Keysight 478A Thermistor
Mount
Operating and
Service Manual
Notices
CAUTION
WARNING
Copyright Notice
© Keysight Technologies 2008 - 2020
No part of this manual may be repro-
duced in any form or by any means
(including electronic storage and
retrieval or translation into a foreign
language) without prior agreement and
written consent from Keysight Technologies as governed by United States and
international copyright laws.
Manual Part Number
00478-90021
Edition
Edition 3, January 23, 2020
Printed in:
Printed in Malaysia
Published by:
Keysight Technologies
Bayan Lepas Free Industrial Zone,
11900 Penang, Malaysia
Technology Licenses
The hardware and/or software
described in this document are furnished under a license and may be
used or copied only in accordance with
the terms of such license.
Declaration of Conformity
Declarations of Conformity for this
product and for other Keysight products may be downloaded from the
Web. Go to http://www.keysight.com/
go/conformity. You can then search by
product number to find the latest Declaration of Conformity.
U.S. Government Rights
The Software is “commercial computer
software,” as defined by Federal Acquisition Regulation (“FAR”) 2.101. Pursuant to FAR 12.212 and 27.405-3 and
Department of Defense FAR Supplement (“DFARS”) 227.7202, the U.S.
government acquires commercial computer software under the same terms
by which the software is customarily
provided to the public. Accordingly,
Keysight provides the Software to U.S.
government customers under its standard commercial license, which is
embodied in its End User License
Agreement (EULA), a copy of which can
be found at http://www.keysight.com/
find/sweula. The license set forth in the
EULA represents the exclusive authority
by which the U.S. government may use,
modify, distribute, or disclose the Software. The EULA and the license set
forth therein, does not require or permit, among other things, that Keysight:
(1) Furnish technical information
related to commercial computer software or commercial computer software
documentation that is not customarily
provided to the public; or (2) Relinquish
to, or otherwise provide, the government rights in excess of these rights
customarily 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 the DFARS and are
set forth specifically in writing elsewhere in the EULA. Keysight shall be
under no obligation to update, revise or
otherwise modify the Software. With
respect to any technical data as
defined by FAR 2.101, pursuant to FAR
12.211 and 27.404.2 and DFARS
227.7102, the U.S. government
acquires no greater than Limited Rights
as defined in FAR 27.401 or DFAR
227.7103-5 (c), as applicable in any
technical data.
Warranty
THE MATERIAL CONTAINED IN THIS
DOCUMENT IS PROVIDED “AS IS,”
AND IS SUBJECT TO BEING
CHANGED, WITHOUT NOTICE, IN
FUTURE EDITIONS. FURTHER, TO THE
MAXIMUM EXTENT PERMITTED BY
APPLICABLE LAW, KEYSIGHT DISCLAIMS ALL WARRANTIES, EITHER
EXPRESS OR IMPLIED, WITH REGARD
TO THIS MANUAL AND ANY INFORMATION CONTAINED HEREIN, INCLUDING BUT NOT LIMITED TO THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE. KEYSIGHT
SHALL NOT BE LIABLE FOR ERRORS
OR FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES IN CONNECTION
WITH THE FURNISHING, USE, OR
PERFORMANCE OF THIS DOCUMENT
OR OF 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.
Safety Information
A CAUTION notice denotes a hazard. It
calls attention to an operating procedure, practice, or the like that, if not
correctly performed or adhered to,
could result in damage to the product
or loss of important data. Do not proceed beyond a CAUTION notice until
the indicated conditions are fully
understood and met.
A WARNING notice denotes a hazard. It
calls attention to an operating procedure, practice, or the like that, if not
correctly performed or adhered to,
could result in personal injury or death.
Do not proceed beyond a WARNING
notice until the indicated conditions are
fully understood and met.
2 Keysight 478A Operating and Service Manual
Certification
Keysight Technologies certifies that this product met its published specifications
at the time of shipment. Keysight further certifies that its calibration
measurements are traceable to the United States National Institute of Standard
and Technology (formerly National Bureau of Standards), to the extent allowed by
that organization’s calibration facility, and to the calibration facilities of other
International Standards Organization members.
Warranty Information
This Keysight Technologies instrument product is warranted against defects in
material and workmanship for a period of one year from date of shipment. During
the warranty period, Keysight Technologies will at its option, either repair or
replace products which prove to be defective. For warranty service or repair, this
product must be returned to a service facility designated by Keysight
Technologies. Buyer shall prepay shipping charges to Keysight Technologies and
Keysight Technologies shall pay shipping charges, duties, and taxes for products
returned to Keysight Technologies from another country. Keysight Technologies
warrants that its software and firmware designated by Keysight Technologies for
use with an instrument will execute its programming instructions when properly
installed on that instrument. Keysight Technologies does not warrant that the
operation of the instrument, or firmware will be uninterrupted or error free.
