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

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SCPI Users Manual

02/- Nov-1998

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.

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

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

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

. . . . . . . . . . . . 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

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

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

. . . . . . . . . . . . . . . . . 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)

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)

3 - 12 USING THE COMBISCOPE INSTRUMENTS

Examples:

MEASure:FALL:TIME? (@3)

Measures the time interval during which the pulse at channel 3 decreases from 90% to 10% of its amplitude.

MEASure:RISE:TIME? 20,80

Measures the time interval during which the pulse at the default channel 1 increases from 20% to 80% of its amplitude.

The following measure functions and parameters can be programmed:

<measure_function><measure_parameters>

:AC :AMPLitude [:DC] :FALL

:OVERshoot :PREShoot :TIME [<reference_low> [,<reference_high> [,<expected_time>

[,<time_resolution>]]]] :FREQuency [<expected_frequency> [,<frequency_resolution>]] :HIGH :LOW :MAXimum :MINimum :NDUTycycle <reference_middle> :NWIDth <reference_middle> :PDUTycycle <reference_middle> :PERiod [<expected_period> [,<period_resolution>]] :PTPeak :PWIDth <reference_middle> :TMAXimum :TMINimum :RISE

:OVERshoot :PREShoot :TIME [<reference_low> [,<reference_high> [,<expected_time>

[,<time_resolution>]]]]

Notes: - :DCYCle = alias for :PDUTycycle

- :F TIMe = alias for :FALL:TIME

- :RTIMe = alias for :RISE:TIME

USING THE COMBISCOPE INSTRUMENTS 3 - 13

3.3.4 Customizing settings

Often, you need more precise control of the measur ements than possible with the MEASure? query. The combination of CONFigure and READ? is provided to allow you to program one or more settings that are vital to your application. Executing this sequence of instructions is equivalent to sending MEASure? For setting up the instrument, CONFigure uses the same measure functions and parameters as MEASure?. The CONFigure command does the instrument setup portion of MEASure?. The READ? query initiates the acquisition, performs the needed calculations, and returns the desired result.

Since READ? no longer changes instrument settings, commands that are executed after CONFigure, but before READ?, are taken into effect by the acquisition. This concept allows you to perform a generic configuration through CONFigure and then customize the measurement by programming the settings that are vital to your application. Next the READ? completes the measurement process.

Example: CONFigure:AC Configures the instrument to perform an RMS

measurement of the AC component at the default input channel 1.

SENSe:AVERage ON Sets averaging on. SENSe:AVERage:COUNT 4 Sets averaging factor at four . READ:AC? Starts the measurement and returns the averaged

AC-RMS value.

READ? uses the same measure functions and parameters as CONFigure. After the instrument has been set up for a particular measure function by the CONFigure command, the same measure function key words can be repeated by the READ? query header. Moreover, it is allowed to request for another signal characteristic by specifying a measure function other than that for which the instrument was configured. However , keep in mind that the instrumen t was set up by CONFigure for another task. As these settings are not affected by READ?, it is not guaranteed that the instrument is able to acquire the signal characteristic that is requested by READ?

Example: CONFigure:AC Sets up the instrument to perform an RMS

measurement of the AC component.

3 - 14 USING THE COMBISCOPE INSTRUMENTS

READ? Requests to execute the default DC measurement.

Since this is not possible with the chosen configuration, an execution error is generated and no result is returned.

CONFigure:RISE:TIME Configures the CombiScope instrument to perform a

rise time measurement.

READ:RISE:OVERshoot? Requests to read the rise time overshoot. Because the

CombiScope instrument is able to calculate the rise overshoot value when it is set up for a rise time measurement, the desired result is calculated and returned.

A READ? also allows the same parameter sets as the correspondin g CONFigure instructions. But, these sets only serve to specify the desired result. They are ignored as far as they affect instrument settings. The parameters can be sent for compatibility with the preceding CONFigure command.

Example: CONFigure:RISE:TIME Configures the oscilloscope to perform a default rise

time measurement (10% to 90% increase of the signal amplitude).

READ:RISE:TIME? 20,80 Requests for the rise time of the 20 to 80% increase

of the signal amplitude. As the CombiScope instrument is able to respond to this request, the desired rise time is calculated and returned.

3.3.5 Multiple measurements

Sometimes it is necessary to perform multiple measurements of the same signal characteristic. This can be realized by executing multiple MEASure? queries. However, this implies that the relative time-consuming configuration portion of MEASure? is unnecessarily repeated. This can be easily avoided by using the CONFigure and READ? concept as described in the preceding chapter. This concept allows you to do the configuration only once by sending the CONFigure command one time. Sending multiple READ? q ueries next, causes the instrument to repeatedly execute the desired measurement.

Example: CONFigure:FREQuency Configures the instrument to perform a frequency

measurement.

USING THE COMBISCOPE INSTRUMENTS 3 - 15

READ:FREQuency? Starts the acquisition and returns the measured

frequency.

READ:FREQuency? Starts a next acquisition and returns the new

frequency result.

READ:FREQuency? Etc.

3.3.6 Multiple characteristics from a single acquisition.

It is often necessary to determine several signal characteristics from the last acquired waveform. Starting a new acquisition, as READ? and MEASure? do, is undesired. For that purpose, READ? is broken down into two additional instructions, which are the INIT iate[:IMMediate] command and the FETCh ? query . Executing this sequence of instructions is equivalent to READ?. The INITiate[:IMMediate] command starts the acquisition. FETCh? determines the requested signal characteristic and returns the re sult. This concept allows you to perform several different FETCh? queries on a single set of acquisition data .

Example: MEASure:AC? Configures the instrument to measure the RMS value

of the AC component of the signal at input channel 1, starts the acquisition, and returns the desired result.

FETCh:FREQuency? Determines and returns the frequency of the signal

that is acquired by the preceding MEASure? query .

FETCh:RISE:TIME? Uses default parameters to determine and return the

rise time of the first pulse.

As distinct from the READ? query, defaulting the measure function part of the FETCh? query, causes the CombiScope instrument to return the characteristic that was requested with the last executed FETCh?, READ? or MEASure? query. For this reason, the measure function should always be exp licitly specified in the header of the FETCh? query.

3 - 16 USING THE COMBISCOPE INSTRUMENTS

3.3.7 Trigger control via GPIB

You need a separate GPIB command to start a measurement synchronized with other instruments. This is done by sending the (Group Execute Trigger) code. The MEASure? and READ? queries do not allow you to do so, because such a setup causes a query error. With the INITiate[:IMMediate] and FETCh? concept, it is possib le to meet the requirements of such applications.

Example: CONFigure:AC Configures the instrument to measure the AC-RMS

voltage.

TRIGger:SOURce BUS Specifies that the acquisition is to be triggered by

GET or

INITiate Starts the measurement process.

TRG Triggers the acquisition.

FETCh:AC? Determines and returns the AC-RMS value.

TRG.

TRG command or the GET

USING THE COMBISCOPE INSTRUMENTS 3 - 17

Configures for channel 2

Switches channel 2 on

Single initiation

Copies CH2-trace to M1_2

Now trace area 2 of memory register 1 is filled with the channel 2 trace.

Fetches AC-RMS of M1_2

Enters AC-RMS value

Prints AC-RMS value

Fetches Peak-To- Peak of M1_2

Enters Peak-To-Peak value

Prints Peak_to_peak value

Fetches amplitude of M1_2

Enters amplitude value

Prints amplitude value

3.3.8 Fetching characteristics from memory traces

The FETCh? query not only allows you to determine a characteristic from the last acquired waveform, it also allows you to calculate a signal characteristic from a waveform that is stored in a trace memory element.

Example: FETCh:RISE:TIME? (@M3_4) Calculates and returns the default rise time

from a waveform that is stored in trace memory M3_4.

FETCh:PERiod? (@M4_1) Determines and returns the period of the

waveform that is stored in trace memory M4_1.

Notice that such a FETCh? query operates properly only when there is valid waveform data stored in the trace memory.

PROGRAM EXAMPLE: In this example the signal acquired via channel 2 is stored in memory register 1.

The AC-RMS, peak-to-peak, and amplitude values of the stored signal are fetched and printed.

DIM response AS STRING * 10 CALL Send(0, 8, "CONFigure:AC (@2)", 1) ’ CALL Send(0, 8, "SENSe:FUNCtion ’XTIMe:VOLTage2’", 1)’ CALL Send(0, 8, "INITiate", 1) ’ CALL Send(0, 8, "TRACe:COPY M1_2,CH2", 1) ’ ’ ’ ’ CALL Send(0, 8, "FETCh:AC? (@M1_2)", 1) ’ CALL Receive(0, 8, response$, 256) ’ PRINT "AC-RMS value : "; response$ ’

CALL Send(0, 8, "FETCh:PTPeak? (@M1_2)", 1) ’ CALL Receive(0, 8, response$, 256) ’ PRINT "Peak-To-Peak value: "; response$ ’

CALL Send(0, 8, "FETCh:AMPLitude? (@M1_2)", 1) ’ CALL Receive(0, 8, response$, 256) ’ PRINT "Amplitude value : "; response$ ’

3 - 18 USING THE COMBISCOPE INSTRUMENTS

3.4 Acquisition

3.4.1 Acquisition control

Several commands exist to control the acquisition process. The following diagram shows the possible states of the acquisition process, and the way they are affected by commands.

IDLE state

*RST

ABORt

power on

INIT

INIT:CONT ON

Yes

INITiated state

INIT:CONT ON

BUS IMMediate INTernal LINE

TRIGger

:SOURce

TRIGger

:LEVel :SLOPe

Start acquisition

Wait for trigger

Acquisition

Wait for TRIGger state

Wait for complete

Acquisition completed

ST7186

Figure 3.3 The Trigger Model for acquisitions

The trigger model shows that after a IDLE state. An acquisition doesn’t start until an INITiate command is received.

RST command, the instrument is in the

Initiation of the oscilloscope occurs by sending the INITiate[:IMMediate] command

USING THE COMBISCOPE INSTRUMENTS 3 - 19

or by setting INITiate:CONTinuous to ON. The INITiate[:IMMediate] command causes the CombiScope instrument to perform one complete acquisition cycle. Upon completion of the cycle the instrument returns to the IDLE state.

