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Theory of Operation

6-4

Figure 6-4

Simplified schematic of input stage

6.3.2 Gain stage

Input preamplifier gain is provided by a single IC operational
amplifier, U309, as shown in Figure 6-5. The input signal
from the input stage is applied to the inverting and non-in-
verting terminals of the op amp, while the output from the IC
is applied to the output stage. The feedback capacitor, C319,
is one of several components that provides stability by limit-
ing the bandwidth of the amplifier.

Figure 6-5

Gain stage

6.3.3 Output stage

The output stage takes on one of two configurations, depend-
ing on the selected function. In the volts and ohms modes,
the output is optimized for voltages as high as ±210V, while
a different configuration (one necessary for high current) is
used in amps and coulombs.

A simplified diagram of the output stage in the volts and
ohms modes is shown in Figure 6-6. Four transistors (Q301,

Q303, Q304, and Q305) are used in this configuration. Each
transistor pair is used for one-half the output voltage swing.
Q301 and Q304 are used for the positive half, while Q303
and Q305 are used for the negative half. Because of the
±210V voltage swing requirement, ±210V supplies are used.
Each transistor pair is operated in series to provide the nec-
essary device breakdown voltage and power rating.

Figure 6-6

Output stage configuration in volts and ohms

Circuit biasing components include R301, R302, R320, R321,
R325, CR315, and CR316. Meanwhile, CR318 and CR314
provide protection for the ±210V supplies in case a high exter-
nal voltage is applied to the PREAMP OUT terminal.

Output voltage V from the gain stage causes a current to flow
through the emitter resistor R

E1

, which is approximately

equal to V

IN

/R

E

. This same current flows through the load re-

sistor, R

L

, which produces a buffered output voltage of V

IN

and is non-inverting.

Output stage configuration for the amps and coulombs func-
tions is shown in Figure 6-7. Q306 and Q307 are the active
devices for this configuration. Since the power supply volt-
ages are much lower (±24V), only a single pair of transistors
is required. As with the high-voltage configuration, signal in-
put is applied through the two diodes to the bases of the tran-

HI

LO

+0.4V (BOOTSTRAPPED)

+5V

-5V

R314

R352

R351

-5V

BOOTSTRAPPED

O
O

C

O

B

O

A

W303

+5

BOOTSTRAPPED

BOOTSTRAPPED

GROUND

R342

B

A

Q308

R333

R334

INPUT

R335

R336

TO GAIN

STAGE

-5V (BOOTSTRAPPED)

TO OUTPUT

STAGE

FROM

INPUT
STAGE

U309

C319

R325

CR315

CR316

R323

R309

RE2

RE1

Q305

R320

CR314

LO

-210V

RL

OUTPUT

+210V

CR318

R301

Q304

R302

INPUT

FROM

GAIN

STAGE

GAIN

STAGE

OUTPUT

GAIN

STAGE

COMMON

R321

Q301

Q303

«
...
100
101
102
103
104
...
»

Содержание 6512

Страница 1: ...c i a n sw i t ho v e r 1 5 0y e a r so f s p e c i a l i z a t i o n 9 0d a yw a r r a n t y 5d a yr i g h t o f r e t u r no na l l e q u i p me n t 1 3y e a r w a r r a n t i e sf o r n e wa n d p...

Страница 2: ...Model 6512 Programmable Electrometer Instruction Manual Contains Operating and Servicing Information...

Страница 3: ...OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS INC HAS BEEN A...

Страница 4: ...Model 6512 Programmable Electrometer Instruction Manual 1994 Keithley Instruments Inc All rights reserved Cleveland Ohio U S A First Printing February 1994 Document Number 6512 901 01 Rev A...

Страница 5: ...orate immediately into the manual Addenda are numbered sequentially When a new Revision is created all Addenda associated with the previous Revision of the manual are incorporated into the new Revisio...

Страница 6: ...ent A good safety practice is to ex pect that hazardous voltage is present in any un known circuit before measuring Users of this product must be protected from electric shock at all times The respons...

Страница 7: ...before performing the indicated procedure The CAUTION heading in a manual explains hazards that could damage the instrument Such damage may invalidate the warranty Instrumentation and accessories sha...

Страница 8: ...y messages 2 2 2 3 1 RAM memory test 2 2 2 3 2 Self test and firmware revision level 2 2 2 4 Front panel familiarization 2 2 2 4 1 Controls 2 2 2 4 2 Display and indicators 2 5 2 4 3 Tilt bail 2 5 2 5...

