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3 – 2

Circuitry

3.1

Circuit Description

The SIM928 isolated voltage source contains five distinct circuit
blocks:

1. a microcontroller,

2. a battery charger circuit,

3. the battery pack,

4. an isolated voltage regulator circuit and

5. a front panel display.

3.1.1

Microcontroller

The single chip microcontroller U103 controls the battery charger, the
isolated voltage regulator, the display, and responds to remote serial
commands.

3.1.2

Battery charger

The SIM928 battery pack contains two identical 25.2 V NiMH batter-
ies. During normal operation at least one battery is connected at any
time to the isolated voltage regulator circuit. The other battery is
either idle (disconnected) or connected to the charger circuit. Once
the microcontroller detects that the battery in use is running low on
charge (via opto U502A), it swaps the two batteries and connects the
now depleted battery to the charger circuit.

Constant charge and discharge currents are used to maximize battery
life and minimize electronics noise on the isolated voltage output.
First the charger algorithm discharges a depleted battery to a fixed
voltage endpoint (23.0 V) to ensure a well defined discharge state.
It then charges the battery with a constant current until the charge
termination endpoint is reached. Charging terminates on either total
charge time or a zero of the NiMH d

V

/

d

t

curve. The charger algo-

rithm is designed to maximize battery life and ensure several years
of uninterrupted operation with a single battery pack.

A complex state machine driven by a timer and battery monitoring
signals implements the discharge-charge-idle cycle for each battery
in such a way that the module is always available after an initial
charge cycle. NiMH batteries su

ff

er from self-discharge on the order

of 1% per day. If the module has been powered down for several
months, insu

ffi

cient charge might remain in either battery to assure

continuous operation, especially if the output is loaded with close to
10 mA current. The initialization algorithm tries to ensure the best
possible availability by comparing the battery voltages to a minimum

SIM928

Isolated Voltage Source

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Содержание SIM928

Страница 1: ...Operation and Service Manual Isolated Voltage Source SIM928 Stanford Research Systems Revision 2 0 August 25 2006 ...

Страница 2: ...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 2005 2006 All rights reserved Stanford Research Systems Inc 1290 D Reamwood Avenue Sunnyvale CA 94089 USA Phone 408...

Страница 3: ... 1 Introduction to the Instrument 1 2 1 2 Front Panel Operation 1 2 1 3 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 6 2 4 Commands 2 7 2 5 Status Model 2 17 3 Circuitry 3 1 3 1 Circuit Description 3 2 3 2 Parts List 3 7 3 3 Schematic Diagrams 3 7 i ...

Страница 4: ...ii Contents SIM928 Isolated Voltage Source ...

Страница 5: ... outlet ground and the metal chassis of the module No dangerous voltages are generated by the SIM928 However if a dangerous voltage is externally applied to the module WARNING it may be present on either binding post connector the chassis or the SIM interface connector and may cause injury or death Do not exceed 40 V to the Earth at either binding post terminal The SIM928 ships from the factory wi...

Страница 6: ...ind 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 SIM928 Isolated Voltage Source ...

Страница 7: ...is 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 SIM928 are set as straight teletype font while responses receive...

Страница 8: ... time 5 h Discharge time 12 h 10 mA load Lifetime 1000 charge cycles 2 yr shelf life Battery switching Automatic when active battery is fully discharged Switchover glitch 1 mV for 1 ms Battery charge override Allows manual switching of batteries Triggered when Battery Override is held for 5 s or more Only armed when standby battery is in ready state Operating Temperature 0 40 C Power 15 5 24 V DC ...

Страница 9: ...SIM928 Isolated Voltage Source In This Chapter 1 1 Introduction to the Instrument 1 2 1 1 1 Overview 1 2 1 1 2 Power on State 1 2 1 2 Front Panel Operation 1 2 1 2 1 Adjust 1 3 1 2 2 Battery 1 4 1 2 3 Output 1 5 1 3 SIM Interface 1 6 1 3 1 SIM interface connector 1 6 1 3 2 Direct interfacing 1 7 1 1 ...

