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Keysight 8478B Thermistor Mount 39

Maintenance
Thermistor Compensation

3. Turn screws (B) clockwise, 1/8 turn alternately.

4.

When meter pointer rises, trim to zero with each adjusting screw.

5. Replace terminal shield and three screws (A). The instrument is now

operative.

The compensating screws are in very close proximity to the thermistors

themselves. Thermistor damage can easily occur if the screws are forced

in any way.
If there is a sudden jump in meter indication when advancing either screw,

back off 1/8 turn, and do not advance that screw further. Check resistance

as in

“If meter remains pegged downscale, measure resistance between

pins 1 and 2, and pins 3 and 4. The resistance should measure between

1000 and 5000 ohms. An open or shorted reading indicates the need for

replacement of the thermistors.” on page 37

. If either screw bottoms, do

not apply force. Thermistor replacement is indicated.

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Содержание 8478B

Страница 1: ...Operating and Service Manual Keysight 8478B Thermistor Mount ...

Страница 2: ...y provided to the public to use modify reproduce release perform display or disclose commercial computer software or commercial computer software documentation No additional government requirements beyond those set forth in the EULA shall apply except to the extent that those terms rights or licenses are explicitly required from all providers of commercial computer software pursuant to the FAR and...

Страница 3: ...able for errors or for incidental or consequential damages in connection with the furnishing use or performance of this document or any information contained herein Should Keysight and the user have a separate written agreement with warranty terms covering the material in this document that conflict with these terms the warranty terms in the separate agreement shall control Duration and conditions...

Страница 4: ...t result from the Buyer s circuitry In addition Keysight does not warrant any damage that occurs as a result of the Buyer s circuit or any defects that result from Buyer supplied products To the extent allowed by local law Keysight makes no other warranty expressed or implied whether written or oral with respect to this product and specifically disclaims any implied warranty or condition of mercha...

Страница 5: ...waste Product category With reference to the equipment types in the WEEE directive Annex 1 this instrument is classified as a Monitoring and Control Instrument product The affixed product label is as shown below Do not dispose in domestic household waste Sales and Technical Support To contact Keysight for sales and technical support refer to the support links on the following Keysight websites www...

Страница 6: ...6 Keysight 8478B Thermistor Mount Certification Sales and Technical Support ...

Страница 7: ...ermistors 14 Specifications 15 Maximum Input 17 Average Power 17 Pulse Energy and Peak Power for 8478B 432 Combination 17 Pulse Energy and Peak Power for 8478B 431 Combination 17 Drift Precaution 19 Operation with 431A B C or 430 Power Meters 19 Zero Set 20 RF Power Turned Off for Zero Set 20 Unbalanced Operation with Model 431A B C and 430 Power Meters 20 Balanced Operation with Model 431C Power ...

Страница 8: ...ith 431 Power Meter 26 432 Power Detection 27 431 Power Meter Detector 28 4 Maintenance Mechanical Shock 30 Performance Tests 32 SWR Measurement 8GHz 32 SWR Measurement 15 and 18GHz 34 Thermistor Resistive Match Test 35 Troubleshooting 37 Thermistor Compensation 38 Repair and Recalibration 42 A Manual Changes CHANGE A 43 CHANGE B 46 CHANGE C 47 ...

Страница 9: ...g and Service Manual 1 General Information Introduction 10 Specifications 10 Instruments Covered By Manual 10 Incoming Inspection 11 This chapter contains information about initial inspection and overview of the Keysight 8478B Thermistor Mount ...

Страница 10: ...ure a common thermal environment This conductor is thermally insulated from the main body of the mount so the thermal noise or shocks applied externally to the mount such as those from handling the mount manually cannot significantly penetrate to disturb the thermistor This thermal immunity enables the thermistors to be used in the measurement of microwave power down to the microwatt region The 84...

Страница 11: ...nical damage Also check it electrically if the mount was subjected to severe mechanical shock during shipment the match between the thermistors may be affected To check thermistor match proceed as described in Performance Tests on page 32 If any damage is found inform the carrier and your nearest Keysight sales and Service office immediately ...

Страница 12: ...12 Keysight 8478B Thermistor Mount General Information Incoming Inspection 1 ...

Страница 13: ...l 2 Operation Precautions 14 Specifications 15 Drift Precaution 19 Zero Set 20 Mount Calibration 21 Calibration Data Application 22 Thermoelectric Effect 23 This chapter contains information about specifications and operation of the Keysight 8478B Thermistor Mount ...

