CAPT? i,j 2 – 16 Query Point in Sensor Calibration SIM921 AC Resistance Bridge...
  • Page 27 2 – 24 Communication Error Status CESE(?) [i,] j 2 – 24 Communication Error Status Enable OVCR? [i] 2 – 24 Overload Condition OVSR? [i] 2 – 24 Overload Status OVSE(?) [i,] j 2 – 25 Overload Status Enable SIM921 AC Resistance Bridge...

  • Page 28: Alphabetic List Of Commands

    2 – 14 Display DTEM(?) z 2 – 15 Display Temperature EXCI(?) i 2 – 11 Excitation EXON(?) z 2 – 11 Excitation On O FREQ(?) f 2 – 10 Frequency FRST 2 – 14 Filter Reset SIM921 AC Resistance Bridge...
  • Page 29 2 – 13 Time Period for Streaming TSET(?) f 2 – 18 Temperature Setpoint TVAL? [i] 2 – 12 Temperature Value VEXC? 2 – 11 Query Excitation Voltage VKEL(?) f 2 – 18 Analog Output Scale (V K) SIM921 AC Resistance Bridge...
  • Page 30 2 – 6 Remote Operation VOHM(?) f 2 – 18 Analog Output Scale (V SIM921 AC Resistance Bridge...

  • Page 31: Introduction

    SIM921 is left unchanged; to reset the instrument, see *RST. The Device Clear signal will also terminate any streaming outputs from the SIM921 due to a TVAL? or RVAL? query of multiple conver- sions. SIM921 AC Resistance Bridge...

  • Page 32: Commands

    CR LF , the following two commands are equivalent: TERM CRLF —or— TERM 3 For queries that return token values, the return format (keyword or integer) is specified with the TOKN command. SIM921 AC Resistance Bridge...

  • Page 33: Notation

    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. The usage examples vary with respect to set query, optional param- eters, and token formats.

  • Page 34: Excitation Commands

    In the following, the excitation is set to 13.7 Hz. FREQ 13.7; FREQ? 13.7025 RANG(?) i Range Set (query) the resistance range to i . Valid range codes are: Range 20 m 200 m 20 k 200 k 20 M Example: RANG 5 SIM921 AC Resistance Bridge...
  • Page 35 VEXC? Query Excitation Voltage Query the actual excitation voltage amplitude, in volts. This is the voltage measured across the sensor itself, not the “nominal” excita- tion across the entire bridge (set by EXCI). Example: VEXC? +1.176760E-05 SIM921 AC Resistance Bridge...

  • Page 36: Measurement Commands

    TPER milliseconds. If the optional i is spec- ified, then i measurement results are returned to the host, separated by TPER milliseconds. If i 0 is specified, then streaming results continues indefinitely until the SOUT command is received. Example: TVAL? +3.067459E+02 SIM921 AC Resistance Bridge...
  • Page 37 6 555 350. The reset value is 1000. Example: TPER 500 SOUT Stop Streaming Turn o streaming output. Streaming is also halted by the Device Clear signal (serial break), but not by *RST. Example: TDEV?0 +8.273926E-01 +8.048706E-01 SOUT SIM921 AC Resistance Bridge...

  • Page 38: Post-Detection Processing Commands

    Set (query) the time constant for the post-detection filter to i . Valid time constant codes are: Time Constant filter o (sync only) 0.3 s 10 s 30 s 100 s 300 s Example: TCON 2 SIM921 AC Resistance Bridge...

  • Page 39: Calibration Curve Commands

    2.4.7 Calibration curve commands DTEM(?) z Display Temperature Set (query) the display temperature mode to z (OFF 0, ON 1) . When ON, the SIM921 display for Value will be in temperature units instead of resistance. Example: DTEM? ATEM(?) z...
  • Page 40 This string can consist of any non-blank characters except the comma “,” or semicolon “;”, and can be up to 15 characters in length. The leading 5 characters will be displayed on the SIM921 front panel when the curve is selected, within the limitations of the seven-segment display hardware.