The INItiate:CONTinuous command is used to select whether the instrument is continuously initiated or not. When INItiate:CONTinuous is set to ON, the instrument immediately exits IDLE and starts an acquisition cycle. On completion of each cycle, the instrument does not return to the IDLE state, but immediately starts another acquisition cycle.

Before the acquisition takes place, the trigger conditions must be satisfied. These conditions are programmable to suit the needs of your application, as described in the next section. After a So, an INITiate command causes the CombiScope instrument to immediately trigger the acquisition.

Executing the measurement instructions MEASure? and READ? causes the acquisition to become initiated automatically . No separate INIT iate commands are needed. When the FETCh? instruction is used, the instrument must have been initiated either by a preceding INITiate[:IMMediate] command, or implicitly by a READ? or MEASure? instruction.

When the CombiScope instrument receives the ABORt command, any acquisition that is in progress is aborted immediately, and the instrument returns to the IDLE state. The same occurs when command distinguishes from settings, whereas, ABORt does not. For example, when INITiate:CONTinuous is set to ON, a the instrument to the IDLE state, but it also sets INITiate:CONTinuous to OFF, preventing the acquisition to initiate again. Since ABORt does not affect the instrument settings, an aborted acquisition cycle is immediately initiated again.

RST command not only aborts the pending acquisition and forces

RST command, there are no trigger conditions to be met.

RST is received. The ABORt

RST in that *RST also resets the instrument

When the instrument is in the IDLE state, the "no-pending operation" flag that is associated with the acquisition is set True. The this flag to signal their "Operation Completed" response. Notice that if INITiate:CONTinuous is set to ON, the instrument does not return to the IDLE state when an acquisition cycle has completed. This means that no "Operation Completed" response is generated after the

OPC and *OPC? commands use

OPC and *OPC? commands.

3 - 20 USING THE COMBISCOPE INSTRUMENTS

3.4.1.1 Triggering

After the measurement is initiated, the CombiScope instrument starts the real acquisition when the trigger conditions are satisfied, e.g., when the selected trigger event occurs. The trigger conditions can be ignored during a specific h oldoff time, which can be programmed using the TRIGger:HOLDoff command. During the hold-off time the event detector is inhibited from acting on any trigger.

Trigger Type

The TRIGger:TYPE command selects the type of triggering, which can be programmed to EDGE triggering (normal trigger mode) , VIDeo triggering (refer to section 3.4.1.2 "Video triggering"), LOGic, or GLITch triggering. After a command, the trigger type is EDGE.

Note: Logic state, pattern, or glitch settings cannot be programmed using SCPI

commands.

Trigger Source

The TRIGger:SOURce command selects the source for the trigger event. The receipt of the GPIB interface message GET (Group Execute Trigger) or the common command trigger source.

TRG serves as the trigger event when BUS is selected as

RST

The trigger event is determined by the AC line voltage when LINE is selected, and is derived from the input signal when INTernal is programmed as trigger source. For the 2-channel CombiScope instruments, EXT e rnal can be programmed as the trigger source. In that case, channel 4 is selected as external trigger input. A numeric suffix is used to specify the channel number. For example, TRIGger:SOURce INT2 selects the signal at input channel 2 to trigger the acquisition.

When IMMediate is selected, an acquisition d oes not wait for a trigger event. So, an INITiate command causes the acquisition to begin immediately. After a command, the trigger source is IMMediate, which means no trigger is required.

Trigger Level

The TRIGger:LEVel command allows you to set the trigger level for all input channels. Programming the trigger level automatically switches off level peakpeak. The trigger level can be programmed only when the TRIGger:SOURce is INTernal. The TRIGger:LEVel:AUTO command allows you to switch level peakpeak on or off. Switching on level peak-peak, deactivates the trigger level. After a

RST command the TRIGger:LEVel is set to its maximum value and level peak-

peak is switched off.

RST

USING THE COMBISCOPE INSTRUMENTS 3 - 21

Configures channel 2

Sets channel 2 ON

Trigger source = channel 2

Trigger level = 0.2 V

'The TRIGger:LEVel command also switches level peak-peak off.

Trigger slope = negative

Single initiation

Queries for peak-to-peak

Enters peak-to-peak

Prints peak-to-peak

Trigger Slope

The TRIGger:SLOPe command allows you to define the trigger ed ge for all input channels, which can be POSitive, NEGative, or EITHer. After a the TRIGger:SLOPe is set to POSitive.

RST command

PROGRAM EXAMPLE:

CALL Send(0, 8, "CONFigure:PTPeak (@2)", 1) ’ CALL Send(0, 8, "SENSe:FUNCtion 'XTIMe:VOLTage2'", 1)’ CALL Send(0, 8, "TRIGger:SOURce INTernal2", 1) ’ CALL Send(0, 8, "TRIGger:LEVel 0.2", 1) ’

CALL Send(0, 8, "TRIGger:SLOPe NEGative", 1) ’ CALL Send(0, 8, "INITiate", 1) ’ CALL Send(0, 8, "FETCh:PTPeak? (@2)", 1) ’ response$ = " " CALL Receive(0, 8, response$, 256) ’ PRINT "Measured peak-to-peak = "; response$ ’

Trigger Coupling

The TRIGger:LPASs and TRIGger:HPASs commands allow you to select the Main Time Base (MTB) trigger coup ling by pro gramming a fixed cutoff frequency. The possible trigger coupling options

reject

High Frequency reject

, and

AC coupling, DC coupling, Low Frequency

are mutually exclusive. The TRIGger:LPASs and TRIGger:HPASs commands are also mutually exclusive. So, activating the Low-Pass filter will switch off the High-Pass filter, and vice versa. After a command, the cutoff frequency is 10 Hertz, which selects trigger coupling AC.

RST

Note: When the trigger source is INTernal<n>, signal coupling for one input

channel (n) can be programmed to AC, DC, or GROund using the INPut<n>:COUPling command.

3 - 22 USING THE COMBISCOPE INSTRUMENTS

Sets CH2 on.

Sets CH2 input signal DC coupled.

Sets trigger source = CH2.

Sets Low-Pass filter on + cutoff frequency = 0 Hz;

this selects MTB trigger DC coupling.

Sets CH3 on.

Sets CH3 input signal AC coupled.

Sets trigger source = CH3.

Sets Low-Pass filter on + cutoff frequency = 0 Hz;

this selects MTB trigger DC coupling.

Sets cutoff frequency = 10 Hz; this selects

MTB trigger AC coupling.

DC COUPLING (0 Hz cutoff frequency):

DC coupling causes the signal to be passed over

0dB

DC COUPLING-3dB

FULL BANDWIDTHDC

FREQ.

the full bandwidth (from 0 Hz to 60/100/200 MHz).

T7427

Figure 3.4 DC Coupling

PROGRAM EXAMPLE:

*** *** Select DC coupling on input signal channel 2. SENSe:FUNCtion:ON "XTIMe:VOLTage2" INPut2:COUPling DC TRIGger:SOURce INTernal2 *** *** Select DC coupling on MTB triggering. TRIGger:FILTer:LPASs:STATe ON

AC COUPLING (10 Hz cutoff frequency):

AC coupling causes the signal to be passed from

0dB

AC COUPLING-3dB

10 Hz to the full bandwidth frequency (60/100/200 MHz).

FULL BANDWIDTH10Hz

FREQ.

Figure 3.5 AC Coupling

PROGRAM EXAMPLE:

*** *** Select AC coupling on input signal channel 3. SENSe:FUNCtion:ON "XTIMe:VOLTage3" INPut3:COUPling AC TRIGger:SOURce INTernal3 *** *** Select AC coupling on MTB triggering. TRIGger:FILTer:LPASs:STATe ON

TRIGger:FILTer:LPASs:FREQuency 10

ST7426

USING THE COMBISCOPE INSTRUMENTS 3 - 23

Sets Low-Pass filter on + cutoff frequency = 0 Hz

(DC coupling).

Sets cutoff frequency = 30 KHz;

this selects MTB trigger LF-reject.

Sets High-Pass filter on;

this selects MTB trigger HF-reject.

LF-REJECT (30 KHz cutoff frequency):

LF reject (HF passed) causes the signal to be passed from the cutoff frequency (30 KHz) to the full bandwidth frequency (60/100/200 MHz).

-3dB

0dB

LF -REJECT

FULL BANDWIDTH30kHz

FREQ.

ST7428

Figure 3.6 LF Reject

PROGRAM EXAMPLE:

TRIGger:FILTer:LPASs:STATe ON

TRIGger:FILTer:LPASs:FREQuency 3E+4

HF-REJECT (30 KHz cutoff frequency)

HF reject (LF passed) causes the signal to be passed from 0 Hz to the cutoff frequency (30 KHz).

-3dB

0dB

HF-REJECT

FULL BANDWIDTH30kHz

FREQ.

ST7429

Figure 3.7 HF Reject

PROGRAM EXAMPLE:

*** *** Select HF-reject on MTB triggering. TRIGger:FILTer:HPASs:STATe ON

3.4.1.2 Video triggering

TV video triggering enables stable triggering on video frames and lines from various TV standards without adjusting the trigger level, and can be selected by programming TRIGger:TYPE VIDeo.

Video triggering can be programmed o n signals wi th a positive or negative si gnal polarity using the TRIGger:VIDeo:SSIGnal command.

3 - 24 USING THE COMBISCOPE INSTRUMENTS

The video trigger mode can be programmed to field1, field2, or lines using the TRIGger:VIDeo:FIELd... commands. The video trigger line can be programmed using the TRIGger:VIDeo:LINE command.

The video system can be selected using the TRIGger:VIDeo:FORMat:... commands. The following standard video systems are supported:

- NTSC : 525 lines per frame

- PAL : 625 lines per frame

- SECAM : 625 lines per frame

- HDTV : 1050/1125/1 250 lines per frame

1) Select video triggering and video standard. Examples: TRIGger:TYPE VIDeo

Selects

TRIGger:VIDeo:FORMat:TYPE SECAM

Selects the

TRIGger:VIDeo:FORMat:LPFRame 1125

Selects the

2) Select video "lines" triggering and program the line to trigger on. Examples: TRIGger:VIDeo:FIELd:SELect ALL

Selects the video

TRIGger:VIDeo:LINE 512

Selects video line number

TV video

triggering.