Limitation of Warranty
The foregoing warranty shall not apply to defects resulting from improper or
inadequate maintenance by Buyer, Buyer-supplied software or interfacing,
unauthorized modification or misuse, operation outside of the environmental
specifications for the product, or improper site preparation or maintenance. NO
OTHER WARRANTY IS EXPRESSED OR IMPLIED. KEYSIGHT TECHNOLOGIES
SPECIFICALLY DISCLAIMS THE IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE.
Keysight 478A Operating and Service Manual 3
Exclusive Remedies
CAUTION
THE REMEDIES PROVIDED HEREIN ARE BUYER’S SOLE AND EXCLUSIVE
REMEDIES. KEYSIGHT TECHNOLOGIES SHALL NOT BE LIABLE FOR ANY DIRECT,
INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WHETHER
BASED ON CONTRACT, TORT, OR ANY OTHER LEGAL THEORY.
Safety Considerations
Read the information below before using this instrument.
The following general safety precautions must be observed during all phases of
operation, service, and repair of this instrument. Failure to comply with these
precautions or with specific warnings elsewhere in this manual violates safety
standards for design, manufacture, and intended use of the instrument. Keysight
Technologies assumes no liability for the customer’s failure to comply with these
requirements.
– This product is designed for use in Installation Category II and Pollution
Degree 2.
– This instrument has been designed and tested in accordance with IEC
Publication 348, Safety Requirements for Electronic Measuring
Apparatus, and has been supplied in a safe condition. The instruction
documentation contains information and warnings which must be
followed by the user to ensure safe operation and to maintain the
instrument in a safe condition.
– “CSA” The CSA mark is a registered trademark of the Canadian Standards
Association.
– Notice for Germany: Noise Declaration LpA < 70 dB am Arbeitsplatz
(operator position) normaler Betrieb (normal position) nach DIN 45635 T.
19 (per ISO 7779).
4 Keysight 478A Operating and Service Manual
Waste Electrical and Electronic Equipment (WEEE) Directive
This instrument complies with the WEEE Directive marking requirement. This
affixed product label indicates that you must not discard this electrical or
electronic product in domestic household 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.
To return this unwanted instrument, contact your nearest Keysight Service Center,
or visit http://about.keysight.com/en/companyinfo/environment/takeback.shtml
for more information.
Sales and Technical Support
To contact Keysight for sales and technical support, refer to the support links on
the following Keysight websites:
– www.keysight.com/find/478a
(product-specific information and support, software and
documentation updates)
– www.keysight.com/find/assist
(worldwide contact information for repair and service)
Keysight 478A Operating and Service Manual 5
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6 Keysight 478A Operating and Service Manual
Table of Contents
Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Limitation of Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Exclusive Remedies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Waste Electrical and Electronic Equipment (WEEE) Directive . . . . . . . . 5
Product category: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Sales and Technical Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
1 General Information
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Instruments Covered by Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Incoming Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
2Operation
Biasing Thermistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Maximum Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Average Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Pulse Energy and Peak Power for 478A/432 Combination . . . . . . .19
Pulse Energy and Peak Power for 478A/431 Combination . . . . . . .20
Zero Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
RF Power Turned Off for Zero-Set . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Thermistor Mount Disconnected for Zero Set . . . . . . . . . . . . . . . . . .23
Thermoelectric Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Thermoelectric Effect Error Correction for 478A / 431
Thermoelectric Error for 478A / 432 Combination . . . . . . . . . . . . . .27
Circuit Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
431 Power Meter Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Combination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Keysight 478A Operating and Service Manual 7
432 Power Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3 Specifications and Characteristics
4Maintenance
Mechanical Shock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Check on Thermistor Match . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Thermistor Assembly Replacement Procedure . . . . . . . . . . . . . . . . 39
Removal Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Installation Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Recalibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
AAppendix A
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
How to Use This Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Manual Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Change A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Change B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