Страница 9: ...erence 2 31 2 13 3 Thermal EMFs 2 31 2 13 4 Electromagnetic interference EMI 2 31 2 13 5 Leakage resistance effects 2 32 2 13 6 Input capacitance effects 2 32 2 13 7 Source resistance 2 33 2 13 8 Sour...

Страница 10: ...n 4 11 5 Performance Verification 5 1 Introduction 5 1 5 2 Environmental conditions 5 1 5 3 Initial conditions 5 1 5 4 Recommended test equipment 5 1 5 5 Verification procedures 5 2 5 5 1 Input curren...

Страница 11: ...s calibration 7 7 7 4 14 Permanent storage of calibration constants 7 7 7 4 15 IEEE 488 bus digital calibration 7 7 7 4 16 Additional calibration points 7 8 7 5 Special handling of static sensitive de...

Страница 12: ...v Appendices A IEE 488 Bus Overview A 1 B General Bus Commands B 1 C Interface Function Codes C 1 D Example Programs D 1 E Model 617 6512 Software Compatibility E 1...

Страница 13: ...ic current configuration 2 24 Figure 2 18 Non decade current gains 2 24 Figure 2 19 Equivalent input impedance with zero check enabled 2 25 Figure 2 20 External trigger pulse specifications 2 28 Figur...

Страница 14: ...2 Basic configuration of electrometer preamplifier 6 2 Figure 6 3 Electrometer preamplifier configuration 6 3 Figure 6 4 Simplified schematic of input stage 6 4 Figure 6 5 Gain stage 6 4 Figure 6 6 O...

Страница 15: ...stants 2 33 Table 2 10 Minimum source resistance 2 33 Table 2 11 Equivalent voltage sensitivity of Model 6512 amps ranges 2 34 Table 2 12 Engineering units conversion 2 34 3 IEEE 488 Programing Table...

Страница 16: ...le 7 10 Ranging amplifier gains 7 14 Table 7 11 A D converter checks 7 15 Table 7 12 Preamplifier checks 7 15 Table 7 13 Ranging amplifier checks 7 16 Table 7 14 Digital circuitry checks 7 16 Table 7...

Страница 17: ...ay be digitally calibrated from the front panel or over the IEEE 488 bus Zero Correct A front panel zero correct control allows you to cancel internal voltage offsets optimizing accuracy Baseline Supp...

Страница 18: ...shipment Report any damage to the shipping agent at once Retain the original packing material in case shipment becomes necessary 1 7 1 Shipment contents The following items are included with every Mod...

Страница 19: ...bled 5 Connect the input cable to the signal source to be mea sured Remember that the Model 6512 measures DC voltages up to 200V 6 Disable zero check to make a measurement 7 Take the reading from the...

Страница 20: ...l 6512 INPUT jack Test fixtures Models 6105 and 8008 Resistivity Chambers The Models 6105 and 8008 are guarded test fixtures for measuring vol ume and surface resistivities The units assure good elect...

Страница 21: ...12 is equipped with 3 wire power cord that contains a separate ground wire and is designed to be used with grounded outlets When proper connections are made instrument chas sis is connected to power l...

Страница 22: ...still under warranty less than one year from the date of ship ment and problems develop it should be returned to Keithley Instruments for re pair See paragraph 1 7 for details on re turning the instru...

Страница 23: ...ge to measure the applied sig nal Note that the instrument will be in the auto range mode when it is first turned on Auto ranging is available for all functions and ranges Auto ranging may be can cell...

Страница 24: ...g will be processed and displayed The displayed reading will flash when the TRIG button is pressed The one shot trigger mode can be cancelled by pressing SHIFT then TRIG a second time Additional infor...

Страница 25: ...om previ ous trigger 8 STATUS indicators These three indicators apply to operation of the Model 6512 over the IEEE 488 bus The REMOTE indicator shows when the instrument is in the IEEE 488 remote stat...

Страница 26: ...units To select the exponent program scroll through the program menu until the following message is displayed dISP Use either of the ADJUST buttons to set the exponent to the desired mode In the numer...

Страница 27: ...he supply voltage is marked adjacent to the receptacle 6 Chassis Ground This jack is a 5 way binding post that is connected to instru ment chassis ground It is intended for use in situations re quirin...

Страница 28: ...rnal trigger pulses to the Model 6512 to trigger the instrument to take one or more readings depending on the selected trigger mode 2 7 Basic measurement techniques The paragraphs below describe the b...

Страница 29: ...ut resistance of 200T 2 1014 al lows it to accurately measure voltage sources with high internal resistances In contrast an ordinary DMM may have an input resistance of only 10M resulting in inaccurat...