SECAM HDTV

standard with

lines

standard with 625 lines per frame.

1125

lines per frame.

trigger mode.

512

3) Select video "field1/2" triggering and program the line to trigger on. Examples: TRIGger:VIDeo:FIELd:SELect NUMBer

field

Selects video

TRIGger:VIDeo:FIELd:NUMBer 2

Selects the video

TRIGger:VIDeo:FORMat:TYPE PAL

Selects the

TRIGger:VIDeo:LINE 123

Selects video line number automatically switched to

TRIGger:VIDeo:LINE 325

Selects video line number automatically switched to

TRIGger:VIDeo:FIELd:NUMBer 1

Selects the video line number is automatically switched to

triggering.

field2

trigger mode.

PAL

standard with 625 lines per frame.

123

. As a result the video mode is

field1

(field1 = lines 1 .. 312).

325

. As a result the video mode is

field2

(field2 = lines 313 .. 625).

field1

trigger mode. As a result the video

(= 325 - 625/2).

USING THE COMBISCOPE INSTRUMENTS 3 - 25

3.4.1.3 The trigger modes

A combination of the INITiate:CONTinuous and TRIGger:SOURce command allows you to define the following trigger modes:

Trigger mode: >>>Single-shot<<<

Generates one sweep, regardless of any trigger settings (valid after

>>>Single-shot<<< Generates one sweep, triggered using trigger settings.

>>> Single-shot <<< Generates one sweep, externally triggered via channel 4 (only for PM33x0B).

>>>Auto trig<<< Generates continuous sweeps, independent of any trigger settings.

>>>Normal trig<<< Generates continuous sweeps, triggered using trigger settings.

>>> Normal trig <<< Generates continuous sweeps, externally triggered via channel 4 (only for PM33x0B).

>>>Single-Shot<<< Generates one sweep triggered by or GET, regardless of any trigger settings.

RST).

TRG

Table 3.1 The TRIGger modes

INITiate :CONTinuous

OFF IMMediate

OFF

OFF EXTernal

ON IMMediate

ON EXTernal

ON or OFF

TRIGger :SOURce

INTernal<n> or LINE

BUS

3 - 26 USING THE COMBISCOPE INSTRUMENTS

OPERATION STATUS BITS:

STATE DESCRIPTION:

bit 5

Wait for TRIG

bit 3

SWEeping

OPC

idle state (after

RST)000Wait for trigger state (INIT received)

Wait for complete (triggered)

110000= armed

or busy

Finished with acquisition

001

= ready

OPERATION STATUS BITS:

STATE DESCRIPTION:

bit 5

Wait for TRIG

bit 3

SWEeping

OPC

idle state (after

RST)000Wait for trigger state (INIT received)

1 00

= armed

Wait for complete (triggered)

010

= busy

Finished with acquisition

001

= ready

Only in the single-shot and multiple-shot trigger mode (INITiate:CONTinuous OFF), the bits 3 (SWEeping) and 5 (W aiting for TRIGger) in the OPERation status are valid. Also the Operation Complete bit (OPC bit 0) in the standard Event Status Register (ESR) is valid. This allows you to detect whether the instrument is armed (initiated), triggered (busy with acquisition), or finished with the last acquisition, i.e., ready for the next acquisition.

SINGLE-SHOT MODE (TB MODE - single): Commands: CONFigure:AC Configures instrument and sets

single-shot mode.

MULTIPLE-SHOT MODE (TB MODE - multi):

The bits 3 (SWEeping) and 5 (Waiting for TRIGger) also reflect the acquisition status, when the "SINGLE ARM'D" button on the front panel was pressed.

Commands: SYSTem:KEY 101 Performs AutoSet.

DISPlay:MENU TBMode Displays TBMODE menu. SYSTem:KEY 1 Sets INIT:CONT OFF and sets

multiple-shot mode.

USING THE COMBISCOPE INSTRUMENTS 3 - 27

1 ms post-trigger

1 ms pre-trigger

3.4.1.4 Pre- and post-triggering

When pre-triggering is selected, the real trace acquisition begins before the moment that the trigger occurs. Triggering occurs when the trigge r conditions are satisfied and the instrument leaves the "Wait for TRIGger" state as shown in the trigger diagram of figure 3.3. In a similar way, post-triggering causes the acquisition to begin after the moment that the trigger occurs.

trigger moment

SENSe:SWEep:OFFSet:TIME

pre trigger

trigger moment

SENSe:SWEep:OFFSet:TIME

post trigger

begin

Trace

total acquisition time

SENSe:SWEep:TIME

Trace

begin

total acquisition time

SENSe:SWEep:TIME

Figure 3.8 Pre-triggering

time axis

end

ST7191

time axis

end

ST7190

Figure 3.9 Post-triggering

Pre- and post-triggering are programmed wi th the SENSe:SW Ee p:OFFSet:TIME command. A positive parameter value specifies a post-trigger delay, whereas, a negative value results in a pre-trigger view.

After

RST, the SENSe:SWEep:OFFSet:TIME is set to -0.005, which results in a

pre-trigger view of 5 ms. Because the (SENSe:SWEep:TIME) is 10 ms, the trigger point is positioned in the middle of

RST value of the total acquisition time

the trace. PROGRAM EXAMPLE:

CALL Send(0, 8, "SENSe:SWEep:OFFSet:TIME 0.001", 1) ’ CALL Send(0, 8, "SENSe:SWEep:OFFSet:TIME -1E-3", 1) ’

3 - 28 USING THE COMBISCOPE INSTRUMENTS

3.4.1.5 External triggering

External triggering is only possible for the PM33x0B CombiScope instruments. Channel 4 is used as the external trigger channel with the following view possibilities:

- attenuato r positions 0.1 and 1 V/div (AMP key).

- trigger slope positive or negative (EXT TRIG key).

- trigger coupling AC or DC (AC/DC key).

The view facility of the external trigger channel is switched on by sending the SENSe:FUNCtion:ON "XTIMe:VOLTage4" command, or by sending the SYSTem:KEY 812 command to simulate the pressing of the TRIG VIEW key on the front panel.

Note: The view facility of the external trigger channel can only be switched on

when:

• EXTernal or INTernal4 (CH4) is programmed as the trigger source.

• Peak detection is off.

Autoset scans for the presence of a signal on channel 1, 2, and the external trigger input. If there is a signal present on the external trigger input, the EXTernal trigger channel is selected as trigger source, and the external trigger view facility becomes active.

Limitation: The amplitude of the external trigger signal must be high enough for

the sensitivity of the external trigger input (0.1 or 1 V/div.).

USING THE COMBISCOPE INSTRUMENTS 3 - 29

3.4.2 Reading trace acquisitions

Once acquisitions are completed, the resulting traces ares placed in TRACe memory, as shown in the following figure.

TRACe

memory

CH 1

CH 2

CH 3

CH 4

ST7160

INPut

INPut[1]

INPut2

INPut3

INPut4

SENSe

:VOLTage[1]

:VOLTage2

:SWEep

:VOLTage3

:VOLTage4

Main Time Base

Figure 3.10 The trace acquisition flow

The last acquired trace at input channel 1 is placed in the TRACe memory element named CH1. The trace acquired at channel 2 in CH2, etc. This trace data can be read by using the TRACe[:DATA]? query.

Example:

TRACe? CH2 Returns the trace that was last acquired at input channel 2.

When new acquisitions are executed, the previously stored traces are not automatically saved, but overwritten by the new result. When these traces need to be saved, they have to be copied into other TRACe memory elements, before a new acquisition is initiated. Refer to section 3.10.2 "Copying traces to memo ry" for a description about how to copy traces.

As response to the TRACe? query the data is returned as block data. Section 3.4.3 "Conversion of trace data" specifies the coding of this data and describes how to convert this data into voltage values.

3 - 30 USING THE COMBISCOPE INSTRUMENTS

Dimensions trace buffer

Resets the instrument

Trigger source becomes IMMediate

Number of trace samples becomes 512

Number of trace sample bits becomes 16

Configures for optimal AC-RMS settings

Initiates single acquisition

Requests for channel 1 trace data

Notice the

WAI; before TRACe?. The

WAI command takes care that the

TRACe? CH1 command is executed when the INITiate command is finished.

Reads the channel 1 trace data

Dimensions trace buffer

Resets the instrument

Trigger source becomes IMMediate

Number of trace samples becomes 512

Number of trace sample bits becomes 16

Configures for optimal AC-RMS settings.

Trigger source = GPIB

Opens file TRACE10

10 sequential trace acquisitions

Initiates an acquisition

Triggers via the GPIB

Requests for channel 1 trace

Notice the

WAI; before TRACe?. The

WAI command takes care that

the TRACe? CH1 command is executed when the INITiate command is finished.

Reads the channel 1 trace

Writes the trace buffer to file

Next trace acquisition

Closes file TRACE10

3.4.2.1 Single-shot acquisition

PROGRAM EXAMPLE: In this example a single-shot trace acquisition is done via channel 1. The trace

bytes are entered as characters in the string response$.

DIM response AS STRING * 1033 ’ CALL Send(0, 8, "*RST", 1) ’

CALL Send(0, 8, "CONFigure:AC", 1) ’ CALL Send(0, 8, "INITiate", 1) ’ CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’ ’ ’ ’ ’ CALL Receive(0, 8, response$, 256) ’

’ ’ ’

3.4.2.2 R ep e titive acquisitions

PROGRAM EXAMPLE: In this example 10 trace acquisitions are done via channel 1. The trace bytes are

entered as characters in the string response$. The 10 trace buffers are written to the file TRACE10 on the hard disk. Tr iggering is done via the GPIB by sendi ng the

TRG command.

