Fluke PM-3384B, PM-3370B, PM-3390B User Manual

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I

SCPI Users Manual

02/- Nov-1998

®

II

TRADEMARKS

Microsoft, and Microsoft QuickBASIC are trademarks of Microsoft Corporation.
IBM is a registered trademark of International Business Machines Corporation.
CombiScope

PCIIA is a trademark of National Instruments Corporation.

HPGL is a trademark of Hewlett-Packard Company.

 is a trademark of Fluke Corporation.

Copyright  1996, 1998 Fluke Corporation
All rights reserved. No part of this manual may be reproduced by any means or in
any form without written permission of the copyright owner.

Printed in the Netherlands

CONTENTS Page

III

1 ABOUT THIS MANUAL

1.1 What this Manual Contains

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

2 GETTING STARTED WITH SCPI PROGRAMMING

2.1 Preparations for SCPI Programming

2.1.1 System setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1.2 Programming environment . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2 Initializing the CombiScope Instrument

2.2.1 How to reset the CombiScope instrument . . . . . . . . . . . . . . 2-4

2.2.2 How to identify the CombiScope instrument . . . . . . . . . . . . 2-4

2.2.3 How to switch between digital and analog mode . . . . . . . . . 2-4

2.3 Error Reporting

2.4 Acquiring Traces

2.4.1 How to acquire a single shot trace . . . . . . . . . . . . . . . . . . . . 2-7

2.4.2 How to acquire repetitive traces . . . . . . . . . . . . . . . . . . . . . . 2-8

2.5 Measuring Signal Characteristics

2.5.1 How to make a single shot measurement . . . . . . . . . . . . . 2-10

2.5.2 How to make repeated measurements . . . . . . . . . . . . . . . 2-10

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

. . . . . . . . . . . . . . . . . . . . . . 2-1

. . . . . . . . . . . . . . . . . . . . 2-4

. . . . . . . . . . . . . . . . . . . . . . . . . 2-9

. . 2-1

3 USING THE COMBISCOPE INSTRUMENTS

3.1 Introduction

3.2 Fundamental Programming Concepts

3.2.1 Measurement instructions . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.2.2 Single function progra mming using the instrument model . . 3-5

3.2.3 Instrument setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3.2.4 Front panel simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

. . . . . . . . . . . . . . . . . . . . . 3-3

. . . . . . . . . 3-1

IV

3.3 Measuring Signal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3.3.1 The MEASure? query . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3.3.2 Benefits of using parameters . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3.3.3 Waveform measurements . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

3.3.4 Customizing settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

3.3.5 Multiple measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

3.3.6 Multiple characteristics from a single acquisition. . . . . . . . 3-15

3.3.7 Trigger control via GPIB . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16

3.3.8 Fetching characteristics from memory traces . . . . . . . . . . 3-17

3.4 Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3.4.1 Acquisition control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3.4.1.1 Triggering

3.4.1.2 Video triggering

3.4.1.3 The trigger modes

3.4.1.4 Pre- and post-triggering

3.4.1.5 External triggering

3.4.2 Reading trace acquisitions . . . . . . . . . . . . . . . . . . . . . . . . . 3-29

3.4.2.1 Single-shot acquisition

3.4.2.2 Repetitive acquisitions

3.4.3 Conversion of trace data . . . . . . . . . . . . . . . . . . . . . . . . . . 3-31

3.4.3.1 Conversion of 8-bit samples to integer

3.4.3.2 Conversion of 16-bit samples to integer

3.4.3.3 Conversion to voltage values

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25

. . . . . . . . . . . . . . . . . . . . . . . . 3-27

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-28

. . . . . . . . . . . . . . . . . . . . . . . . . 3-30

. . . . . . . . . . . . . . . . . . . . . . . . . 3-30

. . . . . . . . . . . . . 3-32

. . . . . . . . . . . . 3-33

. . . . . . . . . . . . . . . . . . . . 3-34

3.5 Averaging Acquisition Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-36

3.6 Channel Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-38

3.7 Signal Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3.7.1 AC/DC/ground coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3.7.2 Input filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