Страница 14: ...onnecting the 8478B to a 431C or 432 series Power Meter set the MOUNT RES switch to the 200Ω position For Mounts with serial numbers prefixed below 1833A set the MOUNT RES switch to 200Ω BAL 431 or 200Ω 432 When using the 8478B with 431A B or 430 Power Meter use Model 11527A or 11528A Adapter respectively and set MOUNT RES switch to 200Ω position Connecting a 200 ohm mount to a power meter set for...

Страница 15: ... the sum of the squares of the individual uncertainties RSS 2 0 3 0 4 0 5 0 6 0 2 60 2 60 2 70 2 70 2 70 1 60 1 60 1 60 1 60 1 60 7 0 8 0 9 0 10 0 11 0 2 70 3 10 3 30 3 40 3 60 1 60 1 80 1 80 2 00 2 00 12 4 13 0 14 0 15 0 16 0 3 70 3 70 4 00 4 00 4 40 2 20 2 20 2 20 2 50 2 50 17 0 18 0 5 20 5 10 3 20 3 20 Input Impedance 50 ohms Operating Resistance 200 ohms unbalanced Power Range with Model 432 1...

Страница 16: ...WR 16 5 dB return loss 12 4 to 18GHz 0 230 1 6 SWR 12 8 dB return loss Elements Thermally balanced thermistor assembly Thermistor assembly is field adjustable so that full zero set capability can be restored in the event of inadvertent overload RF Connector Stainless steel type N male APC 7 also available see Option 11 below Output Connector Mates with power meter cable operates directly with 432 ...

Страница 17: ... by altering the match between the RF and compensation thermistors resulting in excessive drift or zero shift or cause error in indicated power UNDER NO CIRCUMSTANCES APPLY MORE THAN 30mW AVERAGE POWER TO THE MOUNT The 8478B 431 and 8478B 432 combinations can measure average power up to 10mW ranges 1µ W to 10mW To measure power in excess of 10mW insert a calibrated directional coupler such as one ...

Страница 18: ... 2 3 Maximum Power Meter Reading vs Duty Cycle for Pulses Longer than 250µs Square wave modulation is a special case of pulse modulation and maximum power meter reading versus square wave frequency is illustrated in Figure 2 4 This figure also holds for sinewave modulation Figure 2 4 Maximum Power Meter Reading vs Square and Sine Wave Frequency ...

Страница 19: ...ment connected to it are at nearly the same temperature before making a measurement Let the power sensor warm up at least 30 min before perform COARSE and FINE ZERO Operation with 431A B C or 430 Power Meters If the 8478B is used with a 430 Power Meter a Model 11528A Adapter is required Because the mount is unbalanced a large amount of 10kHz audio bias signal may be coupled from the power meter to...

Страница 20: ...ter may be zeroed with the 8478B disconnected from the RF source and unterminated as explained in the previous section If the RF source presents a low 10kHz impedance of 1k ohm or less a zero setting made with the 8478B disconnected from the RF source and unterminated will not be the proper zero setting for power measurement This error can be eliminated by terminating the 8478B in an impedance tha...

Страница 21: ... in the detection thermistor elements 3 dc to microwave power substitution error Calibration Factor is applied as a correction factor to all measurements made without a tuner When these factors and thermoelectric effect refer to Thermoelectric Effect Error Correction for 8478B 431 Combination on page 23 are taken into consideration the power indicated is the power that would be delivered by the RF...

Страница 22: ...ses in the tuner must be considered Calibration Data Application When the 8478B is used with the Model 431 or 432 Power Meters Calibration Factor or Effective Efficiency corrections can be made by setting a front panel switch With the proper setting the 431 or 432 compensates for the Calibration Factor or Effective Efficiency in the 8478B If the 8478B is used with a power meter other than the 431 ...

Страница 23: ...nt of contact does not have identical thermocouple characteristics and in addition the temperatures at each junction may not be the same These differences cause an incomplete cancellation of the thermoelectric voltages resulting in a voltage that causes a thermoelectric effect error The magnitude of the error is important when making dc substitution measurements on the 0 1mW 0 03mW and 0 01mW rang...

Страница 24: ...ers P1 and P2 This mean power includes a correction for thermoelectric effect error Thermoelectric Error for 8478B 432 Combination The thermoelectric errors present in the 431 are minimized in the 432 since the thermoelectric voltage is negligible compared with the dc voltage used to bias the thermistor bridges Power P1 P2 2 ...

Страница 25: ...78B Thermistor Mount Operating and Service Manual 3 Operating Principles General Operation 26 This chapter contains information about operating principles and general operation of the Keysight 8478B Thermistor Mount ...