DIM response AS STRING * 1033 ’ CALL Send(0, 8, "*RST", 1) ’

CALL Send(0, 8, "CONFigure:AC (@1)", 1) ’ CALL Send(0, 8, "TRIGger:SOURce BUS", 1) ’ OPEN "O",#1,"TRACE10" ’ FOR i=1 TO 10 ’

CALL Send(0, 8, "INITiate", 1) ’ CALL Send(0, 8, "*TRG", 1) ’ CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’ ’ ’ ’ ’ CALL Receive(0, 8, response$, 256) ’

PRINT #1, response$ ’ NEXT i ’ CLOSE ’

’ ’ ’

USING THE COMBISCOPE INSTRUMENTS 3 - 31

3.4.3 Conversion of trace data

The trace data is sent as a block of binary codes. T race samples can be formatted to consist of 8 bits (1 byte) or 16 bits (2 bytes) codes, which can be selected by the FORMat command. Refer to section 3.10.1 "Trace formatting" for a further explanation of this command. After When samples are formatted as two bytes, the most signifi cant byte (msb) is se nt

RST the samples are sent as 2 byte codes.

first, followed by the least significant byte (lsb). The sample values that are sent in the block, are coded according to the two’s complement notation. The relation between the screen positions, the values of the trace samples and the decimal value of the corresponding binary codes, is shown in the figure below.

screen

range

Screen

position (Ps)

top

mid

bottom

Trace sample

value (Ts)

(127)

32767

25600 (100)

1(1) 0(0)

-1 (-1)

-25600

(-100)

-32768

(-128)

Decimal value

of byte code

32767 (127)

25600 (100)

1(1) 0(0)

65535

(255)

39936

(156)

32768

(128)

trace range

ST7187

Note: Numbers between parenthesis apply to single byte format.

Figure 3.11 Relation between screen position and trace value

The value of the trace points relate to the vertical position of the corresponding sample on the screen of the CombiScope instrument. As the figu re above shows, the sample with value 25600 corresponds with the top position of the screen. Similarly, the samples with values -25600 and 0 correspond to the bottom and mid-position respectively. This applies to trace samples that are formatted to consist of 16 bits (2 bytes). The values that apply to the 8 bit (1 byte) format are placed between parenthesis.

The ADC allows trace acquisitions that are somewhat outside the vertical screen boundaries. Trace acquisitions use the full dynamic range of the ADC. This results in a dynamic trace range of 65535 points, whereas the screen range is limited to 51200 points.

3 - 32 USING THE COMBISCOPE INSTRUMENTS

Array of 512 integers

Trace response buffer

Resets the instrument

Data format of 8-bits samples

Single shot initiation

Queries for channel 1 trace

Reads the channel 1 trace

IBCNT% = number of read bytes

The contents of the response$ string of this example will be as follows:

# 3 5 1 4 <8> <byte 1> ... <byte 512> <checksum> <10> ’<10> is terminating LF

3.4.3.1 Conversion of 8-bit samples to integer

As an example a conversion of a trace of 512 "8-bit" samples is shown. The format is as follows:

trace bytes

# 3 5 1 4 <8> <byte 1> . . . <byte 512> <checksum> <NL

trace sample 512 trace sample 1 byte with decimal value 8 number of trace bytes (514) number of digits of 514

PROGRAM EXAMPLE: In this example a trace acquisition of 1 byte samples is done. Thereafter , the trace

data is read and converted to integer samples in the array "trace", and the nu mber of trace bytes and trace samples is printed. The conversion from single byte valu e to integer is done as follows (refer to figure 3.12):

≥ 128 then integer = byte - 256.

If byte Example: byte = 255 --> integer = 255 - 256 = -1.

DIM trace(512) ’ DIM response AS STRING * 520 ’ CALL Send(0, 8, "*RST", 1) ’ CALL Send(0, 8, "FORMat INTeger,8", 1) ’ CALL Send(0, 8, "INITiate", 1) ’ CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’ CALL Receive(0, 8, response$, 256) ’ PRINT "Number of read bytes ="; IBCNT% ’ ’ ’ ’ ’ nr.of.digits = VAL(MID$(response$, 2, 1)) nr.of.bytes = VAL(MID$(response$, 3, nr.of.digits)) - 2 PRINT "Number of trace bytes ="; nr.of.bytes sample.length = ASC(MID$(response$, 3 + nr.of.digits, 1)) nr.of.samples = nr.of.bytes / (sample.length / 8) PRINT "Number of trace samples ="; nr.of.samples

FOR i = 1 TO nr.of.samples

trace(i) = ASC(MID$(response$, i + 3 + nr.of.digits, 1))

IF trace(i) > 127 THEN

trace(i) = trace(i) - 256

END IF NEXT i

USING THE COMBISCOPE INSTRUMENTS 3 - 33

Arra

y of 512 i

ntegers

Trace response buffer

Resets the instrument

Sets 16 bit sample data format

Single shot initiation

Queries for channel 1 trace

Reads the channel 1 trace

IBCNT% = length of trace buffer

The contents of the response$ string of this example will be as follows:

# 4 1 0 2 6 <16> <msb1> <lsb1> ... <msb512> <lsb512> <sum> <10>

Pointer to next sample

Most Significant Byte

Least Significant Byte

3.4.3.2 Conversion of 16-bit samples to integer

As an example a conversion of a trace of 512 "16-bit" samples is shown. The format is as follows:

trace bytes

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

trace sample 512 trace sample 1

byte with decimal value 16 number of trace bytes (1026) number of digits of 1026

PROGRAM EXAMPLE: In this example a trace acquisition of 2 byte samples is done. Thereafter , the trace

data is read and converted to integer samples in the array "trace", and the nu mber of trace bytes samples is printed. The conversion from double byte ( byte1 = msb and byte2 = lsb) to integer is done as follows (refer to figure 3.12): If byte1 < 128 then integer = byte1 If byte1

≥ 128 then integer = (byte1 - 256)

Example: byte1 = 255 & byte2 = 32 --> integer = (255 - 256)

DIM trace(512) ’ DIM response AS STRING * 1033 ’ CALL Send(0, 8, "*RST", 1) ’

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

J = 2 * i + 2 + nr.of.digits ’ byte1 = ASC(MID$(response$, J, 1)) ’ byte2 = ASC(MID$(response$, J + 1, 1)) ’ IF byte1 < 128 THEN

trace(i) = byte1 * 256 + byte2 ELSE trace(i) = (byte1 - 256) * 256 + byte2 END IF

NEXT i

256 + byte2.

256 + 32 = - 224.

’

3 - 34 USING THE COMBISCOPE INSTRUMENTS

3.4.3.3 Conversion to voltage values

Screen positions correspond to voltage values. This relation is shown in the figur e below, and is determined by the settings that are programmed by the SENSe:VOLTage:RANGe:PTPeak and SENSe:VOLTage:RANGe:OFFSet commands.

Screen

position (Ps)

top

100%

mid

Trace sample

value (Ts)

(127)

32767

25600

(100)

(0)

PTPeak

0Volt

OFFSet

Amplitude value (Vs)

-OFFSet+PTPeak/2

-OFFSet

-OFFSet-PTPeak/2 bottom

-100%

-25600 (-100)

-32768 (-128)

ST7188

Figure 3.12 Relation between screen position and amplitude value

The relation between the screen position Ps and the corresponding voltage amplitude Vs is expressed by the equations:

Vs = (Ps Vs = (Ps

PTPeak) / 200 - OFFSet (for 8-bit sample traces)

PTPeak) / 51200 - OFFSet (for 16-bit sample traces)

As explained in section 3.4.3, there is also a relat ion between the screen position Ps and the value T s of a trace sample. This relation is expr essed by the equations:

Ps = Ts (for 8-bit sample traces) Ps = (Ts / 25600)

100 = T s / 256 (for 16-bit sample traces)

Eliminating Ps from the preceding equations results in a relation that can be used to calculate the voltage value Vs from a trace sample Ts. This relation is expressed by the equations:

Vs = (Ts / 200) Vs = (Ts / 51200)

PTPeak - OFFSet (for 8-bit sample traces)

PTPeak - OFFSet (for 16-bit sample traces)

USING THE COMBISCOPE INSTRUMENTS 3 - 35

Array of sample voltages

Trace data response string

Peak-to-peak response string

Offset response string

Resets the instrument

Configures for optimal AC-RMS settings

Signal-offset also becomes zero

Initiates single acquisition

Requests channel 1 trace

Reads channel 1 trace

Queries ptp

Reads ptp

IBCNT% = length

Queries offset

Reads offset

IBCNT% = length

1-byte samples

2-byte samples

Pointer to next sample

M.S.B.

L.S.B.

PROGRAM EXAMPLE: In this program example a trace of 512 samples from the actual signal at input

channel 1 is read. The received data block is converted to an array of voltages. After each sample conversion the voltage value is printed. This program example works for traces of 512 samples, consisting of 8 bits (1 byte) or 16 bits (2 bytes) samples.

Note: The program is supplied on floppy under file name EXCNVTRC.BAS.

DIM sample(512) ’ DIM response AS STRING * 1033 ’

DIM peaktop AS STRING * 10 ’ DIM offs AS STRING * 10 ’ ’ CALL Send(0, 8, "*RST", 1) ’ CALL Send(0, 8, "CONFigure:AC (@1)", 1) ’

CALL Send(0, 8, "INITiate", 1) ’ CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’ CALL Receive(0, 8, response$, 256) ’ ’ nr.of.digits = VAL(MID$(response$, 2, 1)) nr.of.bytes = VAL(MID$(response$, 3, nr.of.digits)) - 2 sample.length = ASC(MID$(response$, 3 + nr.of.digits, 1)) nr.of.samples = nr.of.bytes / (sample.length / 8) CALL Send(0, 8, "SENSe:VOLTage:RANGe:PTPeak?", 1) ’ CALL Receive(0, 8, peaktop$, 256) ’ ptpeak = VAL(LEFT$(peaktop$, IBCNT%)) ’ CALL Send(0, 8, "SENSe:VOLTage:RANGe:OFFSet?", 1) ’ CALL Receive(0, 8, offs$, 256) ’ offset = VAL(LEFT$(offs$, IBCNT%)) ’ IF sample.length = 1 THEN

FOR i = 1 TO nr.of.samples ’

trace% = ASC(MID$(response$, i + 3 + nr.of.digits, 1)) IF trace% > 127 THEN trace% = trace% - 256 END IF sample(i) = trace% / 200 * ptpeak - offset PRINT sample(i);

NEXT i

ELSE

FOR i = 1 TO nr.of.samples ’

J = 2 * i + 2 + nr.of.digits ’ byte1 = ASC(MID$(response$, J, 1)) ’ byte2 = ASC(MID$(response$, J + 1, 1)) ’ IF byte1 < 128 THEN trace% = byte1 * 256 + byte2 ELSE trace% = (byte1 - 256) * 256 + byte2 END IF sample(i) = trace% / 51200 * ptpeak - offset PRINT sample(i);

NEXT i

END IF

’

3 - 36 USING THE COMBISCOPE INSTRUMENTS

Dimensions trace string

Dimensions amplitude string

Dimensions frequency string

Configures for AC-RMS

Average factor = 4

Averaging is turned on

Initiates the averaging acquisition

Queries for channel 1 trace

Enters channel 1 trace

The trace samples are averaged over 4 sequential trace acquisitions.

