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SRS Labs SIM964, Руководство по эксплуатации и обслуживанию

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3.1

Circuit Descriptions

3 – 3

3.1.3

Input Overload Detection

Input overload is detected via dual comparator U201 with a wire-or
output arrangement that is level shifted using Q201 and Q202. This
signal is input to the controller.

3.1.4

Limit Levels

The upper and lower limits are generated using two 12-bit multiply-
ing DACS with level shifting op-amps. A 10 V reference signal from
U205, which can be trimmed with R207, is input to the DACs and
the range of the resulting limit voltages is

±

10 V.

3.1.5

Limiting Circuitry

The limiter consists of two cascaded clamping circuits. Each clamp-
ing circuit consists of two operational amplifiers in a feedback ar-
rangement that allows their ouputs to flip between two stable states
depending on whether the input signal is above or below the limit
voltage.

Consider the operation of the clamping circuit for the upper limit.
Op-amp U303 has diode D312 at its output. The diode is in the
(DC) feedback loop of this amplifier, so depending on the polarity of
the di

ff

erence of the amplifier inputs, the output will either turn the

diode on (into forward conduction) or o

ff

.

When diode D312 is on, the amplifier output acts as a current sink
for the resistor combination R302

/

R304. This e

ff

ectively clamps the

output of the resistor combination to whatever the potential is at the
noninverting input of U303. U305 is a current feedback amplifier
whose output, in this limiting situation, will attempt to rise above
the upper limit voltage, causing diode D311 to be reverse-biased.
This means that the noniverting input of U303 will remain at the
upper limit voltage, so the output of R302

/

R304 will also remain at

the upper limit voltage.

If the input signal (U301s output) drops below the upper limit volt-
age, the noninverting input of U305 will also be lower than the upper
limit, so the output of U305 will swing negative and eventually for-
ward biase diode D311. Now current flows through R322

/

R324 and

D311, so that the noninverting input to U303 is no longer pinned to
the upper limit voltage. Now diode D312 becomes reverse biased,
so that current from R302

/

R304 no longer has a sink at U303s output.

When this happens, the feedback path from U303s output, through
U305, and back to U303s noninverting input, stably holds U303s
output about one diode drop above the upper limit.

SIM964

Analog Limiter

Содержание SIM964

Страница 1: ...Operation and Service Manual Analog Limiter SIM964 Stanford Research Systems Revision 1 4 August 28 2006 ...

Страница 2: ...t must be returned to a Stanford Research Systems authorized service facility Contact Stanford Research Systems or an authorized representative before returning this product for repair Information in this document is subject to change without notice Copyright c Stanford Research Systems Inc 2006 All rights reserved Stanford Research Systems Inc 1290 D Reamwood Avenue Sunnyvale CA 94089 USA Phone 4...

Страница 3: ... Overview 1 2 1 2 Front panel Operation 1 3 1 3 Clock Stopping 1 5 1 4 SIM Interface 1 6 2 Remote Operation 2 1 2 1 Index of Common Commands 2 2 2 2 Alphabetic List of Commands 2 4 2 3 Introduction 2 5 2 4 Commands 2 5 2 5 Status Model 2 15 3 Circuitry 3 1 3 1 Circuit Descriptions 3 2 3 2 Parts Lists 3 5 3 3 Schematic Diagrams 3 6 i ...

Страница 4: ...ii Contents SIM964 Analog Limiter ...

Страница 5: ...ety and Preparation for Use The front panel input front panel output and the rear panel output coaxial BNC connectors in the SIM964 are referenced to the Earth and their outer casings are grounded No dangerous voltages are generated by the module Do not exceed 15 volts to the Earth at the center terminal of any BNC WARNING connector Do not install substitute parts or perform any unauthorized modif...

Страница 6: ...ay 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 SIM964 Analog Limiter ...

Страница 7: ...in this manual are Front panel buttons are set as Button Adjust is shorthand for Adjust Adjust Front panel indicators are set as Overload Remote command names are set as IDN 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 SIM964 are set as straight teletype font while responses re...

Страница 8: ...t 1 kHz Slew rate 70 V µs Limit detection TTL level outputs are when corresponding limit upper lower is exceeded Operating temperature 0 C to 40 C non condensing Power 5 V 50 mA typ 100 mA max 15 V 50 mA typ 300 mA max General Characteristics Interface Serial RS 232 through SIM interface Connectors BNC 2 front 2 rear DB 15 male SIM interface Weight 1 5 lbs Dimensions 1 500 W 3 600 H 7 000 D SIM964...

