Manual Part Number:
Revisi on :
Print Date:
September 2000
Series 8540C
Universal Power Meters
Operation & Maintenance Manual
30280
J
................................................................................................ Certified Product
ISO 9001
...................................................................................Certified Process
Registrar: BSI, Certification No. FM 34226
Registered 04 June 1996
Amended on 01 March 2000
Giga-tronics Incorporated
4650 Norris Canyon Road
925.328.4650 or 800.726.4442 ❖ 925.328.4700 (Fax)
800.444.2878 (Customer Service)
San Ramon, California 94583
❖
❖ 925.328.4702 (Fax)
www.gigatronics.com
All technical data and specifications in this manual are subject to change without prior notice and do
not represent a commitment on the part of Giga-tronics Incorporated.
© 2000 Giga-tronics Incorporated. All rights reserved.
Printed in the USA
WARRANTY
Giga-tronics Series 8540C instruments are
warranted against defective materials and
workmanship for one years from date of shipment.
Giga-tronics will at its option repair or replace
products that are proven defective during the
warranty period. This warranty DOES NOT cover
damage resulting from improper use, nor
workmanship other than Giga-tronics service.
There is no implied warranty of fitness for a
particular purpose, nor is Giga-tronics liable for any
consequential damages. Specification and price
change privileges are reserved by Giga-tronics.
Model Numbers
The series 8540C has two model numbers: The single-channel Model 8541C and the dual-channel Model
8542C. Apart from the number of sensors they support, the two models are identical. Both models are referred
to in this manual by the general term 8540C, except where it is necessary to make a distinction between the
models.
Application of Council Directive(s)
Standard(s) to which Conformity is Declared:
89/336/EEC and 73/23/EEC EMC Directive and Low Voltage Directive
EN50081-1 (1992) EMC – Emissions
EN61010-1 (1993) Electrical Safety
Manufacturer’s Name: Manufacturer’s Address:
Giga-tronics Incorporated
4650 Norris Canyon Road
San Ramon, California 94583
USA
Type of Equipment: Model Series Number:
Universal Power Meter 8540C
Model Number(s) in Series:
8541B
8542B
8541C
8542C
With Sensor Series 803XXA, 804XXA, 806XXA
I, the undersigned, hereby declare that the equipment specified above conforms to
the above Directive(s) and Standard(s).
Thomas A. Kramer Director of Quality Assurance
(Full Name) (Signature) (Position)
San Ramon, California October 30, 1999
(Place) (Date)
QUF06001 10/30/99
About This Manual ...................................................................................................... xi
Conventions .............................................................................................................. xiii
Record of Manual Changes ......................................................................................... xv
Special Configurations ...............................................................................................xvii
1
Introduction
1.1 Description ....................................................................................................1-1
Table of Contents
1.1.1 Features .......................................................................................1-1
1.1.2 Performance Characteristics .........................................................1-2
1.1.3 Weight and Dimensions ...............................................................1-2
1.1.4 Power Requirements ....................................................................1-2
1.1.5 Environmental Requirements ........................................................1-2
1.1.6 Items Furnished .... ........... ............ ........... ........... ........... ........... .....1-2
1.1.7 Items Required .............................................................................1-2
1.1.8 Tools and Test Equipment ............................................................1-2
1.1.9 Cooling .............. ...........................................................................1-2
1.1.10 Cleaning .......................................................................................1-3
1.1.11 Installation and Preparation for Use ..............................................1-3
1.1.12 Receiving Inspection .....................................................................1-3
1.1.13 Preparation for Reshipment ......... ........... ........... ........... ........... .....1-3
1.2 Safety Precautions ........................................................................................1-4
1.2.1 Line Voltage and Fuse Selection ...................................................1-4
1.2.2 Power Sensor Precautions ............................................................1-5
1.3 8540C System Specifications ........................................................................1-6
1.3.1 Power Meter .................................................................................1-6
1.3.2 Accuracy ......................................................................................1-6
1.3.3 Uncertainty Due to Instrument Linearity & Zero Set vs. Noise .......1-7
1.3.4 Measurement Rates .....................................................................1-7
1.3.5 Remote Operation ...................................... ............ ........... ........... .1-8
1.3.6 Fast Buffered Mode Controls ........................................................1-8
1.3.7 Meter Function .............................................................................1-8
1.3.8 Remote Inputs/Outputs .................................................................1-8
1.3.9 General Specifications ..................................................................1-9
1.3.10 Accessories Included ..................................... ........... ........... ......... 1-9
1.3.11 Options ........................................................................................1-9
1.3.12 Power Sensors .............................................................................1-9
2
Front Panel Operation
2.1 Introduction ..................................................................................................2-1
2.2 The Front Panel .............................................................................................2-1
2.2.1 Calib rator ....... ........... ........... .........................................................2-2
2.2.2 Display Window ...........................................................................2-2
2.2.3 LEDs .............................................................................................2-2
2.2.4 Power ...........................................................................................2-2
2.2.5 Front Panel Keys ...........................................................................2-2
2.2.6 Sensor Inputs ...............................................................................2-4
2.3 The Rear Panel ..............................................................................................2-5
2.3.1 Inputs & O utputs ..........................................................................2-5
Manual 30280, Rev. J, September 2000 i
Series 8540C Universal Power Meters
2.4 Configuring the 8540C ..................................................................................2-6
2.4.1 How the Menus Work ..................................................................2-6
2.4.2 Menu Structure ............................................................................2-7
2.4.3 Password Protection .....................................................................2-9
2.5 The Submenus ............................................................................................2-10
2.5.1 A, B, A/B, ..., Off .........................................................................2-10
2.5.2 Meas Setup ........ ........................................................................2-10
2.5.3 Sensor Setup ..............................................................................2-12
2.5.4 RF Power On/Off .........................................................................2-13
2.5.5 Config .........................................................................................2-13
2.5.6 Service ........................................................................................2-14
2.5.7 Save Setup .................................................................................2-14
2.6 Measurement Guide ....................................................................................2-15
2.6.1 Using the Power Sweep Calibrator .............. ........... ........... ......... 2-15
2.6.2 806XX Sensor Operation .............................................................2-15
2.6.3 Sensor Calibration ......................................................................2-15
2.6.4 Zeroing at Low Power Levels ......................................................2-16
2.6.5 Measuring Source Output Power ................................................2-17
2.6.6 Using the Peaking Meter .............................................................2-18
2.6.7 High Power Level Measurements ...............................................2-18
2.6.8 Modulated Measurement Modes ................................................2-18
2.6.9 Measurement Collection Modes .................................................2-21
2.6.10 Mode Restrictions .......................................................................2-23
2.6.11 When to use CW, MAP and BAP ............. ........... ............ ........... .2-23
2.6.12 Multi-Tone Tests ........................................................................2-23
2.6.13 Peak Hold ...................................................................................2-24
2.6.14 Crest Factor .... ............ ........... ........... ........... ........... ........... .........2-25
2.6.15 Burst Signal Measurements .......................................................2-26
2.6.16 Burst Start Exclude, Burst End Exclude ......................................2-27
2.6.17 Burst Dropout .............................................................................2-28
2.6.18 Optimizing Measurement Speed .................................................2-29
2.6.19 Peak Power Measurements ........................................................2-30
2.6.20 Measuring an Attenuator (Single Channel Method) ............... .....2-30
2.6.21 Improving Accuracy ....................................................................2-31
2.6.22 Performance Verification ......................................... ........... ......... 2-32
2.6.23 Sources of Error ..........................................................................2-33
2.6.4.1 Low Level Performance Check................................... 2-16
3
Remote Operation
3.1 Introduction...................................................................................................3-1
3.1.1 Sending Commands to the 8540C ........... ........... ............ ..............3-1
3.1.2 Clear Device ........................................................................... .......3-2
3.1.3 Clear Interface ..............................................................................3-2
3.1.4 Local and Remote Control .............................................................3-2
3.1.5 Sensor Selection and Calibrat ion ..................................................3-2
3.1.6 Polling ................................... ........... ........... ........... ........... ........... 3-3
3.1.7 Data Output Formats (Standard Measurement Collection Mode) ..3-4
3.1.8 Data Output Formats (Fast Meas urement Collection Modes) ........3-4
3.1.9 Power-On Default Conditions .......................................................3-4
3.2 Command Syntax ..........................................................................................3-5
3.2.1 Functions .....................................................................................3-5
3.2.2 Prefixes ........................................................................................3-5
3.2.3 Variables ......... ............ ..................................................................3-6
3.2.4 Suffixes ........................................................................................3-6
3.2.5 Separators ....................................................................................3-7
3.2.6 Command Format Illustrations ......................................................3-7
ii Manual 30280, Rev. J, September 2000
Preface
3.3 Series 8540C Command Codes .....................................................................3-8
3.3.1 IEEE 488.2 Common Commands ..................................................3-8
3.3.2 8540C Function Codes .................................................................3-9
3.3.3 HP437 Emulation GPIB Command Set ........................................3-11
3.3.4 HP438 Emulation GPIB Command Set ........................................3-13
3.3.5 HP436 Emulation GBIP Command Set ........................................3-15
3.4 Analog Output.............................................................................................3-16
3.4.1 Standard Output ......................................................................... 3-16
3.4.2 Optional Speed Count .................................................................3-17
3.5 Averaging....................................................................................................3-18
3.5.1 Auto Averaging ..........................................................................3-18
3.5.2 Manual Averaging ...................................................................... 3-19
3.6 Cal Factors .................................................................................................. 3-20
3.7 Calibration ...................................................................................................3-21
3.8 Calibrator Source .........................................................................................3-22
3.9 Crest Factor..... ........... ........... ........... ............ ........... ....................................3-23
3.9.1 Enabling the Crest Factor Fea ture ............................................... 3-23
3.9.2 Reading t he Crest Factor Value ...................................................3-23
3.10 Display Control ............................................................................................ 3-24
3.11 Duty Cycle Commands ................................................................................ 3-25
3.11.1 Activating or Deactivating a Duty Cycle ............................... ....... 3-25
3.11.2 Specifying a Duty Cycle .............................................................. 3-25
3.11.3 Reading Duty Cycle Status .......... ........... ....................................3-25
3.12 EEPROM .....................................................................................................3-26
3.13 Frequency .............. ............ ........... ........... ........... ........... ........... ........... ....... 3-27
3.14 Instrument Identification ............................................................................. 3-28
3.15 Learn Modes ....... ........... ........... ........... ........... ........... ............ ........... .......... 3-29
3.15.1 Learn Mode #1 ........................................................................... 3-30
3.15.2 Learn Mode #2 ........................................................................... 3-31
3.16 Limits ... ........... ........... ........... ........... ............ ........... ........... ........... ........... ...3-32
3.16.1 Setting Limits .............................................................................3-32
3.16.2 Activating Limits ... ........... ............ ........... ........... ........... ........... ...3-32
3.16.3 Measuring with Limits ................................................................3-33
3.17 Measurement Collection Modes (Standard) .................................................3-34
3.17.1 Measurement Triggering ............................................................3-34
3.17.2 Group Execute Trigger ................................................................3-35
3.18 Measurement Collection Modes (Fast) ........................................................3-36
3.18.1 General .......................................................................................3-36
3.18.2 Data Output Formats fo r Fast Modes .........................................3-38
3.18.3 Fast Buffered Mode ...... ........... ........... ........... ........... ........... ....... 3-39
3.18.4 Swift Mode .................................................................................3-41
3.18.5 Fast Modula ted Mode ................................................................ 3-43
Manual 30280, Rev. J, September 2000 iii
Series 8540C Universal Power Meters
3.19 Measurement Mode Commands .................................................................3-44
3.19.1 CW Mode ...................................................................................3-44
3.19.2 MAP Mode .................................................................................3-44
3.19.3 PAP Mode ..................................................................................3-45
3.19.4 BAP Mode ... ........... ........... ........... ..............................................3-45
3.19.5 Peak Mode ......... ........... .............................................................3-45
3.19.6 Measurement Mode Query ........... ........... ........... ............ ............3-46
3.20 Advanced Features......................................................................................3-47
3.20.1 Burst Start Exclude .....................................................................3-47
3.20.2 Burst End Exclude ......................................................................3-47
3.20.3 Burst Dropout Tolerance .............................................................3-48
3.21 Min/Max P ower Value ..... ............ ........... ........... ........... ........... ........... ......... 3-49
3.21.1 Enabling the Min/Max Feature ....................................................3-49
3.21.2 Reading the Min/Max Values ................ ........... ...........................3-49
3.22 Offset Commands .......................................................................................3-51
3.22.1 Enabling/Disabling an Offset .......................................................3-51
3.22.2 Setting an O ffset Value ...............................................................3-51
3.22.3 Measured Offset Entry ................................................................3-52
3.23 Peak Hold ....................................................................................................3-53
3.23.1 Enabling the Peak Hold Feature ................... ........... ........... ......... 3-53
3.23.2 Reading the Peak Ho ld Value ......................................................3-53
3.24 Peak Power Sensor Commands (80350A Series) .............. ........... ........... .....3-54
3.24.1 Setting the Trigger Mode & Trigger Level ................... ........... .....3-54
3.24.2 Setting the Delay ........................................................................3-54
3.24.3 Setting the Delay Offset ..............................................................3-55
3.24.4 Reading Values ....... ........... ........... ........... ...................................3-55
3.25 Peak Power Sensor Commands (80340A Series) .............. ........... ........... .....3-56
3.26 Preset.............................. ............ ........... ........... ........... ........... ........... .........3-57
3.27 Relative Measurements ...................... ........... ........... ........... ............ ........... .3-58
3.28 Resolution ......... ........... ........... ........... ........... ........... ........... ............ ........... .3-59
3.29 Sensor Selection ..........................................................................................3-59
3.30 Status .........................................................................................................3-60
3.30.1 Status Byte Message ..................................................................3-60
3.30.2 Event Status Register .................................................................3-61
3.30.3 Status Message ..........................................................................3-62
3.31 Store and Recall ..........................................................................................3-66
3.31.1 Saving a Configuration .......................................................... .....3-66
3.31.2 Retrieving a Configuration ..........................................................3-66
3.32 Units ...........................................................................................................3-67
3.33 V
F Feature ............................................................................................3-68
PROP
3.33.1 Enabling & Disabling V
3.33.2 Configuring V
F .....................................................................3-68
PROP
F ......................................................3-68
PROP
3.34 Zeroing........................................................................................................3-69
iv Manual 30280, Rev. J, September 2000
4
Theory of Operation
4.1 General..........................................................................................................4-1
4.2 CPU PC Board (A1) ........................................................................................4-2
4.2.1 Power Supply ...............................................................................4-2
4.2.2 Battery Back-Up ...........................................................................4-2
4.2.3 Circuit Description ........................................................................4-3
4.3 Analog PC Board (A2)....................................................................................4-5
4.3.1 Circuit Description ........................................................................4-5
4.3.2 Analog Board Control Lines ................ ........... ...............................4-7
4.4 Calibrator Module......................................... ........... ........... ........... ........... .....4-9
4.4.1 General .......................................................................................4-10
4.4.2 50 MHz Oscillator . ........... ............ ........... ........... ........... ........... ...4-10
4.4.3 RF Output .. ........... ........... ............ ........... ........... .........................4-11
4.4.4 Oven ........................................................................................... 4-11
4.4.5 Thermistor Bridge .......................................................................4-11
4.4.6 Track & Hold and DAC .................................................. ........... ...4-11
4.4.7 Correction Thermistor Circuit ... ...................................................4-11
4.4.8 Calibrator NVRAM Control Ci rcuit ........... ........... ........... ........... ...4-12
4.4.9 Digital Control Circuit ...... ............ ........... ........... ........... ........... ...4-12
Preface
4.5 Front Panel PC Assembly (A3) ....... ........... ........... ........... ........... ........... ....... 4-13
5
Calibration & Testing
5.1 Introduction ..................................................................................................5-1
5.2 Calibration Procedure ....................................................................................5-1
5.2.1 Equipment Required .....................................................................5-1
5.2.2 Calibrator Output Power .. ............ ........... ........... ........... ........... .....5-2
5.2.3 Power Supply Voltage Checks ............ ........... ........... ........... .........5-3
5.2.4 Calib rator Voltages .......................................................................5-4
5.2.5 Calibrator Frequency Check ..........................................................5-4
5.2.6 GPIB Test Functions .....................................................................5-4
5.3 Performance Verification Tests ......................................................................5-6
5.3.1 Equipment Required .....................................................................5-6
5.3.2 Calibrator Output Power Reference Level ......................................5-7
5.3.3 Instrument Plus Power Sensor Linearit y .......................................5-9
5.3.4 GPIB Port Check .........................................................................5-11
6
Maintenance
6.1 Periodic Maintenance ....................................................................................6-1
6.1.1 Testing & Calibration ....................................................................6-1
6.1.2 Cleaning .... ........... ........... ............ ........... ........... ........... ........... .....6-1
6.1.3 Lithium Battery .............................................................................6-1
6.2 Troubleshooting ............................................................................................6-3
6.2.1 General Failure ..... ........... ............ ........... ......................................6-3
6.2.2 Channel-Specific Failure in the 8542C ..........................................6-3
6.2.3 Functional Failures .......................................................................6-3
Manual 30280, Rev. J, September 2000 v
Series 8540C Universal Power Meters
7
Parts Lists
7.1 Introduction...................................................................................................7-1
7.2 Parts Lists for Series 8540C Universal Power Meters ....................................7-1
8541C SINGLE CHANNEL POWER METER, Rev. C .. ........... ........... .......... 7-1
30160 8541C CHASSIS ASSY, Rev. L ................................................... .. 7-2
21331 FRONT PANEL ASSY, 8541C, Rev. B ........................................... 7-3
8542C DUAL CHANNEL POWER METER, Rev. C..................................... 7-3