Reads the amplitude

Enters the amplitude

Fetches the frequency

Enters the frequency

The amplitude and frequency are averaged over 4 sequential measured values.

3.5 Averaging Acquisition Data

Acquired traces and measured signal characteristics can be averaged over a number of acquisitions. The preprocessing AVERAGE function of the CombiScopes instruments can be enabled by using the SENSe:AVERage[STATe] command. When this function is set to ON, averaging is done according to the following formula:

AVG

()n⁄

.. X

∑

In the expression, n specifies the number of acquisitions that is averaged. This parameter can be programmed by using the SENSe:AVERage:COUNt command. X represents the acquisition result to be averaged.

Example:

→ SENSe:AVERage:COUnt 16 ’ This sets the average count factor at

Send

16, which means 16 sequential acquisitions are averaged.

→ SENSe:AVERage ON ’ This enables the AVERAGE function.

Send When SENSe:AVERage is set to ON and an acquisition is initiated, the

CombiScope instrument takes n (SENSe:AVERage:COUNt) successive acquisitions, as shown in the figure on the next page. When sufficien t acquisitions are taken, the final averaged result is returned. Intermediate results cannot be queried.

PROGRAM EXAMPLE: Acquire the trace of the actual signal on channel 1 and measure the amplitude

and frequency (averaged over 4 acquisitions).

DIM trace AS STRING * 1033 ’ DIM amplitude AS STRING * 10 ’ DIM frequency AS STRING * 10 ’ CALL Send(0, 8, "CONFigure:AC (@1)", 1) ’ CALL Send(0, 8, "SENSe:AVERage:COUNt 4", 1) ’ CALL Send(0, 8, "SENSe:AVERage ON", 1) ’ CALL Send(0, 8, "INITiate", 1) ’ CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’ CALL Receive(0, 8, trace$, 256) ’ ’ CALL Send(0, 8, "READ:AMPLitude?", 1) ’ CALL Receive(0, 8, amplitude$, 256) ’ CALL Send(0, 8, "FETCh:FREQuency?", 1) ’ CALL Receive(0, 8, frequency$, 256) ’ ’

USING THE COMBISCOPE INSTRUMENTS 3 - 37

The following diagram shows the possible states of the acquisition process when "averaging" is on, and the way they are affected by commands.

IDLE state

*RST

ABORt

power on

INIT

INIT:CONT ON

Yes

INIT:CONT ON

Wait for AVERage state

SENSe:AVERage:COUNt

INITiated state

Yes

LINE INTernal IMMediate

TRIGger

:SOURce

TRIGger

:LEVel :SLOPe

Wait for completeWait for trigger

acquisition

averaging

Figure 3.13 The Trigger Model during acquisition averaging

ST7189

3 - 38 USING THE COMBISCOPE INSTRUMENTS

Sets CH1+CH2 on

3.6 Channel Selection

Input channels can be switched on or off by using the SENSe:FUNCtion[:ON] or SENSe:FUNCtion:OFF commands. An input channel is selected by specifying the parameter "XTIMe:VOLTage<n>", where the numeric suffix <n> specifies the input channel number. After a other channels off (including the EXTernal input for PM33x0A).

Addition of two channels can be selected by specifying the "XTIMe:VOL T age:SUM" parameter as follows: > Addition of CH1 and CH2: "XTIMe:VOLTage:SUM 1,2" > Addition of CH3 and CH4: "XTIMe:VOLTage:SUM 3,4"

Note: Enabling of the addition of input channels (e.g. CH3+CH4), automatically

switches channel 3 and channel 4 on. Disabling of the addition of two channels (e.g. CH3+CH4), automatically switches channel 3 and channel 4 off, provided at least one channel remains on.

Programming tip:

If CH1+CH2 is on and CH3 and CH4 are off, CH1+CH2 cannot be programmed off by sending: SENSE:FUNCtion:OFF "XTIME:VOLTage:SUM 1,2" Instead, send the command:

SENSe:FUNCtion:ON "XTIME:VOLTage2" ’Sets CH2 on

RST command, channel 1 is turned on and the

PROGRAM EXAMPLE:

CALL Send(0, 8, "SENSe:FUNCtion 'XTIMe:VOLTage:SUM 1,2'", 1)

CALL Send(0, 8, "SENSe:FUNCtion:ON ’XTIMe:VOLTage2’", 1)’

INPut

INPut[1]

INPut2

INPut3

INPut4

SENSe

:VOLTage[1]

:VOLTage2

:VOLTage3

:VOLTage4

:FUNCtion

:OFF

[:ON]

:OFF

[:ON]

:OFF

[:ON]

:OFF

[:ON]

"XTIMe:VOLTage1"

"XTIMe:VOLTage2"

:SWEep

"XTIMe:VOLTage3"

"XTIMe:VOLTage4"

Main Time Base

Figure 3.14 Input channel control

’Sets CH2 on, CH1+CH2 off, CH1 remains off.

TRACe

memory

CH 1

CH 2

CH 3

CH 4

ST7158

’

USING THE COMBISCOPE INSTRUMENTS 3 - 39

Sets channel 1 AC coupled

Sets channel 2 ground coupled

3.7 Signal Conditioning

The INPut subsystem allows you to condition the input signals, such as AC/DC/GROund coupling, input filtering, and input impedance selection.

In the digital mode, the SENSe:VOLTage<n>:RANGe:AUTO command allows you to enable autoranging of the attenuation for each of the input channels <n> separately.

SENSe

:VOLTage[1]

:VOLTage2

:VOLTage3

:VOLTage4

:FUNCtion

:OFF

[:ON]

:OFF

[:ON]

:OFF

[:ON]

:OFF

[:ON]

"XTIMe:VOLTage1"

"XTIMe:VOLTage2"

:SWEep

"XTIMe:VOLTage3"

"XTIMe:VOLTage4"

Main Time Base

ST7159

INPut

INPut[1]

INPut2

INPut3

INPut4

Figure 3.15 Signal conditioning

3.7.1 AC/DC/ground coupling

The INPut<n>:COUPling command allows you to set the vertical input coupl ing at AC, DC, or GROund for each input channel separately. After a all input channels are DC coupled.

RST command,

PROGRAM EXAMPLE:

CALL Send(0, 8, "INPut:COUPling AC", 1) ’ CALL Send(0, 8, "INPut2:COUPling GROund", 1) ’

3 - 40 USING THE COMBISCOPE INSTRUMENTS

Turns the filter on

Requests for the filter frequency

Reads the filter frequency

Prints: Filter freq. = 2.00E+07

Sets channel 4 impedance at 50

Sets INV CH2 off

Sets INV CH4 on

3.7.2 Input filtering

The INPut:FILTer command allows you to turn the common low-pass filter (bandwidth limiter) on or off for all input channels at the same time. The cutoff frequency is fixed at 20 MHz. After a

RST command, the filter is turned off.

PROGRAM EXAMPLE:

CALL Send(0, 8, "INPut:FILTer ON", 1) ’ CALL Send(0, 8, "INPut:FILTer:FREQuency?", 1) ’ response$ = " " CALL Receive(0, 8, response$, 256) ’ PRINT "Filter freq. = "; response$ ’

3.7.3 Input impedance

The INPut<n>:IMPedance command allows you to specify the input impedance low (50

Ω) or high (1 MΩ) for each input channel separately. After a

command, the impedance of each input channel is 1 M

Ω.

RST

PROGRAM EXAMPLE:

CALL Send(0, 8, "INPut4:IMPedance 50", 1) ’

Ω

3.7.4 Input polarity

The INPut<n>:POLarity command allows you to set the polarity of the signal on the input channel 2 and 4. The polarity can be set to NORMal (default) o r INVerte d (inverted signal).

PROGRAM EXAMPLE:

CALL Send(0, 8, "INPut2:POLarity NORMal", 1) ’ CALL Send(0, 8, "INPut4:POLarity INVerted", 1) ’

3.7.5 Vertical range and offset

The SENSe:VOLTage<n>:RANGe:PTPeak command allows you to specify the peak-to-peak range of the signal acquisition over all 8 divisions of the display screen for each input channel separately. From this peak-to-peak value the vertical sensitivity per division is calculated as follows:

<vertical_sensitivity> = <peak-to-peak> / 8.

After a complies to a vertical sensitivity of 200 mV.

RST command, the peak-to-peak value is set at 1.6V for channel 1, which

USING THE COMBISCOPE INSTRUMENTS 3 - 41

This sets the peak-to-peak range at 800 mV.

So, the vertical sensitivity = 800 / 8 = 100 mV.

This sets a positive vertical offset of 100 mV, i.e., 1 division.

Auto triggering

Sets CH2 on

Sets auto attenuation for channel 2 ON and switches to AC signal coupling

Because the programmed PTPeak and OFFSet values directly affect the trace values, they can be used to calculate the voltage amplitude of the corresponding trace samples. As explained in section 3.4.3.3 "Co nversion to voltage values", the voltage amplitude of a trace sample can be calculated from the equations:

Vs = (Ts / 200) Vs = (Ts / 51200)

PTPeak - OFFSet (for 8-bit sample traces)

PTPeak - OFFSet (for 16-bit sample traces)

where Ts = the value of the trace sample and Vs = the corresponding voltage amplitude

The SENSe:VOLTage<n>:RANGe:OFFSet command allows you to specify the vertical offset for each input channel. After a for each input channel is zero.