Страница 30: ...e of the source resistance RS Note that the Model 6512 input resistance is 200G but the cable resistance appears in parallel Figure 2 5 Meter loading considerations ERROR 100RS RS RIN At very high res...

Страница 31: ...eld at signal potential as shown in Figure 2 7 Here a uni ty gain amplifier with a high input impedance and low output impedance is used The input of the amplifier is connected to the signal while the...

Страница 32: ...LIFIER A CONNECTIONS B EQUIVALENT CIRCUIT VOLTS MODE SHOWN GUARD HI LO HI GND GUARD LO WARNING USE SAFETY SHIELD FOR SIGNALS ABOVE 30V VOLTS AND OHMS HI LO COM GND 100 S HI GUARD PREAMP OUT LO SAFETY...

Страница 33: ...4 Connect a suitable triax cable to the rear panel INPUT jack Connect the other end of the circuit to be measured as shown in Figure 2 9 Shielding will be required for low level measurements Connect t...

Страница 34: ...stance RS is shown connected to the input of a pi coammeter The voltage burden is represented by a constant voltage source at the input as EIN If EIN were zero the cur rent as seen by the meter would...

Страница 35: ...bled If desired enable suppress to null out any zero check hop which typically will be in the 10 25 count range 6 Connect the triax cable to the INPUT jack Connect the other end of the cable to the ci...

Страница 36: ...eading The Model 6512 has a max imum input offset current of 5 10 15 A at 23 C This value doubles every 10 C This input offset current translates into a charge of 5 10 15 C per second at a temperature...

Страница 37: ...NALOG OUTPUT INPUT AMPLIFIER A CONNECTIONS B EQUIVALENT CIRCUIT GND HI LO S S IRX INPUT RANGING AMPLIFIER VR RF OFF ON Figure 2 12 Resistance measurement connections At low resistances lead resistance...

Страница 38: ...0nA 200M 10nA 2G 20G 200G 1nA 2 8 1 2V analog output The 2V ANALOG OUTPUT provides a scaled 0 2V output that is inverting in the volts and ohms modes Connections for using this output are shown in Fig...

Страница 39: ...the loop when using external feedback elements To keep loading errors under 0 1 the device connected to the PREAMP OUT should have a minimum input impedance of 100k 2 8 2 Preamp out The PREAMP OUT of...

Страница 40: ...CONNECTIONS S COM VOLTS MODEL 1683 TEST LEAD KIT PREAMP OUT RL PREAMP OUT COM VOUT VIN 100 LO S VIN GND HI S AMPS RL PREAMP OUT COM VOUT IINRF 100 LO S IIN GND RF HI S COULOMBS RL PREAMP OUT COM 100 L...

Страница 41: ...tage span in external feedback is 20V 2 The input impedance in the external feedback mode is given by the relationship ZIN ZFB AV where ZFB is the impedance of the external feedback network and AV is...

Страница 42: ...nt in the external feedback mode by pressing the SHIFT then VOLTS buttons in that order TheAMPS andVOLTS indicators will illuminate simul taneously in the external feedback mode 3 The display will sho...

Страница 43: ...ically varying between 1 and 2 Finally RB constitutes the ohmic bulk resistance of the di ode junction material IO and RB limit the usefulness of the junction diode at low and high currents respective...

Страница 44: ...ive input currents only For bipo lar input signals an external offset bias must be applied or use a PNP transistor for Q1 2 9 6 Non decade current gains The Model 6512 electrometer input uses internal...

Страница 45: ...will be used instead 3 To take readings press ZERO CHECK to disable the zero check mode 4 Readings can now be taken in the normal manner Note that the instrument will remain zeroed even if the instru...

Страница 46: ...00mV on the 200mV range an input voltage of 100mV or more will over range the instrument even though in put voltages up to 199 99mV are normally within the ca pabilities of the 200mV range If the inst...

Страница 47: ...ayed 8 The recall mode can be cancelled simply by pressing SHIFT RECALL The instrument will then return to the normal display mode As long as data store is not dis abled and then re enabled readings a...

Страница 48: ...shown in Figure 2 20 The low logic level should be between 0 0 8V and the high level should be 2 5V The minimum pulse width for reliable trig gering is approximately 10 sec Connections to the rear pan...

Страница 49: ...Model 7001 can switch up to 80 2 pole channels By connecting the triggering inputs of the two instruments together a complete automatic measurement sequence could be performed Data obtained from each...

Страница 50: ...wires will encounter small resistances either in the wires or at the connecting points This small resistance re sults in voltage drops that can affect the measurement Even if the ground loop currents...