30172 CHASSIS ASSY, 8542C, Rev. M ................................................... 7-4
21332 FRONT PANEL ASSY, 8542B, Rev. C (A1) .................................... 7-5
21693 CPU PCB ASSY, 854xB, Rev. J (A1) ............. ........... ..................... 7-5
21693-A00 PCB ASSY PREWARE, CPU, Rev. H (A1) ................................ 7-6
30164 8541C ANALOG PC ASSY, Rev. S (A2)......................................... 7-9
30173 8542C ANALOG PC ASSY, Rev. S (A2)....................................... 7-22
21229 FRONT PANEL PCB ASSY, Rev. C (A3)....................................... 7-38
21240 LCD DISPLAY ASSY, Rev. B (A4) ................................................ 7-38
7.3 List of Manufacturers ..................................................................................7-39
8
Diagrams
8.1 Introduction...................................................................................................8-1
8.2 Applicability ..................................................................................................8-1
8540C Series Power Meter, DW G 30161, Rev. B .. ........... ........... ........... ...... 8-3
8542C Chassis Assy., DWG 30172, Rev. M ................................................ 8-5
CPU PC Assy. (A1), DWG 21693, Rev. J ...................................................... 8-8
CPU Circuit Schematic (A1), DWG 21694, Rev. J ........ ........... ........... .......... 8-9
Analog PC Assy. (A2), DWG 30173, Rev. S ............................................... 8-12
Analog Circuit Schematic (A2), DWG 30165, Rev. R .................................. 8-14
Front Panel PC Assy. (A3), DWG 21229, Rev. C ........................................ 8-20
Front Panel Circuit Schematic (A3), DWG 21230, Rev. C ........................... 8-21
Option 06 (8542C) System Schematic, DW G 30535, Rev. B ...................... 8-22
Option 06 PC Board Assy., DWG 21387, Rev. B ........................................ 8-23
Option 06 Circuit Schematic, DWG 21388, Rev. A ..................................... 8-24
Option 11 (Series 8540C) System Schematic, DWG 30485, Rev. B ........... 8-25
Time Gate Measurement PC Assy. (Option 11), DWG 30442, Rev. B ......... 8-26
Time Gate Measurement Circuit Schm. (Opt. 11), DWG 30443, Rev. B ...... 8-27
A
Typical Applications Programs
A.1 Continuous Data Reading ............................................................................. A-1
A.2 Remote Calibration of a Sensor..................................................................... A-1
A.3 Speed Tests: Normal and Swift .................................... ........... ........... .......... A-2
A.4 Swift Demo 1: FREERUN ............... ........... ............ ........... ........... ........... ...... A-4
A.5 Swift Demo 2: GET...................................................................................... A-5
A.6 Fast Buffered Demo: POST GET .................................................................. A-6
A.7 Fast Buffered Demo: POST TTL ................................................................... A-7
vi Manual 30280, Rev. J, September 2000
B
Power Sensors
B.1 Introduction .... ........... .................................................................................. B-1
B.2 Power Sensor Selection ................................................................................ B-1
B.3 Power Sensor Calibration ..................................................................... ...... B-11
C
Options
C.1 Introduction ................................................................................................. C-1
C.2 Optio n 01: Rack Mount Kit ........................................................................... C-1
C.3 Optio n 02: 256K Buffer ................................................................................ C-2
Preface
B.2.1 Modulation Power Sensors ........................................................... B-2
B.2.2 Modulation Sensor Specifications ................................................. B-5
B.2.3 Peak Power Sensors .................. ........... ........... ........... ........... ....... B-8
B.2.4 Directional Bridges ...... ........... ........... ........... ............ ........... ........ B-10
B.3.1 Local Calibration ......................................................................... B-11
B.3.2 Remote Calibrat ion...................................................................... B-14
C.4 Optio n 03: Rear Panel Connections (8541C) ................................................. C-2
C.5 Optio n 04: Rear Panel Connections (8542C) ................................................ C-2
C.6 Option 05: Soft Carrying Case .......... ............ ........... ........... ........... ............... C-2
C.7 Option 06: Second Analog Output ................................................................ C-3
C.7.1 Introduction .................................................................................. C-3
C.7.2 Theory of Operation ...................................................................... C-3
C.8 Optio n 07: Side-Mounted Carry Ca se ........................................................... C-6
C.9 Option 08: Transit Case................................................................................ C-6
C.10 Option 09: Dual Power Meter Rack Mount Kit .............................................. C-7
C.11 Option 10: Assembled Dual Power Meter Rack Mount ................................. C-8
C.12 Option 11: Time Gating Measurement ......................................................... C-9
C.12.1 Description ................................................................................... C-9
C.12.2 Specifications................................................................................ C-9
C.12.3 Time Gating Menu ...................................................................... C-10
C.12.4 Time Gating Mode ...................................................................... C-11
C.12.5 Measurement Display ...................................... ........... ........... ..... C-14
C.12.6 GPIB Setup ................. ........... ........... ........... ............ ........... ........ C-14
C.13 Option 13: Rear Panel Sensor Connections (8541C) ................................... C-17
C.14 Option 14: Rear Panel Sensor Connections (8542C) ................................... C-17
Index
8540C Universal Power Meters Index .................................................................. Index-1
Manual 30280, Rev. J, September 2000 vii
Series 8540C Universal Power Meters
List of Figures
Figure 1-1: Voltage Select or and Fuse Holder ............. ........... ........... ......................1-4
Figure 1-2: Uncertainty Due to Linearity & Zero Set ................................................1-7
Figure 2-1: 8542C Front Panel ...... ........... ........... ............ ........... ........... ........... .......2-1
Figure 2-2: 8540C Rear Panel .................................................................................2-5
Figure 2-3: Burst Measurement ............................................................................2-20
Figure 2-4: Delay and Dela y Offsets......................................................................2-22
Figure 2-5: Peak Hold ...........................................................................................2-24
Figure 2-6: Crest Factor ......... ........... ........... ........... ..............................................2-25
Figure 2-7: Burst Start Exclude & Burst End Exclude ............................................2-27
Figure 2-8: Burst Dropout .. ........... ........... ........... ............ ........... ........... ........... .....2-28
Figure 4-1: CPU Block Diagram...............................................................................4-2
Figure 4-2: Analog PC Block Diagram .....................................................................4-5
Figure 4-3: Calibrator Internal Power Standard ... ............ ........... .............................4-9
Figure 4-4: Front Panel PC Assembly....................................................................4-13
Figure 5-1: Calibrator Output Test Setup ................................................................5-7
Figure 5-2: Power Linearity Test Setup ............................................. ........... ...........5-9
Figure B-1: 80401A Modulation-Related Uncertainty ............................................ B-6
Figure B-2: 80601A Modulation-Related Uncertainty ............................................ B-7
Figure C-1: Time Gating Option Menu Structure ................................................. C-10
Figure C-2: External Gated Time Measurement ................................................... C-11
Figure C-3: External Trigger Gated Time Measurement ....................................... C-13
Figure C-4: GPIB Syntax for Time Gating Measurement .. ........... ........... ........... ... C-14
viii Manual 30280, Rev. J, September 2000
Preface
List of Tables
Table 1-1: Collection Modes Measurement Rates ................................................. 1-7
Table 2-1: Configuration Menu Structure ............................................................. 2-7
Table 3-1: Implemented IEEE Standards .................. ........... ............ ........... ........... 3-1
Table 3-2: IEEE 488.2 Command Set .................................................................... 3-8
Table 3-3: 8540C Function Codes ............ ............ ........... ........... ........... ........... .... 3-9
Table 3-4: 8540C Command Set for HP437 Emulation ....................................... 3-11
Table 3-5: 8540C Command Set for HP438 Emulation ....................................... 3-13
Table 3-6: 8540C Command Set for HP436 Emulation ....................................... 3-15
Table 3-7: Measurement Setting Target Default Values ...................................... 3-18
Table 3-8: Numbering Averaging........................................................................ 3-19
Table 3-9: Learn Mode #1 Output Format .......................................................... 3-30
Table 3-10: Preset (Default) Conditions ................................................................ 3-57
Table 3-11: Status Byte and Service Request Mark .............................................. 3-60
Table 3-12: Event Status & Event Status Enable Register ......... ........... ........... ...... 3-61
Table 3-13: Error Code Returned in Position AA ................................................... 3-63
Table 3-14: Error Code Returned in Position aa .................................................... 3-64
Table 3-15: Other Codes in the Status Message................................................... 3-65
Table 4-1: 8540C Circuit Board Assemblies.......................................................... 4-1
Table 5-1: Equipment Required for Calibration ..................................................... 5-1
Table 5-2: DC Power Supply Test Points .............................................................. 5-3
Table 5-3: Equipment Required for Performance Testing ...................................... 5-6
Table 7-1: List of Manufacturers ........................................................................ 7-39
Table B-1: Power Sensor Selection Guide ............................................................ B-2
Table B-2: Power Sensor Cal Factor Uncertainties ............................................... B-4
Table B-3: 804XXA Modulation Sensor Specifications ......................................... B-5
Table B-4: Peak Power Sensor Selection Guide .................................................... B-8
Table B-5: Peak Power Sensor Cal Factor Uncertainties ....................................... B-9
Table B-6: Directional Bridge Selection Guide ............. ........... ........... ........... ...... B-10
Table C-1: Output Voltages .................................................................................. C-3
Manual 30280, Rev. J, September 2000 ix
Series 8540C Universal Power Meters
x Manual 30280, Rev. J, August 2000
About This Manual
About This Manual
About This ManualAbout This Manual
This manual contains the following chapters and appendices to describe the operation and
maintenance of Giga-tronics Series 8540C Universal Power Meters:
Preface:
In addition to a comprehensive Table of Contents and general information about the manual, the
Preface also contains a record of changes made to the manual since its publication, and a description
of Special Configurations. If you have ordered a user-specific manual, please refer to page xvii for a
description of the special configuration.
Chapter 1 – Introduction:
This chapter contains a brief introduction to the instrument and its performance parameters.
Chapter 2 – Front Panel Operation:
This chapter is a guide to the instrument’s front panel keys, display and configuration menus.
Chapter 3 – Remote Operation:
This chapter is a guide to the instrument’s GPIB remote control interface.
Chapter 4 – Theory of Operation:
This chapter provides an instrument block diagram level description and its circuits for maintenance
and applications.
Chapter 5 – Calibration & Testing:
This chapter provides procedures for inspection, calibration and performance testing.
Chapter 6 – Maintenance:
This chapter contains procedures for maintenance and troubleshooting.
Chapter 7 – Parts Lists:
This chapter lists all components and parts and their sources.
Chapter 8 – Diagrams:
This chapter contains schematics and parts placement diagrams for all circuits.
Manual 30280, Rev. J, September 2000 xi
Series 8540C Universal Power Meters
Appendix A - Sample Programs:
This appendix provides examples for controlling the 8540C remotely over the GPIB.
Appendix B – Power Sensors:
This appendix provides selection data, specifications and calibration procedures.
Appendix C - Options:
This appendix describes options available for the Series 8540C.
Index:
A comprehensive word index of the various elements of the 8540C manual.
Changes that occur after publication of the manual, and Special Configuration data will be inserted
as loose pages in the manual binder. Please insert and/or replace the indicated pages as detailed in the
Technical Publication Change Instructions included with new and replacement pages.
xii Manual 30280, Rev. J, September 2000
Conventions
Conventions
ConventionsConventions
The following conventions are used in this product manual. Additional conventions not included
here will be defined at the time of usage.
Warning
WARNING
The WARNING statement is enclosed in dashed lines and centered
in the page. This calls attention to a situation, or an operating or
maintenance procedure, or practice, which if not strictly corrected
or observed, could result in injury or death of personnel. An
example is the proximity of high voltage.
Caution
CAUTION
Notes
☛
☛
☛☛
The CAUTION statement is enclosed with single lines and centered
in the page. This calls attention to a situation, or an operating or
maintenance procedure, or practice, which if not strictly corrected
or observed, could result in temporary or permanent damage to the
equipment, or loss of effectiveness.
NOTE: A NOTE Highlights or amplifies an essential operating or maintenance
procedure, practice, condition or statement.
Manual 30280, Rev. J, September 2000 xiii
Series 8540C Universal Power Meters
p
p
Symbols
Block diagram symbols frequently used in the manual are illustrated below.
Course
MOD
Pulse
Modulator
DAC
Digital to
Analog
Converter
Step-Recovery
Diode Multi
lier
Fine
YIG-Tuned
Oscillator
RF Level
Detector
Digital
YIG
Data
Mixer
Coupler
V
R
Phase Lock
Loo
Switch
Fixed
Reference
Oscillator
DIV
N
Frequency
Divider
STEP
ATTEN
Step
Attenuator
LOW
PA SS
Filter
Isolator
LVL
PIN-Diode
Leveler
Voltage-
Controlled
Oscillator
Amplifier
xiv Manual 30280, Rev. J, September 2000
Record of Manual Changes
Record of Manual Changes
Record of Manual ChangesRecord of Manual Changes
This table is provided for your convenience to maintain a permanent record of manual change data.
Corrected replacement pages will be issued as Technical Publication Change Instructions, and will be
inserted at the front of the binder. Remove the corresponding old pages, insert the new pages, and
record the changes here.
Change
Instruction
Number
Change
Instruction
Date
Date
Entered Comments
Manual 30280, Rev. J, September 2000 xv
Series 8540C Universal Power Meters
xvi Manual 30280, Rev. J, September 2000
Special Configurations
Special Configurations
Special ConfigurationsSpecial Configurations
When the accompanying product has been configured for user-specific application(s), supplemental
pages will be inserted at the front of the manual binder. Remove the indicated page(s) and replace it
(them) with the furnished Special Configuration supplemental page(s).
Manual 30280, Rev. J, September 2000 xvii
Series 8540C Universal Power Meters
xviii Manual 30280, Rev. J, September 2000
1.1 Description
The Series 8540C is a digital-controlled, self-calibrating power meter. It can measure RF and
microwave signal power over a wide range of frequencies and levels in a variety of measurement modes.
They can be operated locally from the front panel or remotely over the General Purpose Interface Bus
(GPIB). See Section 1.3 for performance specifications.
The Series 8540C is available as the single-channel Model 8541C or the dual-channel Model 8542C,
which can simultaneously measure and display signal data for two channels.
The 8540C and the Series 80600 line of power sensors offer enhanced performance in the measurement
of complex modulation signals in the communication industry. The 8540C maintains all the
functionality of Giga-tronics 8540B power meters as well as compatibility with all existing power sensor
models.
1.1.1 Features
1
Introduction
• CW, modulated and peak power sensors
• > 2000 readings/second in the Fast Buffered Mode (GPIB only)
• 90 dB dynamic range CW sensors
• +0.5% linearity
• True dual-channel display
• HP 438A, 437B, and 436 native mode emulation (GPIB only)
• EEPROM based CAL FACTOR correction sensors
• Modulated Average Power (MAP) mode
• Pulse Average Power (PAP) mode
• Burst Average Power (BAP) mode
• Wide modulation bandwidth – The 8540C is capable of accurately measuring signals with
modulation frequencies up to 1.5 MHz with the 80601A sensor
• Dual-channel modulated measurements with the 8542C and 80400 or 80600 series power sensors
• Time-gating (Option 11) allows you to specify a time period referenced to a rear panel trigger
during which power measurements are taken
• Password protection against unauthorized changes in data stored in EEPROMs
Manual 30280, Rev. J, September 2000 1-1
Series 8540C Universal Power Meters
1.1.2 Performance Characteristics
Performance specifications for models in the 8540C are presented in Section 1.3. Sensor specifications
are contained in Appendix B. Options are detailed in Appendix C.
1.1.3 Weight and Dimensions
Series 8540C instruments weigh 10 lbs. (nominal).
Dimensions are 3.5" high x 8.4" wide x 14.5" deep.
1.1.4 Power Requirements
100/120/220/240 Vac ±10%, 48-440 Hz, 20 W, typical. See Section 1.2.1 for details to set the voltage
and install the correct fuse for the area in which the instrument will be used.
1.1.5 Environmental Requirements
The Series 8540C instruments are type tested to MIL-T-28800E, Type III, Class 5 for Navy shipboard,
submarine and shore applications except as follows:
• Operating temperature range is 0 °C to 50 °C (calibrator operating temperature range is 5 °C to
35 °C).
• Non-operating (storage) temperature range is -40 °C to +70 °C.
• Relative humidity is limited to 95% non-condensing.
• Altitude and EMI requirements are not specified.
1.1.6 Items Furnished
In addition to options and/or accessories specifically ordered, items furnished with the instrument are:
1 ea. - Power Cord
1 ea. - Detachable Sensor Cable (for Model 8541C), or
2 ea. - Detachable Sensor Cables (for Model 8542C)
1 ea. - Operation Manual
1.1.7 Items Required
The 8540C requires an external power sensor; see Appendix B for Power Sensor Specifications.
1.1.8 Tools and Test Equipment
No special tools are required to operate the 8540C. Test equipment required for calibration or
performance verification is described in Chapter 4.
1.1.9 Cooling
No cooling is required if the instrument is operated within its specified operating temperature range
(0 to 50 ° C).
1-2 Manual 30280, Rev. J, September 2000
1.1.10 Cleaning
The front panel can be cleaned using a cloth dampened with a mild detergent; wipe off the detergent
residue with a damp cloth and dry with a dry cloth. Solvents and abrasive cleaners should not be used.
1.1.11 Installation and Preparation for Use
The instrument is shipped in an operational condition and no special installation procedures are
required.
1.1.12 Receiving Inspection
Use care in removing the instrument from the carton and check immediately for physical damage, such
as bent or broken connectors on the front and rear panels, dents or scratches on the panels, broken
extractor handles, etc. Check the shipping carton for evidence of physical damage and immediately
report any damage to the shipping carrier.
Each Giga-tronics instrument must pass rigorous inspections and tests prior to shipment. Upon receipt,
its performance should be verified to ensure that operation has not been impaired during shipment. The
performance verification procedure is described in Chapter 5 of this manual.
Introduction
1.1.13 Preparation for Reshipment
Follow these instructions if it is necessary to return the product to the factory.
To protect the instrument during reshipment, use the best packaging materials available. If possible use
the original shipping container. If this is not possible, a strong carton or a wooden box should be used
Wrap the instrument in heavy paper or plastic before placing it in the shipping container. Completely
fill the areas on all sides of the instrument with packaging material. Take extra precautions to protect
the front and rear panels.
Seal the package with strong tape or metal bands. Mark the outside of the package
DELICATE INSTRUMENT
DELICATE INSTRUMENT”
DELICATE INSTRUMENTDELICATE INSTRUMENT
regarding reshipment, please reference the full model number and serial number. If the instrument is
being reshipped for repair, enclose all available pertinent data regarding the problem that has been
found.
NOTE:
Giga-tronics Customer Service at 800.444.2878 or Fax at 925.328.4702 so that a return
☛
☛
☛☛
authorization number can be assigned. You can also contact Customer Service via our
e-mail address repairs@gigatronics.com.
If you are returning an instrument to Giga-tronics for service, first contact
. If corresponding with the factory or local Giga-tronics sales office
“FRAGILE —
FRAGILE —
FRAGILE — FRAGILE —
Manual 30280, Rev. J, September 2000 1-3
Series 8540C Universal Power Meters
1.2 Safety Precautions
This instrument has a 3-wire power cord with a 3-terminal polarized plug for connection to the power
source and safety-ground. The ground (or safety ground) is connected to the chassis.
WARNING
If a 3-to-2 wire adapter is used, connect the ground lead from the
adapter to earth ground. Failure to do this can cause the instrument to float above earth ground, posing a shock hazard.
The 8540C is designed for international use with source voltages of 100, 120, 220, or 240 Vac, ±10% at
50 to 400 Hz. The 8540C uses an internationally approved connector that includes voltage selection,
fuse, and filter for RFI protection (see Figure 1-1).
CAUTION
The instrument can be damaged if connected to a source voltage
with the line voltage selector set incorrectly. Before connecting
the instrument to power, make sure that the line voltage selector
is set for the correct source voltage.
1.2.1 Line Voltage and Fuse Selection
The instrument is shipped in an operational condition and no special installation procedures are
required except to check and/or set the operating voltage and fuse selection as described in the
following.
When the instrument is shipped from the factory, it is set for a power line voltage (120 Vac for domestic
destinations). The power line fuse for this setting is 0.50 A Slo-Blo. If the source voltage is to be 220 to
240 Vac, the fuse must be changed to 0.35 A Slo-Blo (see Figure 1-1).
1
1
VOLTAGE
SELECTION
WHEEL
COVER
FUSE AND
FUSE HOLDER
0
1
2
0
AC POWER
INPUT
Figure 1-1: Voltage Selector and Fuse Holder
1-4 Manual 30280, Rev. J, September 2000
The voltage selector and fuse holder are both contained in the covered housing directly above the AC
power connector on the rear panel. To gain access to them, use a small screwdriver or similar tool to
snap open the cover and proceed as follows:
1. To change the voltage setting:
Use the same tool to remove the voltage selector (a small barrel-shaped component marked
with voltage settings). Rotate the selector so that the desired voltage faces outward and replace
the selector back in its slot. Close the housing cover; the appropriate voltage should be visible
through the window (see Figure 1-1).
2. To replace the fuse:
Pull out the small drawer on the right side of the housing (marked with an arrow) and remove
the old fuse. Replace with a new fuse, insert the drawer and close the housing cover
(see Figure 1-1).
1.2.2 Power Sensor Precautions
Power sensor safety precautions, selection, specifications, and calibration are detailed in Appendix B to
this manual.
Introduction
Manual 30280, Rev. J, September 2000 1-5
Series 8540C Universal Power Meters
1.3 8540C System Specifications
1.3.1 Power Meter
Frequency Range: 10 MHz to 40 GHz
Power Range: -70 dBm to +47 dBm (100 pW to 50 Watt)
Single Sensor
Dynamic Range:
CW Power Sensors: 90 dB
Peak Power Sensors: 40 dB Peak, 50 dB CW
Modulation Sensors: 87 dB CW; 80 dB MAP/PAP; 60 dB BAP
Display Resolution: User-selective from 1 dB to 0.001 dB in Log mode and from 1 to 4
1.3.2 Accuracy
0.0dBm Accuracy: ±1.2% worst case for one year over a temperature range of 5 to 35 °C
1
1
1
digits of display resolution in Linear mode.
Calibrator
Frequency: 50 MHz nominal
Settability: The 1 mW (0.0dBm) level in the Power Sweep Calibrator is factory set
Connector: Type N, 50 Ω
VSWR: <1.05 (Return Loss >33 dB)
Power Sweep calibration signal to dynamically linearize the sensors
to ±0.7% traceable to National Institute of Standards and Technology.
Measure with 15 seconds of setting calibrator to 0.0 dBm.