3.7.3 Input impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

3.7.4 Input polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

3.7.5 Vertical range and offset . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

3.7.6 Autoranging attenuators . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41

3.8 Time Base Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42

3.8.1 Number of samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42

3.8.2 Time base speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-42

3.8.3 Real time acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-43

3.8.4 Autoranging time base . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-44

3.9 Post Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-45

3.9.1 How to do post processing . . . . . . . . . . . . . . . . . . . . . . . . . 3-45

3.9.1.1 Select the source for the post processing function.

3.9.1.2 Specify the settings of the post processing function.

3.9.1.3 Enable the post processing function.

. . . . . . . . . . . . . . 3-46

3.9.1.4 Check the result of the post processing function.

3.9.2 Mathematical calculations . . . . . . . . . . . . . . . . . . . . . . . . . 3-48

3.9.3 Differentiating and integrating traces . . . . . . . . . . . . . . . . . 3-48

3.9.4 Frequency domain transformations . . . . . . . . . . . . . . . . . . 3-49

3.9.5 Histogram functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-55

3.9.6 Frequency filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-55

3.10 Trace Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-56

3.10.1 Trace formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-57

3.10.2 Copying traces to memory . . . . . . . . . . . . . . . . . . . . . . . . . 3-58

3.10.3 Writing data to trace memory . . . . . . . . . . . . . . . . . . . . . . . 3-59

3.10.4 Reading data from trace memory . . . . . . . . . . . . . . . . . . . . 3-60

3.11 Screen/Display Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-61

3.11.1 Brightness control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-61

3.11.2 Display functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-61

3.11.2.1 Readout of measurement data

3.11.2.2 Display of user-defined text

3.11.2.3 Selection of softkey menus

. . . . . . . . . . . . . . . . . . . 3-62

. . . . . . . . . . . . . . . . . . . . . 3-65

. . . . . . . . . . . . . . . . . . . . . . 3-65

. . . 3-45

. . 3-46

. . . . . 3-47

V

3.12 Print/Plot Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-66

3.13 Real-Time Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-68

3.14 Auto Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-68

3.15 Status Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-70

3.15.1 Status data for the CombiScope instruments . . . . . . . . . . . 3-70

3.15.1.1 Operation status data

3.15.1.2 Questionable status data

3.15.2 How to reset the status data . . . . . . . . . . . . . . . . . . . . . . . 3-73

3.15.3 How to enable status reporting . . . . . . . . . . . . . . . . . . . . . 3-74

3.15.3.1 Program example using the status byte (STB)

3.15.3.2 Program example using a service request (SRQ)

3.15.4 How to report errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-76

3.15.4.1 Error-reporting routine

3.15.4.2 Error-reporting using th e SRQ me ch an ism

. . . . . . . . . . . . . . . . . . . . . . . . . . 3-71

. . . . . . . . . . . . . . . . . . . . . . . 3-72

. . . . . . . 3-74

. . . . 3-75

. . . . . . . . . . . . . . . . . . . . . . . . . 3-76

. . . . . . . . . 3-77

VI

3.16 Saving/Restoring Instrument Setups . . . . . . . . . . . . . . . . . . . . . 3-78

3.16.1 How to restore initial settings . . . . . . . . . . . . . . . . . . . . . . . 3-78

3.16.2 How to save/restore a setup via instrument memory . . . . . 3-78

3.16.3 How to save/restore a setup via the GPIB controller . . . . . 3-78

3.17 Front Panel Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-79

3.17.1 How to simulate the pressing of a front panel key . . . . . . . 3-79

3.17.2 How to simulate the operation of a softkey menu . . . . . . . 3-80

3.18 Functions not Directly Programmable . . . . . . . . . . . . . . . . . . . . 3-81

4 COMMAND REFERENCE

4.1 Notation Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1.1 Syntax specification notations . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1.2 Data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.2 Command Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.3 Command Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13

A APPLICATION PROGRAM EXAMPLES

A.1 Measuring Signal Characteristics . . . . . . . . . . . . . . . . . . . . . . . A-2

A.1.1 Making automatic measurements . . . . . . . . . . . . . . . . . . . A-2

A.1.2 Making programmed measurements . . . . . . . . . . . . . . . . A-4

A.1.3 Reading measurement values . . . . . . . . . . . . . . . . . . . . . A-5

A.2 Acquiring Waveform Traces . . . . . . . . . . . . . . . . . . . . . . . . . . . A-5

A.3 Saving/Recalling Instrument Setups . . . . . . . . . . . . . . . . . . . . A-6

A.3.1 Save/recall settings to/from internal memory . . . . . . . . . . A-6

A.3.2 Save/recall settings to/from computer disk memory . . . . . A-7

A.4 Making a Hardcopy of the Screen . . . . . . . . . . . . . . . . . . . . . . . A-9

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

. . . . . . . . . . . . . A-1

A.5 Pass/Fail Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-10

A.5.1 Saving a pass/fail test setup . . . . . . . . . . . . . . . . . . . . . . A-10

A.5.2 Restoring a pass/fail test setup . . . . . . . . . . . . . . . . . . . . A-11

A.5.3 Running a pass/fail test . . . . . . . . . . . . . . . . . . . . . . . . . . A-12

VII

B CROSS REFERENCES

B.1 Cross Reference Front Panel Keys / Commands

B.2 Cross Reference Softkey Menus / Commands

B.2.1 ACQUIRE menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-3

B.2.2 CURSORS menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-4

B.2.3 DISPLAY menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-5

B.2.4 MATHPLUS MATH menu . . . . . . . . . . . . . . . . . . . . . . . . . B-6

B.2.5 MEASURE menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-9

B.2.6 DTB (DEL’D TB) menu . . . . . . . . . . . . . . . . . . . . . . . . . . . B-9

B.2.7 SAVE/RECALL menu . . . . . . . . . . . . . . . . . . . . . . . . . . . B-10

B.2.8 SETUPS menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-10

B.2.9 TB MODE menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-11

B.2.10 TRIGGER menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-12

B.2.11 UTILITY menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-14

B.2.12 VERTICAL menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-16

B.3 Cross Reference Functions / Commands

C MANUAL CONVENTIONS

C.1 Abbreviations Used

C.2 Glossary of Symbols Used

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4

. . . . . . . . . . B-1

. . . . . . . . . . . . B-3

. . . . . . . . . . . . . . . B-17

C.3 List of Tables

C.4 List of Figures

C.5 Documents Referenced

D STANDARDS INFORMATION

D.1 SCPI Conformance Information

D.2 List of Implemented IEEE-488.2 Syntactical Elements

E SUMMARY OF SYSTEM SETTINGS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-6

. . . . . . . . . . . . . . . . . . . . . . . . D-1

. . . . . . . . . . . . . . . . . . . . . . . . D-1

. . . . . . . . . . . . . . . . . E-1

. . . . . . D-2

ABOUT THIS MANUAL 1 - 1

1 ABOUT THIS MANUAL

The SCPI Programming Manual for the CombiScope instruments describes
how to program your CombiScope instrument via the IEEE bus using SCPI
commands.

1.1 What this Manual Contains

A complete table of contents is given at the beginning of the manual.
Chapter 1 ABOUT THIS MANUAL

Explains what the SCPI programming manual for the CombiScopes
instruments contains.

Chapter 2 GETTING STARTED WITH SCPI PROGRAMMING

T ells you how to get started quickly with your CombiScope instrument.
You can execute the program examples per (sub)section or from the
beginning until the end.

Chapter 3 USING THE COMBISCOPE INSTRUMENTS

Explains how SCPI works for your CombiScope instrument from
the functional point of view. Section 3.1 is an introduction and
section 3.2 explains the fundamental programming concepts. The
other sections and subsections represent the functional use of your
CombiScope instrument.

Chapter 4 COMMAND REFERENCE

Is a complete alphabetical reference of all implemented SCPI
commands. In the beginning a command summary is given to
provide you with a quick reference.