Страница 10: ...lly by the SIM900 Mainframe Absent any external power the SIM928 will be off 1 1 2 Power on State The SIM928 stores its operation state programmed voltage and on off configuration in non volatile memory At power on the SIM928 will return to its previous configuration after a brief system check and initialization The power on system check includes a brief test of both internal bat teries If either ...

Страница 11: ...e front panel Brief taps on 100 mV increment or decre ment the setting by 100 mV similarly the 10 mV and 1 mV step the setting by 10 mV and 1 mV respectively Holding any of these keys for 1 second begins an accelerating auto repeat for faster voltage changes Note that the auto repeat function will not scroll across 0 V when decreasing a positive setting or increasing a nega tive setting the auto r...

Страница 12: ...cuit 1 2 2 1 Battery cycle Under typical operation a fully charged battery should run for 12 18 hours before being depleted When the On battery is nearly dis charged an internal threshold circuit signals the SIM928 controller to begin a battery switch over The stand by battery which at this point is typically in the Ready state is switched onto the output circuit after which the discharged battery...

Страница 13: ...he battery pack must be replaced The yellow service batteries indicator turns on when the battery pack has reached this limit The SIM928 will continue to operate properly with reduced capacity batteries the only effect will be the battery switch over will occur more frequently It is also possible if a SIM928 is left in storage for several years with out operation that the batteries will have lost ...

Страница 14: ...t terminals To clear an overvoltage TRIP press On Off This will return the SIM928 to the Off state a second press of On Off will attempt to switch the instrument back on If the overvoltage condition still exists the output will again trip off 1 3 SIM Interface The primary connection to the SIM928 Isolated Voltage Source is the rear panel DB 15 SIM interface connector Typically the SIM928 is mated ...

Страница 15: ...irectly interface the module to their own systems without the use of additional hardware The mating connector needed is a standard DB 15 receptacle such as Amp part 747909 2 or equivalent Clean well regulated supply voltages of 15 5 24 VDC must be provided following the pin out specified in Table 1 1 Ground must be provided on pins 1 and 8 with chassis ground on pin 9 The STATUS signal may be moni...

Страница 16: ...3 5 VDC 15 24 VDC 8 9 Ground P S return current 1 Signal Ground separate wire to Ground Table 1 2 SIM928 Direct Interface Cable Pin Assignments 1 3 2 2 Serial settings The initial serial port settings at power on are 9600 Baud 8 bits no parity 1 stop bit and RTS CTS flow control These may be changed with the BAUD FLOW or PARI commands The maximum standard baud rate that the SIM928 supports is 3840...

Страница 17: ...4 3 Examples 2 8 2 4 4 Output commands 2 9 2 4 5 Battery commands 2 9 2 4 6 Serial communication commands 2 10 2 4 7 Status commands 2 11 2 4 8 Interface commands 2 13 2 5 Status Model 2 17 2 5 1 Status Byte SB 2 18 2 5 2 Service Request Enable SRE 2 19 2 5 3 Standard Event Status ESR 2 19 2 5 4 Standard Event Status Enable ESE 2 20 2 5 5 Communication Error Status CESR 2 20 2 5 6 Communication Er...

Страница 18: ...ger override BATS 2 10 Battery State BIDN z 2 10 Battery Identification Serial Communications BAUD i 2 11 Baud Rate FLOW z 2 11 Flow Control PARI z 2 11 Parity Status CLS 2 11 Clear Status STB i 2 12 Status Byte SRE i j 2 12 Service Request Enable ESR i 2 12 Standard Event Status ESE i j 2 12 Standard Event Status Enable CESR i 2 12 Communication Error Status CESE i j 2 12 Communication Error Stat...

Страница 19: ...dex of Common Commands 2 3 OPC 2 14 Operation Complete LEXE 2 14 Execution Error LCME 2 15 Device Error LBTN 2 15 Button TOKN z 2 16 Token Mode TERM z 2 16 Response Termination SIM928 Isolated Voltage Source ...