System Linearity at 50 MHz
for Standard Sensors: ±0.02 dB over any 20 dB range from -70 to +16 dBm
±0.02 dB ±0.05 dB/dB from +16 to +20 dBm
±0.04 dB from -70 to +16 dBm
Temperature Coefficient of
Linearity: <0.3%/ °C temperature change following Power Sweep
Zeroing Accuracy (CW
(Standard Sensors):
Zero Set <±50 pW
Zero Drift <±100 pW during 1 hour
Noise <±50 pW measured over any 1 minute interval. Three standard
Notes:
1. Depending on sensor used (see Power Sensor details in Appendix B).
2. Specifications applies at -50 dBm for 803XXA Standard sensors. When measuring power levels Po other than -50 dBm,
divide noise and zero specifications by (10
above the minimum specified reading level. For Peak Sensors, see Appendix B and the 80350A Series Peak Power Sensor
Data Sheet. Specified performance applies with Maximum averaging and 24 hour warm-up temperature vision <3
Calibration.
24-hour warm-up required.
2
Modulation Power Sensors
<±200 pW with 80400A and 80600A Series Sensors
deviations.
<±100 pW with 80400A and 80600A Series Sensors
<±100 pW with 80400A and 80600A Series
2, 3
2
-Po/10
)/(10-5). For other 80300 Series CW Sensors, specification applies at 20 dB
°
C.
1-6 Manual 30280, Rev. J, September 2000
Introduction
0
6
0
0
4
0
3. Zero Drift Measurement
a. Set the meters Average to 512. Perform Calibration. Connect a 50-ohm load to the sensor after Calibration and
Zero meter.
b. Temperature stabilize at 25 °C for 24 hours.
°
c. After the 24 hour stabilization at 25
C, perform a Zero Drift test.
d. Zero meter and take an initial measurement reading.
e. Take one reading every 10 minutes until the one hour period elapses.
f. Plot the 6 readings, Zero Drift should be ±100pW.
1.3.3 Uncertainty Due to Instrument Linearity & Zero Set vs. Noise
3
2
1
0
-1
Typical Error (dB)
-2
-3
80401A (CW)
SENSORS
80401A (MAP, PAP)
80401 (BAP)
80601 (CW)
80601 (MAP, PAP)
80601 (BAP)
80301A
80310A
80320A
80321A
80322A
80325A
80330A
-60
-50
-40
-30
-20
-10
0
-70
-54
-44
-34
-24
-64
-50
-40
-60
-40
-30
-50
-30
-20
-40
-30
-20
-40
-20
-10
-30
-57
-47
-67
-50
-40
-60
-40 -33 -27 -21 -15 -9 -33 9 15 20
-50
-40
-60
-45
-35
-55
-40 -33 -27 -21 -15 -9 -33 9 15 20
-30
-20
-20
-10
-10
-10
0
-37
-27
-30
-20
-30
-20
-25
-15
Input (dBM)
-14
-10
0
0
0
0
10
10
20
-17
-10
0
-5
10
-4
6
16
0
10
20
10
20
30
20
20
40
20
30
40
-7
3
13
0
10
20
10
20
5
15
2
2
3
4
4
5
Figure 1-2: Uncertainty Due to Linearity & Zero Set
1.3.4 Measurement Rates
Measurement speed increases significantly using the 8540C data storage capabilities. Storing data in the
power meter’s memory for later downloading to your controller reduces GPIB protocol overhead. Up to
128,000 readings can be buffered. Table 1-1 illustrates typical maximum measurement rates for different
measurement collection modes. The rate of measurement depends on several factors including the
controller speed and the number of averages. The Fast Buffered Mode speed does not include bus
communication time.
Table 1-1: Collection Modes Measurement Rates
Measurement
Collection Mode
Normal (TR3), Continuous Single Readings >30 15
Swift Mode, Continuous or
Buffered, Bus/TTL triggered >175 N/A
Swift Mode, Continuous or
Buffered, Free-run triggered
Fast Buffered Mode, Buffered Data, Time
Interval = 0
Fast Modulated Mode, Continuous Single
Readings
Readings per Second
(CW Measurement)
>200 N/A
2600 N/A
N/A 30
Readings per Seco nd
(MAP, PAP, BAP
Measurement)
Manual 30280, Rev. J, September 2000 1-7
Series 8540C Universal Power Meters
Individual data points are read immediately after measurement in the Normal mode. The Normal mode
and the Swift mode both slow down at low power levels (<-37 dBm for Standard Sensors) to average the
effects of noise. The Swift mode allows triggering of individual data points and can store the data in the
8540C memory. The Fast Buffered mode also buffers measurement data. Measurement timing of
individual data points is controlled by setting the time interval (1 to 5000 ms) between the data points
following a trigger.
1.3.5 Remote Operation
GPIB Interface: All front panel operations and some GPIB-only operations to be
remotely programmed in IEEE 488.2 or IEC-625 formats.
Interrupts: SRQs are generated for the following conditions:
Power Up, Front Panel key actuation, Operation Complete and Illegal
Command and instrument self-test error.
1.3.6 Fast Buffered Mode Controls
Trigger Source: TTL or GPIB
Data Buffer Control: Pre- or Post-measurement data is collected immediately either before
or after receipt of the TTL or GPIB trigger.
Time Interval: TIME ### - controls time interval in milliseconds between
measurements. Accurate to 5%, typical.
1.3.7 Meter Function
Averaging: User-selectable auto-averaging or manual, 1 to 512 readings.
Automatic noise compression in auto averaging mode.
dB Rel and Offset: Allows both relative readings and offset readings. Power Display can
be offset by -99.999 dB to +99.999 dB to account for external loss/
gain.
Configuration Storage
Registers: Allows up to 20 front panel setups plus a last instrument state at
power-down to be stored and recalled from non-volatile memory.
Power Requirements and
Display Configuration: Any two of the following channel configurations simultaneously:
A, B, A/B, B/A, A-B, B-A, DLY
sensor is being used for MAP, BAP, PAP or BAP
measurements).
, DLYB (provided that neither
A
1.3.8 Remote Inputs/Outputs
V
F Input (BNC): Corrects power readings for sensor frequency response using
PROP
Analog Output (BNC): Provides an output voltage of 0 to 10V from either Channel A or
Blanking Output (BNC): TTL high during power meter zero. Can be used to shut off RF output
Trigger Input (BNC): Accepts a TTL trigger input signal for swift and fast measurement
GPIB Interface: Interfaces power meter to controller, IEEE 488.2 and IEC-625 remote
1-8 Manual 30280, Rev. J, September 2000
sweeper voltage output. Input resistance = 50K. Does not operate in
the fast measurement collection modes (normal mode only).
Channel B in either Log or Lin units. Does not operate in the swift and
fast measurement buffered modes.
during sensor zero.
buffered modes.
programming.
1.3.9 General Specifications
Temperature Range:
Operating: 0 to 50 °C (32 to 122 °F)
Storage: -40° to 70 °C (-40° to 158 °F)
Power Requirements: 100/120/220/240Vac ±10%, 48 to 440 Hz, 20 VA typical
Physical Characteristics:
Dimensions: 215 mm (8.4 in) wide, 89 mm (3.5 in) high, 368 mm (14.5 in) deep
Weight: 4.55 kg (10 lbs)
1.3.10 Accessories Included
1 ea 8540C Operation Manual (P/N 31470)
1 ea Power Cord
1 ea Detachable Sensor Cable (for Model 8541C)
or
2 ea Detachable Sensor Cables (for Model 8542C)
Introduction
1.3.11 Options
Refer to Appendix C for a full descriptions of options.
OPTION 01:
OPTION 02:
OPTION 03:
OPTION 04:
OPTION 05:
OPTION 06:
OPTION 07:
OPTION 08:
OPTION 09:
OPTION 10:
OPTION 11:
OPTION 13:
OPTION 14:
Rack Mount Kit.
Add 256K buffer for Fast Buffered Power Readings. Stores 128,000 readings.
8541C Rear Panel Connections (Sensor & Calibrator - Deletes front panel
connections)
8542C Rear Panel Connections (Sensor & Calibrator - Deletes front panel
connections)
Soft Carrying Case
Second Analog Output on 8542C (-10 V to +10 V)
Side Mounted Carrying Handle
Transit Case (includes Soft Carrying Case)
Dual Rack Mount Kit (with assembly instructions)
Dual Rack Mount Kit (factory assembled)
Time Gating Measurement
8541C Rear Panel Connection (Sensor only - Deletes front panel sensor connection)
8542C Rear Panel Connections (Sensor only - Deletes front panel sensor
connections)
1.3.12 Power Sensors
See Appendix B for power sensor selection, specifications and calibration data.
Manual 30280, Rev. J, September 2000 1-9
Series 8540C Universal Power Meters
1-10 Manual 30280, Rev. J, September 2000
2.1 Introduction
This chapter describes how to operate the Series 8540C Universal Power Meters. It includes
descriptions of the front and rear panels, configuration, display menus, and practical applications.
Section 2.2 describes the front panel; Section 2.3 describes the rear panel; Section 2.4 presents
Configuration procedures; Section 2.5 describes the display submenus, and Section 2.6 offers guidelines
for practical applications.
See Chapter 3 for information on remote operation with the General Purpose Interface Bus (GPIB).
2.2 The Front Panel
Although the 8540C has many modes of operation, the front panel design is very simple. The
instrument is configured and controlled by means of displayed menus, which can be accessed and
controlled with front panel pushbuttons.
2
Front Panel Operation
The dual-channel Model 8542C front panel is illustrated in Figure 2-1. The single-channel Model
8541C is the same in appearance but does not include Channel B.
Universal Power Meter
CALIBRATE
A
B
A
B
ZERO
CAL FREQ
MENU
ESCAPE
8542C
.
5
2
0
P
K
dB/mW
Figure 2-1: 8542C Front Panel
5
REL
RECALL
.
E
N
T
E
R
LOCAL
6
1
d
B
m
m
d
B
A
B
CW
M
MOD AVG
O
PEAK
D
PULSE AVG
E
BURST AVG
OFFSET
FREQ CORR
AVG
CW
M
MOD AVG
O
PEAK
D
PULSE AVG
E
BURST AVG
OFFSET
FREQ CORR
AVG
REMOTE
SRQ
GPIB
TAL K
LISTEN
POWER
1
0
Manual 30280, Rev. J, September 2000 2-1
Series 8540C Universal Power Meters
2.2.1 Calibrator
The CALIBRATOR connector provides a reference power output for calibrating the amplitude
response of a power sensor. The frequency of the output is fixed at 50 MHz. The level of the output is
programmable. During a calibration run, the output level automatically sweeps from -30 dBm to
+20 dBm in 1-dB steps.
2.2.2 Display Window
A two-line alphanumeric LCD screen displays measurements and configuration data.
2.2.3 LEDs
The LEDs to the right of the display window indicate operating modes and GPIB status. The column of
LEDs can also be configured for use as a peaking meter display.
2.2.4 Power
The push-push power switch turns line power on and off.
2.2.5 Front Panel Keys
The front panel keys are located below the display window, and function as described below:
ZERO/CAL
This key is for zeroing and calibration of a power sensor.
If zeroing and calibration are both required, the sensor must first be connected to the CALIBRATOR output connector. When the ZERO/CAL key is pressed, the sensor is zeroed, and then calibrated by an automatic program, which tests the sensor’s response to different reference power levels
and stores the resulting data in the 8540C memory.
For zeroing only, the sensor does need not to be connected to the CALIBRATOR output. If the
ZERO/CAL key is pressed when the sensor is not connected to that output, the 8540C performs the
zeroing function only.
When zeroing a sensor, it is best to connect the sensor to the device under test exactly as it will be
used in measurement, and deactivate the RF output of that device. Zeroing the sensor in place is the
best way to counteract system noise which could significantly effect low-level measurements. The
RF Blanking output signal, which goes low during sensor zeroing, is provided by a BNC on the rear
panel; this can be used as a control signal to turn off the RF source.
All active sensors should be zeroed whenever any sensor (whether it is calibrated or not) is added or
removed.
2-2 Manual 30280, Rev. J, September 2000
Front Panel Operation
FREQ
This key specifies the frequency of an input signal, so that the 8540C can apply the appropriate frequency-specific cal factor to the measurement. These cal factors are retrieved from the sensor
EEPROM.
If the frequency of the input signal changes so often that it is impractical to keep entering the frequency with the FREQ key, the frequency information can be conveyed to the 8540C by the use of
a voltage input that is proportional to frequency (see the V
When the 8540C is controlled remotely over the GPIB, the frequency information can be sent over
the bus.
REL
This key is for relative measurements (measurement values are not absolute but are expressed in dB
relative to a reference level). The REL key establishes the currently measured power level as the reference for all subsequent measurements. Press [REL] a second time to disable relative measurement.
MENU/ESCAPE
The MENU key accesses the configuration menus. It also functions as the ESCAPE key because it
exits a configuration menu, abandoning any configuration choices that were made within the menu
up to that point.
F connector on the rear panel).
PROP
dBm/mW
This key toggles between logarithmic measurement units (dBm, which is the default condition) and
linear units (mW). The display can be configured to use both units simultaneously, but this must be
done through the Meas Setup configuration menu).
RECALL
The recall button retrieves a stored configuration of the 8540C (configurations are saved in registers 1 through 20, using the Save Setup configuration menu). Use the left/right cursor keys to
choose between Preset and Reg#, and the up/down cursor keys to select a register number. Choosing
the Preset configuration restores the 8540C default conditions (it does not undo the calibration of
the sensors, however). Choosing register 0 restores the conditions which existed prior to the last
configuration change.
ENTER/LOCAL
The ENTER key makes menu selections and enters selected option or values. It is also called the
LOCAL key because it switches from remote control to local control.
Cursor Keys
These four keys are arranged in a diamond pattern and move the display vertically through available submenus, and move the display cursor (underline) horizontally within specific menus.
Manual 30280, Rev. J, September 2000 2-3
Series 8540C Universal Power Meters
2.2.6 Sensor Inputs
The A and B sensor input connectors (located directly below the CALIBRATOR connector) connect
the cables from the power sensors to the power meter. In instruments with Option 03, the sensor inputs
are reloctated to the rear panel.
CAUTION
When connecting sensor cables to these inputs, the cable pins
must be aligned properly. Orient the cable so that the guide on
the end of it aligns with the notch on the sensor input. If the connector does not seem to fit, forcing it will only damage the connector pins.
2-4 Manual 30280, Rev. J, September 2000
2.3 The Rear Panel
The rear panel for the 8541C and 8542C are identical and are illustrated in Figure 2-2.
Front Panel Operation
U.S.Patent 4,794,325
OPTION 01
WARNING
For continued fire protection
replace fuse with same
type and rating
WARNING
No operator serviceable parts
inside. Refer servicing to
service trained personnel
110/120V
T250 .5A
220/240V
T250V .25A
~
48 - 440Hz
2.3.1 Inputs & Outputs
BNCs
Five BNC-type connectors provide input and output signals for interfacing the 8540C to other
equipment.
• RF Blanking provides a TTL output that goes high during zeroing of a sensor to send a temporary
RF OFF trigger to a signal source.
• Trigger Input accepts a TTL input for triggering of high speed measurements under GPIB
control.
• V αααα FIn accepts a voltage input that is proportional to frequency and causes the 8540C to apply
appropriate frequency-related cal factors.
• Analog Output provides an output voltage that is proportional to the measured power level.
• Spare I/O is for a second Analog Output when Option 06 is installed.
LINE VOLTAGE
SELECTION
120Vac
Fuse
Line
50VA
MAX
~
~
Contrast
Figure 2-2: 8540C Rear Panel
GPIB
RF
Blanking
V
F
∞
I/O
Trigger
Input
Analog Output
Spare
In
Others
• GPIB (a 24-pin connector to connect the 8540C to other equipment over the GPIB).
• Line Voltage Selection houses the ac power connector and includes the fuse and line voltage
selector (see Section 1.2.1 for setting the voltage and fuse).
Manual 30280, Rev. J, September 2000 2-5
Series 8540C Universal Power Meters
2.4 Configuring the 8540C
The 8540C front panel LCD window normally displays measurement data, but it also displays
configuration menus. To select the menu mode, press [MENU]. While in menu mode, the display can be
returned to the measurement mode by pressing [MENU] again (in this context, the MENU button is the
ESCAPE button).
The 8540C can be password-protected to prevent unauthorized changes in Calibrator and Cal Factor
data stored in EEPROMs in the 8540C or its sensors. It is activated with the front panel menus (see
Section 2.4.3 for a description of the menus and their usage). The 8540C is shipped from the factory
with no password specified.
2.4.1 How the Menus Work
There is a hierarchy of menus; each line on the main menu represents a submenu, and some of the items
on those submenus are further submenus.
Menus are displayed one line at a time, with the word more accompanied by up or down arrows to
indicate whether there are additional lines above or below the line currently displayed. The Up/Down
cursor buttons also browse through the lines of a menu. To select the currently displayed line, press
[ENTER].
When an entry window is reached (that is, when the line that has been selected represents a
configuration choice to be made, not a submenu), the cursor buttons (usually the Left/Right buttons)
are step through the list of choices. If a numeric value is to be entered, a base value is displayed, and the
cursor buttons increment or decrement this value (the Left/Right cursor buttons select a digit, and the
Up/Down cursor buttons then step the value of that digit up or down).
After the desired value is set, or the desired choice selected, press [ENTER].
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Entering a selection usually returns the display window to the measurement mode. However, if the
selection you made requires further configuration choices, another menu may be displayed.
The menus are dynamic rather than fixed; the display adapts itself to the current operating mode and
the type of sensor or sensors connected. For example, the DLY measurement options are applicable only
to peak power measurement; therefore, the menu displays these options only if a peak sensor is attached
and is set up to measure peak power.
NOTE: If you leave the menu mode without pressing [ENTER], the selections you
made will not take effect.
2-6 Manual 30280, Rev. J, September 2000
2.4.2 Menu Structure
Table 2-1 illustrates the menu structure. For specific information about the individual menu items, see
Section 2.5. The format of these menus, as they are actually displayed, is context-dependent; some
menu options shown here may not be displayed if they are not applicable to the sensors that are
currently connected, or if they are not applicable to the measurement mode that is currently selected.
For example, menu options related to the PAP mode will not be displayed if a CW sensor is attached,
because a CW sensor cannot be used in the PAP mode.
Table 2-1: Configuration Menu Structure
Main Menu Item Subsequent Menus / Entry Windows
Front Panel Operation
A, B, A/B, ..., OFF
Meas Setup
Top Line Choose from: OFF, A, B, A/B, B/A, A-B, B-A, DLY
Average Avg A
Offset A (dB)
Resolution Top Line = x.xx
Peak Hold Choose from: OFF, ON
Crest Factor Choose from: OFF, ON
Min/Max Choose from: OFF, ON
Limits Top Line
dBm/mW
Setup
Rel Setup Top Line
Advanced Burst Start Exclude Num. of Samples: A
[The format of this entry window is particularly subject to context-dependent
variations; see Section 2.5.1]Bot Line
Avg B
B (dB)
Bot Line = x.xx
(and Bottom Line/Top Line if applicable)
Bot Line
Top Line
Bot Line
Bot Line
Burst Dropout Time: A / Time: B
Choose from:
Auto, 1, 2, 4, 8, 16, 32, 64, 128,
256, 512
[increment or decrement the
displayed value]
[adjust left or right as needed]
Choose from: OFF, ON
[if ON is chosen, the limits must be
defined; increment or decrement]
Choose from:
Lin, Log
Choose from:
ON, OFF
Num. of Samples: B [increment or
decrement]Burst End Exclude
Choose from:
.017, .026, .035, etc
(values in ms).
, DLY
A
B
Sensor Setup:
CW sensor
Sensor Setup:
Peak Sensor
[select A or B]
Manual 30280, Rev. J, September 2000 2-7
(No configuration is required if a CW sensor is connected.)
CW (No further configuration is required if CW is selected.)
Int Set Trig Level (dBm) [increment or decrement the
Set Samp Delay (ns)
DLY Offset (ns)
Ext Set Trig Level (V)
Set Samp Delay (ns)
DLY Offset (ns)
displayed value]
Series 8540C Universal Power Meters
Table 2-1: Configuration Menu Structure (Continued)
Main Menu Item Subsequent Menus / Entry Windows
Sensor Setup:
Modulation
Sensor
[80400 Series]
[select A or B]
Ref Power On/Off
Config
CW (No further configuration is required if CW is selected.)