Страница 51: ...measurements made at higher levels in extreme cases Low thermal connections should be used whenever thermal EMFs are known to be a problem Crimped copper to copper connections should be used to minimi...

Страница 52: ...is as high as possible Use only good quality triaxial cable for signal connections and make sure that the circuit under test and connectors are kept free of contamination Even with these steps howeve...

Страница 53: ...While input capacitance does increase rise time it can help to filter out some noise present at the input by effectively re ducing electrometer bandwidth If we assume that all input capacitance is lu...

Страница 54: ...ummarizes equiva lent voltage sensitivity of Model 6512 amps ranges OutputENOISE InputENOISE 1 ZF ZS ZF RF 2 fRFCF 2 1 ZS RS 2 fRSCS 2 1 In general as CS becomes larger the noise gain increases An app...

Страница 55: ...Operation 2 35 Table 2 12 Engineering units conversion Symbol Prefix Exponent f p n m k M G femto pico nano micro milli kilo mega giga 10 15 10 12 10 9 10 6 10 3 103 106 109...

Страница 56: ...erminated with an ASCII X character which tells the instrument to execute the command string Commands sent without the execute character will not be executed at that time but they will be retained wit...

Страница 57: ...mand default conditions are summarized in Table 3 1 Device dependent command summary Device dependent commands that control the Model 6512 are listed in Table 3 2 These commands are covered in detail...

Страница 58: ...with Prefix and Buffer Suffix if in B1 NDCV 1 234556E 00 012 3 2 5 EOI and Bus Hold off K0 K1 K2 K3 Enable both EOI and Bus Hold off on X Disable EOI Enable Bus Hold off on X Enable EOI Disable Bus Ho...

Страница 59: ...riggered by Talk One shot Triggered by Talk Continuous Triggered by GET One shot Triggered by GET Continuous Triggered by X One shot Triggered by X Continuous Triggered by External Trigger One shot Tr...

Страница 60: ...Format B0 Electrometer reading B1 Data store reading B2 Maximum reading B3 Minimum reading Default Upon power up or after a DCL or SDC command the instrument will be in the B0 electrom eter mode Descr...

Страница 61: ...Programming 1 In general zero check should be enabled when changing input connections except Notes for the coulombs function 2 After sending a zero correct command the instrument will be ready for a...

Страница 62: ...es the general data format Note that the prefix identifies a normal or overflow reading as well as the measuring function The mantissa is always 5 digits although the most significant digit will assum...

Страница 63: ...es In this case suppressing EOI with the K command may cause the controller input sequence to hang up unless other terminator sequences are used The bus hold off mode allows the instrument to temporar...

Страница 64: ...could affect instrument accuracy Example L1X Perform non volatile RAM storage 3 2 8 SRQ mask M and status byte format Purpose To control which instrument conditions will cause the unit to generate an...

Страница 65: ...100 readings in the data store buffer have been stored Cleared by reading a stored reading over the bus B1X Reading Done Bit 3 Set when the Model 6512 has completed the present reading conversion Clea...

Страница 66: ...r the error bit and restore operation of SRQ on error after the error byte is read Programming 1 Note that the status byte should be read to clear the SRQ line once the instrument has Notes generated...

Страница 67: ...n the displayed value For example if a 150VDC baseline is stored an applied voltage of 175V will result in a displayed reading of only 25V 4 Enable baseline suppression by sending N1X over the bus The...

Страница 68: ...aximum and minimum values may be recalled by using the B command as described in paragraph 3 2 2 Once the unit has stored all 100 readings it will stop data storage until another Q command is sent to...

Страница 69: ...20mA 200G 20nC 20V R12 Cancel auto ranging for all functions Default Upon power up or after receiving a DCL or SDC command the instrument will be in the R0 auto range mode Description The range comma...

Страница 70: ...le trigger stimulus is used to restart a continuous series of readings In a one shot mode a single reading will be processed each time the appropriate trigger stimulus is given The trigger modes are p...

Страница 71: ...tions to be accessed StatusWord When the command sequence U0X is transmitted the instrument will transmit the status word instead of its normal data string the next time it is addressed to talk The st...

Страница 72: ...0mA 200G 20nC 20 V 12 Auto off for all functions ZERO CHECK 0 OFF 1 ON ZERO CORRECT 0 OFF 1 ON TRIGGER 0 CONTINUOUS TALK 1 ONE SHOT TALK 2 CONTINUOUS GET 3 ONE SHOT GET 4 CONTINUOUS EXTERNAL 5 ONE SHO...

Страница 73: ...d will be sent only once each time the U1 command is transmitted Note that the error condition wor id actually a string of ASCII characters representing binary bit positions An error condition is also...