1 - 2 ABOUT THIS MANUAL

Appendix A APPLICATION PROGRAM EXAMPLES

Appendix A describes some application program examples. The
application programs are supplied on floppy.

Appendix B CROSS REFERENCES

Appendix B gives cross references between SCPI commands and
front panel keys, softkey menu options, and instrument functions.

Appendix C MANUAL CONVENTIONS

Appendix C explains which abbreviations and symbols ar e used i n
the manual. It also gives a list of the tables, figures, and documents
referenced.

Appendix D STANDARDS INFORMATION

Appendix D gives information regarding SCPI and IEEE-488.2
standards.

Appendix E SUMMARY OF SYSTEM SETTINGS

Appendix E lists the system settings per functional group (node),
plus the applicable instrument settings per node.

A full alphabetical index is given at the end of the manual.

GETTING STARTED WITH SCPI PROGRAMMING 2 - 1

2 GETTING STARTED WITH SCPI

PROGRAMMING

2.1 Preparations for SCPI Programming

To program your CombiScope instrument, you need a system setup and a
programming environment. Various program examples (refer to PROGRAM
EXAMPLE:) are given in the following sections. These progra m examples can be
executed one at a time or chained together for a complete tutorial. The program
examples are based on the system and programming environment as described
below.

Note: All PROGRAM EXAMPLE's in this chapter are supplied on floppy under

the file name EXGETSTA.BAS. They are chained together in order of
appearance.

2.1.1 System setup

The CombiScope instrument contains a factory-installed IEEE option.

•

A PC is used as controller. In the PC an IEEE-488.2 interface (GPIB) board

•

must be installed to turn the PC into a GPIB controller. The GPIB controller
must be connected to the CombiScope instrument via an IEEE cable.

Note: The program examples throughout this manual have bee n executed

on an IBM-compatible PC with the GPIB interface board and
software of the product PM2201/03 installed. The PM2201 board is
equivalent to the PCIIA board from National Instruments.

2.1.2 Programming environment

MS-QuickBASIC is used as the programming language.

•

A number of standard IEEE-488.2 drivers are used to control the CombiScope

•

instrument via the GPIB. These drivers must be included in the application
program. Therefore, the first statement of an application program must be as
follows:

REM $INCLUDE: ’<path>QBDECL.BAS’

Note: The program examples throughout this manual have bee n executed

using the IEEE-488.2 drivers and the device handler GPIB.COM of
the product PM2201/03.

2 - 2 GETTING STARTED WITH SCPI PROGRAMMING

The parameters of these drivers are defined by the device handler GPIB.COM
and by the QuickBASIC program code. The following drivers a nd param eters ar e
used in the program examples:

The IEEE-488.2 driver "Send" is used to send a command or query to an

•

instrument.

CALL Send (<board>, <address>, <command>, <eot>)

The IEEE-488.2 driver "SendSetup" is used to prepare one or more devices

•

to receive data bytes. The controller becomes talker and the device b ecomes
listener.

CALL SendSetup (<board>, <addresslist>)

The IEEE-488.2 driver "SendDataBytes" is used to send data bytes from a

•

talking controller to a listening device.

CALL SendDataBytes (<board>, <data>, <eot>)

The IEEE-488.2 driver "Receive" is used to read a response string from an

•

instrument.

CALL Receive (<board>, <address>, <response>, <term>)

The IEEE-488.2 driver "SendIFC" is used to clear the GPIB interface.

•

CALL SendIFC (<board>)

The IEEE-488.2 driver "IbTMO" is used to specify a time out period for the

•

interface board.

CALL IbTMO (<board>, <timeout>)

Explanation of the parameters used in the IEEE-488.2 drivers:

<board> IEEE board identification inside the PC (default board

•

<address> IEEE instrument address (default CombiScope instrument

•

<addresslist> Array containing GPIB device addresses, terminated by the

•

<command> A command or query string to be sent to the instrument. The

•

<data> One or more data characters to be sent to the listener device.

•

address =0).

address = 8).

constant -1 (FFFF hex.).

"short form" commands are specified in UPPER CASE. The
additional characters in lower case complete the "long form"
commands.

GETTING STARTED WITH SCPI PROGRAMMING 2 - 3

Includes GPIB drivers

Clears text from PC screen

Clears the GPIB interface

Sets time out at 10 seconds

<response> A response string sent by the instrument as a response to a

•

<eot> An "end of text" indication:

•

<term> A "terminate" indication:

•

<timeout> A time out indication, e.g., 11 = 1 second, 12 = 3 seconds,

•

PROGRAM EXAMPLE:

’

*****

’Initial program statements:
’

*****

REM $INCLUDE:’c:\pc-gpib\488driv\QBDECL.BAS’ ’
CLS ’
CALL SendIFC(0) ’
CALL IbTMO(0, 13) ’

query .

0 = program message to be continued (no action)
1 = end of program message (sends End-message + EOI
true)

0 = response message to be continued (no detection of EOL
character)
256 = end of response message (stops reading after EOL
character)

13 = 10 seconds.

PROGRAMMING NOTE:

The variable IBCNT% contains the number of response bytes (including NL
after reading a response message using the Receiv e dr iver.

)

2 - 4 GETTING STARTED WITH SCPI PROGRAMMING

Resets the instrument

Clears the status data

Requests for identification

Reads the ident string

Prints the ident string

Requests for options

Reads the options string

Prints the options string

Switches to analog mode

Switches back to digital mode

2.2 Initializing the CombiScope Instrument

2.2.1 How to reset the CombiScope instrument

The instrument itself can be reset by sending the
instrument to a fixed setup optimized for remote operation. The status and error
data of the instrument can be cleared by sending the

RST command. This sets the

*

CLS command.