Modulated
Avg
Pulse Avg Duty Cycle [increment or decrement the displayed value]
Burst Avg (No further configuration is required if Burst Avg is selected.)
(No further configuration is required if Modulated Avg is selected.)
Choose from: On or Off
Peaking
Meter
GPIB Mode Choose from:
Analog Out Std Output
V prop F
[select A or
B]
Sound Choose from: ON, OFF
Choose from:
Status, PkA, PkB
8541, 8542, 436A, 437B, 438A
Address Choose from:
[if Option 06 is installed, there are
two outputs; if so, select OFF in order
to get to the menu for that option]
Mode Choose from: Log, Lin
Choose from: OFF, ON
If ON is selected, two values must be
defined
0-30 (listen & talk), 40 (listen only)
and 50 (talk only).
Choose from:
Off, Bot Line, Top Line
Freq. at 0 Volts (GHz)
Scale Factor (V/GHz)
[increment or decrement the
displayed values]
Service Sensor ROM
Save Setup Save to Reg#
[select A or
B]
Calibrator Power Choose from: OFF, or a value
Te s t
Functions
Software
Versio n
Clear All
Memory
[specify a number from 1 to 20]
Choose from a wide variety of parameters that can be set.
in dBm
[increment or decrement the
displayed value].
EEPROM
[data to be entered:
Serial#, Cal Factor, Date, Time,
WRITE ]
Choose from a wide variety of diagnostic tests.
Displays information about the currently installed software.
Clear RAMs of configuration data.
WRITE:
CALIB Clear, or
PASSWORD Set
2-8 Manual 30280, Rev. J, September 2000
2.4.3 Password Protection
The password feature prevents unauthorized changes in Calibrator and Cal Factor data stored in
EEPROMs in the 8540C or its sensors. It is activated with the front panel menus (see Table 2-1 for a
description of the menus and their usage). The 8540C is shipped from the factory with no password
specified.
To get to PASSWORD set, select the Service menu, then the Calibrator submenu (or the Sensor ROM
submenu to provide password protection of sensor memory). Then select EEPROM, then WRITE. At
WRITE, the choice is between CALIB Clear and PASSWORD Set; select the latter. The password is a
numeric code. To enter it, use the cursor keys to increment or decrement the digits displayed in the
screen and press [ENTER]. Press [ENTER] again to confirm the password. The password is now stored in
the 8540C memory, and EEPROM data cannot be changed without entering the password.
The password can be changed or cleared by repeating the above steps and entering the existing
password, then set a new password by selecting SET. Clear the password by selecting CLEAR, or just
rewrite the data by selecting ON.
If a password was set previously and is not known, you can disable password protection by moving the
A2W1 jumper on the Analog PC board (A2) from the factory-set position A to position B.
Front Panel Operation
Manual 30280, Rev. J, September 2000 2-9
Series 8540C Universal Power Meters
2.5 The Submenus
2.5.1 A, B, A/B, ..., Off
This submenu determines what will be shown on the top and bottom lines of the display window. The
existing measurement setup determines which choices are shown in the menu; options which do not
apply to the power meter and its sensors, as they are currently configured, will not be shown.
The top and bottom lines of the display are configured independently; use the up/down cursor keys to
choose the top or bottom line, then use the right/left cursor keys to choose one of the available display
formats. Any of the options shown below can be selected for either the top line or the bottom line.
A the display line for Sensor A
B the display line for Sensor B (Model 8542C only)
A/B the reading of Sensor A divided by the reading of Sensor B (Model 8542C only)
B/A the reading of Sensor B divided by the reading of Sensor A (Model 8542C only)
A-B the reading of Sensor A less the reading of Sensor B (Model 8542C only)
B-A the reading of Sensor B less the reading of Sensor A (Model 8542C only)
TOP or BOTTOM: A B A/B B/A A-B B-A OFF
The top and bottom line settings are chosen as a unit for the PEAK mode. One line of the display shows
the measurement, and the other line shows the delay value. The choices in this mode are:
TOP:
BOTTOM:
2.5.2 Meas Setup
This submenu is defines conditions of measurement for each sensor. The items on the submenu are:
Avg, Offset, Resolution, Min/Max, Limits, dBm/mW, and Relative. Use the up/down cursor keys to
view these items, and the ENTER key to select one of them.
Average
Measurements can be averaged over a period of time which is referred to as the filter time. Increasing
the filter time increases the stability of the display, at the cost of increased time required for a
measurement. The filter time is equal to 40 ms times the averaging factor (for an averaging factor of 1,
the filter time is equal to 40 ms or the reading update time, whichever is greater). To increase
measurement speed, choose a lower averaging factor. The choices are: AUTO, 1, 2, 4, 8, 16, 32, 64, 128,
256, and 512. Use the up/down cursor keys to view these choices, and the Enter key to select one of
them. If AUTO is selected, the filter time is automatically adjusted for the ambient noise level.
Display Line Formats for the CW Mode
Display Window Formats for the PEAK Mode
A
DLY
A
DLY
B
B
DLY
A
A
DLY
B
B
2-10 Manual 30280, Rev. J, September 2000
Front Panel Operation
Offset
A specific offset in dB (positive or negative) can be added to the measured power. A beginning value of
0.000 dB is displayed. Use the left/right cursor keys to select a digit, and the up/down cursor keys to
increment or decrement the selected digit. Use the ENTER key to select the adjusted offset value.
Resolution
The display resolution can be set independently for the top line and bottom line of the display. Use the
up/down cursor buttons to select the top line or the bottom line. Use the right/left cursor buttons to
modify the resolution as symbolized by x’s (the range of choices is x through x.xxx). Use the ENTER key
to select the adjusted resolution.
Peak Hold
In modulated measurement modes (MAP, PAP, or BAP), this feature is holds the maximum value
measured since it was enabled. The displayed value changes only when it is rising to a new maximum (or
when it is reset by pressing [ENTER], in which case the displayed value drops to the present measured
value and the process resumes).
Crest Factor
This feature is very similar to the Peak Hold feature described above, except that what is displayed is the
ratio of the held maximum value to the average value, expressed in dB.
Min/Max
The Min/Max feature provides a continuously updated display of the highest and lowest values
measured so far; both are displayed on one line, while the other line displays the current measurement of
the channel being monitored. Use the Up/Down cursor buttons to select OFF, Bottom Line, or Top
Line, and press [ENTER]. The line that is selected represents the channel to be monitored; the other
line displays the minimum and maximum measured values. To reset these values to the current
measurement, return to the Min/Max entry window and press [ENTER] twice.
Limits
High and low limits can be defined for each channel; if the sound function is activated, an audible tone
is generated when a limit is violated. Arrows pointing up or down are displayed during a limit violation,
to indicate whether the upper limit or the lower limit was violated.
dBm/mW
The top and bottom lines of the display can be configured for logarithmic (dBm) or linear (mW) display
modes. Ratio measurements (A/B or B/A), are expressed in dBr (logarithmic) or %r (linear).
Rel Setup
Normally, when [REL] is pressed, each line of the display shows a relative measurement (when the key is
pressed, the present measured value is recorded, and all subsequent measurements are expressed in dB or
% relative to that recorded value). The Rel Setup entry menu provides a means of selectively enabling
or disabling the relative measurement mode for the top line, the bottom line, or both. Use the Up/Down
cursor keys to select the top line or the bottom line; then use the Right/Left cursor keys to select ON or
OFF, and press [ENTER].
Manual 30280, Rev. J, September 2000 2-11
Series 8540C Universal Power Meters
Advanced
This menu includes three special features which may be of use in certain applications of the Burst
Average Power measurement mode.
Burst Start Exclude:
This feature masks a portion of the beginning of a burst to exclude overshoot and other distortions from the measurement. The number of samples to be excluded must be defined; use
the Up/Down cursor keys to select the desired number of samples, and press [ENTER]
(selecting zero samples effectively disables this feature).
Burst End Exclude:
This feature is masks off a portion of the end of a burst to exclude overshoot and other distortions from the measurement. The number of samples to be excluded must be defined; use
the Up/Down cursor keys to select the desired number of samples, and press [ENTER]
(selecting zero samples effectively disables this feature).
Burst Dropout:
This feature is modifies the definition of a burst, so that a brief dropout is not interpreted as
the end of a burst. A dropout time must be defined; use the Up/Down cursor keys to select
one of a series of values displayed in ms (.17, .26, .35, etc.), and press [ENTER].
2.5.3 Sensor Setup
This menu is dynamic; its contents are determined by the type of sensor which has been connected to
the selected sensor input port (the 8540C is able to identify the sensor by reading its EEPROM data).
CW Sensor Setup
If a CW sensor is connected, no sensor configuration is needed.
Peak Sensor Setup
The Series 80350A peak sensor can be used in three modes: CW, Internally Triggered and Externally
Triggered. Use the Left/Right cursor buttons to select the desired mode, and press [ENTER].
CW
No further configuration is required if the CW mode is selected.
Int
In the Internally Triggered mode, peak power will be sampled at a point which is defined
by a trigger level, a delay, and a delay offset. The delay offset feature is a convenience in
some applications (for example, when measuring pulse width from a point other than the
trigger level, or when comparing the levels of various pulses within a pulse train). When
Set Trig Level is displayed, use the cursor buttons to adjust the displayed value (in dBm),
and press ENTER. When Set Samp Delay is displayed, use the cursor buttons to adjust the
displayed value (in ns, µs, or ms), and press [ENTER]. When Dly Offset is displayed, use
the cursor buttons to adjust the displayed value (in ns, µs, or ms), and press [ENTER].
Ext
The Externally Triggered mode is very similar to the Internally Triggered mode described
above, except that the basis of triggering is a voltage input from an external source. Configuration of this mode is the same as for the internal mode, except that the trigger level is
specified in volts rather than dBm.
2-12 Manual 30280, Rev. J, September 2000
Modulation Sensor Setup
CW
No further configuration is required if the CW mode is selected.
Modulated Avg
No further configuration is required if the Modulated Average mode is selected.
Pulse Avg
The Pulse Average is similar to the Modulated Average mode, except that the user is able
to specify a duty cycle (for pulse modulated inputs). When Set Duty Cycle is displayed, use
the cursor button to adjust the displayed value (in %), and press [ENTER]. The range is
0.001% to 99.999%.
Burst Avg
No further configuration is required if the Burst Average mode is selected.
2.5.4 RF Power On/Off
This entry window submenu activates and deactivates the front panel CALIBRATOR output (to adjust
the value of the output, see the Service submenu). Use the left/right cursor buttons to select ON or OFF,
and press [ENTER].
Front Panel Operation
2.5.5 Config
Peaking Meter
The 20 status LEDs on the front panel can be configured to serve as a peaking meter (that is, the stack of
the LEDs turn on from the bottom up to give a rough visual indication of changes in the currently
measured power level). The options are Status, PkA, and PkB. If PkA is selected, the LEDs serve as a
peaking meter for Channel A. If PkB is selected, they serve as a peaking meter for Channel B. If Status
is selected, the LEDs revert to their original role as status indicators.
GPIB
This option gives the user an opportunity to specify the IEEE 488 GPIB address and the emulation mode
for the 8540C. The choices of address are 0 through 30 (listen & talk), 40 (listen only), and 50 (talk
only). The choices of emulation mode are 8541, 8542, 436A, 437B and 438A.
Analog Out
The analog output is an output voltage, proportional to measured power, that can be applied to auxiliary
test equipment (such as a data recorder). The choices of output source are Top Line, Bottom Line, and
Off. The choices of mode are Log and Linear. The output source choices are displayed under the
heading Std Output. If Option 06 is installed, there are two outputs to be configured; in that case, select
OFF under Std Output in order to reach the Option 06 configuration menu.
V
F
PROF
The V
F (voltage proportional to frequency) connector accepts a voltage input in the range of 0 to
PROP
+10V, which the 8540C uses to determine the frequency of the RF input, so that appropriate correction
factors (stored in the probe’s EEPROM) can be applied. The voltage input is supplied by a V/GHz
output from the signal source. Select ON to activate this function. Two values must be defined for
V
F: the frequency at 0 Volts (specified in GHz) and the scale factor (specified in V/GHz). The V/
PROP
GHz output connector on the frequency source is usually labeled with the scale factor.
Manual 30280, Rev. J, September 2000 2-13
Series 8540C Universal Power Meters
Sound
A speaker within the chassis produces audible clicks and tones, in order to register keystrokes, and to
draw attention to certain conditions (for example, if a limit has been exceeded, or a calibration process
has been completed). To activate or deactivate this speaker, select ON or OFF.
2.5.6 Service
Sensor ROM
This menu is records data in a power sensor’s EEPROM. Select the sensor (A or B), and a series of entry
windows appears. Normally, this menu is used only at the factory for instrument configuration. It should
not be used in the field except under direction by the Giga-tronics customer service department.
Carefully record all existing settings before changing them, so that they can be restored if necessary.
Calibrator
The CALIBRATOR output produces a reference signal to calibrate power sensors. The reference signal
is at 50 MHz (CW); its level is programmable in 1 dB increments over a range of -30 to +20 dBm. The
level at 0 dBm is factory set to ±0.7%, traceable to the National Institute of Standards Technology
(within 15 seconds of setting a 0.0 dBm level). Output levels are subject to drift over time, and are
considered accurate during a calibration run or within a few minutes of setting a fixed reference level.
Test Functions
This menu makes available a number of diagnostic tests which are normally used only by factory
personnel. If you consult the Giga-tronics customer service department, you may be given instructions
on how to use one or more of these tests.
Software Version
Selecting this menu item causes the window to display the version of software that is installed in the
instrument.
Clear All Memory
Selecting this item causes all configuration data currently stored in the 8540C RAM to be cleared. Data
stored in sensor EEPROMs is not affected.
2.5.7 Save Setup
Up to twenty different configurations can be stored in non-volatile memory. When Save Setup is
selected, the entry window shows Save to Reg# 1. The Up/Down cursor buttons increment or
decrement the number under which the current configuration will be saved. The range of numbers is
1 to 20. A setup that has been saved in memory can be retrieved by means of the RECALL button on
the front panel.
2-14 Manual 30280, Rev. J, September 2000
2.6 Measurement Guide
This section of the manual presents simple guidelines for practical application of the 8540C. See
Section 2.6.10 for mode restrictions.
2.6.1 Using the Power Sweep Calibrator
The Power Sweep Calibrator automatically calibrates the power sensor to the power meter. The power
sweep operates from -30 to +20 dBm (the complete, non-square-law operating region) and transfers the
inherent linearity of an internal, thermal-based detector to the balanced diode sensors. Output is NISTtraceable at 50 MHz, 0 dBm to an accuracy of ±0.7% (±1.2% over one year).
Front Panel Operation
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NOTE: NIST is the National Institute of Standards and Technology.
2.6.2 806XX Sensor Operation
The Series 806XX power sensors are designed for the precise measurement of signals with wide
modulation bandwidths (up to 1.5 MHz). In terms of the various measurement modes (i.e., MAP, BAP,
etc), the 806XX sensors are operated exactly as the Series 804XX sensors described in Section B.1.
There is one distinction regarding the operation of the 806XX sensors. Below 200 MHz, the modulation
bandwidth of the sensor is limited by a filter which is electronically switched in the sensor. This is done
to keep the RF signal out of the base band signal processing circuitry. When a 806XX sensor is calibrated
on the meter for the first time (the meter reads UNCALIBRATED before calibration), the unit is set to
the default setting of MAP mode with frequency correction set to 1 GHz. This allows the sensor to
measure signals with wide-bandwidth modulation. For frequencies of 200 MHz or below, the frequency
correction must be set to the measurement frequency to avoid measurement error.
The Series 806XX sensors are compatible with the 8541C and 8542C and later configurations.
2.6.3 Sensor Calibration
The procedure for calibrating a sensor is:
1. Connect the power sensor to the 8540C power meter with the power sensor cable.
2. Connect the power sensor to the 8540C CALIBRATOR output.
3. Press ZERO/CAL.
The 8540C will automatically verify that a sensor is attached to the CALIBRATOR connector. It will
then zero and calibrate the sensor.
Refer also to the Power Sensor Calibration Procedures in Appendix B of this manual.
Manual 30280, Rev. J, September 2000 2-15
Series 8540C Universal Power Meters
2.6.4 Zeroing at Low Power Levels
The sensor should be zeroed just before recording final readings in the lower 15 dB of the power sensor’s
90 dB dynamic range (that is, for readings below -55 dBm, in the case of standard sensors).
1. Turn off the source output before you zero the sensor. The microwave source must output less
than -74 dBm of total noise power during RF Blanking for proper zeroing. The source signal
power should be less than -90 dBm.
2. Press the ZERO/CAL key to start the zeroing process. If more than one sensor is connected to
the power meter, a channel selection menu will appear.
The sensor should remain connected to the signal source during zeroing. By turning off the source
instead of disconnecting the detector, the zeroing process automatically accounts for ground line
voltages and connector interface EMF.
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NOTE:
with the source. This could be up to 15 minutes for moderate initial temperature
differences.
Sufficient time must be allowed for the module to reach thermal equilibrium
CAUTION
Sensor diodes can be destroyed by momentary or continuous exposure to excess input power. The maximum power (peak or average) that can be applied to the detector elements without
resulting damage is printed on the side of the sensor housing. For
standard CW sensors, and peak power sensors, this maximum
level is +23 dBm (200 mW). Standard sensors should not be used
above +20 dBm (100 mW), because this may degrade the sensor’s
performance even if it does not burn out the diodes.
When measuring pulsed signals, it is important to remember that the peak power may be much greater
than the average power (it depends upon the duty cycle). It is possible to overload the sensor with a
pulsed signal, even though the average power of the signal is far below the maximum level.
To measure higher power levels, use a high power sensor, or else reduce the signal amplitude using a
directional coupler or a precision attenuator.
2.6.4.1 Low Level Performance Check
This procedure provides a quick-check list for evaluating meter/sensor performance for low-level
measurements. It is not intended to verify performance of specifications such as Noise, Temperature
Coefficient and Zero Set. For complete verification, please refer to sections one and five in the power
meter operation manual.
1. This test is meant to check the low level performance of the meter and sensor. In order to do so,
the meter and sensor should first be separated from any external amplifiers, test systems, etc. Turn
the meter on and allow stabilization at ambient for 30 minutes. Connect the sensor to the meter
but not connected to the test port.
2-16 Manual 30280, Rev. J, September 2000
Front Panel Operation
2. Calibration.... Connect the power sensor to the calibrator port on the power meter and press
Zero/Cal.
NOTE: During calibration an approximate zero is established for calibration purposes only.
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3. Zeroing. Validation of meter and sensor noise floor will be checked using an attenuator or
4. Set averaging to 512 and configure for CW operation. After the unit has thermally stabilized, push
5. Immediately after zeroing, confirm that the meter reading is at least 3 dB below the minimum CW
This zero is not valid for actual measurements and can limit the measurement range as high
as -50 dBm. For proper low-level measurements, the sensor must be zeroed at the test port
of the system being tested.
termination. Connect the attenuator or termination to the sensor and allow the unit to stabilize for
3 minutes. The sensor must be thermally stabilized for proper zeroing. If the thermal condition of
the sensor varies during the zero procedure, the zero will not be valid.
the Cal/Zero button.
operating range of the sensor. This checks the noise floor and zero set capabilities of the meter and
sensor.
6. Zero Drift. Zero Drift is a measure of the change in noise over time. Each family sensor will
have a specified expectation of drift over a one-hour period. To confirm, set the meter to linear
display (Watts) after verifying noise floor and check that the display does not drift beyond
specification over a one-hour period.
Verification for specifications such as noise, zero drift and temperature coefficient of linearity are
difficult, time consuming tests. This checklist is useful to quickly determine if there is a catastrophic
system failure. Failure to meet the above guidelines is not necessarily an indication of specification
failure. Final confirmation of system specification performance is achieved using the verification
procedures found in the meter operation manual.
2.6.5 Measuring Source Output Power
The procedure is:
1. Connect the power sensor to the RF output of the microwave source.
2. Verify that the microwave source RF output is ON.
3. Press [FREQ]; enter the operating frequency (use the cursor keys to adjust the value), and press
[OK].
4. The 8540C will now display the microwave source output power. Adjust the source amplitude to
the desired level.