RST command, the vertical offset

PROGRAM EXAMPLE:

CALL Send(0,8 "SENSe:VOLTage2:RANGe:PTPeak .8", 1) ’ ’ ’ CALL Send(0,8 "SENSe:VOLTage2:RANGe:OFFSet .1", 1) ’

3.7.6 Autoranging attenuators

The AUTO RANGE function automatically selects the vertical input sensitivity to keep the signal amplitude between 2 and 6.4 divisio ns on the screen. Autoranging attenuators work independently on the following acquisition channels: > Input channel 1, 2, 3, and 4 for the PM33x4B CombiScope instruments. > Input channel 1, and 2 for the PM33x2B CombiScope instruments.

Auto attenuation uses a peak-to-peak calculation to determine the maximum and minimum value of an acquisition, regardless of the input coupling. When auto attenuation is switched on for an input channel <n>, the input signal is automatically forced to AC coupling. Still, it is possible to switch to DC coupling by programming the INPut<n>:COUPling DC command. However, in that case, the proper operation cannot be guaranteed.

LIMITATION:

Auto attenuation is limited to 50 mV minimum per division. This minimum value is used as the noise level to prevent auto attenuation from trying to adjust noise on an open input channel.

PROGRAM EXAMPLE:

CALL Send(0, 8, "INITiate:CONTinuous ON", 1) ’ CALL Send(0, 8, "SENSe:FUNCtion 'XTIMe:VOLTage2'", 1) ’ CALL Send(0, 8, "SENSe:VOLTage2:RANGe:AUTO ON", 1) ’

3 - 42 USING THE COMBISCOPE INSTRUMENTS

Acquisition length = 512 samples.

Acquisition lengthd = 8192 samples.

3.8 Time Base Control

In the digital mode, the SENSe:SWEep:TIME:AUTO command allows you to enable autoranging of the main timebase (MTB).

3.8.1 Number of samples

The TRACe:POINts command allows you to set the number of sample points, which is the total acquisition length for all traces. The number of samples i s limited to discrete values; refer to the TRACe:POINts command reference for a detailed specification of these values. After a *RST command, the number of samples is 512.

Note: If the number of samples is changed, the contents of all trace memories

is cleared. So, all previously stored traces are lost!

PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’ CALL Send(0, 8, "TRACe:POINts CH1,8192", 1) ’

3.8.2 Time base speed

The SENSe:SWEep:TIME command specifies the time base of a sweep, which is the time duration of one complete trace acquisition. Because the SENSe:SWEep:TIME values are limited in the digital mode by permitted MTB values, only particular values can be specified with this command. Refer to the SENSe:SWEep:TIME command reference for a detailed specification of these values.

Together with the number of trace points (TRACe:POINTs), the SENSe:SWEep:TIME command determines the Main Time Base (MTB). The MTB is expressed in seconds per division. Since there are 50 points in each division, the MTB can be calculated from the following equation:

MTB = 50

SENSe:SWEep:TIME / (TRACe:POINts -1 )

USING THE COMBISCOPE INSTRUMENTS 3 - 43

Requests sweep time

Reads sweep time

Requests number of trace points

Reads number of trace points

Converts string to variable

Calculates the MTB

Prints the MTB

Real time mode off

Real time mode on

Sets peak detection on.

PROGRAM EXAMPLE:

CALL Send(0, 8, "SENSe:SWEep:TIME?, 1) ’ CALL Receive(0, 8, STIME$, 256) ’ CALL Send(0, 8, "TRACe:POINts? CH1, 1) ’ CALL Receive(0, 8, TPOINTS$, 256) ’ SWETIM = VAL(STIME$) ’ TRAPOI = VAL(TPOINTS$) ’ MTB = 50 * SWETIM / (TRAPOI-1) ’ PRINT "Main Time Base ="; MTB ’

In a similar way , the time value Ts that is associated with a trace sample point can be calculated from the following expression:

Ts = <sample_index >

SENSe:SWEep:TIME / (TRACe:POINts - 1)

where <sample_index> is the point number of the sample in the trace.

3.8.3 Real time acquisition

Since there is a physical limit to the maximum sample rate of the ADC , traces with a duration which is less than 200 ns cannot be sampled within one real-time acquisition. To allow you to go below the 200 ns limit, the CombiScope instrument uses particular random sampling techniques, where points in the requested tra ce are collected from a number of successive acquisitions. The result returned is a reconstruction of the original signal out of several acquisitions, which is not real time.

When real time acquisition needs to be guaranteed, the command SENSe:SWEep:REALtime[:STATe] must be set to ON. This disables the random sampling techniques. The trade-off is that the SENSe:SWEep:TIME range is limited to 200 ns. After

RST the :REALtime command is set to OFF.

The "peak detection" function allows the Analog-to-Digital Converters (ADC) to operate at their highest speed, even when a lower time base speed is selected. The result is that maximum and minimum peaks of the signal are detected, even at lower time base speeds. This is called oversampling. The SENSe:SWEep:PDETection[:STATe] command allows you to switch peak detection on or off.

PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’ CALL Send(0, 8, "SENSe:SWEep:REALtime ON", 1) ’ CALL Send(0, 8, "SENSe:SWEep:PDETection ON", 1) ’

3 - 44 USING THE COMBISCOPE INSTRUMENTS

Auto triggering

Sets CH1 trigger source

Sets auto time base on

3.8.4 Autoranging time base

The AUTO RANGE function of the Main Time Base (MTB) adjusts the time base automatically, so that two to six waveform periods are displayed on the screen. If a waveform doesn't contain enough information to calculate its period, the time base is adjusted to acquire a minimum of two periods. One period of a signal is determined by three successive crossings of the hysteresis band with the input signal. The level of the hysteresis band can be set using the TRIGger:LEVel command.

X3X1

HYSTERESIS

TRIGGER LEVEL

LIMITATION: When operating with an acquisition length of 512 points, the maximum input frequency is 25 MHz. For all other acquisition lengths, the maximum input frequency is 50 MHz. When the input frequency is greater than the maximum alias detection frequency, it is no longer possible to detect aliasing.

PROGRAM EXAMPLE:

CALL Send(0, 8, "INITiate:CONTinuous ON", 1) ’ CALL Send(0, 8, "TRIGger:SOURce INTernal1", 1) ’ CALL Send(0, 8, "SENSe:SWEep:TIME:AUTO ON", 1) ’

PERI

D LEN

THPERI

D LEN

Figure 3.16 Definition of a signal period

ST7430

USING THE COMBISCOPE INSTRUMENTS 3 - 45

3.9 Post Processing

TRACe

SENSe

CH 1 CH 2 CH 3 CH 4

M1_1 M1_2 M1_3 M1_4

Figure 3.17 Post processing control

3.9.1 How to do post processing

The post processing functions CALCulate1 and CALCulate2 comply with the front panel functions MATH1 and MATH2 of the CombiScope instrument. They work only in the digital mode. The use of the CALCulate functions is as follows: 1 Select the source for the post processing function. 2 Specify the settings of the post processing function. 3 Enable the post processing function. 4 Check the result of the post processing function.

M2_1 M2_2 M2_3 M2_4

M3_1 M3_2 M3_3 M3_4

M50_1 M50_2 M50_3 M50_4

CALCulate1

CALCulate2

ST7161

3.9.1.1 Select the source for the post processing function.

Select the trace that is to be sourced into the CALCulate function by sending the CALCulate<n>:FEED command.

Examples:

→ CALCulate2:FEED "CH3" ’Channel 3 = source for CALC2

Send Send

→ CALCulate:FEED "M2_1" ’M2_1 = source for CALC1

Empty traces may not be selected as input trace. A memory register 1 location (M1_ j) may not be specified as the source (feed) for CALCulate1 and a memory register 2 location (M2_ j) may not be the source (feed) for CALCulate2. After a

RST command, CH1 becomes the input trace for both CALculate functions.

Note: CH3 and CH4 cannot be selected as source for the PM33x0B

CombiScope instruments.

3 - 46 USING THE COMBISCOPE INSTRUMENTS

CALCulate

CALCulate[1]

CALCulate2

ST7162

SENSe

TRACe

CH 1 CH 2 CH 3 CH 4

M1_1 M1_2 M1_3 M1_4

M2_1 M2_2 M2_3 M2_4

M3_1 M3_2 M3_3 M3_4

CALCulate:FEED "M3_2"

CALCulate2:FEED "M2_4"

M50_1 M50_2 M50_3 M50_4

Figure 3.18 Post processing feed definition

3.9.1.2 Specify the settings of the post processing function.

When desired, specify the settings of the post processing function to be used. The following settings can be programmed:

- the filter type of the FFT function RECTanguler | HAMMing | HANNing

- the width of the low-pass filter window 3, 5, 7, .., 39, 41 points

- the width of the differential window 3, 5, 7, .., 127, 129 points Example:

→CALCulate2:TRANsform:FREQuency:WINDow HAMMing

Send

’Defines the Hamming filter for the FFT process.

3.9.1.3 Enable the post processing function.

Enable the desired post processing function by using the :STATe command of the calculate function concerned. The following post processing functions are available: STANDARD AVAILABLE:

- mathematical calculations :MATH

- frequency filtering :FILTer:FREQuency

- frequency domain transformations (FFT) :TRANsform:FREQuency OPTIONAL:

- histogram transformation :TRANsform:HISTogram

- integratin g tr ace s :INTegra l

- differentiating traces :DERivative (alias :DIFFerential) Example:

→ CALCulate2:TRANsform:FREQuency:STATe ON ’Enables FFT

Send The post processing is automatically executed when a trace that is fed into the

CALCulate function is changed. If a mathematical function is switched on, the other functions are automatically switched off.

USING THE COMBISCOPE INSTRUMENTS 3 - 47

Dimensions trace buffer

Channel 3 = source CALC2

Enables FFT-Hamming

Requests for M2_1 trace

Reads the M2_1 trace

3.9.1.4 Check the result of the post processing function.

The results of the post processing functions :MATH

:TRANsform:FREQuency

:TRANsform:HISTogram are stored in M1_1 for CALCulate1 and in M2_1 for CALCulate2, regardless of the input (feed) trace.

The results of the post processing functions :FILTer:FREQuency

:INTegral

:DERivative (or :DIFFerential) are stored in M1_n or M2_n, depending of the input source. When CHn or Mi_n is the input trace for CALCulate1, the result is placed in M1_n (n = 1, 2, 3, 4). When CHn or Mi_n is the input trace for CALCulate2, the result is placed in M2_n (n = 1, 2, 3, 4).