*

PROGRAM EXAMPLE:

’

*****

’Reset the instrument and clear the status data:
’

*****

CALL Send(0, 8, "*RST", 1) ’
CALL Send(0, 8, "*CLS", 1) ’

2.2.2 How to identify the CombiScope instrument

The identity of the instrument can be queried by sending the
followed by reading the instrument response message. The options of the
instrument can be queried by sending the
instrument response message.

OPT? query, followed by reading the

*

IDN? query,

*

PROGRAM EXAMPLE:

’

*****

’Read and print the identity and options of the instrument:
’

*****

response$ = SPACE$(65)
CALL Send (0, 8, "*IDN?", 1) ’
CALL Receive (0, 8, response$, 256) ’
PRINT "Ident: "; LEFT$(response$, IBCNT%) ’
CALL Send (0, 8, "*OPT?", 1) ’
CALL Receive (0, 8, response$, 256) ’
PRINT "Options: "; LEFT$(response$, IBCNT%) ’

2.2.3 How to switch between digital and analog mode

After power on, a CombiScope instrument can be either in the digital or analog
mode. After a
system allows you to switch between the two modes. This can be done by speci­fying a predefined name (DIGital, ANALog) or the corresponding number
(1 = digital, 2 = analog).

PROGRAM EXAMPLE:

’

*****

’Initialize and change the operating mode of the CombiScope instrument:
’

*****

CALL Send (0, 8, "INSTrument ANALog", 1) ’
CALL Send (0, 8, "INSTrument:NSELect 1", 1) ’

RST command the digital mode is selected. The INSTrument sub-

*

GETTING STARTED WITH SCPI PROGRAMMING 2 - 5

Requests for error

Reads error message

Displays error message

2.3 Error Reporting

Instrument errors are usually caused by programming or setting err ors. They are
reported by the instrument during the execution of each command. To make sure
that a program is running properly, you must query the instrument for possible er­rors after every functional command. This is done by sending the
SYST em:ERR or? query or the STAT us:QUEue? qu ery to the instrument, followed
by reading the response message. However , through this practice the same "error
reporting" statements must be repeated after sending each SCPI command . This
is not always practical. Therefore, one of the following approaches is advised:

1) Send the SYST em:ERRor? or ST ATus:QUEue? query and read the instrument
response message after every group of commands that functionally belong to
each other.

2) Program an error-reporting routine and call this routine after each command
or group of commands. For an example of an error-reporting routine, refer to
section 3.14.4.1.

3) Program an error-reporting routine and use the "Service Request (SRQ)
Generation" mechanism to interrupt the execution of the program and to
execute the error-reporting routine. Therefore, refer to section 3.14.4.2.

PROGRAM EXAMPLE:

’

*****

’Read error message:
’

*****

er$ = SPACE$(60)
CALL Send(0, 8, "SYSTem:ERRor?", 1) ’
CALL Receive(0, 8, er$, 256) ’
PRINT "Response to error query = ";
PRINT LEFT$(er$, IBCNT%-1) ’

2 - 6 GETTING STARTED WITH SCPI PROGRAMMING

2.4 Acquiring Traces

Trace acquisitions are started via the INITiate commands. A single acquisition is
done by sending a single INITiate command . Continuous acquisitions are done by
sending the INITiate:CONTinuous ON command.

The TRACe? query allows you to acquire a trace of signal samples from one of
the following sources:

An input channel, e.g., CH2 (input channel 2).

•

A trace area in a memory register, e.g., M2_3 (Memory register 2, trace 3).

•

The number of trace samples (acquisition length) can be specified using the
TRACe:POINts command. If your instrument has standard memory, you can
specify 512, 2048, 4096, or 8192 trace samples. If your instrument has extended
memory, you can specify 512, 8192, 16384, or 32768 trace samples. A
TRACe:POINts command specifies the acquisition length for all channels and
memory registers.
Example: Send --> TRACe:POINts CH1,8192 ’Selects 8192 sample points

for all traces

The number of trace sample bits can be specified using the FORMat command.
This gives you the possibility to define samples of 8 bits (1 byte) or 16 bits
(2 bytes). A FORMat command specifies the number of sample bits for all
channels and memory registers.
Example: Send --> FORMat INT,16 ’Formats 16-bits samples

The format of the trace response data is as follows:

# n x . . x f b . . . . . b s <NL>

NewLine code (10 decimal)
checksum byte over all trace bytes

trace sample data bytes (see Note)
trace data format byte (see Note)
number of trace bytes (fbb...bbs)
number of digits of x..x

Note: If f=8 decimal, each trace sample is one byte (8 bits).

Example:

# 4 1 0 2 6 <16> <msb 1> <lsb 1> . . . <msb 512> <lsb 512> <checksum> <10>

If f=16 decimal, each trace sample is two bytes (16 bits), i.e., most significant byte
(msb) + least significant byte (lsb).

trace sample 512
trace sample 1
decimal 16
number of trace bytes (N)
number of digits of N

GETTING STARTED WITH SCPI PROGRAMMING 2 - 7

Formats 8-bits sample

Formats 8192 sample points

Trigger-source = channel 1

Trigger-level = 0.1

Single shot initiation

Waits for previous commands

to finish

Queries for channel 1trace

Reads channel 1 trace

The contents of the tracebuf$ string is as follows:

# 4 8194 <8> <byte 1> ... <byte 8192> <sum> <10>

IBCNT% = number of bytes

2.4.1 How to acquire a single shot trace

In the program example, a single shot trace acquisition of 8192 8-bit samples is
done with a probe connected to input channel 1. The trace sample byte s are read
from the GPIB as string characters. The number of response bytes and the
number of samples are printed.

The TRIGger:SOURce command is used to specify input channel 1 as a trigger
source. The TRIGger:LEV el command is used to reset the trigg er level to e.g., 0.1
volts.

PREPARATIONS:

Connect a probe to channel 1. After start up of the program you will be asked

•

to trigger the acquisition with the open end of the probe, i.e., touch the probe
or strike the probe on the table.