Страница 9: ...og Limiter In This Chapter 1 1 Overview 1 2 1 2 Front panel Operation 1 3 1 2 1 Upper limit 1 3 1 2 2 Lower limit 1 3 1 2 3 Shortcuts 1 4 1 2 4 Input 1 4 1 2 5 Output 1 4 1 2 6 Rear panel outputs 1 4 1 3 Clock Stopping 1 5 1 4 SIM Interface 1 6 1 4 1 SIM interface connector 1 6 1 4 2 Direct interfacing 1 6 1 1 ...

Страница 10: ...f the input signal exceeds one of the limits the output of the SIM964 will be clamped to that limit for as long as the signal is in excess of the limit When the input signal returns to the range between the limits the output immediately recovers and follows the input signal again Mathematically this can be expressed as Vo VUL Vi VUL Vi VUL Vi VLL VLL Vi VLL The input and output signals are applied...

Страница 11: ... the value of VUL in volts with 10 mV resolution Pressing UL will raise the upper voltage limit while UL will lower it Short presses of either key will step the limit in 10 mV increments holding the key continuously will cause the limit setting to continuously change upwards or downwards at an accelerating rate The upper limit voltage VUL can be set within the range 10 V VUL VLL 100 mV 1 2 2 Lower...

Страница 12: ... 100 mV Similarly pressing the two buttons LL simultaneously will step the VLL setting between 10 V 5 V 0 V and 5 V 1 2 4 Input The user signal Vi is input at the front panel upper BNC connector which presents a 1 MΩ input impedance 1 2 5 Output The analog output Vo is available at the front panel lower BNC connector Note that the SIM964 has a 50 Ω output impedance When driving an external 50 Ω us...

Страница 13: ... An input overload 5 An upper or lower limit clamp The clock runs for as long as is necessary to complete a limit setting adjustment or to communicate the output of a query through the remote interface However the clock will remain active for as long as the overload or limit condition exists This default behavior can be modified with the remote com mand AWAK Setting AWAK ON will prevent the clock ...

Страница 14: ... connector signals are specified in Table 1 1 Direction Pin Signal Src 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 unused in SIM964 4 CTS SIM MF HW handshake unused in SIM964 5 REF 10MHZ MF SIM 10 MHz reference no connection in SIM964 6 5 V MF SIM Power supply no connection in SIM964 7 15 V ...

Страница 15: ...IM964 directly to RD on the PC TXD directly to TD In other words a null modem style cable is not needed To interface directly to the DB 9 male DTE RS 232 port typically found on contemporary personal computers a cable must be made with a female DB 15 socket to mate with the SIM964 and a female DB 9 socket to mate with the PC s serial port Separate leads from the DB 15 need to go to the power suppl...

Страница 16: ... Serial settings The initial serial port settings at power on are 9600 Baud 8 bits no parity 1 stop bit and no flow control The serial baud rate is fixed but the parity may be changed with the PARI commands SIM964 Analog Limiter ...

Страница 17: ...5 2 4 1 Command Syntax 2 6 2 4 2 Notation 2 7 2 4 3 Examples 2 7 2 4 4 Configuration Commands 2 8 2 4 5 Monitor Commands 2 9 2 4 6 Serial Communication Commands 2 9 2 4 7 Status Commands 2 10 2 4 8 Interface Commands 2 11 2 5 Status Model 2 15 2 5 1 Status Byte SB 2 16 2 5 2 Service Request Enable SRE 2 17 2 5 3 Standard Event Status ESR 2 17 2 5 4 Standard Event Status Enable ESE 2 18 2 5 5 Commu...

Страница 18: ...r Limit Condition LLCR 2 9 Lower Limit Condition OVLD 2 9 Overload Condition Serial Communications PARI z 2 9 Parity Status STB i 2 10 Status Byte SRE i j 2 10 Service Request Enable CLS 2 10 Clear Status ESR i 2 10 Standard Event Status ESE i j 2 10 Standard Event Status Enable CESR i 2 11 Comm Error Status CESE i j 2 11 Comm Error Status Enable PSTA z 2 11 Pulse STATUS Mode Interface RST 2 11 Re...