Страница 26: ... the dc bridge parallel connected to RF In this manner D appears to the dc bridge in the 432 Power Meter as a 2000 resistance that terminates the coaxial cable into 50Ω Capacitor C1 blocks any dc and audio power that may be present in the incoming signal and passes only RF power Operation with 431 Power Meter The RF detection bridge balance is affected by RF power input to the 8478B and the bridge...

Страница 27: ...or pair D see Figure 3 1 consists of 1 RF signal 2 heat from the environment 3 dc bias The total power supplied to heat thermistor C consists of 1 dc bias 2 heat from the same environment As D and C are matched thermally the total amounts of heat applied to reduce their series resistance equally must be equal Figure 3 1 8478B Connected to a 432A Power Meter ...

Страница 28: ...ure 3 2 consists of 1 RF signal 2 10 kHz bias 3 heat from the environment The total power supplied to heat thermistor pair C consists of 1 dc bias 2 an equal amount of 10kHz bias 3 heat from the same environment As D and C are matched thermally the total amounts of heat applied to reduce their series resistance equally must be equal Figure 3 2 8478B Connected to a 431C Power Meter ...

Страница 29: ...rvice Manual 4 Maintenance Mechanical Shock 30 Performance Tests 32 Troubleshooting 37 Thermistor Compensation 38 Repair and Recalibration 42 This chapter contains information about maintenance and troubleshooting of the Keysight 8478B Thermistor Mount ...

Страница 30: ...e replaced by the ZERO VERNIER control Table 4 1 Recommended Test Equipment Instrument Type Critical Specifications Recommended HP Model Sweep Oscillator Accuracy 1 full scale for all RF Units Leveling Capabilities Frequency Range 8GHz to 18GHz 8690A 8694A 8695A SWR Meter Sensitivity 0 15μV for full scale deflection Accuracy 0 05 dB 10 dB step Range 70 dB in 10 dB steps 415E Directional Detector F...

Страница 31: ... Digital Voltmeter Input Impedance 10 Megohm Resolution 4 significant digits Accuracy 0 05 3466A Power Supply Output Voltage 29 Vdc 6217A Cables 1 Coax Type N connectors 2 BNC BNC male connectors 11500A 10502A Battery Voltage 2 0 to 3 1 Vdc See Thermistor ResistiveMatch Test Resistor 2 2K ohm 5 0698 4262 Table 4 1 Recommended Test Equipment Instrument Type Critical Specifications Recommended HP Mo...

Страница 32: ...uipment as shown in Figure 4 1 Make sure all connections are secured tightly 2 Set the instrument controls as follows SPECIFICATION SWR at 8GHz 1 35 1 DESCRIPTION SWR measurement using standard SWR measurement techniques 8690B 8692A SWEEP SELECTOR CW FUNCTION START STOP ALC IN AMPLITUDE MOD INT SQ WAVE START CW 8GHz POWER LEVEL Adjust to maximum with the UNLEVELED light off ...

Страница 33: ...rols to set the SWR meter reading to 1 0 SWR on the 415E meter 7 Move the 415E RANGE DB EXPAND switch to 0 Adjust the GAIN VERNIER controls for a 1 0 SWR reading 8 Move the 809C carriage adjustment for a minimum SWR reading on the 415E The SWR at 8GHz should be less than 1 35 1 HP 415E 8GHz _________ 1 35 1 9 Repeat steps 1 through 8 to determine the SWR at 12 4GHz The SWR at 12 4GHz should be les...

Страница 34: ...ents shown in Figure 4 2 2 Repeat steps 1 through 8 to determine the SWR at 15GHz The SWR at 15GHz should be 1 6 1 maximum HP 415E 15GHz ________l 6 1 maximum 3 Move the 8690B START CW control to 18GHz Repeat steps 1 through 8 to determine the SWR at 18GHz The SWR should be 1 6 1 maximum HP 415E 18GHz ________1 6 1 maximum SPECIFICATION SWR at 15 and 18GHz 1 6 1 maximum DESCRIPTION SWR measurement...

Страница 35: ...ge drop across each thermistor is measured to check thermistor match EQUIPMENT REQUIRED POWER SUPPLY HP 6217 A Power Supply DIGITAL VOLTMETER HP 3466A Digital Voltmeter BATTERY See Note RESISTOR 2 2K 5 HP 0698 4262 The small battery connected in series with the DVM is in opposition to the power supply The value of this reverse voltage should be selected to provide voltmeter resolution of 0 001 vol...