8 Keysight 478A Operating and Service Manual
List of Figures
Figure 1-1 Keysight Model 478A Thermistor Mount . . . . . . . . . . .14
Figure 2-1 Maximum Power Meter Reading vs PRF for Pulses
Figure 2-2 Maximum Power Meter Reading vs Duty Cycle for
Figure 2-3 Maximum Power Meter Reading vs Square and Sine-
Figure 2-4 Source Impedance Shunting One RF Thermistor
Figure 2-5 Schematic Diagram of a Model 478A Thermistor
Figure 4-1 Schematic Diagram of a Model 478A Thermistor
Figure 4-2 Check on Model 478A Thermistor Resistance Match . 35
Figure 4-3 Thermistor Compensation . . . . . . . . . . . . . . . . . . . . . .37
Figure 4-4 Model 478A Thermistor Mount Assembly . . . . . . . . . . 41
Figure 4-5 Keysight Model 478A Printed Circuit Assy Wiring . . . .42
Figure A-1 Schematic Diagram of a Model 478A Thermistor
Figure A-2 Schematic Diagram of a Model 478A Thermistor
Figure A-3 Check on Model 478A Thermistor Resistance Match
Figure A-4 Source Impedance Shunting One RF Thermistor
Figure A-5 Schematic Diagram of a Model 478A Thermistor
Figure A-6 Schematic Diagram of a Model 478A Thermistor
Figure A-7 Thermistor Compensation (P/O Change B) . . . . . . . . .53
Shorter than 250 μs . . . . . . . . . . . . . . . . . . . . . . . .19
Pulses Longer than 250 ms . . . . . . . . . . . . . . . . . . .20
Wave Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Mount . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Mount when Connected to a 431 Power Meter . . .25
Mount when Connected to a 432 Power Meter . . .34
Mount when Connected to a 431 Power Meter.
(P/O Change A) . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
Mount when Connected to a 432 Power Meter.
(P/O Change A) . . . . . . . . . . . . . . . . . . . . . . . . . . . .48
(P/O Change A) . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
Mount (P/O Change B) . . . . . . . . . . . . . . . . . . . . . .50
Mount when Connected to a 431 Power Meter.
(P/O Change B) . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Mount when Connected to a 432 Power Meter.
(P/O Change B) . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Keysight 478A Operating and Service Manual 9
Figure A-8 Model 478A Thermistor Mount Assembly
(P/O Change B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Figure A-9 Keysight Model 478A Printed Circuit Assembly Wiring
(P/O Change B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
10 Keysight 478A Operating and Service Manual
List of Tables
Table 2-1 Methods of Switching Off RF Output of Various Keysight
Signal Generators . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 4-1 Replaceable Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Table A-1 Manual Changes by Serial Number . . . . . . . . . . . . . . .46
Keysight 478A Operating and Service Manual 11
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12 Keysight 478A Operating and Service Manual
Keysight 478A Thermistor Mount
Operating and Service Manual
1 General Information
Introduction 15
13
1 General Information
Figure 1-1 Keysight Model 478A Thermistor Mount
14 Keysight 478A Operating and Service Manual
Introduction
General Information 1
The Keysight model 478A coaxial thermistor mount is designed for use with
Keysight model 431 and 432 power meters to measure microwave power from 1
μw to 10 mw. Design of the mount minimizes adverse effects from environmental
temperature changes during measurement. For increased measurement accuracy,
Effective Efficiency and Calibration Factor are measured for each mount, and at
selected frequencies across the operating range; the results are marked on the
label of the instrument (see “Mount Calibration Data” in Chapter 3, "Specifications
and Characteristics"). The model 478A can be used over the 10-HMZ to 10-GHz
frequency range. Throughout the range, the mount terminates the coaxial input in
a 50 Ω impedance, and has a SWR of not more than 1.75 without external tuning.
Each mount contains two series pairs of thermistors, which are matched to cancel
the effects of drift with ambient temperature change. Thermal stability is
accomplished by mounting the leads of all four thermistors on a common thermal
conductor to ensure 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 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.
Instruments Covered by Manual
Instruments with serial numbers 79401 and below are documented directly by this
manual. Some instruments with serial numbers lower than 79401 may be
documented in Appendix A; other instruments with serial numbers higher than
79401 may be documented in a MANUAL CHANGES supplement.
Incoming Inspection
Inspect the model 478A upon receipt for mechanical damage. Also check it
electrically; if the mount was subjected to severe mechanical shock during
shipment, the match between thermistors may be affected. To check the
thermistor match, proceed as described in “Check on Thermistor Match” on
page 34.
If any damage is found, inform the carrier and your nearest Keysight Sales and
Service Office immediately.
Keysight 478A Operating and Service Manual 15
1 General Information
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16 Keysight 478A Operating and Service Manual
Keysight 478A Thermistor Mount
Operating and Service Manual
2 Operation
Biasing Thermistors 18
17
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