Страница 20: ... Baud Rate BCOR 2 9 Battery charger override BIDN z 2 10 Battery Identification C CESE i j 2 12 Communication Error Status Enable CESR i 2 12 Communication Error Status CONS z 2 14 Console Mode E EXON z 2 9 Excitation On Off F FLOW z 2 11 Flow Control L LBTN 2 15 Button LCME 2 15 Device Error LEXE 2 14 Execution Error O OPOF 2 9 Output Off OPON 2 9 Output On OVCR i 2 13 Overload Condition OVSE i j...

Страница 21: ...2 2 Alphabetic List of Commands 2 5 PSTA z 2 13 Pulse STATUS Mode T TERM z 2 16 Response Termination TOKN z 2 16 Token Mode V VOLT f 2 9 Voltage SIM928 Isolated Voltage Source ...

Страница 22: ...dface 2 3 2 Buffers Incoming data from the host interface is stored in a 32 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 SIM928 are buffered in a 128 byte output queue If the input buffer overflows then all data in both the input buffer and the outpu...

Страница 23: ...s are always required Do not send or or 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 termin...

Страница 24: ...er 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 SIM928 are set as straight teletype font while responses received the host computer from the SIM928 are set as slanted teletype font The usage examples vary with respect to set query optional param eters and token formats T...

Страница 25: ...t can also be turned on with the OPON command and turned off with the OPOF command EXON Example ON 2 4 5 Battery commands These commands directly query and control the battery system of the SIM928 Battery charger override BCOR Forces the SIM928 to switch the active output battery BCOR follows the same rules as the front panel Battery Override button see section 1 2 2 2 In particular the command wi...

Страница 26: ...d parameters to query are Value Definition PNUM 0 Battery pack part number SERIAL 1 Battery pack serial number MAXCY 2 Design life of charge cycles CYCLES 3 charge cycles used PDATE 4 Battery pack production date YYYY MM DD The MAXCY parameter returns the estimated maximum number of charge discharge cycles that each battery in the pack can sustain be fore suffering a significant reduction in charg...

Страница 27: ...n chronous serial communication is no greater than 5 mismatch in baud rates BAUD 9600 Example Flow Control FLOW z Set query flow control to z NONE 0 RTS 1 XON 2 At power on the SIM928 defaults to FLOW RTS flow control FLOW 0 Example Parity PARI z Set query parity to z NONE 0 ODD 1 EVEN 2 MARK 3 SPACE 4 At power on the SIM928 defaults to PARI NONE PARI EVEN Example 2 4 7 Status commands The Status ...

Страница 28: ...rd Event Status ESR i Reads the Standard Event Status Register bit i Upon executing ESR the returned bit s of the ESR register are cleared ESR Example 64 Standard Event Status Enable ESE i j Set query the Standard Event Status Enable Register bit i to j ESE 6 1 Example ESE 64 Communication Error Status CESR i Query Communication Error Status Register for bit i Upon executing a CESR query the retur...

Страница 29: ...e Register bit i to j OVSE 3 Example Pulse STATUS Mode PSTA z Set 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 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 Reset RST Reset the SIM928 to default c...

Страница 30: ...rmware revision level IDN Example Stanford Research Systems SIM928 s n003075 ver1 1 Operation Complete OPC Operation Complete Sets the OPC flag in the ESR register The query form OPC writes a 1 in the output queue when complete but does not affect the ESR register OPC Example Execution Error LEXE Query the last execution error code Valid codes are Value Definition 0 No execution error since last L...

Страница 31: ...ll 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 Valid codes are Value Definition 0 no button pressed since last LBTN 1 On Off 2 100 mV 3 100 mV 4 10 mV 5 10 mV 6 1 mV 7 1 mV 8 Battery O...

Страница 32: ...Thus the only possible responses to the TOKN query are ON and 0 At power on TOKN OFF is set 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 carriage return and or 10 line feed At power on TERM CRLF is set TERM Example 3 ...

Страница 33: ... write registers define a bitwise mask for their cor responding event register If any bit position is set in an event register while the same bit position is also set in the enable register then the corresponding summary bit message is set Enable register names end with SE 7 X 5 4 3 2 1 0 CESB MSS ESB IDLE undef undef undef OVSB 7 6 5 4 3 2 1 0 Status Byte SB SRE 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 OP...