Страница 19: ...2 1 Index of Common Commands 2 3 SIM964 Analog Limiter ...

Страница 20: ...yte A AWAK z 2 8 Keep Clock Awake C CESE i j 2 11 Comm Error Status Enable CESR i 2 11 Comm Error Status CONS z 2 12 Console Mode L LBTN 2 13 Button LCME 2 13 Command Error LEXE 2 12 Execution Error LLCR 2 9 Lower Limit Condition LLIM f 2 8 Lower Limit O OVLD 2 9 Overload Condition P PARI z 2 9 Parity PSTA z 2 11 Pulse STATUS Mode T TERM z 2 14 Response Termination TOKN z 2 14 Token Mode U ULCR 2 ...

Страница 21: ...nterface is stored in a 64 byte input buffer Characters accumulate in the input buffer until a command terminator either hCRi or hLFi is received at which point the mes sage is parsed and executed Query responses from the SIM964 are buffered in a 64 byte output queue 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 ...

Страница 22: ... as part of the command Multiple parameters are separated by commas Multiple commands may be sent on one command line by separating them with semi colons so long as the input buffer does not overflow Commands are terminated by either hCRi or hLFi characters Null commands and whitespace are ignored Execution of command s does not begin until the command terminator is received Token parameters gener...

Страница 23: ...meter for both set and query forms 2 4 3 Examples Each command is provided with a simple example illustrating its usage In these examples all data sent by the host computer to the SIM964 are set as straight teletype font while responses received the host computer from the SIM964 are set as slanted teletype font The usage examples vary with respect to set query optional param eters and token format...

Страница 24: ...e VLL to f in volts If LLIM is set outside the range VUL 100 mV VLL 10 V then the command will fail setting the EXE bit in the ESR register and setting the LEXE parameter to invalid parameter 16 LLIM 8 042 Example LLIM 8 04 Keep Clock Awake AWAK z Set query the SIM964 keep awake mode to z OFF 0 ON 1 Ordinarily the clock oscillator for the SIM964 microcontroller is held in a stopped state and only ...

Страница 25: ...lower limit detector Returns 1 if input signal exceeds the lower limit voltage Vi VLL Returns 0 otherwise LLCR returns the complement of the rear panel output LLCR returns 1 when the Lower Limit Detect output is and 0 when LLCR Example 1 Overload Condition OVLD Query the input overload detector Returns 1 if the input is over loaded or 0 otherwise OVLD Example 0 2 4 6 Serial Communication Commands ...

Страница 26: ...esently causing the STATUS signal See also the PSTA command STB Example 16 Service Request Enable SRE i j Set query the Service Request Enable register bit i to j SRE 0 1 Example Clear Status CLS CLS immediately clears the ESR and CESR status registers CLS Example Standard Event Status ESR i Reads the Standard Event Status Register bit i Upon executing ESR the returned bit s of the ESR register ar...

Страница 27: ...e 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 is to latch STATUS low until a STB query is received At power on PSTA is set to OFF PSTA Example OFF 2 4 8 Interface Commands Interface commands provide generic control over the interface be tween the SIM964 and the host computer Reset RST Reset the SIM964 ...

Страница 28: ...r OPC Example Console Mode CONS z Set query the Console mode to z OFF 0 ON 1 CONS causes each character received at the Input Buffer to be copied to the Output Queue At power on and Device Clear CONS is set to OFF CONS Example 0 Execution Error LEXE Query the last execution error code A query of LEXE always clears the error code so a subsequent LEXE will return 0 Valid codes are Value Definition 0...

Страница 29: ...er s 6 Extra parameter s 7 Null parameter s 8 Parameter buffer overflow 9 Bad floating point 10 Bad integer 11 Bad integer token 12 Bad token value 13 Bad hex block 14 Unknown token IDN Example LCME 4 The error 4 Illegal set is due to the missing Button LBTN Query the last button press code A query of LBTN always clears the button code so a subsequent LBTN will return 0 Valid codes are Value Defin...

Страница 30: ...le responses to the TOKN query are ON and 0 On reset TOKN is set to OFF TOKN OFF Example Response Termination TERM z Set query the htermi sequence to z NONE 0 CR 1 LF 2 CRLF 3 LFCR 4 The htermi sequence is appended to all query responses sent by the module and is constructed of ASCII character s 13 car riage return and 10 line feed The token mnemonic gives the sequence of characters At power on TE...