Страница 74: ...word is always current Figure 3 5 U2 status data condition format The various bits in the data condition word include Data Store Full Set when all 100 readings have been stored in the data store memor...

Страница 75: ...the controller input sequence to hang up Examples Y X Program character as terminator YX Disable terminator 3 2 15 Execute X Purpose To instruct the Model 6512 to execute device dependent commands Fo...

Страница 76: ...for subsequent readings If the instrument is zero corrected with zero check disabled the previously stored zero value will be used instead Note that the specifications at the front of this manual ass...

Страница 77: ...rom other instruments as required 4 Make sure the other end of the cable is properly connect ed to the controller NOTE The IEEE 488 bus is limited to a maxi mum of 15 devices including the control ler...

Страница 78: ...ple NDCV 1 2345E 01 41 Talk only mode without prefix on data string Example 1 2345E 01 To place the instrument in the talk only mode perform the following steps 1 Press the PROGRAM SELECT button so th...

Страница 79: ...com mand A value is sent to the instrument Under these condi tions the instrument will display the following error message n Err The command string will be accepted but the calibration val ue will rem...

Страница 80: ...fA An example of a situation requiring low current measure ment is shown in Figure 4 1 In this example the gate leak age current of a JFET is to be measured Although the device manufacturer may specif...

Страница 81: ...A D CONVERTER B EQUIVALENT CIRCUIT HI LO GND INPUT TRIAX CABLE A CONNECTIONS V GUARD HI LO SHIELDED TEST FIXTURE MODEL 230 VOLTAGE SOURCE 6512 PREAMP OUTPUT COMMON 230 VOLTAGE SOURCE LO HI TEST FIXTU...

Страница 82: ...ING Up to 300V may be present between the high and low terminals in ohms 4 3 Diode characterization When the Model 6512 is placed in the ohms mode constant current values between 1nA and 100 A are ava...

Страница 83: ...t value can be decreased for larger capacitor values However values under 10k are not recommended Refer to paragraph 2 13 8 At the start of the test the Model 6512 should be placed in the amps mode an...

Страница 84: ...citance value is 4 6 Insulation resistance measurements At the moderate impedance levels of many circuits insula tion resistance is seldom a consideration as it is generally many orders of magnitude a...

Страница 85: ...d in the unguarded mode the shield should be connected to input low Since the inner shield carries the guard signal the COM ter minal acts as circuit LO 4 6 3 V I resistance measurements with external...

Страница 86: ...IVALENT CIRCUIT V GUARD OFF HI GUARD GND COM UNKNOWN RESISTANCE WARNING SAFETY SHIELD RECOMMENDED FOR GUARDED RESISTANCE MEASUREMENTS ABOVE 30G UP TO 300V MAY BE PRESENT ON GUARD V SIGNAL GUARD SAFETY...

Страница 87: ...CABLE RX A CONNECTIONS V GUARD HI LO UNKNOWN RESISTANCE I SHIELDED TEST FIXTURE MODEL 230 VOLTAGE SOURCE 6512 PREAMP OUTPUT COMMON 230 VOLTAGE SOURCE LO HI TEST FIXTURE MODEL 6512 OFF ON COMMON OUTPU...

Страница 88: ...ut resistance of 200T its error in this exam ple would be Note that this error term is so small as to be insignificant as it would be dominated by the instruments s accuracy specification Thus the inp...

Страница 89: ...act vary with different voltage increments in the same ap proximate range 100 1 10 8 1 10 10 5 Voltage Coefficient V A D CONVERTER RX B EQUIVALENT CIRCUIT HI LO GND INPUT TRIAX CABLE RX A CONNECTIONS...

Страница 90: ...meter such as a quart paint can The two cans must be insulated from one another Although the type of insulator is not all that critical ceramic or Teflon insulators can be used For convenience a BNC c...

Страница 91: ...de at 18 28 C 65 82 F and at less than 70 relative humidity unless otherwise noted 5 3 Initial conditions The Model 6512 must be turned on and allowed to warm up for at least two hours before beginnin...

Страница 92: ...nt amps coulombs volts and ohms Input current may remain high for several minutes following measurement of high volts or ohms Place the V GUARD switch in the OFF position un less otherwise noted 5 5 1...

Страница 93: ...5 Verify that the Model 6512 reading is between 1 8943 and 1 9057nC 5 5 4 Volts verification NOTE Current and charge verification must be performed before volts verification Connect the Model 6512 and...

Страница 94: ...Performance Verification 5 4 10 Enable zero check on the Model 263 and turn off the external calibration 190V source...