PROGRAM EXAMPLE:

’

*****

’Acquire a single shot trace:
’

*****

DIM tracebuf AS STRING * 16500
CALL Send(0, 8, "FORMat INTeger,8", 1) ’
CALL Send(0, 8, "TRACe:POINts CH1,8192", 1) ’
CALL Send(0, 8, "TRIGger:SOURce INTernal1", 1) ’
CALL Send(0, 8, "TRIGger:LEVel 0.1", 1) ’
CALL Send(0, 8, "INITiate", 1) ’
PRINT "Trigger the CombiScope instrument by touching the probe tip."
PRINT ">>> Press any key when finished."
WHILE INKEY$ = "": WEND
CALL Send(0, 8, "*WAI", 1) ’

CALL Send(0, 8, "TRACe? CH1", 1) ’
CALL Receive(0, 8, tracebuf$, 256) ’
’
’
’
’
nr.of.digits = VAL(MID$(tracebuf$, 2, 1))
nr.of.bytes = VAL(MID$(tracebuf$, 3, nr.of.digits)) - 2
sample.length = ASC(MID$(tracebuf$, 3 + nr.of.digits, 1)) / 8
nr.of.samples = nr.of.bytes / sample.length
PRINT "Number of bytes received ="; IBCNT% ’
PRINT "Number of trace samples ="; nr.of.samples

Note: Refer to section 3.4.3 "Conversion of trace data" about how to convert

this string data.

2 - 8 GETTING STARTED WITH SCPI PROGRAMMING

Resets the instrument

Configures channel 2

Switches channel 2 on

Opens file TRACE5.DAT

Single initiation

Queries for channel 2 trace

Notice the

*

WAI; before TRACe?. The

*

WAI command takes care that the TRACe? CH2 command is

executed when the INITiate command is finished.

Reads channel 2 trace

Writes trace header to file

Writes trace buffer to file

Closes file TRACE5.DAT

2.4.2 How to acquire repetitive traces

In the program example, 5 trace acquisitions of 512 16-bit samples are done via
a probe connected to channel 2. The trace sample bytes are read from the GPIB
as string characters and written to the file TRACE5.DAT on the hard disk.

PREPARATIONS:

Connect a probe from the Probe Adjust signal to channel 2.

•

PROGRAM EXAMPLE:

’

*****

’Acquire 5 sequential traces and store in file TRACE5.DAT:
’

*****

DIM tracebuf AS STRING * 1050
CALL Send(0, 8, "*RST", 1) ’
’
’After *RST a trace acquisition is defined at 512 samples of 16 bits
’(2 bytes).
’
CALL Send(0, 8, "CONFigure:AC (@2)", 1) ’
CALL Send(0, 8, "SENSe:FUNCtion ’XTIMe:VOLTage2’", 1)’
OPEN "O",#1,"TRACE5.DAT" ’

FOR i=1 TO 5

CALL Send(0, 8, "INITiate", 1) ’
CALL Send(0, 8, "*WAI;TRACe? CH2", 1) ’
’
’
’
’
CALL Receive(0, 8, tracebuf$, 256) ’
PRINT #1, "Trace buffer:"; i ’
PRINT #1, LEFT$(tracebuf$, IBCNT%) ’

NEXT i

CLOSE ’

Note: Refer to section 3.4.3 "Conversion of trace data" about how to convert

this string data.

GETTING STARTED WITH SCPI PROGRAMMING 2 - 9

MEASure?

CONFigure

READ?

INITiate

FETCh?

2.5 Measuring Signal Characteristics

The measurement instructions allow you to make a complete measurement. This
includes the configuration of the instrument, the initiation of the trigger system,
and the fetching of the acquisition data. The measurement instructions can be
used at different levels, varying in processing time. The highest level is the most
easy to use, but takes more time to complete than the lowest level. The following
levels of measurement instructions can be used:

The highest level:
(easy to use)

The middle level:
(gives more programming flexibility)

The lowest level:
(to acquire more signal characteristics)

The following table shows which measurement tasks are executed by the
measurement instructions:

Configures the instrument: YES YES
Initiates the trigger system: YES YES YES
Fetches the acquired data: YES YES YES

MEASure?

CONFigure

INITiate

+

+

READ?

FETCh?

(equivalent to MEASure?)

(equivalent to READ?)

2 - 10 GETTING STARTED WITH SCPI PROGRAMMING

Measures the AC-RMS value

Reads the AC-RMS value

Fetches the Peak-To-Peak value

Reads the PTP value

Fetches the amplitude value

Reads the amplitude value

Configures for AC-RMS

Performs 5 measurements

Initiates AC-RMS reading

Reads the AC-RMS value

Fetches the Peak-T o-Peak value

Reads the PTP value

Fetches the amplitudevalue

Reads the amplitude value

2.5.1 How to make a single shot measurement

The MEASure? query allows you to make a single-shot measurement, and the
FETCh? query allows you to fetch more signal characteristics.

PROGRAM EXAMPLE:

’

*****

’Measure and print the AC-RMS, peak to peak, and amplitude of
’the signal on channel 1.
’

*****

response$ = SPACE$(30)
CALL Send (0, 8, "MEASure:AC? (@1)", 1) ’
CALL Receive (0, 8, response$, 256) ’
PRINT "AC-RMS value : "; LEFT$(response$, IBCNT% -1)
CALL Send (0, 8, "FETCh:PTPeak?", 1) ’
CALL Receive (0, 8, response$, 256) ’
PRINT "Peak-To-Peak value: "; LEFT$(response$, IBCNT% - 1)
CALL Send (0, 8, "FETCh:AMPLitude?", 1) ’
CALL Receive (0, 8, response$, 256) ’
PRINT "Amplitude value : "; LEFT$(response$, IBCNT% - 1)

2.5.2 How to make repeated measurements

The measurement instructions allow you to make repeated measuremen ts. The
CONFigure command allows you to configure the instrument, the READ? query
allows you to make a measurement, and the FETCh? query allo ws you to fetch
more signal characteristics.