Страница 34: ...egister has become true IDLE Indicates that the Input Buffer is empty and the command parser is idle Can be used to help synchronize SIM928 query responses ESB Event Status Bit Indicates whether one or more of the enabled events in the Standard Event Status Register is true MSS Master Summary Status Indicates whether one or more of the enabled status messages in the Status Byte register is true No...

Страница 35: ... 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 Operation Complete Set by the OPC command INP Input Buffer Error Indicates data has been discarded from the Input Buffer QYE Query Error Indicates data in the Output Queue has been lost DDE Device Dependent Error Indicates a SIM928 had a delayed execution error due to an illegal ...

Страница 36: ...y 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 present a steady logic level during each asynchronous bit period window HWOVRN Hardware Overrun Set when an incoming serial data byte is lost due to internal processor latency Causes the Input Buffer to be flushed and re...

Страница 37: ...ts current limit 15 mA Overvoltage TRIP The protection circuitry tripped off This happens if the voltage across the outputs exceeds 25 V and typically can only occur if an external voltage is applied to the instrument Battery Switch Indicates a battery switch over event has occured either due to the On battery being depleted or a user initiated Battery Over ride event Battery Fault Indicates a gro...

Страница 38: ...ble OVSE 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 SIM928 Isolated Voltage Source ...

Страница 39: ... A complete parts list and circuit schematics are included In This Chapter 3 1 Circuit Description 3 2 3 1 1 Microcontroller 3 2 3 1 2 Battery charger 3 2 3 1 3 Battery pack 3 5 3 1 4 Isolated voltage regulator stage 3 5 3 1 5 Display and buttons 3 6 3 2 Parts List 3 7 3 3 Schematic Diagrams 3 7 3 1 ...

Страница 40: ...life and minimize electronics noise on the isolated voltage output First the charger algorithm discharges a depleted battery to a fixed voltage endpoint 23 0 V to ensure a well defined discharge state It then charges the battery with a constant current until the charge termination endpoint is reached Charging terminates on either total charge time or a zero of the NiMH dV dt curve The charger algo...

Страница 41: ...uch as 21 cells 1 5 V cell 31 5 V potential accross them while leaving enough headroom for transistor and sense resistor voltage drops 3 1 2 2 Thermal considerations Batteries are chemical storage devices with finite efficiency They have temperature dependent efficiencies and life times NiMH bat teries are best operated at temperatures close to room temperature The SIM928 power dissipation and the...

Страница 42: ... is further increased by averaging The effective voltage resolution per NiMH cell is better than 100 µV allowing it to follow battery charging very precisely 3 1 2 4 Switches and voltage regulators The batteries are connected to the charger and the isolated voltage regulator through relays K201 K204 The microcontroller algorithm makes sure that only combinations of switches can be activated which ...

Страница 43: ...tery needs to be switched over Each battery pack carries a non volatile EEPROM with information about cell type voltage capacity production date charge cycles and serial number This information is used by the microcontroller to determine the optimum charging time and when to turn on the Sevice Battery indicator 3 1 4 Isolated voltage regulator stage The output stage is built around the low power p...

Страница 44: ...he feed back opamp The DAC s output voltage is programmed by the microcontroller through an optically isolated U501 U504 serial interface Since the batteries can only supply unipolar 24 V polarity inversion is implemented with a relay switch K501 K502 by commutating the output terminals The module s firmware makes sure that polarity switching only happens when the regulator output voltage is 0 V A...

Страница 45: ...00600 4x100pF R125 R503 R610 R612 4 01551 1 0M RN113 4 00908 270X4D D101 D103 D613 3 00945 BAT54S R203 R204 4 01487 2 2K RN201 RN203 RN501 4 00912 10KX4D D205 D209 D211 D501 3 00544 BAV70LT1 R205 4 00997 56 2 RN503 D502 D603 D606 D608 R207 R208 R209 4 01675 100 OHM 5 5W RN405 RN413 4 00407 2 7K D401 D404 D409 3 00424 GREEN MINI R217 4 01320 130K RT301 RT302 4 00766 RXE030 D410 D412 3 00426 YELLOW ...

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