The 8540C responds rapidly to amplitude changes. Ranging is automatically performed in real time
through a 90 dB dynamic range using CW or modulated sensors. The peak sensor dynamic range is 40
dB Peak and 50 dB CW. Entering the operating frequency enables the 8540C to automatically apply
frequency calibration factors appropriate to the sensor being used. The operating frequency can be
communicated to the 8540C using the front panel menus, the GPIB, or the V
input connector for the V
Manual 30280, Rev. J, September 2000 2-17
F function is labeled V α F In on the 8540C rear panel.)
PROP
F voltage input. (The
PROP
Series 8540C Universal Power Meters
2.6.6 Using the Peaking Meter
The LEDs on the right side of the 8540C front panel can be configured as a 20-segment bar graph.
1. Press [MENU]. Select the Config menu. Select Peaking meter.
2. Use the cursor to select PkA or PkB, and press [ENTER].
3. Adjust the source’s amplitude control and observe the peaking meter.
The LED bar graph provides a linear display of power level on a decade range basis. For example, a
power level of 3 dBm produces an approximate 50% response on the peaking meter.
2.6.7 High Power Level Measurements
High power amplifiers and transmitters can damage standard sensors. Use only high power sensors to
measure these devices without using attenuators and measurements.
For example, if the output of an RF source is amplified to +30 dBm (1 Watt), this signal cannot be
measured directly using a standard sensor because the sensor’s maximum input level is +23 dBm (and
any level above +20 dBm is potentially harmful to a standard sensor). The signal would have to be
attenuated, and the attenuation would have to be corrected for by means of a measurement offset.
However, if a 5 Watt high power sensor is used, any power level up to +37 dBm can be measured directly
without the use of an attenuator.
2.6.8 Modulated Measurement Modes
The 8540C series of power meters expands upon the capabilities of the previous 8540 power meters in a
number of ways. In the past, power measurements of modulated signals (pulse, multi-tone, AM, etc.)
required that the signals be attenuated to levels less than -20 dBm to avoid errors due to sensor
nonlinearity. The 8540C with a 80401A series sensor, eliminates this restriction, and brings the speed
and accuracy of diode sensors to the power measurement of modulated signals. Basic measurement
procedures are presented below, along with some useful tips on how to get the most out of the modulated
measurement modes.
The new modulated measurement modes are available through the sensor setup menu when the active
sensor a modulated series. The 8540C features three modulated measurement modes:
• Modulated Average Power (MAP)
• Pulse Average Power (PAP)
• Burst Average Power (BAP)
MAP and PAP modes measure the true average power of modulated and pulsed signals. PAP mode
differs from MAP mode only in that it allows you to specify a duty cycle figure, which is automatically
factored into the measurement. In BAP mode, the true average power within the pulse is measured (the
pulse pattern is detected automatically, so there is no need for you to specify the duty cycle).
MAP Mode
The Modulated Average Power (MAP) mode measures RF signals, which are amplitude modulated,
pulse modulated, or both. In the MAP mode the 8540C calculates the average RF power received by the
sensor over a period of time controlled by the time constant of the internal digital filter. The result is
comparable to measurement by a thermal power sensor.
2-18 Manual 30280, Rev. J, September 2000
Front Panel Operation
In this mode, the 8540C measures the average power of CW and modulated signals, such as:
•AM
• Two-tone
• Multi-carrier
• Pulse modulation
• Digital modulation (QPSK, QAM, etc...)
For example, if an RF signal pulse modulated at 50 Hz with a 10% duty cycle is measured with the
averaging factor set to 128, the filter setting time will be 5.12 seconds (40 ms times 128) and each
reading will include 256 pules (50 Hz times 5.12 seconds); the measured power reading will be 10% of
the peak power during pulse ON periods. Because the signal is modulated at a low pulse rate (below
about 1 kHz), the 8540C will synchronize the readings precisely with the start of a pulse so that each
displayed reading is averaged over a whole number of pulses (that is, there are no fractional pulses
included in the measurement). This eliminates a significant amount of noise from the readings. It is
important to remember that even though the filter settling time has been set to a long time constant of
5.12 seconds, the update rate of the meter will be much faster, and even the first reading will be very
close to the fully settled value.
PAP Mode
The Pulse Average Power (PAP) mode is similar to the MAP mode, but it measures pulse-modulated
signals having a known duty cycle. You can specify this duty cycle and the 8540C will automatically
correct the measurements so that the displayed readings indicate the peak RF power during pulse ON
periods.
For example, when measuring a pulse modulated signal with 50% duty cycle, MAP mode would give a
reading 3 dB lower than the reading that would be given by PAP mode with the duty cycle factor set to
50%.
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NOTE: The duty cycle correction presumes a perfectly rectangular profile for the RF
pulse shape. Any abnormality such as overshoot, undershoot, slow rise time or fall
time, inaccuracy of the duty cycle, or deviation from a flat pulse response will cause
errors in the indicated reading.
Manual 30280, Rev. J, September 2000 2-19
Series 8540C Universal Power Meters
BAP Mode
The Burst Average Power (BAP) mode measures the average power during an RF burst. This mode is
very useful for measurement of pulse modulated signals which are not flat or have amplitude modulation
during the pulse ON period, as in the case of TDMA (Time Division Multiple Access) communications
signals. In this mode, the 8540C recognizes the beginning and end of a burst of RF power and takes an
average of the power during that burst. The RF level can vary over a wide range during the burst as long
as it remains above a noise threshold, which is automatically calculated by the 8540C. As soon as the
RF power drops below the noise threshold, the RF burst is complete and all further readings are
discarded until the next burst starts.
Powe r
Start of Burst
End of Burst
Noise Threshold
Time
Figure 2-3: Burst Measurement
In BAP mode, the 8540C automatically determines which portions of the signal are in the pulse and
which are not. In computing the average power, the 8540C uses only those portions that are within the
pulse. The result is that, independent of the signal’s pulse duty cycle, the meter always reads the average
power in the pulse or burst. As with the PAP mode, when measuring a pulse modulated signal with 50%
duty cycle, the reading in the BAP mode would be 3 dB higher than in the MAP mode. However, in the
BAP mode, the signal’s duty cycle can change dynamically in time without affecting the meter reading.
In the PAP mode, the duty cycle factor must be entered to match the duty cycle of the pulsed signal.
2-20 Manual 30280, Rev. J, September 2000
2.6.9 Measurement Collection Modes
Using a wide range of CW and Peak Power Sensors and the GPIB fast measurement collection modes,
the Series 8540C meters provide typical reading speeds of >200 readings per second in the free-run Swift
mode, 800 readings per second in the Fast Modulated mode, and >2,000 readings per second in the Fast
Buffered mode. Three Swift mode triggering controls are available: Fast free-run, bus triggered, and TTL
triggered modes. Bus and TTL allow triggering control of individual measurement points. Data can be
stored in an internal data buffer or read immediately.
Fast buffered power readings are internally buffered for readout at the completion of the fast buffered
interval. Maximum measurement rate is about 2,600 readings per second. Data conversion and GPIB
communication time are not included in this figure. The maximum buffer size is 5000 readings, or about
2.1 seconds at the maximum reading rate. Option 02 buffer increases this to 128,000 readings.
CW Mode
This mode is for measuring an unmodulated Continuous Wave (CW) signal. In this mode the RF signal
level must be constant for accurate readings to be made. If the signal level changes, a settling time for
the internal digital filter is required in order for measurements to be made to the specified accuracy.
The settling time (the time required for a measurement based on an averaging of samples to adapt to a
changed condition and become accurate again) is affected by various factors. The maximum settling
time is equal to 20 ms multiplied by the averaging factor (for example, if the averaging factor is 128, the
maximum settling time is 2.56 seconds). In most situations the actual settling time is well below the
maximum.
Front Panel Operation
PEAK Mode (80350A Peak Power Sensor)
The Peak mode is for instantaneous peak measurements of the RF power level of a pulse modulated
signal during pulse ON periods. The measurement is based on an instantaneous sample taken at a
particular point in time. Sampling is triggered by a pulse rising edge either in the modulated signal itself
or in a supplied trigger input signal, followed by a programmable delay. The trigger/delay combination
makes it possible for you to specify exactly what part of the pulse is sampled.
In the peak mode, each displayed reading can consist of a single sample or of an average of multiple
samples, each taken at the exact same time relative to the pulse’s rising edge. If the averaging factor is
set to 1, single samples are used. If it is other than 1, the averaging factor will determine the filter
settling time over which the multiple samples will be taken and averaged.
Because the peak mode measures the RF power instantaneously (at the top of the pulse, provided that
the delay has been set correctly), no assumptions are made about the pulse shape or duty cycle. In fact, it
is possible to profile the pulse by sweeping the delay time over a range of values to reveal the pulse shape
from start to finish.
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NOTE:
pulse where it is told to sample the pulse whether or not the point sampled is really the
peak point. This mode is therefore less intelligent than the BAP mode and must be used
carefully, but its flexibility makes it a powerful tool for studying modulated signals.
In the peak mode the 8540C does not know where the peak is. It samples the
Peak power measurements are made by sampling the RF input at a point which is defined by a trigger
level, a delay, and a delay offset (see Figure 2-4). The initial triggering event occurs when the power
input (or in the case of external triggering, a voltage input) reaches a threshold, which you have defined
as the trigger level. The sample is then taken after a delay, which you have defined. To this delay can be
added a positive or negative delay offset.
Manual 30280, Rev. J, September 2000 2-21
Series 8540C Universal Power Meters
The delay offset is not necessary for peak measurement, but in some applications it is a convenience. For
example, a small offset (even a negative offset) might compensate for the difference between the trigger
point and some other point of interest (such as the half-power point) especially in applications where
pulse width is being measured. Or if it is necessary to measure the levels of various pulses within a pulse
train, the pulses can be sampled successively by changing the delay offset. A fixed delay insures that
each pulse is sampled at the same point in its cycle.
Peak Power, Sampled After a 120 ns Delay
Sample
120 ns
Delay
Powe r
Trigger
Level
Trigger
Point
Time
Sample
Trigger
Powe r
(No Offset)
2.8 s
µ
Offset
Peak Power, Sampled After a 120 ns Delay
and a 10 ns Delay Offset
Sample
120 ns
Delay
Half-Power
Point
Trigger
Point
Powe r
Offset
Trigger
Level
10 ns
Delay
Peak Power, Sampled With a Fixed Delay
But Various Delay Offsets
Sample Sample
(11 µ s Offset)
Delay Offset
Delay Offset
Time
(22 µ s Offset)
6
0
4
2
810
12
16
14
Time (Microseconds)
20
18
24
22
26 28
32
30
Figure 2-4: Delay and Delay Offsets
2-22 Manual 30280, Rev. J, September 2000
2.6.10 Mode Restrictions
In certain modes the 8540C has highly specific restrictions on its operation:
• In the fast measurement collection modes (swift and fast buffered), it is not possible to make
measurements which compare the two channels. In other words, it is possible to make
measurements using sensor A, or B, or both, but measurements such as A/B and A-B are not
permitted.
• In GPIB remote operation, only one reading can be sent over the bus (it can be A, or B, or a
comparative measurement such as A/B, but it is not possible for separate measurements of A and
B to be sent over the bus). The exception is that in the swift and fast buffered measurement
collection modes, it is possible for both A and B to be sent over the bus.
2.6.11 When to use CW, MAP and BAP
For measuring signals with any kind of modulation, MAP mode should be used. In this mode, the 8540C
makes use of its digital signal processing algorithms to ensure that the reading is the correct average
power level regardless of modulation type (see Section B.2.2 for limits on modulation rate, etc.).
Of course, CW signals may also be accurately measured in MAP mode. This raises the question, why use
CW mode? CW mode offers a few more dB of dynamic range at low power levels when using a CW
power sensor, such as the 80301A. In addition, in CW mode the 8540C is form, fit, and function
compatible with its predecessor, Model 8540.
Front Panel Operation
BAP mode should be used only for the measurement of signals which are pulse modulated. In this mode
the meter will accurately measure the average power of the signal during the on-time of the pulse. This
mode works equally well regardless of whether the signal is modulated during the pulse on time.
2.6.12 Multi-Tone Tests
Multi-tone testing refers to more than one RF carrier combined into one signal to be measured. Twotone intermodulation testing, for example, is a common test performed on a wide variety of RF
components and subsystems. MAP mode should be selected for these applications. The 8540C test
procedure is as follows:
1. Calibrate the sensor according to the procedure outlined earlier in this section.
2. From the Main Menu press [Sensor Setup]. From the Sensor Setup menu, press [Modulated Sensor]
and then select the MAP mode by pressing [MAP].
3. Press [FREQ] and enter the operating carrier frequency.
4. Connect the sensor to the multi-tone source and record the power level.
For two-tone testing, small errors in the measurement will result when the carriers are separated by more
than about 50 kHz. The amount of error is also a function of average power level. For average power less
than about -20 dBm, there is no modulation-induced measurement error at any tone separation. Consult
the error charts found in Section B.2.2.
Multi-carrier testing usually refers to more than two carriers combined into one signal. Common multicarrier tests combine 10 to 20 carriers. In determining expected measurement error for these types of
signals, the maximum difference in frequency between any two carriers should be used as the tone
separation when applying the error charts in the manual.
Manual 30280, Rev. J, September 2000 2-23
Series 8540C Universal Power Meters
Another important feature of multi-carrier signals is that they can have a high peak-to-average power
ratio. This ratio can be as high as 10 dB for ten carriers. The significance of this in terms of making
power measurements is two-fold. First, care should be taken to keep the peak power level applied to the
sensor below the maximum recommended level. Second, when trying to minimize modulation-induced
measurement error for carriers separated by more than 50 kHz, it is the peak power level that should be
kept below about -20 dBm.
2.6.13 Peak Hold
When the Peak Hold feature is selected, the 8540C displays the highest instantaneous power measured
from the time the feature is enabled until it is reset by the user. In other words, the displayed value
tracks the measured value only when the measured value is rising to a new maximum. When the
measured value falls, the displayed value holds at the maximum. When the peak hold feature is reset,
the displayed value falls to the current measured value and the process begins again.
The Peak Hold feature is available in the MAP, PAP, and BAP measurement modes; it may be enabled
from the front panel under the Display Data Line Configuration setup menu, or over the GPIB. Peak
Hold is reset by pressing [Reset Line n] (or, in remote control, by sending the command which activates
the Peak Hold feature.
The reset function controls the time resolution of the reading (that is, for finer resolution, reset more
frequently).
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NOTE: [Reset Line n] for Peak Hold also resets the Crest Factor
Peak Hold
Hold
Hold
Hold
Powe r
Hold
(Reset)
Time
Figure 2-5: Peak Hold
Hold
Peak
Hold
Instantaneous
(Reset)
2-24 Manual 30280, Rev. J, September 2000
2.6.14 Crest Factor
The Crest Factor feature is very similar to the peak hold feature, in that it holds on to the maximum
level until a reset occurs, but in this case the displayed value is expressed (in dB) as a ratio of the held
maximum power to the average power.
The Crest Factor feature is available in the CW, MAP, PAP, or BAP modes only. It can be enabled
from the front panel under the Display Data Line Configuration setup menu, or over the GPIB. The
Crest Factor feature is reset by pressing [Reset Line n] of the appropriate line or, in remote control, by
sending the GPIB command which activates the Crest Factor feature (see Section 3.9).
In Figure 2-6, the same power input trace is used in two graphs to illustrate the effect of a drop in average
power, with and without a reset. In the top graph, the power drop is followed by a reset. The held value
drops to the current measured value, and the crest factor represents the ratio between the new maximum
level and the new average level. In the bottom graph, there is no reset after the power drop, and the
crest factor represents the ratio between the old maximum level and the new average level. For this
reason, the crest factor feature should be reset after an input power level change.
Front Panel Operation
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NOTE: [Reset Line n] for the Crest Factor also resets Peak Hold.
Crest Factor With a Power Drop Followed by a Reset
Hold
Hold
Hold
Powe r
Crest Factor With a Power Drop But No Reset
Hold
Hold
Hold
Powe r
Crest
Factor (dB)
Hold
Crest
Factor (dB)
Hold
(Reset)
Time
Avg.
Avg.
Crest
Factor (dB)
Crest
Factor (dB)
Hold
Avg.
Hold
Avg.
Time
Figure 2-6: Crest Factor
Manual 30280, Rev. J, September 2000 2-25
Series 8540C Universal Power Meters
2.6.15 Burst Signal Measurements
In a burst signal, the RF is pulsed on and off (i.e., pulse modulated). Often, the RF is modulated during
the pulse on time. Typical examples are TDMA digital cellular telephone formats such as NADC, JDC,
and GSM. These formats and many others produce amplitude modulation of the RF during bursts.
Two types of power measurement can be made on these types of signals. If the total average power is
desired, MAP mode should be used. Total average power includes both the off and on time of the pulses
in the averaging. Often it is desired to know the average power just during the bursts. BAP mode makes
this type of measurement very easy. The procedure is as follows:
1. Calibrate the sensor according to the procedure outlined earlier in this section.
2. Press [MENU] and select Sensor Setup. Select Burst Avg. and press [ENTER].
3. Press [FREQ] and enter the operating carrier frequency.
4. Connect the sensor to the burst signal source and record the power level.
The 8540C will automatically find the portions of the signal which are in the burst and include only
those portions in the average.
Burst signals can have a high peak power-to-average power ratio depending on duty cycle. This ratio is
proportional to the duty cycle and is given by:
Duty Cycle [%]
●
10
log
(
100
This assumes no modulation during the burst. Modulation during the burst will increase this ratio by its
own peak-to-average ratio. Due to this characteristic of burst signals, care must be taken to keep the
peak power below the maximum rated input power of the sensor.
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NOTE: If the burst average power is too low or if the bursts are too narrow, the 8540C may
lose sync with the bursts and fail to display the burst average power. When this happens, the
BAP mode indicator on the front panel will flash and the meter will display total average power
as in MAP Mode. The conditions under which the 8540C may lose sync are listed in Section
B.2.2.
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2-26 Manual 30280, Rev. J, September 2000
Front Panel Operation
2.6.16 Burst Start Exclude, Burst End Exclude
When measuring burst signals, it is sometimes desirable to mask the beginning or the end of a burst so
that overshoot and other distortions do not affect the reading. For example, the GSM test specification
for burst power measurements requires exclusion of the first 5% of the burst.
The Burst Start Exclude and Burst End Exclude features make it possible for BAP mode measurements
to exclude the beginning or the end of a burst in this way. Both features can be used simultaneously, but
this requires caution: if the excluded periods overlap, there is nothing left of the burst to be measured. If
the entire burst is excluded, the BURST AVG LED on the front panel will flash on the screen to the
right of the sensor power units, and the meter will revert to average measurement in the style of the
MAP mode.
The duration of the excluded period is not specified directly; instead, the number of samples to be
excluded is specified, which yields a guaranteed minimum exclude time of 90 µs × (n + .5) where n is
the number of samples. The actual amount of time excluded may substantially exceed this minimum.
In typical applications, it is sufficient to exclude one sample, which yields a guaranteed minimum
exclude time of 135 µs.
Burst Start Exclude
Burst Width
Exclude
Powe r
Include
Time
Burst End Exclude
Burst Width
Include
Powe r
Exclude
Time
Figure 2-7: Burst Start Exclude & Burst End Exclude
Manual 30280, Rev. J, September 2000 2-27
Series 8540C Universal Power Meters
2.6.17 Burst Dropout
In the BAP mode, average power is measured only during bursts. Because, in this mode, the bursts are
automatically detected by the power meter, the user need not be aware of the burst repetition rate in
order to make the measurement.
However, the BAP measurement algorithm defines bursts in a way which may be considered undesirable
in some applications. In the example illustrated below, a 3.5 ms burst is followed by an OFF period of the
same duration. During the burst, two brief dropouts occur. Normally, in BAP mode, each dropout would
be interpreted as the end of a burst; the BAP algorithm would interpret the burst as three separate
bursts, and the dropouts would be excluded from the average power measurement. As a result, the
average power reading would be artificially raised.
When the Burst Dropout feature is enabled, the BAP algorithm is modified so that a dropout of
sufficiently brief duration is not interpreted as the end of a burst. In the example below, dropout time is
specified at 350 µs. The two dropouts, which occur during the burst have a duration of less than 350 µs;
therefore the entire burst is interpreted as a single burst, and the dropouts are included in the average
power measurement. The 3.5 ms OFF period following the burst is interpreted as the end of the burst,
because it exceeds 350 µs in duration.