PROGRAM EXAMPLE:

’

*****

’Measure and print 5x the AC-RMS, peak to peak, and
’amplitude of the signal on channel 1.
’

*****

response$ = SPACE$(30)
CALL Send (0, 8, "CONFigure:AC (@1)", 1) ’
FOR i = 1 TO 5 ’

CALL Send (0, 8, "READ:AC?", 1) ’
CALL Receive (0, 8, response$, 256) ’
PRINT "AC-RMS: "; LEFT$(response$, IBCNT%-1);
CALL Send (0, 8, "FETCh:PTPeak?", 1) ’
CALL Receive (0, 8, response$, 256) ’
PRINT " / Peak-To-Peak: "; LEFT$(response$, IBCNT%-1);
CALL Send (0, 8, "FETCh:AMPLitude?", 1) ’
CALL Receive (0, 8, response$, 256) ’
PRINT " / Amplitude: "; LEFT$(response$, IBCNT%-1)

NEXT i

USING THE COMBISCOPE INSTRUMENTS 3 - 1

3 USING THE COMBISCOPE

INSTRUMENTS

3.1 Introduction

This chapter explains how to access the functions of the CombiScope instruments
family in a remote programming environm ent. Fo r tha t purp os e, the Comb iScope
instrument is equipped with an IEEE-488 compatible GPIB interface and
implements a full SCPI compatible command set which provides an extensive
range of remote control facilities.

Traditionally, ther e was no standard for the remote operation of instruments. A
wide range of different command sets existed. Each set had its own te rminology
and trade-offs, based upon the implementations and corresponding limitations of
the instrument. Similar functions in different instruments were controlled by
different commands. And, vice versa, identical commands could easily exist in
another instrument to control a different function. With new technologies and
increasing complexity , other prog ramming concepts were introd uced. This caused
programs with identical functions to look different when written for another
instrument.

The remote control of instruments became a cumbersome process, which
required a high learning curve for each new instrument and each additional
instrument. The time and costs to create and maintain application programs were
unnecessarily high due to the lack of standardization.

With the introduction of the Standard Comm ands for Pr ogra mma ble Instr umen ts,
commonly called SCPI, a lot of progress has been made in this area. The
development time of an application program for SCPI-compatible instruments, like
the CombiScope instrument, is considerably reduced. This is mainly achieved by
the consistent programming environment for instrument control and data usage
across all types of instruments that, regardless of the manufacturer , is provided by
SCPI.

The standardized commands allow the same functions in different types of
instruments to be controlled by the same commands. For example, the que ry
MEASure:FREQuency? acquires the frequency characteristic of the input signal,
regardless of whether the instrument is a frequency counter, an oscilloscope, or
any other measuring instrument.

3 - 2 USING THE COMBISCOPE INSTRUMENTS

As the example already shows, the commands are easy to learn and self­explanatory to both novice and expert users. The learning curve is considerably
decreased for new instruments or instrument functions with which the
programmer is not familiar.

Efficiency is not only gained when creating or debugging new application
programs. The easily understandable programs greatly simplify maintenance and
modification of existing application programs that have been written by other
persons or for other instrument functions.

All major CombiScope instrument functions are controlled by standard SCPI
commands. Although the functionality provided is the same, the way the
oscilloscope is controlled via the remote interface dif fers in some aspects from the
front panel operation. This is because the local fr ont pan el opera tion is d esigned
to allow you to take maximum advantage of the interactive communication
possibilities offered by the display screen. This allows for additional information
and guidance during the process of local operation.

The remote command set is based upon an instrument model that is easy to
understand. This model provides a structured survey of the implemented
instrument functions and serves as a guide towards t he commands that control
these functions. This other view allows for optimal and easy access of the
instrument functions when operated from the remote interface. Additionally, a
measurement instruction set allows for easy programm ing of measur ement tas ks
for a wide variety of signal characteristics.

USING THE COMBISCOPE INSTRUMENTS 3 - 3

3.2 Fundamental Programming Concepts

The remote operation of your CombiScope instrumen t can be accessed using
different programming concepts. The concept to be cho sen depends upon the
application of the instrument in the remote programming environment. Each of the
four concepts has it own benefits and trade-offs.

1) Using measurement instructions
Advantage: Easy to program. No instrument knowledge required to make

measurements. So, you can start programming quickly and get
measurement results rightaway.

Trade-off: A measurement takes some time to complete, because the

instrument automatically searches for optimal settings.

Example:

2) Single function programming using the instrument model
Advantage: Allows you to program individual functions separately throug h

Trade-off: Requires understanding of the remote operation of the instrument

Example:

MEASure:FREQuency?

single commands. The instrument model gives the relation
between the commands and the functions of the CombiScope
instrument.

functions.

TRACe? CH1

Measures the frequency of the
signal at channel 1.

Returns the acquisition trace of
the signal at channel 1.

3) Programming the complete instrument setup
Advantage: Simple to program. No worry about individual settings. This

method can also be used to save and recall settings, which are
not individually programmable.

Trade-off: Processes complete instrument setups. Individual settings

must be set or programmed separately.

Example:

4) Programming through front panel simulation
Advantage: Gives the possibility to program settings for which no remote

SAV 3

*

RCL 3

*

commands are available, i.e., to match a front panel setup.

Saves actual instrument settings
to internal memory 3.
Recalls instrument settings from
internal memory 3.

3 - 4 USING THE COMBISCOPE INSTRUMENTS

Trade-off: This way of programming is cumbersome and tricky, because

additional information on the front panel display is not always
available remotely.

Example: DISPlay:MENU TRIGger Activates the TRIGGER softkey

menu.

SYSTem:KEY 4 Simulates the pressing of softkey 4.

The effect is that TRIGGER menu
option "noise" is switched on or
off.

3.2.1 Measurement instructions

This is a completely new approach in the remote operation of programmable
instruments, which provides a set of task-oriented measurement instructions.
Rather than programming every instrument setting separately with starting the
acquisition and calculating the result, just specify the desired signal characteristic,
and the CombiScope instrument returns the requested re sult. Depending upon
the actual available signal, your CombiScope instrument automatically
determines the optimal settings to acquire and calculate the requested result.