  • Page 41: Autoranging Commands

    AGAI ON ADIS(?) z Autorange Display Set (query) autoranging of the display to z (OFF 0, ON 1) . The ADIS setting has no e ect on the SIM921 measurement, and only modifies the front-panel data presentation. Example: ADIS ON 2.4.9 Autocalibration command...

  • Page 42: Interface Commands

    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, but this value is not modified by *RST. Example: AOUT -1.234 2.4.11 Interface commands SIM921 AC Resistance Bridge...
  • Page 43 2.4 Commands 2 – 19 *RST Reset Reset the SIM921 to default configuration. *RST executes the follow- ing commands: FREQ 10 RANG 6 EXCI 1 EXON ON MODE PASSIVE TPER 1000 DISP 0 TCON 1 PHLD OFF DTEM OFF ATEM OFF ADIS ON RSET 1.0...
  • Page 44 Set (query) the console mode to z (OFF 0, ON 1) . CONS causes each character received at the input bu er to be copied to the output queue. At power-on and Device-Clear, CONS is set to OFF. Example: CONS? SIM921 AC Resistance Bridge...
  • Page 45 Null parameter(s) Parameter bu er overflow Bad floating-point Bad integer Bad integer token Bad token value Bad hex block Unknown token Example: *IDN LCME? 4 The error (4, “Illegal set”) is due to the missing “?”. SIM921 AC Resistance Bridge...
  • Page 46 TOKN(?) 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 return the text keyword; otherwise they return the decimal integer value.

  • Page 47: Status Commands

    Example: TERM? 2.4.12 Status commands The Status commands query and configure registers associated with status reporting of the SIM921. Status Byte *STB? [i] Reads the Status Byte register [bit i]. The *STB? query causes the STATUS signal to be released if as- serted.
  • Page 48 Query Overload Condition Register [for bit i]. Example: OVCR? OVSR? [i] Overload Status Query Overload Status Register [for bit i]. Upon executing a OVSR? query, the returned bit(s) of the OVSR register are cleared. Example: OVSR? SIM921 AC Resistance Bridge...
  • Page 49 2.4 Commands 2 – 25 OVSE(?) [i,] j Overload Status Enable Set (query) Overload Status Enable Register [for bit i] to j Example: OVSE 3 SIM921 AC Resistance Bridge...

  • Page 50: Status Model

    The SIM921 status registers follow the hierarchical IEEE–488.2 for- mat. A block diagram of the status register array is given in Figure 2.1. There are three categories of registers in the SIM921 status model: Condition Registers : These read-only registers correspond to the real-time condi- tion of some underlying physical property being monitored.

  • Page 51: Status Byte (Sb)

    2 – 27 2.5.1 Status Byte (SB) The Status Byte is the top-level summary of the SIM921 status model. When masked by the Service Request Enable register, a bit set in the Status Byte causes the STATUS signal to be asserted on the rear- panel SIM interface connector.

  • Page 52: Service Request Enable (Sre)

    Bit 1 of the SRE (binary weight 2) is a special function, “KEYLOCK”, firmware release 4.0 and is unrelated to the SIM921 status system. Setting this bit re- sults in the SIM921 ignoring all front panel key presses, essentially implementing a local lockout function.

  • Page 53: Standard Event Status Enable (Ese)

    HWOVRN : Hardware Overrun. Set when an incoming serial data byte is lost due to internal processor latency. Causes the input bu er to be flushed, and resets the command parser. SIM921 AC Resistance Bridge...

  • Page 54: Communication Error Status Enable (Cese)

    OVR : Input bu er Overrun. Set when the input bu er is overrun by incoming data. Causes the input bu er to be flushed, and resets the command parser. RTSH : Undefined for the SIM921. Command Error. Indicates a parser- detected error. CTSH : Undefined for the SIM921.