This feature must be configured and interpreted with care. The dropout time is selected from a series of
discrete values (.17 ms, .26 ms, .35 ms, and so on up to 31.96 ms); however, these are only the
guaranteed minimum values. In practice, the BAP algorithm may tolerate dropouts up to 2.15 times as
long as the minimum value. Therefore, the time between bursts must be at least 2.2 times as long as the
selected dropout time (because, if the time between bursts is less than the tolerated dropout time, the
BAP algorithm never recognizes the end of a burst, and the signal is simply averaged, as if the MAP
mode had been selected). Also, dropouts occurring at the end of a burst are a problem, because the BAP
algorithm cannot distinguish them from the end of the burst itself; there should be at least 250 µs of
burst remaining after the last dropout within that burst.
(dropout time)
Powe r
350 s
m
Burst Dropout
(Dropped Time = 350 s)
Burst definition covers this
entire time period, including
the two dropouts because
they are <350 s
245 s
m
Dropout
m
280 s
m
Dropout
Time
Figure 2-8: Burst Dropout
m
Burst definition does not
cover this 3.5 ms period
because it exceeds 350 s
m
2-28 Manual 30280, Rev. J, September 2000
2.6.18 Optimizing Measurement Speed
In many power measurement situations, measurement speed is defined in terms of settling time
following a step change in average power. In other words, it is desired to know the average power level
within some specified tolerance as quickly as possible following a power level change. This is often
accomplished by setting up the power meter in free-run mode over the GPIB and monitoring the
collected measurement data with the host computer until it falls within the predetermined tolerance
window.
The Auto average feature of the 8540C eliminates the need for the host computer to do any data
monitoring and can be set up to automatically output measurement data when it has settled to within
the specified tolerance. This is done by triggering each measurement with a TR2 command and waiting
for the meter to signal the host with an SRQ. The SRQ is asserted and the data is put on the bus as soon
as the power measurement has averaged long enough to be within the specified tolerance.
The tolerance is specified by including the measurement settling tolerance parameter with an FA
command (Auto average on). This parameter is specified in terms of percentage. For example, if a
measurement settling tolerance of 1% is specified, the 8540C Auto average algorithm will specify an
averaging time just long enough so that the result put on the bus is within ±0.5% (that is, ±0.02 dB) of
the average power. Thus, the settled measurement data is available on the bus in the minimum time
necessary to be within the specified tolerance.
Front Panel Operation
The tolerance specified in the FA command is a target tolerance. For example, it is possible that the
peak-to-peak power variation of the signal being measured is so great that the maximum averaging time
of 20 seconds is not long enough to reduce the variation to within the specified tolerance. It is also
possible that the rate of power variation is so slow that more than 20 seconds of averaging is required. In
these cases, further averaging would have to be done by the host computer.
The following example program shows how to set up a triggered measurement, optimized for speed using
the auto averaging feature:
Tr2: ! Read using TR2 command
ON INTR 7 GOSUB Srq_interrupt ! Set up SRQ interrupt
ENABLE INTR 7 ! Enable SRQ interrupt
OUTPUT 713;*SRE41 ! Set service request mask
OUTPUT 713;CS ! Clear status byte
OUTPUT 713;TR2 ! Trigger measurement
Data_ready=0 ! Clear flag
WHILE Data_ready=0 ! Wait for data ready
END WHILE
RETURN
Srq_interrupt: ! SRQ jumps here
State=SPOLL(713) ! Get status byte
IF BIT(State,0) THEN ! If the Data Ready bit is set...
Data_ready=1 ! Set the flag
ENTER 713;Tr2_reading ! Read the measurement
OUTPUT 713;CS ! Clear the status byte
OUTPUT 713;*SRE0 ! Clear the service request mask
END IF
RETURN
Manual 30280, Rev. J, September 2000 2-29
Series 8540C Universal Power Meters
2.6.19 Peak Power Measurements
Peak power sensors directly measure the amplitude of pulsed microwave signals. The direct sampling
technique is more accurate than traditional duty cycle correction methods. The sample position can be
displayed on an oscilloscope.
1. Calibrate a peak power sensor and connect it to a pulsed microwave source.
2. Press [MENU]. Go to Sensor Setup, and select internal, external, or CW triggering.
3. Select the desired trigger level (for internal or external triggering).
4. Select the desired sample delay (for internal or external triggering).
5. Optionally, set the desired delay offset (for internal or external triggering).
6. Connect the peak power sensor’s Detector Out to an oscilloscope to view the sample position.
For 80350A Peak Power Sensors, also connect the sensor’s Sample Delay output to the
oscilloscope and trigger on that channel.
2.6.20 Measuring an Attenuator (Single Channel Method)
Attenuators are useful for many applications. With the 8540C, attenuators can be calibrated quickly
and accurately. The single channel calibration procedure outlined below is efficient for calibrating at a
single frequency or at a limited number of frequencies.
1. Connect the power sensor to the signal source through a 6 dB attenuator (a matching pad) and
adjust the source output power to about 0 dBm. Verify that the source output is stable.
2. Press [FREQ] and enter the operating frequency (this step is optional).
3. From the Main menu, press [Rel] to set the reference level.
4. Insert the attenuator to be calibrated between the matching pad and the power sensor.
5. Record the attenuator value.
2-30 Manual 30280, Rev. J, September 2000
2.6.21 Improving Accuracy
Mismatch uncertainty is the largest source of error in power measurement. The 6 dB pad that is used in
the attenuator calibration procedure above reduces mismatch uncertainty by effectively improving the
return loss (or reducing the SWR) of the source. Mismatch uncertainty is large when a device has a
poor impedance match relative to 50 Ω.
Poorly matched devices reflect a large proportion of incident signals and create standing waves along
the transmission line. At various points along the transmission line, the standing wave will be at
maximum or minimum amplitude. Mismatch uncertainty is a measure of the deviation between these
amplitude levels.
Inserting an attenuator into the transmission line reduces mismatch uncertainty by reducing the
amplitude of the reflected signal, thereby reducing the difference between a standing wave’s maximum
and minimum levels.
Compared to an attenuator, most microwave sources have poor impedance matching. Using the 6 dB
attenuator during the calibration has the effect of lowering the SWR of the microwave source. The only
compromise is a corresponding 6 dB reduction in the source’s dynamic range when the 6 dB attenuator
is attached.
Front Panel Operation
Manual 30280, Rev. J, September 2000 2-31
Series 8540C Universal Power Meters
2.6.22 Performance Verification
Verifying accuracy and calibrating test equipment are essential to microwave engineers and technicians.
Accurate, repeatable measurements are required for validating designs, certifying calibrations, making
engineering decisions, approving product components, certifying standards, and verifying performance
specifications.
1. A 6 dB attenuator is placed at the input port of a power splitter to provide a good impedance match
from the source. This effectively reduces the VSWR of the source. Depending on the signal quality
of your source over frequency, additional attenuation may be desirable. A two-resistor power splitter
provides consistently matched power levels at its output ports, X and Y. The largest sources of error
are power splitter tracking errors and mismatch uncertainty.
2. Connect the reference standard power meter to power splitter output X, and the power meter to be
verified to splitter output Y.
3. Adjust the source frequency to a standard reference frequency (50 MHz for most power meters).
4. Enter the operating frequency or frequency cal factors into the power meters.
5. Adjust the source amplitude to the maximum sensor operating level (+20 dBm for standard
sensors).
6. Zero each power meter and record the measurement values immediately after settling.
7. Adjust the source for +19 dBm output level and repeat Step 6.
8. Continue testing at 1 dB increments through the rest of the standard sensor’s 90 dB dynamic range.
9. Calculate measurement uncertainty and compare the measured results to the specified tolerances.
At low power levels, be sure to zero the sensor prior to taking measurements. At levels below -55 dBm,
the measurements should be recorded just after zeroing is completed. The zeroing process must be
repeated periodically, depending on the operating level, due to drift characteristics.
2-32 Manual 30280, Rev. J, September 2000
2.6.23 Sources of Error
In the previous accuracy verification procedure, there are four sources of error:
• Source output level variation
• Power splitter output tracking
• Power meter X total measurement uncertainty
• Power meter Y total measurement uncertainty
Worst case uncertainty, which should be used for calibration purposes, is the arithmetic sum of all four
of these sources of error.
Source output level variation occurs in all microwave sources. This happens when the signal source
output level changes during the time it takes to record the displayed value on power meter X and then
to read the displayed value on power meter Y. This source of error can be minimized by using a
laboratory grade signal source.
Power splitter output tracking errors are the maximum signal level variation at the splitter X output as
compared to the splitter Y output.
Total measurement uncertainty for each of the power meters is the worst case combination of mismatch
uncertainty, instrument accuracy, and sensor accuracy.
Front Panel Operation
Mismatch uncertainty is calculated from the reflection coefficients of the sensor and the splitter
(source) according to the following formula:
M (dB) = 20 log
where ρ =
10
VSWR
VSWR
_
-
1
+
1
SENSOR
) (ρ
SOURCE
)]
[1+ (ρ
For a source mismatch specified in terms of return loss (RL), the equation should be modified according
to:
ρ
SOURCE=
where ρ =
r
10
-
RL (dB)
20
The following factors affect instrument accuracy:
• Instrument linearity or instrumentation uncertainty
• Reference calibrator setability or power reference uncertainty
The following factors affect sensor accuracy:
• Calibration factor uncertainty
• Calibrator to sensor (or power reference to sensor) mismatch uncertainty
•Noise
•Zero set
• Calibration pad uncertainty (for thermal-based power meters only)
• Sensor linearity
Manual 30280, Rev. J, September 2000 2-33
Series 8540C Universal Power Meters
2-34 Manual 30280, Rev. J, September 2000
3.1 Introduction
The Series 8540C can be operated from a remote host over the General Purpose Interface Bus (GPIB)
using either Standard Commands for Programmable Instruments (SCPI) or IEEE Standard 488-1978
(Digital Interface for Programmable Instruments)commands.
Table 3-1 shows which functions of the IEEE 488 standards are implemented in the 8540C.
Table 3-1: Implemented IEEE Standards
Function 8540C Implementation
Source Handshake SH1 (complete capability)
Acceptor Handshake AH1 (complete capability)
Talker T5 (basic talker, serial poll, talk only mode, unaddressed if MLA)
Extended Talker TE0 (no capability)
3
Remote Operation
Listener L3 (basic listener, listen only mode, unaddressed if MTA)
Extended Listener LE0 (no capability)
Service Request SR1 (complete capability)
Remote/Local RL1 (complete capability)
Parallel Poll PP1 (remote configuration)
Device Clear DC1 (complete capability)
Device Trigger DT1 (complete capability)
Controller C0 (no capability)
3.1.1 Sending Commands to the 8540C
The 8540C power meter uses standard protocols for communication over the GPIB. Commands
conform to IEEE 488.1 or IEEE 488.2 guidelines. Three emulation modes (HP436, HP437, and HP438)
are available for users of power meters who cannot rewrite their application software.
The program examples in this chapter are written in HTBasic™ format (HTBasic is a trademark of
TransEra Corporation). Other languages would use different commands but the string that is sent or
received will always be the same. In HTBasic, the OUTPUT command sends a string to the GPIB. The
number after OUTPUT is the GPIB address of the instrument.
The factory-set default address of the 8540C is 13 and the address of the GPIB is assumed to be 7;
therefore, examples of command strings in this manual are preceded by OUTPUT 713;.
Manual 30280, Rev. J, September 2000 3-1
Series 8540C Universal Power Meters
The GPIB address can be set from the front panel to any number from 0 to 30. GPIB address 40 will set
the instrument to the listen only mode. Address 50 sets the instrument to the talk only mode. To
change the GPIB operating mode or address, enter the menu system with the MENU key. Select the
SETUP menu using the up/down arrow keys. ENTER this sub menu system and select the GPIB setup
menu key. The operating mode and GPIB address can be set in the GPIB setup menu using the arrow
keys. Press ENTER to save your selection or press ESCAPE (the menu key) to exit without saving.
3.1.2 Clear Device
The interface command CLEAR 713 resets the GPIB and sets the 8540C to its preset condition.
3.1.3 Clear Interface
The interface command ABORT 7 resets the GPIB without resetting the 8540C to its preset condition.
The 8540C will not be addressed after the abort.
3.1.4 Local and Remote Control
The interface command LOCAL 713 places the 8540C into the local control mode.
The interface command REMOTE 713 places the 8540C into the remote control mode. Enter LOCAL
713 to return the instrument to local mode.
The interface command LOCAL LOCKOUT 7 places the 8540C in the local lockout mode. This is a
remote control mode in which all of the 8540C front panel keys are disabled. The GPIB LOCAL
command must be issued to return the 8540C to local mode (disconnecting the GPIB cable will also
return the instrument to local mode).
3.1.5 Sensor Selection and Calibration
Power sensor selection data, specifications, and calibration (local and remote) are contained in
Appendix B of this manual.
3-2 Manual 30280, Rev. J, September 2000
3.1.6 Polling
The GPIB supports parallel and serial polling. The example programs below show how to use the
parallel and serial poll capabilities of the 8540C to determine when a requested zeroing operation is
completed.
Parallel Polling
Ppoll_zero ! zero using parallel poll
PRINT entering parallel poll zero routine
PPOLL CONFIGURE 713;8 ! configure response on bit zero
OUTPUT 713;CS AEZE ! clear status byte, zero channel A
State=0 ! initialize variable
WHILE State 1 ! stay here until zero done
PRINT parallel zero done RETURN
Serial Polling
Remote Operation
State=PPOLL(7) ! read the poll
END WHILE PPOLL UNCONFIGURE 713 ! cancel parallel poll mode
Srq_zero: ! zero with an srq interrupt
PRINT entering SRQ interrupt zero routine
ON INTR 7 GOSUB Srq_interrupt
OUTPUT 713;CS ! clear status byte
ENABLE INTR 7;2 ! enable srq interrupts
OUTPUT 713;@1;CHR$(2) ! enable srq handshake
OUTPUT 713;AEZE ! execute zero command
Flag=0 ! test flag reset to false
WHILE Flag=0 ! stay here until test flag set true
WAI T 1
PRINT Still inside while loop
END WHILE
PRINT SRQ interrupt zero done
RETURN
Srq_interrupt: ! SRQ interrupts jump here
PRINT an SRQ interrupt has occurred
Example:OUTPUT 713;CS ! clear status byte
Flag=1 ! set control flag true
RETURN
Manual 30280, Rev. J, September 2000 3-3
Series 8540C Universal Power Meters
3.1.7 Data Output Formats (Standard Measurement Collection Mode)
The data output format for the standard measurement collection mode is:
±±±±D.DDDDE±±±±NNCRLF
±: Sign of the Mantissa
D.DDDD: Mantissa (5 digits)
E: Exponent (indicates that an exponent follows)
±: Sign of the Exponent
NN: Magnitude of the Exponent
CR: Carriage Return
LF: Line Feed
3.1.8 Data Output Formats (Fast Measurement Collection Modes)
Data output formats for the swift and fast buffered modes are expressed in the form of a signed five-digit
number with two digits to the right of the decimal and no exponents. In some cases multiple values are
sent:
One sensor swift mode: ±DDD.DD CRLF
Two sensor swift mode: ±DDD.DD,±DDD.DD CRLF
Fast buffered mode: ±DDD.DD, . . . . .±DDD.DD CRLF
3.1.9 Power-On Default Conditions
The interface wake-up state is:
GPIB Local Mode
Unaddressed, Service Request Mask Cleared
Status Byte Cleared
TR3 Free Run Trigger Mode Set
GT2 Group Execute Trigger Mode Set
Parallel Poll Data Line Unassigned
Display Enabled
Service Request Mask Cleared
Event Status Register = 128
Event Status Mask Clear
3-4 Manual 30280, Rev. J, September 2000
3.2 Command Syntax
The elements of the 8540C interface commands are introduced below. The discussion is general.
Because some commands are included for the sake of compatibility with earlier models, there are some
variations in syntax from one command to another which must be carefully accommodated.
3.2.1 Functions
At a minimum, the interface command includes a function code. The function indicates the nature and
purpose of the command. Some commands contain a function code and nothing else. For example, the
function AP, which causes the 8540C to measure power using the A sensor, stands alone as a command.
Commands which consist only of a function code are referred to in this manual as simple commands.
However, most commands consist of a function code combined with other elements.
Functions are listed alphabetically in the Command Set tables (see Section 3.3).
3.2.2 Prefixes
Some commands must begin with a prefix that identifies the sensor to which the command applies. For
example, function code ZE (which causes a sensor to be zeroed) must be combined with a prefix in order
to specify which sensor is zeroed. The full command is either AE ZE (for sensor A) or BE ZE (for
sensor B).
Remote Operation
Many of the commands described in this chapter are stated to require an AE or BE prefix, which
specifies the sensor that will be affected by the command. In some situations, the prefix can be omitted.
When the 8540C receives a command containing a sensor-specific prefix, it assumes that all subsequent
commands refer to the same sensor until a command is received which specifies the other sensor.
Therefore, if a command prefixed by AE is received, subsequent commands can omit the prefix provided
that they are intended for Sensor A.
Because Model 8541C supports only one sensor, the AE and BE prefixes can be omitted from any
command issued to that model.
It does no harm to include the prefix even when it is superfluous; some users may find that the most
convenient approach is to include the prefix in all applicable commands.
Manual 30280, Rev. J, September 2000 3-5
Series 8540C Universal Power Meters
3.2.3 Variables
Some commands must include one or more variables to specify quantities or options for the command.
For example, the function code ANALOG (which is used in commands that configure the analog
output) is combined with many different variables to specify different aspects of the analog output. In
the command
ANALOG STD TOP LOG -80.0, 20.0, 0.0, 10.0
the variables are interpreted as follows:
STD Specifies the standard analog output (as opposed to the optional second output).
TOP Specifies the top line of the display.
LOG Specifies that power is to be measured in logarithmic units (that is, dB or dBm).
-80.0 Specifies that the low end of the analog output voltage range represents -80 dBm in.
+20.0 Specifies that the high end of the analog output voltage range represents +20 dBm in.
0.00 Specifies that the low end of the analog output range is 0 volts.
10.0 Specifies that the high end of the analog output range is 10 volts.
In the above example, the numeric variables are strung together, with separator characters between
them (see Separators below). However, in some commands, numeric variables are preceded in the
command string by the variable name. For example, in the command FBUF PRE TTL BUFFER 200
TIME 1300, the numeric variables known as buffer and time are identified by name within the string.
Many variables are qualitative rather than quantitative; they select from among the various modes or
options available for a particular function.
3.2.4 Suffixes
Some commands require a terminating suffix. For example, the function code DY specifies a duty cycle.
It requires an AE or BE prefix (to indicate which channel is meant), and a numeric variable (to indicate
the duty cycle as a percentage). Finally, the command must include a terminating suffix (the choices of
suffix in this case are EN, PCT, and %). The command AE DY 50 % sets the duty cycle for channel A
to 50 percent.
NOTE: Some commands that include numeric variables require a terminating suffix. However,
many other commands do not require terminating suffixes, and interface problems will occur if
☛
☛
the suffixes are used in commands which don’t need them. Each command must be used so
☛☛
that its particular syntax requirements are met.
3-6 Manual 30280, Rev. J, September 2000
3.2.5 Separators
Spaces, commas, colons, and semicolons can be used as separators between the various elements of a
command (function codes, variables, etc.). Commands are usually spelled out in this manual with spaces
inserted between the elements (for example, SWIFT PRE GET BUFFER 100), for the sake of
readability. Although separators within a command are permitted, they are usually not required; in the
command descriptions in this chapter (beginning with Section 3.4), required separators are noted.
3.2.6 Command Format Illustrations
A command format is used in this chapter to show the possible elements of a command, as shown below:
[AE or BE] DY [n] [EN or PCTor %]
Variables are shown within brackets. In this example, the prefix can be AE or BE, the function is
DY, a numerical variable [n] follows the function, and the suffix at the end can be EN, PCT, or %.
Possible commands which use this example format include AE DY 42 % and BE DY 29.5 EN.