An example of such a command is the MEASure:FREQuency? query, which not
only works on oscilloscopes, but also on different types of SCPI-compatible
instruments, such as counters and multimeters.

With traditional oscilloscopes you had to do the following:

- set up all function s of the oscilloscope separately.

- start the acquisition of the data.

- position the cursor markers.

- calculate the frequency from the acquired data.

- read the calculat ed frequency from the instrument.
A single, simple SCPI query replaces all of the above, namely the

MEASure:FREQuency? query which does the following:

- auto configures the oscilloscope to the best possible setting for the requested
measurement task.

Note: This process is different from the traditional AUTOSET process in

that the autoset function determines the instrument settings based
on the input signal only, whereas, the auto configure algorithm also
takes the desired measurement task into account.

- starts the acquisition process.

- takes care that the measurement is triggered.

- calculates the desired characteristic from the acquired data.

- returns the calculated value.

USING THE COMBISCOPE INSTRUMENTS 3 - 5

The measurement instructions are easy to use and do not require any special
knowledge of the instrument. The programming concept reduces simple
measurement tasks with complex instruments to simple instructions, leaving the
setup complexity to the instrument. The measurement instructions are extremely
useful when the application does not require the precise setting of instrume nt
functions. The concept is extendible with separate control of parameters that are
vital to the application.

3.2.2 Single function programming using the instrument model

All major instrument functions such as time base, input impedance, etc, are
separately programmable using "single parameter" commands. The easy to
understand command set is comparable with the way instruments are traditiona lly
controlled. This concept gives you full control over all functions and power of a
modern oscilloscope. However , for maximum b enefit of all the advanced fe atures
of your CombiScope instrument, you need some understanding of their remote
operation.

Functions of the CombiScope instrument th at belong together are grouped into
subsystems. There are several subsystems, each representing a particular
function. The instrument model in the following figure gives an overview of the
most important subsystems.

DISPlay

INPut SENSe

TRIGger

Figure 3.1 The Instrument Model for CombiScope instruments

EXPLANATION OF THE INSTRUMENT MODEL:

All functions that deal with signal conditioning are part of the INPut subsystem.

•

In a similar way the SENSe subsystem contains the data acquisition part

•

where the analog signal is converted into a digital value.
The results of the acquisition are stored in a TRACe subsystem memory.

•

Post-processing functions on the acquired data are available in the

•

CALCulate subsystem.
The TRIGger subsystem deals with the control of the acquisition process.

•

The DISPlay subsystem handles the front panel display functions.

•

TRACe CALCulate

ST7155

3 - 6 USING THE COMBISCOPE INSTRUMENTS

Functions in a particular subsystem are always controlled by commands that
begin with the name of that subsystem. For example, a command that programs
the input coupling is INPut:COUPling DC.

All programmable settings can be queried easily. The query form is obtained from
the command by simply removing the parameter and adding a question mark. For
example, the command to program the input impedance of your oscilloscope is
INPut:IMPedance 50. This impedance value can be queried by sending
INPut:IMPedance? which returns 50.

3.2.3 Instrument setup

This concept allows you to program instrument settings with a single command.
Several instrument setups can be saved, either created by remote programming
or by front panel control. This concept can also be use d to program instrument
functions that cannot be directly accessed using individual pr ogram instructions.
Complete instrument setups can be saved either in the internal memory of the
oscilloscope or externally in the remote controller. A part of the instrument setup
can also be saved externally.

The oscilloscope is equipped with a number of internal memories in which the
complete instrument set up can be saved and from which it can be restored.

→

Send
Send

Instead of using an internal oscilloscope memory, the instrument setup can be
queried using the SYSTem:SET? query. The result of this query is that the
oscilloscope sends a part or the complete setup in a compact block data format.
Sending this data back as a parameter with the SYSTem:SET command
reprograms the oscilloscope to the same settings.

SAV 3 Saves the current set up into memory 3.

*

→

RCL 3 Recalls the instrument set up that was saved in memory 3.

*

Example for the complete instrument settings:

→ SYSTem:SET? Queries the oscilloscope for the complete

Send

instrument setup.

← <block_data> Reads the <block_data> response, which

Read

contains the requested instrument setup,
from the oscilloscope.

→ SYSTem:SET <block_data> Sends the previously read instrument

Send

setup back to the oscilloscope in the
same <block_data> format.

USING THE COMBISCOPE INSTRUMENTS 3 - 7

Example for the instrument cursor settings:
Send

→ SYSTem:SET? 32 Queries the oscilloscope for the

instrument settings of node 32, which are
the cursor settings.

← <settings> Reads the cursor settings.

Read
.
.
Send

→ SYSTem:SET <settings> Restores the cursor settings.

3.2.4 Front panel simulation

This concept allows you to send commands that simulate the pressing of a front
panel key. This method allows the remote operation to precisely match a front
panel setup. In particular, this method can be used to access instrument functions
that cannot be programmed directly by remote commands.

As described in the beginning of this section, there is a difference between the
front panel operation and the remote control of an instrument. If you use the front
panel simulation commands via the remote interface, be aware that no use can
be made of the additional information that is presented on the screen of the
oscilloscope. As this causes the front panel simulation method to be a tedious
process, it is certainly not recommended as a common programming practice.

For example, the SYSTem:KEY 507 command switches the AVERAGE function
on when it was switched off before. When this function was switched on before,
the AVERAGE function is switched off. The effect of the SYSTem:KEY command
completely depends upon the state of the instrument at the moment the command
is received. In a remote programming environment it is not immediately clear
whether a state is on or off. For that reason the command SENSe:AVERage ON
is much better.

To select functions that cannot b e programmed directly, you might use the front
panel simulation commands. For example, the command SYSTem:KEY 4
switches the "noise suppression" option in the TRIGGER menu of the front panel
ON or OFF.