  • Page 55: Overload Status (Ovsr)

    The OVSE acts as a bitwise AND with the OVSR register to produce the single bit OVSB message in the Status Byte Register (SB). It can be set and queried with the OVSE(?) command. This register is cleared at power-on. SIM921 AC Resistance Bridge...
  • Page 56 2 – 32 Remote Operation SIM921 AC Resistance Bridge...
  • Page 57 3 Parts Lists and Schematics This chapter presents a brief description of the SIM921 circuit design. A complete parts list and circuit schematics are included. In This Chapter 3.1 Circuit Discussion ....3 – 2 3.1.1...

  • Page 58: Circuitry

    3.1.1.1 Clock and MCU All functions of the SIM921 are coordinated by the microcontroller, U103, which operates in “single-chip” mode (internal RAM and ROM). Extended non-volatile memory is provided by U105 for stor- age of user calibration curves.

  • Page 59: Front-Panel Board

    3.1.2 Front-panel board The front-panel board (page 3) contains the drive cicuitry for the display components of the SIM921. Note that all LEDs are driven statically from U307–U318. The readout for the button switches is somewhat subtle. Initially, the BUTTON SENSE lines are all driven low, and the BUTTON PRESS lines are diode-or’d together (D103, D104, page 1) to detect any...

  • Page 60: Amplifier Board

    LSK389 dual JFET for inputs. During an autocalibration cycle, the two relays K701, K702 are both switchted to the set position, tying both preamps to the I SENSE internal signal (K517 is also switched closed, providing a complete SIM921 AC Resistance Bridge...
  • Page 61 3 – 5 internal current path, and disconnecting all circuitry from the exter- nal resistor). Since the fundamental measurement of the SIM921 is ratiometric, this cross-calibration of the two amplifier channels is suf- ficient to remove gain-dependent systematic errors in the resistance measurement.

  • Page 62: Parts Lists

    R104,R106,R113,R118,R245, 4-01503 X101,X102,X103,X104,X105, 5-00299 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 X209,X210,X211,X212,X213, R109 4-01405 1.00M X214,X215,X216,X217,X218, R110,R115,R117,R121 4-01455 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 X308,X309,X310,X311,X312 R122 4-01510 Y101 6-00571 10.000MHz SIM921 AC Resistance Bridge...

  • Page 63: Source Board

    OPA2277U R415 4-01050 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 U602,U603,U604,U605,U606 3-00787 74HC595 R422 4-00925 10.0 X401,X402,X403,X404,X405, 5-00299 R426,R424 4-00218 10.00K X406,X601,X602,X603,X604, R501,R509,R530 4-01405 1.00M X605,X606 SIM921 AC Resistance Bridge...

  • Page 64: Schematic Diagrams

    5534 R714,R715,R750,R751 4-01649 1.000K U901 3-00662 74HC14 R716,R752 4-00954 U902,U903,U904 3-00787 74HC595 R718,R728,R748,R762 4-01141 1.78K X701,X702,X706,X707,X709, 5-00299 R719,R756 4-00971 30.1 X710,X714,X715,X801,X802, R720,R734,R749,R765,R817, 4-01431 X803,X804,X805,X806,X807, R818,R820,R823,R825,R826, X808,X809,X810,X811,X812, R844,R845,R847,R850,R852, X901,X902,X903,X904 3.3 Schematic Diagrams Schematic diagrams follow this page. SIM921 AC Resistance Bridge...
  • Page 65 Page 1 of 9...
  • Page 66 Page 2 of 9...
  • Page 67 Page 3 of 9...
  • Page 68 Page 4 of 9...
  • Page 69 Page 5 of 9...
  • Page 70 Page 6 of 9...
  • Page 71 Page 7 of 9...
  • Page 72 Page 8 of 9...
  • Page 73 Page 9 of 9...

Table of Contents