Remote Operation
Manual 30280, Rev. J, September 2000 3-7
Series 8540C Universal Power Meters
3.3 Series 8540C Command Codes
3.3.1 IEEE 488.2 Common Commands
Table 3-2 lists the IEE 488.2 common commands that are implemented in the 8540C. For further
information refer to the manual section cited in Table 3-2.
Table 3-2: IEEE 488.2 Command Set
Command Description Section
*CLS Clear status byte 3.30.1
*ESE Set Event Status Enable Register 3.30.2
*ESE? Ask for current status of Event Status Enable Register 3.30.2
*ESR? Ask for and clear Event Status Register bits 3.30.2
*IDN? Ask for instrument ID 3.14
*RST Software reset1 3.26
*SRE Set the service request mask 3.30.1
*SRE? Ask for service request mask 3.30.1
*STB? Ask for status byte 3.30.1
3-8 Manual 30280, Rev. J, September 2000
3.3.2 8540C Function Codes
Table 3-3 lists the function codes that are applicable when the instrument is in the 8541C mode or the
8542C mode. Most of these codes do not stand alone; commands; prefixes, variables, and suffixes must
be combined with them. For further information refer to the sections cited in Table 3-3.
Table 3-3: 8540C Function Codes
Command Description Section
@1 Set service request mask 3.30.1
@2 Set learn mode 2 data 3.15.2
?ID Ask for instrument ID 3.14
AD Measure A-B 3.29
ANALOG Configure analog output 3.4
AP Measure sensor A 3.29
AR Measure A/B 3.29
BAP BAP mode 3.19.4
BD Measure B-A 3.29
BP Measure sensor B 3.29
BR Measure B/A 3.29
BSPE Burst end exclude 3.20
BSTE Burst start exclude 3.20
BTDP Burst dropout 3.20.3
CH Select active measurement line for subsequent commands 3.4.1
CL Calibrate sensor 3.7
CRF Ask for crest factor val ue 3.9
CR Crest factor 3.9
CS Clear status byte 3.30.1
CW CW mode 3.19
DA Test LCD display 3.10
DC0 Duty cycle disable 3.11
DC1 Duty cycle enable 3.11
DD Display disable 3.10
DE Display enable 3.10
DU Display user message 3.10
DY Set duty cycle 3.11
EEPROM Sensor EEPROM query 3.12
FA Auto averaging 3.5
FBUF Fast buffered mode 3.18.3
FH Hold current averaging number 3.5.1
FM Set averaging number 3.5.2
FMOD Fast modulated mode 3.18.5
FR Frequency 3.13
GT0 Cancel GET 3.17.2
GT1 GET single measurement 3.17.2
GT2 GET full measurement with settling 3.17.2
Remote Operation
Manual 30280, Rev. J, September 2000 3-9
Series 8540C Universal Power Meters
Table 3-3: 8540C Function Codes (Continued)
Command Description Section
ID Ask for instrument ID 3.14
KB Enter cal factor 3.6
LG Log units (dB or dBm) 3.32
LH Set high limit 3.16
LL Set low limit 3.16
LM0 Disable limit checking 3.16
LM1 Enable limit checking 3.16
LN Linear units (Watts or %) 3.32
LP1 Ask for learn mode #1 string 3.15.1
LP2 Ask for learn mode #2 output 3.15.2
MAP MAP mode 3.19
MAX Ask for max value 3.21
MEAS Ask for measurement mode 3.19.6
MIN Ask for minimum value 3.21
MN0 Min/max disable 3.21
MN1 Min/max enable 3.21
OC0 Disable calibrator source 3.8
OC1 Enable calibrator source 3.8
OF0 Offset disable 3.22
OF1 Offset enable 3.22
OS Set offset value 3.22 & 3.22.3
PAP PAP mode 3.19
PEAK Peak sensor settings 3.24 & 3.25
PH Peak hold 3.23
PKH Ask for peak hold value 3.23
PR Preset the 8540C1 3.26
RC Recall a saved instrument state 3.31
RE Display resolution 3.28
RL0 Disable relative measurement 3.27
RL1 Enable relative measurement 3.27
RL2 Use old reference for relative measurement 3.27
RV Ask for service request mask 3.30.1
SM Ask for status message 3.30.3
ST Store instrument state 3.31
SWIFT Swift mode 3.18.4
TR0 Trigger hold mode 3.17
TR1 Trigger single measurement 3.17
TR2 Trigger full measure with settling 3.17
TR3 Free run trigger mode 3.17
F Configure V
V
PROP
ZE Sensor zeroing 3.34
F feature 3.33
PROP
3-10 Manual 30280, Rev. J, September 2000
3.3.3 HP437 Emulation GPIB Command Set
The GPIB commands that are available when the instrument is placed in the HP437 emulation mode.
Footnotes appear at the end of Table 3-4.
Table 3-4: 8540C Command Set for HP437 Emulation
Command Description
*CLS Clear all Status Registers
*ESE set the event status enable mask
*ESE? event status register enable mask query
*ESR? event status register query
*IDN? GPIB identification query
*RST Software reset
*SRE Set the Service Request Mask value
*SRE? Service Request Mask query
*STB? Read the Status Byte
*TST? Self test query
@1 Prefix for Status Mask
@2 Learn mode prefix
CL CAL
1
CS Clear the Status Byte
CT0 - CT9 clear sensor data tables 0 thru 9 [ignored]
DA All display segments on
DC0 Duty Cycle on
DC1 Duty Cycle off
DD Display disable
DE Display enable
DN down arrow emulation [ignored]
DU Display user message
DY Duty Cycle (enter duty cycle value)
ERR? device error query
ET0 - ET9 edit sensor cal factor table 0 thru 9 [ignored]
EX exit [ignored]
FA automatic filter selection
FM manual filter selection
FR frequency entr y
GT0 ignore Group Execute Trigger (GET) bus command
GT1 trigger immediate response to GET command
GT2 trigger with Delay response to GET command
ID GPIB identification query
KB Cal Factor
1
LG Log display
LH High limit
LL Low limit
1
1
LM0 Disable limits checking function
LM1 Enable limits checking function
LN Linear display
2
3
3
3
2
2
1
Remote Operation
Manual 30280, Rev. J, September 2000 3-11
Series 8540C Universal Power Meters
Table 3-4: 8540C Command Set for HP437 Emulation (Continued)
Command Description
LP2 HP437 learn mode
LT Left arrow [ignored]
OC0 Reference oscillator off
OC1 Reference oscillator on
OD Output display text [ignored]
OF0 Offset off - Local
OF1 Offset on - Local
OS Offset (enter offset value)
PR Preset
RA Auto range
RC Recall
RE Resolution
RF0 - RF9 Enter sensor ref cal factor [ignored]
RH Range hold
RL0 Exit REL mode
RL1 Enter REL mode using REL value
RL2 Use old ref number
RM Set range
RT Right arrow [ignored]
RV Read Service Request Mask value
SE Sensor [ignored]
SM Status Message
SN0 - SN9 enter sensor serial number [ignored]
ST Store instrument state
TR0 Trigger hold
TR1 Trigger immediate
TR2 Trigger with delay
TR3 Trigger - free run
UP Up arrow [up arrow]
ZE Zero
4
1
1
4
1, 4
Notes:
1. A numeric entry is required by these GPIB codes, followed by the code EN (ENTER).
2. This GPIB code uses the next 6 characters (0-9, A-Z, or an underscore) as input data.
3. The asterisk (*) must be included as part of the GPIB command string.
4. The 8540C can always measure over its entire dynamic range; there is no need to specify the range. Therefore, range-related
commands have no effect on the measurement capability of the 8540C. The auto range, range hold, and set range commands
only offset the analog output voltage, and only in HP436, HP437, or HP438 GPIB emulation modes. In these emulation
modes (when using a single sensor, and not measuring in a relative mode), the power will be scaled to a range of 0 to 1 volts,
representing the relative power within the current 10 dB range of the 8540C. The range hold and set range commands will
simulate locking the range of power represented by the output voltage.
3-12 Manual 30280, Rev. J, September 2000
3.3.4 HP438 Emulation GPIB Command Set
These are the GPIB commands that are available when the instrument is placed in the HP438
emulation mode. Footnotes appear at the end of Table 3-5.
Table 3-5: 8540C Command Set for HP438 Emulation
Command Description
?ID Ask for ID (the old way)
@1 Prefix for Service Request Mask
@1;CHR$(4) Set Service Request Mask to 4
AD Measure A-B
AE Specifies the A sensor
AP Measure sensor A
AR Measure A/B
BD Measure B-A
BE Specifies the B sensor
BP Measure sensor B
BR Measure B/A
1
CL
CS Clear status byte
DA Test LCD display
DD Display disable
DE Display enable
FA Set auto average filtering (precede with AE or BE)
FH Hold preset average number (precede with AE or BE)
FM Set averaging number
GT0 Group execute trigger cancel
GT1 Group execute trigger single measurement
GT2 Group execute trigger full measurement with settling
KB Cal Factor
LG Set Log units (dB or dBm)
LH High limit
LL Low limit
LM0 Disable limit checking
LM1 Enable limit checking
LN Set linear units (Watts or %)
LP1 Set learn mode #1
LP2 Set learn mode #2
OC0 Turn off calibrator source
OC1 Turn on calibrator source
OS Offset
PR Preset the instrument to a known state
2
RA
Calibrate sensor (precede with AE or BE)
Resume autorange [not supported]
Remote Operation
Manual 30280, Rev. J, September 2000 3-13
Series 8540C Universal Power Meters
Table 3-5: 8540C Command Set for HP438 Emulation (Continued)
Command Description
RC Recall previous instrument state
2
Notes:
RH
RL0 Turn off rel mode
RL1 Turn on rel mode
2
RM
RV Ask for status request mask
SM Ask for status message
ST Store instrument state
TR0 Trigger hold mode
TR1 Trigger single measurement
TR2 Trigger full measurement with settling
TR3 Free run trigger mode
ZE Zero sensor (precede with AE or BE)
Do a range hold
Set manual range
1. A numeric entry is required by these GPIB codes, followed by the EN suffix.
2. The 8540C is always able to measure over its entire dynamic range; there is no need to specify the range. Therefore, range-
related commands have no effect on the measurement capability of the 8540C. The auto range, range hold, and set range
commands only offset the analog output voltage, and only in HP436, HP437, or HP438 GPIB emulation modes. In these
emulation modes (when using a single sensor, and not measuring in a relative mode), the power will be scaled to a range of
0 to 1 volts, representing the relative power within the current 10 dB range of the 8540C. The range hold and set range
commands will simulate locking the range of power represented by the output voltage.
3-14 Manual 30280, Rev. J, September 2000
3.3.5 HP436 Emulation GBIP Command Set
Table 3-6 lists the GPIB commands that are available when the instrument is placed in the HP436
emulation mode:
Table 3-6: 8540C Command Set for HP436 Emulation
Command Description
1
5
1
4
1
3
1
2
1
1
1
9
A Set linear units (Watts)
B Set relative mode
C Set relative value
D Set Log units (dBm)
Z Zero sensor
+ Enable cal factors
- Disable cal factors (ignored)
H Set TR0 mode
T Set TR2 mode
I Set TR1 mode
R Set TR3 mode
V Set TR3 mode
Set range 5
Set range 4
Set range 3
Set range 2
Set range 1
Set auto range
Remote Operation
Notes:
1. The 8540C is always able to measure over its entire dynamic range; there is no need to specify the range. Therefore, rangerelated commands have no effect on the measurement capability of the 8540C. The auto range, range hold, and set range
commands only offset the analog output voltage, and only in HP436, HP437, or HP438 GPIB emulation modes. In these
emulation modes (when using a single sensor, and not measuring in a relative mode), the power will be scaled to a range of
0 to 1 volts, representing the relative power within the current 10 dB range of the 8540C. The range hold and set range
commands will simulate locking the range of power represented by the output voltage.
In HP436 emulation, the specified range is also indicated in the power data strings returned to the host.
Manual 30280, Rev. J, September 2000 3-15
Series 8540C Universal Power Meters
3.4 Analog Output
3.4.1 Standard Output
Commands relating to the standard analog output (that is, the rear panel analog output which is
installed in all instruments, not the optional second output) are based on the ANALOG function code,
as described below.
Enabling and Disabling the Output
The ANALOG function can enable or disable the analog outputs. The command format for this
purpose is:
Syntax: ANALOG STD STATE [ON or OFF]
STD indicates that the standard analog output (not the optional output) is being configured.
STATE indicates that the analog output ON/OFF status is being configured.
The variables ON and OFF indicate whether the analog output is to be enabled or
disabled.
Example: OUTPUT 713;ANALOG STD STATE ON ! Enable analog output
OUTPUT 713;ANALOG OPT STATE OFF ! Disable analog output
Setting Options for the Output
The ANALOG function can also configure various aspects of the analog output. The command format
is:
Syntax: ANALOG STD [TOP or BOT] [LG or LN] [a b c d]
STD indicates the standard analog output (not the optional output) is being configured.
[TOP or BOT] specifies the top or bottom line of the display.
[LG or LN] specifies logarithmic (dBm) or linear (Watts) measurement.
The command string ends with four numeric variables (with at least one separator character between each pair of them), which define the relationship between the input power
range and the output voltage range:
a: power level represented by the minimum output voltage,
b: power level represented by the maximum output voltage,
c: minimum output voltage,
d: maximum output voltage.
Valid power range numbers are -100 to +100 [dBm] for LOG, or 0 to 1E15 [Watts] for LIN. Valid
voltage range numbers are 0.00 to +10.00 [VDC].
Examples: OUTPUT 713;ANALOG STD TOP LOG -80.0, 20.0, 0.0, 10.0
! Configure the analog output top line display channel as follows:
! logarithmic units, -80 to +20 dBm input, 0 to 10 volt output
OUTPUT 713;ANALOG STD BOT LIN 0.00, 1.00E-3, 0.0, 1.0
! Configure the analog output bottom as follows
! linear units, 0 to 1.00 mW, 0 to 1 volt output
3-16 Manual 30280, Rev. J, September 2000
3.4.2 Optional Speed Count
Commands relating to the optional second analog output (also see Option 06 in Appendix C) are based
on the ANALOG function code, as described below.
Enabling and Disabling the Output
The ANALOG function can enable or disable the optional analog output. The command format for
this purpose is:
Syntax: ANALOG OPT STATE [ON or OFF]
OPT indicates that the standard analog output (not the optional output) is being configured.
STATE indicates that the analog output ON/OFF status is being configured.
The variables ON and OFF indicate whether the analog output is to be enabled or
disabled.
Example: OUTPUT 713;ANALOG OPT STATE ON ! Enable second analog output
OUTPUT 713;ANALOG OPT STATE OFF ! Disable second analog output
Remote Operation
Setting Options for the Output
The ANALOG function can also configure various aspects of the analog output. The command format
is:
Syntax: ANALOG OPT [TOP or BOT] [LG or LN] [a b c d]
OPT indicates the standard analog output (not the optional output) is being configured.
[TOP or BOT] specifies the top or bottom line of the display.
[LG or LN] specifies logarithmic (dBm) or linear (Watts) measurement.
The command string ends with four numeric variables (with at least one separator character between each pair of them), which define the relationship between the input power
range and the output voltage range:
a: power level represented by the minimum output voltage,
b: power level represented by the maximum output voltage,
c: minimum output voltage,
d: maximum output voltage.
Valid power range numbers are -100 to +100 [dBm] for LOG, or 0 to 1E15 [Watts] for LIN. Valid
voltage range numbers are 0.00 to +10.00 [VDC] (or -10.00 to +10.00, depending on Option 06
configuration).
Examples: OUTPUT 713;ANALOG OPT TOP LOG -80.0, 20.0, 0.0, 10.0
! Configure the second analog output top line display channel
! as follows:
! logarithmic units, -80 to +20 dBm input, 0 to 10 volt output
OUTPUT 713;ANALOG OPT BOT LIN 0.00, 1.00E-3, 0.0, 1.0
! Configure the second analog output bottom line display
! channel as follows:
! logarithmic units, -80 to +20 dBm input, 0 to 10 volt output
Manual 30280, Rev. J, September 2000 3-17
Series 8540C Universal Power Meters
3.5 Averaging
3.5.1 Auto Averaging
The 8540C is normally used in the auto averaging mode. The power meter chooses an averaging factor
that is appropriate for the ambient noise level.
Activating the Auto Filter Mode
The command which activates auto averaging for a sensor is based on the FA function. The command
format is:
Syntax: [AE or BE] FA
[AE or BE] prefix specifies Sensor A or Sensor B.
FA activates the auto filter mode for the selected sensor.
Example: OUTPUT 713;AE FA ! activate auto averaging filtering for sensor A
Setting the Measurement Settling Target
In the auto averaging mode, the 8540C chooses the lowest averaging factor that will yield a stable
measurement at the present resolution setting. Stability is defined in terms of peak to peak variation in
the measurement; the variation target value is expressed as a percentage of average power. Default
values for this Measurement Settling Target are:
Table 3-7: Measurement Setting Target Default Values
Resolution Peak to Peak Variation
xx. 25% (∼1 dB)
xx.x 4.7% (∼.2 dB)
xx.xx 0.46% (∼.02 dB)
xx.xxx 0.10% (∼.004 dB)
Because the target value affects the speed of measurement, it is possible to increase measurement speed
by increasing the target value (a small increase in the target value can result in a large increase in
speed). If the auto averaging mode is selected using the front panel menus, or the AE FA or BE FA
commands as described above, the default target values shown in the table are used. However, it is
possible to add a numeric variable after FA in order to specify a different target value:
Syntax: [AE or BE] FA [t] [EN % or PCT]
[t] represents the measurement settling target value in per cent, and has a valid range of
0.10 to 100.00.
Example: OUTPUT 713;BE FA .8 % ! activate auto averaging filtering for sensor B, with
! a measurement settling target of .8%
3-18 Manual 30280, Rev. J, September 2000
Freezing the Present Averaging Number
The command which causes auto filtering to hold its present averaging number is based on the FH
function. The command format is:
Syntax: [AE or BE] FH
[AE or BE] prefix specifies sensor A or Sensor B.
FH causes the 8540C to hold its present averaging number; auto averaging is deactivated.
Example: OUTPUT 713;BE FH ! hold present average number for sensor B
3.5.2 Manual Averaging
The averaging number can be specified directly. The commands for this purpose are based on the FM
function. The command format is:
Syntax:[AE or BE] FM [v] EN
[AE or BE] prefix specifies Sensor A or Sensor B.
FM specifies manual averaging.
[v] has allowable values of 0 through 9. Each value represents a particular averaging number. The
numbers are shown in Table 3-8.
A terminating suffix is required (EN).
Remote Operation
Table 3-8: Numbering Averaging
Value of v Averaging Number Va lue of v Averaging Number
01532
12664
247128
388256
4169512
Examples: OUTPUT 713;AE FM 2 EN ! set averaging number to 4
OUTPUT 713;AE FM 8 EN ! set averaging number to 256
Manual 30280, Rev. J, September 2000 3-19
Series 8540C Universal Power Meters
3.6 Cal Factors
You should not need to employ the command described below with the 8540C; it is included here for
the sake of compatibility with remote programs written for older power meters.
When a sensor is attached to the 8540C, the power meter automatically loads calibration factors from
an EEPROM in the sensor. This data is frequency related, and in order for the 8540C to make use of it,
the user must supply frequency information to the power meter, either by means of the front panel
FREQ key, by means of the GPIB FR command (see FREQUENCY, Section 3.13), or by means of the
V
F input. Once the frequency has been specified, the 8540C automatically applies the appropriate
PROP
cal factor to each reading.
The KB function code specifies a cal factor which is to be used in place of the cal factors stored in the
sensor EEPROM. The command format is:
Syntax: [AE or BE] KB [n] EN
[AE or BE] prefix specifies Sensor A or Sensor B.
[n] specifies a cal factor, expressed as a percentage with a valid range of 1.0 to 150.0.
A terminating suffix is required (EN).
Examples: OUTPUT 713;AE KB 96 EN ! enter a 96% cal factor for sensor A
OUTPUT 713;BE KB 102 EN ! enter 102% cal factor for sensor B
3-20 Manual 30280, Rev. J, September 2000
3.7 Calibration
Commands which cause the 8540C to calibrate a sensor are based on the CL function code. The
command format is:
Syntax: [AE or BE] CL [n] [EN or PCT or %]
[AE or BE] prefix specifies Sensor A or Sensor B.