Страница 31: ...egories of registers in the SIM964 status model Condition Registers These read only registers correspond to the real time condi tion of some underlying physical property being monitored Queries return the latest value of the property and have no other effect Condition register names typically end with CR OVLD being an exception Event Registers These read only registers record the occurrence of def...

Страница 32: ...ed This corresponds to a 0 1 transition on ULCR LLIM Lower Limit Event Indicates the lower limit clamp has been activated This corresponds to a 0 1 transition on LLCR IDLE Indicates that the Input Buffer is empty and the command parser is idle Can be used to help synchronize SIM964 query responses ESB Event Status Bit Indicates whether one or more of the enabled events in the Standard Event Status...

Страница 33: ...r is cleared at power on 2 5 3 Standard Event Status ESR The Standard Event Status register consists of 8 event flags These event flags are all sticky bits that are set by the corresponding event and cleared only by reading or with the CLS command Reading a single bit with the ESR i query clears only bit i Weight Bit Flag 1 0 OPC 2 1 INP 4 2 QYE 8 3 DDE 16 4 EXE 32 5 CME 64 6 URQ 128 7 PON OPC Ope...

Страница 34: ...r with the CLS command Reading a single bit with the CESR i query clears only bit i Weight Bit Flag 1 0 PARITY 2 1 FRAME 4 2 NOISE 8 3 HWOVRN 16 4 OVR 32 5 RTSH 64 6 CTSH 128 7 DCAS PARITY Parity Error Set by serial parity mismatch on incoming data byte FRAME Framing Error Set when an incoming serial data byte is missing the STOP bit NOISE Noise Error Set when an incoming serial data byte does not...

Страница 35: ...2 hbreaki Clears the Input Buffer and Output Queue and resets the command parser 2 5 6 Communication Error Status Enable CESE The CESE acts as a bitwise AND with the CESR register to produce the single bit CESB message in the Status Byte Register SB It can be set and queried with the CESE command This register is cleared at power on SIM964 Analog Limiter ...

Страница 36: ...2 20 Remote Operation SIM964 Analog Limiter ...

Страница 37: ...e parts list and circuit schematics are included In This Chapter 3 1 Circuit Descriptions 3 2 3 1 1 Microcontroller 3 2 3 1 2 Front Panel Display 3 2 3 1 3 Input Overload Detection 3 3 3 1 4 Limit Levels 3 3 3 1 5 Limiting Circuitry 3 3 3 1 6 Output Cicuit 3 4 3 2 Parts Lists 3 5 3 3 Schematic Diagrams 3 6 3 1 ...

Страница 38: ... start bit of the incoming data When the microcontroller has completed all pending activity it drives the STOP signal high pin 36 of U103 effectively halting its own processor clock In this way the SIM964 guarantees no digital clock artifacts can be generated during quiescent operation The fast start time of the RC oscillator ensures that incoming se rial data will be correctly decoded by the micr...

Страница 39: ... the diode on into forward conduction or off When diode D312 is on the amplifier output acts as a current sink for the resistor combination R302 R304 This effectively clamps the output of the resistor combination to whatever the potential is at the noninverting input of U303 U305 is a current feedback amplifier whose output in this limiting situation will attempt to rise above the upper limit volt...

Страница 40: ...303s output is used by the differential amplifier circuit of U308 along with the upper limit voltage to gen erate a TTL signal that indicates whether the input signal is above or below the upper limit The signal output from the R302 R304 combination is buffered by the follower U302 before passing to a nearly identical lower limit clamping circuit as the one for the upper limit The only differences...

Страница 41: ...5 D106 3 00901 BAS40 06 R402 R403 R501 R502 4 01489 2 7K D307 D308 D309 D310 3 01243 BAS40 04 R404 R405 R406 4 01487 2 2K D311 D312 D313 D314 3 00004 1N4148 R604 4 00913 49 9 FP D501 D502 3 00424 GREEN R605 4 01104 732 D503 3 00425 RED R612 4 01065 287 JP101 1 00302 6 PIN DIF CES S501 S502 S503 S504 2 00053 B3F 1052 JP103 1 00367 15 PIN D U102 3 01405 74AC00 J101 J102 J301 J601 1 00003 BNC U103 3 ...

Страница 42: ...3 6 Circuitry 3 3 Schematic Diagrams Schematic diagrams follow this page SIM964 Analog Limiter ...

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