Страница 95: ...to cancel offset and test lead resistance 6 On the Model 263 source the 1k resistor to the Model 6512 The actual value of the output resistance is displayed on the Model 263 7 Record the Model 263 rea...

Страница 96: ...eat steps 6 through 9 by sourcing the appropriate resistance to the electrometer Note that guard must be enabled on both the Models 6512 and 263 when verifying the G rang es Also note that COM of the...

Страница 97: ...ent error Limit 2k 20k 200k 2M 20M 200M 2G 20G 200G 1k 10k 100k 1M 10M 100M 1G 10G 100G Off Off Off Off Off Off On On On ____ 0 16 0 0004k ____ ____ 0 13 0 001k ____ ____ 0 23 0 01k ____ ____ 0 225 0...

Страница 98: ...lect the 200G range and press ZERO to source zero ohms Make sure the Model 263 is in OPERATE 5 Set the DC calibrator to output 19 000V 6 On the Model 6512 disable ZERO CHECK and note the reading 7 Ena...

Страница 99: ...nts The input stage is a proprietary FET amplifier designed for high input impedance 200T and low input offset current less than 5fA The output stage provides fur ther amplification thus allowing the...

Страница 100: ...essary input impedance functions a gain stage which provides the needed amplification and an output stage which supplies the required voltage or current drive capability Additional feedback and switch...

Страница 101: ...he coulombs mode the feedback element is a capacitor 6 3 1 Input stage A simplified schematic of the input stage is shown in Figure 6 4 The primary purpose of this stage is to provide low leak age cha...

Страница 102: ...transistor pair is operated in series to provide the nec essary device breakdown voltage and power rating Figure 6 6 Output stage configuration in volts and ohms Circuit biasing components include R3...

Страница 103: ...ory to provide an accurate 10V output The actual source output is 10V but this value is divided to 1V and 0 1V by a voltage divider made up of elements of R304 Q302 buffers the output of U304 since R3...

Страница 104: ...e re sistors in and out of the circuit with FETs Figure 6 11 Simplified schematic of ranging amplifier 6 4 2 Multiplexer and buffer amplifier The multiplexer selects among the three signals that are p...

Страница 105: ...ses an A D converter that utilizes both constant frequency charge balance and single slope tech niques This combination gives the instrument both high ac curacy and relatively fast conversion times A...

Страница 106: ...8A BUFFER 1 2288MHz CLOCK U128D CLOCK GENERATOR U127 Q2 Q3 Q4 Q5 U135B CR113 CHARGE BALANCE COMPARATOR SINGLE SLOPE ENABLE DISABLE U210B D1 Q1 CLK S1 U135A INPUT ENABLE DISABLE CHARGE BALANCE CURRENT...

Страница 107: ...ary storage as well as for data store readings Calibration con stants the display mode and the IEEE 488 primary address are stored in the NVRAM U104 During the power up cycle NVRAM data is transferred...

Страница 108: ...ogram As with the Meter Complete Output protection of the Exter nal Trigger Input is necessary to protect the device from over voltage inputs External Trigger protection components include R101 CR102...

Страница 109: ...30V position the T101 windings are placed in series T101 has a secondary winding which is used to supply the 5V supply used to power the digital circuitry Rectification is done by elements of CR110 wh...

Страница 110: ...ollows WARNING Disconnect the Model 6512 from the power line and all other sources before removing the top cover 1 Remove the screws securing the top cover to the rear panel and carefully lift the cov...

Страница 111: ...bra tion capabilities Instead of the more conventional time con suming method of adjusting numerous calibration potentio meters the technician need only apply an appropriate cali bration signal and di...

Страница 112: ...en subject ed to extreme temperature or humidity allow at least one ad ditional hour for the instrument to stabilize before beginning the calibration procedure NOTE While rated accuracy of the Model 6...

Страница 113: ...current pot R348 on the electrometer board It is accessible through a small hole in the shield see Figure 7 2 8 Carefully adjust R348 for a reading of 0 0000 15 counts on the display Iterative adjust...

Страница 114: ...lowing procedure to calibrate the 20nC range Once this range is calibrated the two remaining ranges are automatically calibrated 1 Connect the Model 263 Calibrator Source to the Model 6512 as shown in...

Страница 115: ...steps 3 through 9 for the 2V and 20V ranges 11 With the Model 343A set to zero volts connect it to the Model 263 as shown in Figure 7 4 Leave the Model 263 connected to the Model 6512 as shown in Figu...