Страница 36: ...in 4 of the thermistor mount jack 3 Record the DVM Reading 3466A_____________ 4 Connect point A to pin 1 of the thermistor mount jack and point B to pin 2 of the thermistor mount jack 5 Record the DVM Reading 3466A_____________ 6 Thermistor match 0 5Ω is satisfactory if the two readings do not differ by more than 0 03 volt Difference ______________ 0 03 volt 6217A METER RANGE 30 VDC VOLTAGE ADJUST...

Страница 37: ...act at the mount connector Poor contact will show up as intermittence or a great deal of noise visible on the power meter when the cable is gently flexed near the connector end To troubleshoot a damaged mount proceed as follows 1 Connect mount to Model 432 2 Set 3 Rotate COARSE ZERO from one limit to the other If meter remains pegged upscale the thermistor elements have been damaged However it may...

Страница 38: ...te measurements The Effective Efficiency and Calibration Factor imprinted on the label will no longer be valid refer to Repair and Recalibration There are two adjusting screws which permit re compensation within limits Figure 4 4 Printed Circuit Board Refer to Figure 4 5 and proceed as follows 1 Remove the three screws A 2 Slide terminal shield away from instrument 3 Plug connector J2 into Model 4...

Страница 39: ... Thermistor damage can easily occur if the screws are forced in any way If there is a sudden jump in meter indication when advancing either screw back off 1 8 turn and do not advance that screw further Check resistance as in If meter remains pegged downscale measure resistance between pins 1 and 2 and pins 3 and 4 The resistance should measure between 1000 and 5000 ohms An open or shorted reading ...

Страница 40: ...40 Keysight 8478B Thermistor Mount Maintenance Thermistor Compensation 4 Figure 4 5 Thermistor Mount Assembly ...

Страница 41: ...instrument is now operative The compensating screws are in very close proximity to the thermistors themselves Thermistor damage can easily occur if the screws are forced in any way If there is a sudden jump in meter indication when advancing either screw back off 1 8 turn and do not advance that screw further Check resistance as in If meter remains pegged downscale measure resistance between pins ...

Страница 42: ... Recalibration 4 Repair and Recalibration If repair or recalibration of the mount is desired the instrument may be returned to Keysight for repair and recalibration or for recalibration only Arrangements can be made with any Keysight Sales and Service office ...

Страница 43: ...red If the 8478B is used with a 430 Power Meter a Model 11528A Adapter is required The use of an adapter breaks the balanced circuit and an unbalanced circuit results In this unbalanced condition a large amount of IO kHz audio bias signal may be coupled from the power meter to the RF source output 3 Delete first sentence of Because the mount is unbalanced a large amount of 10kHz audio bias signal ...

Страница 44: ...age 19 4 Change the section title of Unbalanced Operation with Model 431A B C and 430 Power Meters on page 20 to 8478B with Model 43IA B and 430 PowerMeters And add the following to the next paragraph The Model 11527A or 11528A Adapter is required when operating the 8478B with 43IA B or 430 Power Meters respectively 5 Replace Figure 3 1 and Figure 3 2 with Figure A 2 and Figure A 2 respectively Fi...

Страница 45: ...8B Operation and Service Manual 45 Manual Changes CHANGE A Figure A 2 84788 Connected to a 431 C Power Meter P 0 Change A 6 Replace Figure 4 4 on page 38 to Figure A 3 Figure A 3 Printed Circuit Board P 0 CHANGE A ...

Страница 46: ...anual Manual Changes CHANGE B CHANGE B 1 Replace Figure 3 1 and Figure 3 2 with Figure A 4 and Figure A 5 respectively Figure A 4 84788 Connected to a 432A Power Meter P 0 Change B Figure A 5 84788 Connected to a 431 C Power Meter P 0 Change B ...

Страница 47: ...nges CHANGE C 6 For Figure 4 4 on page 38 Return C6 as it is shown in the manual it was deleted by CHANGE C CHANGE C 1 Replace Figure 3 1 and Figure 3 2 with Figure A 6 and Figure A 7 respectively Figure A 6 8478B Connected to a 432A Power Meter P 0 Change C ...

Страница 48: ... 8478B Operation and Service Manual Manual Changes CHANGE C Figure A 7 84788 Connected to a 431 C Power Meter P 0 Change C 2 Replace Figure 4 4 on page 38 to Figure A 8 Figure A 8 Printed Circuit Board P 0 Change C ...

Страница 49: ...This information is subject to change without notice Keysight Technologies 1981 2018 Edition 3 March 2018 08478 90015 08478 90015 www keysight com ...

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