[n] represents a reference calibration factor of n%. The 8540C makes no use of this
variable; instead it reads cal factors from the sensor EEPROM. The variable is included in
the command format only for compatibility with power meters which require it. Any value
between 50 and 120 can be entered for n.
A terminating suffix is required (EN, PCT, or %).
Examples: OUTPUT 713;AE CL 100 EN ! Calibrate sensor A
OUTPUT 713;BE CL 100 EN ! Calibrate sensor B
The appropriate sensor must be attached to the calibrator output for the calibration process to function.
If the sensor is not attached, the calibration will fail, and operation will continue as before.
Calibration Routine
Remote Operation
The following is an example of a GPIB program to calibrate a sensor. It is strongly recommended that
this format be followed for remote calibration. Note that the service request feature is used to determine
when the calibration has completed; this will result in the fastest calibration routine.
Calibrate: ! calibration routine
ON INTR 7 GOSUB Srq_interrupt ! setup serial poll interrupt
! jump location
ENABLE INTR 7;2 ! enable SRQ interrupts
OUTPUT 713;*SRE010 ! set service request mask to 2
OUTPUt 713;CS ! clear status byte
OUTPUT 713;CL100EN ! start calibration
Flag=0 reset control flag
WHILE Flag=0 ! wait while calibrating
END WHILE
RETURN
Srq_interrupt: ! SRQ interrupts jump here
OUTPUT 713;*STB?
ENTER 713;State
IF BIT(State, 1) THEN
PRINT GOOD CAL
ELSE
IF BIT(State, 3) THEN
PRINT BAD CAL
ENDIF
ENDIF
OUTPUT 713;CS ! clear status byte
Flag=1 ! set control flag true
RETURN
Manual 30280, Rev. J, September 2000 3-21
Series 8540C Universal Power Meters
3.8 Calibrator Source
The 8540C Calibrator output (a fixed 50 MHz signal at 0 dBm) is activated and deactivated by means of
two simple commands:
Syntax: [OC1 or OC0]
Examples: OUTPUT 713;OC ! turn on calibrator source
OUTPUT 713;OC0 ! turn off calibrator source
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NOTE:
automatically during calibration of a sensor.
This command is needed for test purposes only. The calibrator source is enabled
3-22 Manual 30280, Rev. J, September 2000
3.9 Crest Factor
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The Crest Factor feature holds on to the highest instantaneous power measured from the time the
feature is enabled until it is reset; it is similar to the Peak Hold feature, except that the measurement is
expressed as a ratio in relation to average power.
Remote Operation
NOTE:
modes (not in the fast modes), and only in a modulated measurement mode (MAP, PAP, or
BAP). Crest Factor is not recommended for use in combination with the V
The Crest Factor feature can only be used in the standard measurement collections
3.9.1 Enabling the Crest Factor Feature
The Crest Factor feature is enabled or disabled by one of two function codes:
Syntax: [CR0 or CR1]
Examples: OUTPUT 713;CR1 ! Enable the Crest Factor feature
OUTPUT 713;CR0 ! Disable the Crest Factor feature
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NOTE: Like the PH0 and MN0 commands, the CR0 command will disable Peak Hold and
Min/Max measurements.
3.9.2 Reading the Crest Factor Value
The Crest Factor value is read over the bus using a simple command:
F function.
PROP
Syntax: CRF
Example: OUTPUT 713;CRF ! Send the crest factor value
The Crest Factor feature monitors the maximum power as it is measured, but does not provide any
feedback to the controller until a CRF command is received. To monitor for a limit violation, the Limits
feature may be more useful (see Section 3.1.6).
The Crest Factor feature returns the current ratio between held power and average power, as displayed
on the front panel. A CRF command does not initiate data collection in same manner as a trigger
command, such as TR1. To get a good reading of the Peak Hold value, the procedure is:
1. Set up the signal being measured, and send CR1 to reset the Crest Factor measurement.
2. Send TR2.
3. Read the TR2 data, or wait for the data ready service request (this allows for settling).
4. Send CRF.
5. Read the Crest Factor value.
Manual 30280, Rev. J, September 2000 3-23
Series 8540C Universal Power Meters
3.10 Display Control
Testing the Displays
The LCD display window and status LEDs on the 8540C front panel can be tested remotely, by means of
three simple commands:
Syntax: DE (Enable the display)
DA (Test the display)
DD (Disable the display)
Examples: OUTPUT 713;DE ! activate the LCD display
OUTPUT 713:DA ! Performs a test of the display
OUTPUT713;DD ! Disable the display
Displaying a Message
The DU function can show a test message in the LCD display window. The command format for this
purpose is:
Syntax: DU [string]
! (this has the effect of canceling a DA or DD command)
The test message string can contain up to 32 characters; the first sixteen characters will
be shown on the top line of the LCD display window, and the remaining characters will be
shown on the bottom line.
Example: OUTPUT 713;DU THIS IS A TEST ! show the message THIS IS A TEST on the
! LCD display window
3-24 Manual 30280, Rev. J, September 2000
3.11 Duty Cycle Commands
3.11.1 Activating or Deactivating a Duty Cycle
The commands which activate or deactivate a duty cycle are based on the DC0 and DC1 functions. The
command format is:
Syntax: [AE or BE] [DC0 or DC1]
[AE or BE] prefix specifies Sensor A or Sensor B.
[DC0] turns the duty cycle off (for the specified sensor); if the sensor is in Pulse Average
Power measurement mode, this command will change the sensor measurement mode to
Modulated Average Power. If the sensor is not measuring Pulse Average Power at the time
this command is received, then this command will have no effect.
[DC1] turns the duty cycle on. This is equivalent to the PAP command (see Measurement
Mode Commands in Section 3.19).
Examples: OUTPUT 713;AE DC0 ! turn off the duty cycle for sensor A
OUTPUT 713;BE DC1 ! turn on the duty cycle for sensor B
3.11.2 Specifying a Duty Cycle
Remote Operation
The commands which specify a duty cycle are based on the DY function. The command format is:
Syntax: [AE or BE] DY [n] [EN or PCT or %]
[AE or BE] prefix specifies Sensor A or Sensor B.
DY specifies a duty cycle value; it also configures the sensor to Pulse Average Power
mode. Therefore, this function includes the capabilities (and entry error reporting) of the
PAP function (see Measurement Mode Commands in Section 3.19).
[n] species the duty cycle value in percent with a valid range of .001 to 99.999).
A terminating suffix is required (EN, PCT, or %).
Examples: OUTPUT 713;AE DY 50 % ! set 50% duty cycle for sensor A
OUTPUT 713;BE DY 25.000 EN ! set 25% duty cycle for sensor B
OUTPUT 713;BE DY 40.412 PCT ! set 40.412% duty cycle for sensor B
3.11.3 Reading Duty Cycle Status
The status message bit O indicates whether the duty cycle function is active for the selected sensor.
0 indicates OFF; 1 indicates ON.
Manual 30280, Rev. J, September 2000 3-25
Series 8540C Universal Power Meters
3.12 EEPROM
The EEPROM command is used to query the cal factor data in the sensor EEPROM. The cal factor data
is typically stored in the EEPROM at 1 GHz steps over the frequency range of the sensor. Additional cal
factors may also be stored at additional special frequencies. When a measurement frequency is specified
which does not exactly match the frequencies at which cal factors have been stored, the power meter
determines the appropriate cal factor via interpolation.
Commands to read EEPROM cal factor data are based on the EEPROM function code. The command
format is:
Syntax: EEPROM [A or B] [CALF? or FREQ?]
[A or B] specifies Sensor A or Sensor B.
[CALF?] queries the cal factors. The cal factor data is output as a table of cal factors
expressed in dB, separated by commas.
[FREQ?] queries the frequencies which correspond to the cal factors. The frequency data
is output as a table of frequencies expressed in Hz, separated by commas.
Examples: OUTPUT 713;EEPROM A CALF? ! Query sensor A EEPROM whole cal factor
! table
! (This example is from an 80301A sensor)
Response: 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00,
0.00, 0.00
OUTPUT 713;EEPROM A FREQ? ! Query sensor A EEPROM whole
! frequency table
! (This example is from an 80301A sensor)
Response: 5.000e7, 2.000e9, 3.000e9, 4.000e9, 5.000e9, 6.000e9, 7.000e9, 8.000e9, 9.000e9,
1.000e10, 1.100e10, 1.200e10, 1.300e10, 1.400e10, 1.500e10, 1.600e10, 1.700e10,
1.800e10
3-26 Manual 30280, Rev. J, September 2000
3.13 Frequency
Cal factors are stored in the sensor’s EEPROM by frequency. Specifying a frequency causes the 8540C to
apply the cal factor appropriate to that frequency. To cancel the use of cal factors, specify a frequency of
50 MHz (this is the frequency of the front panel Calibrator reference output, and has a cal factor of
zero).
Commands which specify a frequency are based on the FR function. The command format is:
Syntax: [AE or BE] FR [n] [HZ or KZ or MZ or GZ]
[AE or BE] prefix specifies Sensor A or Sensor B.
FR specifies a frequency value.
[n] specifies the frequency value (the units are Hz, kHz, MHz, or GHz, depending on the
terminating suffix used).
A terminating suffix is required (HZ, KZ, MZ, or GZ).
Examples: OUTPUT 713;AE FR 5.67 GZ ! frequency for sensor A is 5.7 GHz
OUTPUT 713;AE FR 1.0E9 HZ ! frequency for sensor A is 1E9 Hz (1 GHz)
OUTPUT 713;BE FR 84.6 MZ ! frequency for sensor B is 84.6 MHz
Remote Operation
OUTPUT 713;BE FR 4E6 KZ ! frequency for sensor B is 4E6 kHz (4 GHz)
Manual 30280, Rev. J, September 2000 3-27
Series 8540C Universal Power Meters
3.14 Instrument Identification
The 8540C can be queried over the GPIB for purposes of identification; user application programs make
use of such queries in order to verify that the appropriate equipment is connected. The 8540C will reply
to an ID query by sending back an identification string.
The simple commands which query the instrument ID consist of any of three function codes:
Syntax: [ID or ?ID or *IDN?]
Example: OUTPUT 713;*IDN? ! ask for ID string
ENTER 713; Name ! read ID into string variable Name
Identification Strings
The ID string is determined by the configuration choices that were made (from the front panel) under
the Config/GPIB menu. In the 8541 or 8542 mode, the ID string consists of four fields separated by
commas:
Field 1 is the manufacturer (GIGA-TRONICS).
Field 2 is the model (8541C or 8542C).
Field 3 is the serial number field (it displays the serial number of the calibrator EEPROM)
Field 4 is the software version number.
Example strings:
8451C mode Name = GIGA-TRONICS,8451C,9544112,3.00
8452C mode Name = GIGA-TRONICS,8452C,9548024,3.00
However, the ID strings for the following emulation modes are fixed, as follows:
HP437B mode Name = HEWLETT-PACKARD,437B,1.8
HP438A mode Name = HP438A,VER1.10
HP436A mode Not Applicable
HP and Hewlett Packard are registered trademarks of the Hewlett Packard Company.
3-28 Manual 30280, Rev. J, September 2000
3.15 Learn Modes
The 8540C has the ability to send information regarding its current configuration to the controller. The
controller requests this information by sending a learn mode command. At a later time, the controller
can send the configuration information back to the power meter in order to reconfigure the 8540C to
the same state it was in when it received the learn mode command.
Conceptually this feature is similar to the store and recall capability of the 8540C but with several
important differences:
• The configuration information is stored in the controller’s memory and not in the 8540C
memory.
• Learn Mode #1 returns information regarding the current GPIB operational configuration
(such as the trigger mode) which would not be covered by the store/recall function.
• The learn modes do not support many of the advanced features of the 8540C.
• The learn modes involve transmission of long strings of data between the controller and the
8540C. These strings must be transmitted without interruption; transmissions cannot be
considered complete until EOI is read.
The two learn modes are discussed under separate headings on the following pages.
The learn modes are provided for the sake of compatibility with remote programs written for older
power meters. The configuration information returned to the host is not as complete as the information
that would be stored in the 8540C memory using the store/recall function; the configuration data for
many features of the 8540C are not included in the learn mode data.
Remote Operation
Manual 30280, Rev. J, September 2000 3-29
Series 8540C Universal Power Meters
3.15.1 Learn Mode #1
Learn Mode #1 is used to return the configuration of the 8540C to the controller in the form of a
sequence of GPIB commands.
Requesting the String
The simple command which requests the Learn Mode #1 string has the following format:
Syntax:LP1
Example: OUTPUT 713;LP1 ! requests learn mode #1 string
After receiving the LP1 command, the 8540C will return the Learn Mode #1 string the next time it is
addressed to talk. The string will consist of up to 128 ASCII characters. The last character is sent with
EOI true. Table 3-9 shows the information contained in the Learn Mode #1 string, and the order in
which it is sent.
Table 3-9: Learn Mode #1 Output Format
Parameter Output from the Power Meter
Tr i gg e r M od e T Rd
Measurement Mode AP, BP, AR, BR, AD, or BD
Offset
Filter
Offset
Filter
AE
KB ddd.d EN
OS±dd.dd EN
RA d EN
FA or FM d EN
LL ±ddd.ddd EN
LH ±ddd.ddd EN
BE
KB ddd.d EN
OS ±dd.dd EN
RA d EN
FA or FM d EN
LL ±ddd.ddd EN
LH ±ddd.ddd EN
SENSOR A PARAMETERS
Cal Factor
Range
Low Limit
High Limit
SENSOR B PARAMETERS
Cal Factor
Range
Low Limit
High Limit
Active Entry Channel AE or BE
Measurement Units LG or LN
Reference Oscillator Status OC0 or OC1
Group Trigger Mode GTd
Limits Checking Status LM0 or LM1
Carriage Return Line Feed EOI
1
± indicates sign; d indicates a single digit.
1
Sending the String
The power meter can be restored to the configuration described in the Learn Mode #1 string, by sending
the string to the 8540C.
3-30 Manual 30280, Rev. J, September 2000
3.15.2 Learn Mode #2
Learn Mode #2 is used to return the 8540C configuration information to the controller in the form of a
series of binary values.
Requesting the String
The simple command which requests the Learn Mode #2 string has the following format:
Syntax: LP2
Example: OUTPUT 713;LP2 ! requests learn mode #2 string
After receiving the LP2 command, the 8540C will return the Learn Mode #2 string the next time it is
addressed to talk. The string starts with two ASCII characters, @ and 2, followed by a string of 28 (58 for
the 437 emulation mode) 8-bit binary bytes. The last byte is sent with EOI true. Learn Mode #2 requires
a controller that can receive and send information in binary form.
The Learn Mode #2 string contains the following information:
• Measurement mode
• REL mode status (on or off)
• Reference oscillator status (on or off)
• Current reference value if in REL mode
• Measurement units (Log or Lin)
• Cal Factor for each sensor
• Offset for each sensor
• Range for each sensor
• Filter for each sensor
Remote Operation
Sending the String
The command that sends the Learn Mode #2 data to the 8540C is based on the @2 function. The
command format is:
binary bytes
The 8540C will change its configuration to match the configuration defined by the Learn Mode #2
string.
Manual 30280, Rev. J, September 2000 3-31
Series 8540C Universal Power Meters
3.16 Limits
3.16.1 Setting Limits
Commands which set limits are based on the LH and LL function codes. The command format is:
Syntax: [AE or BE] [LH or LL] [n] EN
For limit commands, the [AE or BE] prefix specifies a line of the display rather than a
sensor.
[AE] specifies the top line of the display.
[BE] specifies the bottom line.
[LH] specifies the high limit; LL specifies the low limit.
[n] is a limit value, expressed in dBm or dB as appropriate.
A terminating suffix is required (EN).
Examples: OUTPUT 713;AE LH 12.34 EN ! set top line high limit to +12.34 dB
OUTPUT 713;AE LL -2.58 EN ! set top line low limit to -2.58 dB
OUTPUT 713;BE LH 2.34 EN ! set bottom high limit to +2.34 dB
OUTPUT 713;BE LL -100.00 EN ! set bottom line low limit to -100.00 dB
NOTE: These commands must be preceded by CH [n] EN command.
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3.16.2 Activating Limits
Limit-checking is activated or deactivated by simple commands consisting of one of two function codes:
Syntax: [AE or BE] [LM0 or LM1]
For line commands, the [AE or BE] prefix specifies a line of the display rather than a
sensor.
[AE] specifies the top line of the display.
[BE] specifies the bottom line.
[LM0] disables limit checking.
[LM1] enables limit checking.
Examples: OUTPUT 713; AE LM0 ! disable limit checking for the top line
OUTPUT 713; BE LM1 ! enable limit checking for the bottom line
Before enabling limit checking (LM1), you must set the high and low limits (LH and LL). Once
enabled, the Status Byte (bit 4) will signal a too high or too low condition. The status message AA bytes
will indicate a too high condition (error code 21), or a too low condition (error code 23). Status
Message bytes L or M contains the limit status for the top line display and the bottom line display
respectively . 0 indicates within limits, 1 indicates too high, and 2 indicates too low.
The LCD display will indicate a too high condition with an up arrow displayed to the left of the reading,
and a down arrow displayed to the left of the reading for a too low condition. If the sound mode is
enabled, a high or low pitched sound will be generated. Sound can be disabled using the Config menu.
NOTE: These commands must be preceded by CH [n] EN command.
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3-32 Manual 30280, Rev. J, September 2000
3.16.3 Measuring with Limits
For Sensor A or B, measurements with limits are enabled by the command
Syntax:LM1.
Example: OUTPUT 713; AP LM1 ! Measure sensor A and enable limit checking
This measures Sensor A with the previously set AE, LL and LH limits.
Example: OUTPUT 713; BP LM1 ! Measure sensor B and enable limit checking
This measures Sensor B with previously set BE, LL and LH limits.
To measure Sensor A and B simultaneously (Model 8542C only) with limits enabled (LM1),
1. Press [ENTER]
2. Press [MENU]
3. Enter the menu format (A, B, A/B..., OFF).
Remote Operation
4. Select Top Line and press the left/right cursor keys until A appears.
5. Select Bottom Line and press the left/right cursor keys until B appears.
6. Press [ENTER].
Example: OUTPUT 713; AE LM1 ! Enable limit checking for the top line
OUTPUT 713; BE LM1 ! Enable limit checking for the bottom line
This allow the power meter to display both sensor readings and enables both of the previously set AE
and BE, LL and LH limits for Sensors A and B.
Manual 30280, Rev. J, September 2000 3-33
Series 8540C Universal Power Meters
3.17 Measurement Collection Modes (Standard)
3.17.1 Measurement Triggering
Trigger modes determine when a measurement will be made. Four simple commands consisting of one of
four function codes select the desired mode:
Syntax: [TR0 or TR1 or TR2 or TR3]
All four modes discussed here are standard measurement collection modes (as opposed to the fast modes
described in Section 3.18), and use the standard data output format.
Trigger Hold (TR0)
This command places the instrument in standby mode. The LCD display is frozen at the current values.
The display will be updated when the instrument receives a TR1 or TR2 command. To resume the
normal free run mode of the instrument and display, use the TR3 command. During the standby mode,
the instrument continues to make measurements and update the internal digital filter, but does not
update the display or the GPIB buffer.
Example: OUTPUT 713;TR0 ! Select the trigger hold mode
Trigger Immediate (TR1)
This command triggers a single reading; the reading is added to the internal digital filter. An ENTER
statement will return the updated filter power level. After a TR1 command, the instrument returns to
the standby mode.
Example: OUTPUT 713;TR1 ! Trigger a single measurement
Trigger Immediate with Full Averaging (TR2)
This mode triggers a new series of readings; enough to update the digital filter for a noise free reading at
the current power level. An ENTER statement will return the fully updated filter power level. After a
TR2 command, the instrument returns to the standby mode.
Example: OUTPUT 713;TR2 ! Trigger a full measurement, with settling
Free Run (TR3)
This free run trigger mode (which is the default mode) allows the user to read the power at any time
with an ENTER statement. There is no need to send the TR3 command again. Multiple ENTER
statements can be executed. The power meter will return the present power level just as if you had
looked at the LCD display.
Example: OUTPUT 713;TR3 ! Free run trigger mode
3-34 Manual 30280, Rev. J, September 2000
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