Страница 116: ...the Model 263 The actual value of that resistor will be dis played by the Model 263 16 Adjust the displayed reading on the Model 6512 to cor respond to the reading on the Model 263 7 4 14 Permanent s...

Страница 117: ...in the disabled position place the in strument in the desired function and select the range to be calibrated Apply the necessary calibration signal and enter that value into the instrument s memory e...

Страница 118: ...efore completely installing it 2 Remove the electrometer board as follows A Remove the four screws that secure the top shield to the electrometer board B Carefully lift the shield clear of the board C...

Страница 119: ...Maintenance 7 10 Figure 7 5 Exploded view...

Страница 120: ...If a RAM error occurs the instrument will be completely in operative and you should assume that a problem exists with in the instrument The problem should be rectified before using the instrument If...

Страница 121: ...st to make sure they are within the required limits If the various oper ating voltages are not within the required limits trouble shooting the remaining circuitry can be quite difficult Table 7 8 outl...

Страница 122: ...to digital common Referenced to analog common Referenced to analog common Referenced to analog common Referenced to bootstrap common Referenced to preamp out Table 7 9 Relay configuration Relay Functi...

Страница 123: ...UT should be 1 9V If the PREAMP OUT sig nal is correct but the 2V ANALOG OUTPUT is not the ranging amplifier or associated control circuits are not func tioning properly 7 7 7 A D converter and displa...

Страница 124: ...lock A D synchronous clock A D synchronous clock Charge balance synchroniza tion signal Comparator reference Comparator output Reference current generator A D data output Control line for charge bal a...

Страница 125: ...n then goes high 4V 655kHz clock 655kHz clock Variable pulse train Variable pulse train Negative going pulse every 350msec All voltages referenced to digital common 5V digital supply Interrupt clock M...

Страница 126: ...ting or otherwise working inside the in strument care should be taken not to touch PC board traces and open wires to avoid contaminating them with body oils or other foreign matter In particular there...

Страница 127: ...ordering parts in clude the following information 1 Instrument Model Number 2 Instrument Serial Number 3 Part Description 4 Circuit designation including schematic diagram and component layout number...

Страница 128: ...R107 R108 109 R114 R119 R128 R131 R133 R138 R142 R143 R144 R145 R146 R149 R150 R153 RES 100 5 1 4W COMPOSITION OR FILM RES 330 5 1 4W COMPOSITION OR FILM RES 10M 5 1 4W COMPOSITION OR FILM RES NET 1K...

Страница 129: ...HIFT STORE REGISTER 4094 IC TRIPLE 2 CH MULTI DEMUX 4053 IC DUAL VOLTAGE COMPARATOR LM393 INTEGRATED CIRCUIT IC 18V OP AMP TLC 271 IC TRIPLE 3 INPUT OR 4075 IC 412 IC 341 IC 299 IC 298 IC 239 IC 337 I...

Страница 130: ...TAL DISPLAY DOUBLE DIGIT PILOT LIGHT RED LED PILOT LIGHT YELLOW LED 617 603 617 604 DD 39 PL 71 PL 72 P1016 CABLE ASSEMBLY 24 CONDUCTOR CA 30 1 R201 202 RES NET 82 5 25W TF 141 S201 215 217 218 SWITCH...

Страница 131: ......

Страница 132: ...1 617 607C TG 145 TG 177 TG 91 R301 302 320 321 R303 R304 R305 308 R306 307 R309 323 324 R311 R312 R313 R314 348 R315 R316 R317 R318 R319 329 337 R322 R324 327 R326 R328 354 R330 R331 R332 R333 355 R3...

Страница 133: ...STORE REGISTER 4094 IC HEX INVERTER 74HC04 IC 18V OP AMP 741 IC 5V REGULATOR 500mA 7805 IC 3 TERM ADJ REGULATOR LM337 IC VAR POS VOLTAGE REG 100MA 78L05A IC 20V OP AMP 1012 IC 251 IC 354 IC 42 IC 93 I...

Страница 134: ...20 PUSHBUTTON 228 317 4 PUSHBUTTON 228 317 6B SHIELD BOTTOM COVER 617 305B SHIELD INPUT TUBE 30472 BINDING POST RED BP 11 2 CAP PROTECTIVE CAP 30 1 CAP 1000PF 10 1000V CERAMIC C 64 1000P PUSHBUTTON 22...

Страница 135: ...at least one control ler and one or more devices to which commands are given and in most cases from which data is received Generally there are three categories that describe device operation con trol...

Страница 136: ...tegories data lines management lines and hand shake lines The data lines handle bus data and commands while the management and handshake lines ensure that prop er data transfer and bus operation takes...