3 - 8 USING THE COMBISCOPE INSTRUMENTS

3.3 Measuring Signal Characteristics

As explained in section 3.2.1 "Measurement instructions", the measurement
instruction set is a new approach in the remote operation of programmable
instruments. This instruction set allows you to request a particular characteristic
of the input signal. The CombiScope instrument th en chooses the best possible
settings, executes the requested task, and returns the desired result.

Within the measurement instruction set, different programming levels can be
distinguished. The highest level is the easiest to use, but the trade-off is less
flexibility. Lower levels provide more flexibility by offering more control over the
instrument functionality. This requires more knowledge about the remote
operation of your instrument.

The measurement instructions specify a particular task in terms of the expected
signal and the desired result. The instructions refer to the sig nal characteristics of
the signal being measured. This makes them independent from the
implementation of the instrument functions. For example, when the instruction
MEASure:FREQuency? is executed, it is not important whether t his frequency is
measured by precisely counting the signal period, or if it is calculated from a
sampled waveform. For this reason, the measurement instru ctions provide the
best compatibility among different types of instruments. But, as a trade-off, the
compatibility decreases when more flexibility is needed and lower measurement
instruction levels are used.

3.3.1 The MEASure? query

This is the easiest instruction to use and provides the best compatibility. However,
it does not offer access to the full capability of the CombiScope instrument. The
MEASure? query configures the instrument for optimal settings, starts the data
acquisition, and returns the result in one operation. The signal characteristics that
can be acquired in this way are shown in figure 3.2.

Example:

MEASure:AC?

This query measures the RMS voltage of the AC component at the default
input channel 1. After the acquisition, the result is sent to the controller. The
instrument itself selects an optimal setting for this purpose and carries out the
requested measurement as "well" as possible. Moreover, it automatically
starts the measurement.

USING THE COMBISCOPE INSTRUMENTS 3 - 9

3.3.2 Benefits of using parameters

The generic form of a measurement instruction is as follows:

MEASure[:VOLTage]:<measure_function>?

[[<voltage_parameters>,]<measure_parameters>][,<channel_list>]

The :VOL Tage keyword is a default node, which specifies the signal characteristic
to be measured, relates to the voltage component of the signal. The
<measure_function> specifies the desired signal characteristic.

The parameters can be used to provide additional information to the instrument
about the expected signal and the desired result. The oscilloscope uses this
information to determine the best settings for the requested task. As the syntax
shows, the parameters can be left out (defaulted). In that case, the oscilloscope
chooses it own settings based upon the actual available input signal and its own
trade-offs. The result of defaulting parameters is that the measurement needs
more time to complete.

The VOLTage parameters relate to the :VOLTage node in the header. These
parameters specify the expected voltage and the desired resolution:

<voltage_parameters> = [<expected_voltage>[,<resolution>]]

The expected voltage in the parameter specification is assumed to be the value
at the BNC input of the oscilloscope. When a detectable probe is attached, it is
assumed to be the value at the probe tip.

When the <expected voltage> parameter is defaulted, the oscilloscope performs
an autorange, which needs some additional time. When a particular value was
specified instead, the oscilloscope immediately selects the range next higher to
the specified voltage, omitting the relative time-consuming autoranging.

Notice that when voltage parameters are used, the :VOLtage node must be sent
explicitly in the command header . Or, in other words, when the :VOLTage node is
defaulted, the voltage parameters must also be defaulted.

3 - 10 USING THE COMBISCOPE INSTRUMENTS

Examples:

MEASure:AMPLitude?

This query measures the amplitude of a waveform at the default input
channel 1. After the acquisition, the resulting amplitude is returned.

MEASure:VOLTage:AMPLitude? 10, (@2)

This query measures the amplitude of a signal at channel 2 (@2). But, since
it specifies the expected voltage value (10 volts), it will complete the
measurement faster.

In a similar way the measure function parameters provide the oscilloscope with
information about the signal characteristic to be measured. The parameters that
are allowed depend upon the requested signal char acteristic (mea sure function).

The measure function parameters that specify a voltage characteristic, such as
:AC, :AMPLitude, :HIGH, :MINimum, etc, use the voltage parameters for that
purpose. Measure functions, such as fall and rise tim e, frequency and period, use
time units. Their expected value and desired resolution are specified in seconds
or Hertz as separate measure parameters.

Examples:

MEASure:VOLTage:FREQuency? 10E6, (@3)

This query measures the frequency of the signal at input channel 3. The
expected frequency is 10 MHz, whereas, the expected voltage is defaulted.
Notice that this command is equivalent to the MEASure:FREQuency? 10E6,

(@3) command.

MEASure:VOLTage:FREQuency? 5, 10E6, (@3)

This query does the same as the previous example, except that the expected
voltage is 5 volts.

USING THE COMBISCOPE INSTRUMENTS 3 - 11

3.3.3 Waveform measurements

The following figure shows the terms used for pulse measurements and the key
words that are used as header nodes in the measurement instructions.

TMAXimum

MAXimum

HIGH

LOW

RISE
OVERshoot

REFerence
HIGH

REFerence
MIDDle

REFerence
LOW

RISE TIME

RISE
PREShoot

TMINimum

AMPLitude

FALL

OVERshoot

FALL TIME

PERiod

FALL
PREShoot

NWIDthPWIDth

PTPeak

MINimum

ST7154

Figure 3.2 Pulse characteristics

The reference high and low parameters determine the desired interval for rise
time and fall time measurements. The default low and high references are 10%
and 90% of the pulse amplitude (= HIGH - LOW).
Default REFerence LOW =LOW + 0.1
Default REFerence HIGH =LOW + 0.9

(HIGH - LOW)

*

(HIGH - LOW)

*

In a similar way, the reference middle parameter determines the desired interval
for pulse width (PWIDth, NWIDth) and duty cycle (PDUTycycle, NDUTycycle)
measurements. When defaulted, the reference middle value is assumed to be at
50% of the amplitude.
Default REFerence MIDDle =LOW + 0.5

(HIGH - LOW)

*