Страница 137: ...e accepted the data Each device will release NDAC at its own rate but NDAC will not be re leased to go high until all devices have accepted the data byte Once NDAC goes high the source then sets DAV h...

Страница 138: ...ch com mand Each command is sent by setting the corresponding bus line true REN Remote Enable REN is sent to set up instruments on the bus for remote operation Generally REN should be as serted before...

Страница 139: ...ice dependent commands The meaning of the device dependent commands will depend on the configuration of the instrument Generally these com mands are sent as one or moreASCII characters that tell the d...

Страница 140: ...S GS RS US LLO DCL PPU SPE SPD SP 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 UNL A B C D E F G H I J K L M N O 0 1 2 3 4 5 6 7 8 9 10 11 12...

Страница 141: ...stead the instrument must be addressed to listen after setting REN true before it will go into remote Indicates typical controller syntax required to send corresponding general bus commands Hewlett Pa...

Страница 142: ...Both disabled CR LF B 3 IFC Interface Clear The IFC command is sent by the controller to place the Mod el 6512 in the local talker and listener idle states The unit will respond to the IFC command by...

Страница 143: ...bilities as follows SH Source Handshake Function SH1 defines the ability of the Model 6512 to initiate the transfer of message data over the data bus AH Acceptor Handshake Function AH1 defines the abi...

Страница 144: ...el 6512 to have its readings triggered is provided by the DT function C Controller Function The Model 6512 does not have controller capabilities TE Extended Talker Function The Model 6512 does not hav...

Страница 145: ...el 7007 D 3 Computer software requirements In order to use the example programs you will need the fol lowing software Microsoft QBasic supplied with MS DOS 5 0 or later QuickBASIC version 4 5 or later...

Страница 146: ...rompt When typ ing in commands keep the following points in mind Be sure to use only upper case letters for commands Be certain to terminate each command string with the X character After each command...

Страница 147: ...E 27 Put 6512 in remote PRINT 1 CLEAR Send DCL CLS PRINT 1 OUTPUT 27 M2X SRQ on data store full PRINT 1 OUTPUT 27 Q0C0X Enable data store conversion rate PRINT Storing data DO PRINT 1 SRQ Loop until S...

Страница 148: ...and status byte program Program to demonstrate Model 6512 SRQ and status byte OPEN IEEE FOR OUTPUT AS 1 Open IEEE 488 output path OPEN IEEE FOR INPUT AS 2 Open IEEE 488 input path PRINT 1 REMOTE 27 Pu...

Страница 149: ...gram 4 Status word program Program to obtain status words from Model 6512 OPEN IEEE FOR OUTPUT AS 1 Open IEEE 488 output path OPEN IEEE FOR INPUT AS 2 Open IEEE 488 input path PRINT 1 REMOTE 27 Put 65...

Страница 150: ...address of the Model 6512 to 27 5 Enter the calibration program into the computer See the introduction of this appendix for complete details 6 To calibrate the instrument run the program and follow th...

Страница 151: ...nge PRINT 1 OUTPUT 8 Z1O1X 263 output 0A to 6512 SLEEP 2 PRINT 1 OUTPUT 27 Z1X 6512 zero correct unit SLEEP 1 PRINT 1 OUTPUT 27 C0X 6512 disable zero check SLEEP 5 PRINT 1 OUTPUT 27 N1X 6512 enable su...

Страница 152: ...ing FOR I 8 TO 2 STEP 1 IF I 7 THEN BEEP PRINT Set 6512 GUARD switch to OFF position PRINT Press any key to continue SLEEP PRINT Continuing PRINT 1 OUTPUT 8 W0X 263 disable guard END IF PRINT 1 OUTPUT...

Страница 153: ...trument The Model 617 includes a three character prefix 617 while the Model 6512 has a four character prefix 6512 If your cur rent parsing routines expect a specific string length to identi fy bit pos...

Страница 154: ...s 3 19 Data format G 3 7 Data lines A 2 Data storage 2 27 DATA STORE 2 5 Data store mode Q 3 13 Data store program D 3 DCL Device Clear B 2 Default conditions 3 2 Device dependent command program ming...

Страница 155: ...ty E 1 Multiple commands 3 1 Multiplexer and buffer amplifier 6 7 N No Remote error 3 24 Non decade current gains 2 24 Non standard coulombs ranges 2 23 Non volatile memory storage L 3 9 Normal charge...

Страница 156: ...nds A 5 Unguarded resistance measurements 4 5 Uniline commands A 4 Universal commands A 4 Unpacking and inspection 1 2 Using the coulombs function to mea sure current 2 16 Using external feedback 2 21...

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