Example:

→ CALCulate2:FEED "CH3"

Send

→ CALCulate2:INTegral:STATe ON

Send ’The result is that the integral of the channel 3 trace is placed in M2_3.

When the result of a calculation is saved in a trace memory location, the other trace locations of the same memory register are used by the calculate process. Data stored in these locations may be destroyed. For example, a CALculate1 process that stores the result in M1_2, may also destroy the contents of M1_1, M1_3, and M1_4. The result of a CALCulate function that is stored in a trace memory can be read into the controller by using the TRACe? query.

Example: Send Read

Note: The result of a CALCulate block can be used as source for the other

PROGRAM EXAMPLE:

DIM response AS STRING * 1033 ’ CALL Send(0, 8, "CALCulate2:FEED ’CH3’", 1) ’ CALL Send(0, 8, "CALCulate2:TRANsform:FREQuency:WINDow HAMMing", 1) CALL Send(0, 8, "CALCulate2:TRANsform:FREQuency:STATe ON", 1)

CALL Send(0, 8, "TRACe? M2_1", 1) ’ CALL Receive(0, 8, response$, 256) ’

→ TRACe? M2_1 ’Requests for M2_1 trace

← <trace_buffer> ’Reads M2_1 trace

CALCulate block, but not

as source for the same CALCulate block.

’

3 - 48 USING THE COMBISCOPE INSTRUMENTS

Channel 1 + channel 2

Math function enabled

The resulting trace (CH1 + CH2) is stored in M1_1.

M1_1 - channel 2

The resulting trace (which is the CH1 trace) is stored in M2_1.

Channel 3 = input source

Channel 3 + channel 2

Math function enabled

The resulting trace (CH3 + CH2) is stored in M1_1.

3.9.2 Mathematical calculations

Mathematical calculations can be performed on 2 traces using the CALCulate1:MATH and CALCulate2:MATH functions. These functions comply with the front panel features MA TH1 and MA TH2 respectively. The calculation can be an addition (+), a subtraction (-), or a multiplication ( resulting trace is automatically set higher than the sum of the attenuations of the

). The attenuation of the

individual traces. PROGRAM EXAMPLE:

CALL Send(0, 8, "CALCulate:MATH (CH1+CH2)", 1) ’ CALL Send(0, 8, "CALCulate:MATH:STATe ON", 1) ’ ’ CALL Send(0, 8, "CALCulate2:MATH (M1_1 - CH2)", 1) ’ ’

The first argument in the expression that defines the mathematical operation to be performed, is a trace that may be specified either implicitly, or explicitly by its trace name. A trace is specified implicitly when the keyword IMPLied is used as argument in the expression. When IMPlied is specified, the trace that is programmed with the CALCulate:FEED command is used as the first argument in the expression. The trace that determines the second argument must always be specified explicitly by its trace name.

PROGRAM EXAMPLE:

CALL Send(0, 8, "CALCulate:FEED ’CH3’", 1) ’ CALL Send(0, 8, "CALCulate:MATH (IMPLied+CH2)", 1)’ CALL Send(0, 8, "CALCulate:MATH:STATe ON", 1) ’ ’

3.9.3 Differentiating and integrating traces

The INTegral function performs a point-to-point integration on a trace. The result of the integration process is a trace. Each point in the trace is the integral up to the corresponding point in the original (input) trace.

The DERivative (DIFFerential) function calculates the differential quotient of the trace points. Each point in the resulting trace is the derivative of the correspon ding point in the original (input) trace. The width of the differential window can be programmed from 3 to 129 points in increments of 2 points by the CALCulate:DERivative:POINts command. After a points is 5.

RST command, the number of

USING THE COMBISCOPE INSTRUMENTS 3 - 49

Integral CALC1 on

35 differential points

Differential CALC2 on

Scaling can be adjusted with the "CURSORS TRACK and delta" knobs via the MATHPLUS - PARAM me nu option.

PROGRAM EXAMPLE:

CALL Send(0, 8, "CALCulate:INTegral:STATe ON", 1) ’ CALL Send(0, 8, "CALCulate2:DERivative:POINts 35", 1)’ CALL Send(0, 8, "CALCulate2:DERivative:STATe ON", 1) ’

3.9.4 Frequency domain transformations

The result of an FFT (Fast Fourier Transformation) calculation is displayed as a trace of amplitude values (vertically) versus frequency values (horizontally). The vertical result can be expressed as a relative or an absolute amplitude value. The CALCulate:TRANsform:FREQuency:TYPE command selects between the RELative and ABSolute result. The DISPlay:WINDow:TEXT<n>:DATA? query allows you to read the calculated amplitude and frequency value.

RELATIVE FFT:

A relative FFT calculation consists of a frequency (Hz) and an amplitude in (dB), relative to the frequency component with the largest amplitude.

ABSOLUTE FFT:

An absolute FFT calculation consists of a frequency (Hz) and an amplitude in dBm (dB with respect to 1 milliwatt), dBµV (dB with respect to 1 microvolt), or Vrms (Volt RMS) as selected via the front panel CURSORS - READOUT softkey menu.

The following FFT window functions can be selected using the CALCulate:TRANsform:FREQuency:WINDow command:

•

The resulting FFT trace is a MIN/MAX (envelope) trace, which means that each trace point is determined twice (one for the MINimum envelope and one for the MAXimum envelope). The FFT trace points are scaled between +4 and -4 divisions on the screen. So, the samples values that are returned as response to a TRACe? query are shifted 4 divisions upwards. The value s of the resultin g FFT trace points are between -0 dB and -80 dB. This results in the following relation between screen position and sample value:

The FFT RECTangular function transforms a repetitive time amplitude trace into its power spectrum.

The FFT HAMMing and HANNing functions reduce the side lobes by applying a Hamming respectively Hanning window to the input signal. This improves the visibility of the minor frequency components if the limited area is not accurately selected.

3 - 50 USING THE COMBISCOPE INSTRUMENTS

Trace sample value Trace point

8-bits

top - - - - - 100 25600 - 0 dB

- - - - - - - 75 19200 - 10 dB

- - - - - - - 50 12800 - 20 dB

screen range

TRACE POINT VALUES: FFT trace sample values, as entered with the TRACe:DATA? query, can be

converted to FFT point value as follows:

Subtract from the sample value the offset value for 4 divisions:

•

- for 8-bit samples: 4

- for 16-bit samples: 4 Multiply the result with the following correction factor:

•

- for 8-bit samples: -10(dB) / -25 = 0.4

- for 16-bit samples: -10(dB) / -6400 = 0.0015625

- - - - - - - 25 6400 - 30 dB

mid- - - - - 0 0 - 40 dB

- - - - - - - - 25 - 6400 - 50 dB

- - - - - - - - 50 - 12800 - 60 dB

- - - - - - - - 75 - 19200 - 70 dB

bottom - - - 100 - 25600 - 80 dB

Figure 3.19 Relation between screen position and FFT value

25 = 100

6400 = 25600

16-bits value

trace range

So, the conversion from a trace sample value (Ts) to a trace point value (Ps) is expressed by the equations:

- for 8-bit samples: Ps = (Ts - 100)

- for 16-bit samples: Ps = (Ts - 25600)

Note: For an explanation of Ts and Ps, refer to section 3.4.3 "Conversion of

trace data".

When relative FFT calculation is selected, the amplitude trace point values represent the relative strength of the frequency components. The component with the highest amplitude is taken as the reference level, referred to as the 0 dB level.

When absolute FFT calculation is selected, the amplitude trace point values depend on the absolute reference level as selected via the CURSORS - READOUT front panel menu, which can be one of the following:

- dBm (refere nce = 1 mW) with REFerence IMPedance of 50Ω

- dBm (refere nce = 1 mW) with REFerence IMPedance of 600Ω

-dBµV (reference = 1 µV)

- Vrms (reference = RMS signal amplitude)

0.4

0.0015625

USING THE COMBISCOPE INSTRUMENTS 3 - 51

Absolute FF T amplitudes are calculated fro m the true signal using the information on the actual attenuator setting in the range from 5 V/div. to 2 mV/div. This results in an offset value to be added to the relative FFT amplitude for each attenuator setting. In any attenuator setting, the reference level fo r the absolute FFT value is calculated from a peak-to- peak amplitude of a sine wave on a screen of 6.34 divisions. This amplitude equals an RMS value of:

6,34 2⁄ 2 2,24≈

This level is used as the reference level (top of screen) for the FFT amplitude display. For any attenuator setting, the reference level can be calculated as follows:

2,24 * <number of millivolts per divisions>

Examples: At 20mV/div. : 2.24

At 100mV/div.: 2.24

For a 50Ω system, a signal amplitude of 224 mVrms corresponds to the following signal power:

P 0,224()

This can also be expressed as a signal level of 0dBm at 50Ω impedance. The same voltage measured in a 600Ω system corresponds to the following

power level:

P0,224()

This can be calculated as a signal level of:

10 * log

Vrms offset calculation:

A signal of 1 mW at 50Ω impedance is taken as voltag e refere nce at 1 00 mV/div. From this signal the RMS voltage is calculated as follows:

Urms P *R() 1E-3 *50()0,2236068== =

For a whole screen of 10 divisions, Urms = 2.236068. Depending on the attenuator setting, the Vrms offset voltage is calculated as follows:

Vrms offset = attenuation

Example for attenuator setting 0.5 V/div.:

50⁄ 0,001 W 1 mW≈≈=

600⁄ 0,0000836 W 83,6 µW≈≈=

83.6E-6 1 mW⁄()10 * log1083.6E-3()10.7 dBm–≈=

20 ≈ 44.8 mVrms

100 ≈ 224 mVrms

Urms

Vrms offset 0,5 *2,236068 1,118034==

3 - 52 USING THE COMBISCOPE INSTRUMENTS

dBm - 50Ω offset calculation:

From the Vrms offset value the dBm-50Ω offset value is calculated as follows:

dBm 50Ω offset– 20 * Vrms offset 0,2236068⁄()log

Note:

P *R() 1E-3 *50()0,2236068==

Example for attenuator setting 0.5 V/div.:

dBm 50Ω offset– 20 * 1,118034 0,2236068⁄()log

13,9794==

dBm - 600Ω offset calculation:

From the Vrms offset value the dBm-600Ω offset value is calculated as follows:

Note:

dBm 600Ω offset– 20 * Vrms offset 0,7745967⁄()log

P *R() 1E-3 *600()0,7745967==

Example for attenuator setting 0.5 V/div.:

dBm 600Ω offset– 20 * 1,118034 0,7745967⁄()log

3,1875874==

dBµV offset calculation:

From the Vrms offset value the dBµV offset value is calculated as follows:

dBµV offset 20 * Vrms offset 1.0E-6⁄()log

Note: 0 dBµ V = 1 µV (1.0E-6 V) at 50Ω impedance. Example for attenuator setting 0.5 V/div.:

dBµV offset 20 * 1,118034 1E-6⁄()log

120,9691==

USING THE COMBISCOPE INSTRUMENTS 3 - 53

ATTENUATOR

SETTING:

Vrms:

dBm-50

dBm-600

dBµV:5V/div2 ,, 1 ,,+11.18034

4.4721359

2.236068

33.9794

26.0206

20.0+23.187588

15.228787

9.2081872

140.9691

133.0103

126.9897

0.5

0.2

0.1

,, +1.118034

0.4472136

0.2236068

13.9794

6.0206

0.0+3.1875874

4.771213

10.791813

120.9691

113.0103

106.9897

mV/div

,, 10 ,,+0.1118034

0.0447214

0.0223607

6.0206

13.979392

20.0-16.812413

24.771206

30.791813

100.9691

93.010308

86.989708

,,2,,+0.0111803

0.0044721

26.020632

33.97947

36.812444

44.771282

80.96907

73.01023

SUMMARY OF CALCULA TED OFFSET VALUES:

Ω

Note: The PROGRAM EXAMPLE on the next page shows how it is

programmed.

TRACE POINT FREQUENCIES: The horizontal frequency values (in Hz per point) are calculated from the trace

sample index (point number of the sample in the trace), the acquisition length (TRACe:POINts), and the MTB (calculated from the SENSe:SWEep:TIME) by the following equation:

Fs = (<sample_index>

Restriction: Only trace sample data can be queried from trace memories; no

trace administration data, such as acquisition length and MTB value. This means that these values must be queried from the actual input channel signal, which is taken as the source for the FFT process. So, take care that the acquisition length nor the MTB is changed between activating the post processing function and reading the trace memory where the post processing trace is stored.

1250) / (TRACe:POINts * MTB * 50)

3 - 54 USING THE COMBISCOPE INSTRUMENTS

PROGRAM EXAMPLE: The following program example converts a relative or absolute FFT trace of 512

samples of 1 or 2 bytes from the signal on channel 1 via the MATH1 feature as follows:

Before running this program, first make the FFT selections desired via the

•

front panel, such as: > MATH - MATH1 "on" and "fft". > CURSORS "on" and "m1.1". > MATH - PARAM - FILTER "hamming", "hanning", or "re c tang". > MATH - PARAM - READOUT "rel" to select relative FFT. > MATH - PARAM - READOUT "abs" to select absolute FFT.

+ CURSORS - READOUT "dBm + 50Ω", "dBm + 600Ω", "dBµV", or "Vrms".

Request the following values:

•

> The acquisition length using the TRACe:POINts? CH1 query. > The sweep time to calculate the MTB using the SENSe:SWEep:TIME?

query. MTB = (sweep_time The calculation factor to determine the sample point frequencies is determined as follows: calc = 1250 / (acquisition_length

> The peak-to-peak voltage to calculate the attenuation using the

SENSe:VOLTage:RANGe:PTPeak? query. Attenuation = peak-to=peak / 8.

> The FFT type, i.e., ABSolute or RELative, using the

CALCulate:TRANsform:FREQuency:TYPE? query.

50) / (acquisition_length - 1).

MTB * 50).

Read the FFT trace from memory register m1.1 using the TRACe? M1_1

•

query. Convert and print the frequency and amplitude values of the FFT trace sample

•

points according to the formulas as explained before.

Note: The program prints the calculated values in groups of 20 sample

points on the screen of your computer.

Note: The program is supplied on floppy under file name EXFFTTRC.BAS.

USING THE COMBISCOPE INSTRUMENTS 3 - 55

This turns the histogram function on

35 filter points

Filter CALC1 on

3.9.5 Histogram functions

The HIST ogram function calculates an amplitude distribution of the incoming trace. The number of points in the histogram trace is 512. Each point in the histogram specifies the number of times that a data point of the incoming trace is within a particular amplitude belt. Since there are 512 histogram points, there are also 512 amplitude belts. The range of the amplitude belts is determined by the selected peak-to-peak range (SENSe:VOLTage:RANGe:PTPeak) and is expressed by the following equation:

amplitude belt = peak-to-peak range / 512

Notice that a histogram contains 512 valid data points. The number of points (TRACe:POINts) of the trace memory location where the histog ram is stored, may exceed this value. In that case the values of the trace positions above 512 have to be ignored.

The histogram is displayed on the screen in the area between +3 and -2 divisions vertically, and between the third and the seventh division horizontally. The horizontal axis represents the amplitude in volts. The vertical axis represents the number of occurrences of an amplitude in percents.

PROGRAM EXAMPLE:

CALL Send(0, 8, "CALCulate:TRANsform:HISTogram:STATe ON", 1)

’

3.9.6 Frequency filtering

The FILTer function performs digital low-pass filtering to suppress undesired frequency noise. The width of the filter window can be programmed from 3 to 41 points in increments of 2 points. After a

PROGRAM EXAMPLE:

CALL Send(0, 8, "CALCulate:FILTer:FREQuency:POINts 35", 1)

CALL Send(0, 8, "CALCulate:FILTer:FREQuency:STATe ON", 1)

RST command, the number of points is 19.

’

3 - 56 USING THE COMBISCOPE INSTRUMENTS

3.10 Trace Memory

The trace memory of the CombiScopes instruments consists of space for channel acquisition traces (CH1 to CH4) and memory regi ster traces (M1 to M8 and M9 to M50 extended). The amount of acquisition and register space depends on the following:

Whether the CombiScope instrument is equipped with standard or with

•

extended memory. The specified acquisition length (number of trace samples) with the

•

TRACe:POINts command. Example:

Send → TRACe:POINts CH1,8192 This command specifies an acquisition length of 8192 samples for all traces.

Notes: - Only the following trace acquisition lengths can be programme d:

512, 2024 (2K), 4096 (4K), 8192 ( 8K), 16384 (16K), or 32768 (32K)

- If a different acquisition length is programmed, the contents of all acquisition and register space is cleared. So, all previously stored traces are lost!

- After a

- The resulting traces of the post processing functions are always stored in memory register 1 for CALCulate1 functions and in memory register 2 for CALCulate2 functions.

RST command, the number of trace samples is 512.

TRACe

M50_1 M50_2 M50_3 M50_4

SENSe

CH 1 CH 2 CH 3 CH 4

M1_1 M1_2 M1_3 M1_4

M2_1 M2_2 M2_3 M2_4

M3_1 M3_2 M3_3 M3_4

Note: For standard memory, 8 memory registers are available (M1 to M8).

For extended memory, 50 memory registers are available (M1 to M50).

Figure 3.20 Trace memory control

Note: CH3 and CH4 cannot be selected as the source for the PM33x0B

CombiScope instruments. Instead the external channel can be selected, e.g., M1_E.

ST7163

USING THE COMBISCOPE INSTRUMENTS 3 - 57

Length of trace samples = 16 bits

Length of trace samples = 8 bits

The following table shows the relation between the trace acquisition length (TRACe:POINts) and the available channel (CHx) and memory traces (Mx).

TRACe:POINts CHANNELS: MEMORY REGISTERS: STANDARD:

512 2K 4K 8K

(PM33x0B) 4(2+EXT) 4(2+EXT) 2(2) 1(1)

M1 .. M8 M1 .. M2 M1 .. M2 M1 .. M2

EXTENDED:

512 8k 16K 32K

Examples:

- Standard memory 4K acquisition length allows, for example: CH1 + M1_1 + M2_1 + CH3 + M1_3 + M2_3

- Extended memory 32K acquisition length allows, for example: CH2 + M1_2 + M2_2

(PM33x0B) 4(2+EXT) 4(2+EXT) 2(2) 1(1)

M1 .. M50 M1 .. M2 M1 .. M2 M1 .. M2

Table 3.2 Relation between acquisition length and available trace memory

Note: Delayed Time Base (DTB) acquisition traces are only saved in th e CH1

to CH4 memory, when the acquisition length is 512 samples. DTB acquisitions can only be defined via front panel operations.

3.10.1 Trace formatting

The FORMat command allows you to format the resolution of trace sample values. The resolution is determined by specifying the number of bits used to code the sample values of all trace acquisitions. Trace samples can be programmed to be formatted as 16 bits (2 bytes) or as 8 bits (1 byte). After a command, the number of trace sample bits is 16 (2 bytes). Notice that the contents of acquisition and register space is not cleared when a different trace format is programmed.

RST

PROGRAM EXAMPLE:

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

3 - 58 USING THE COMBISCOPE INSTRUMENTS

Channel 1 on

Channel 2, 3, 4 off

Channel 3 also on

’ The result is that the acquisition traces of the channels 1 and 3 are copied to M2_1 respectively M2_3

The result is that the previously stored traces in M2_1 and M2_3 are copied to M3_1 respectively m3_3

3.10.2 Copying traces to memory

The TRACe:COPY command allows you to copy the contents of a memory register to another memory register. This allows you to fill a memory register with traces from one of the following sources:

Copy an acquisition trace from one of the input channels.

•

Example: Send → TRACe:COPY M1_2,CH2 ’ Copies from CH2 to M1_2

Note: The result of this command is also that the acquisition traces of other

channels (CHn) are copied into M1_n, provided channel CHn is on. So, all previously stored traces in M1 are lost!

Copy a previously stored trace from another trace memory register.

•

Example: Send → TRACe:COPY M2_2,M1_2 ’ Copies from M1_2 to M2_2

Note: The result of this command is also that all stored traces of M2_N are

copied into M1_n, provided a trace was stored before. So, all previously stored traces in M2 are lost!

PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’

CALL Send(0, 8, "SENSe:FUNCtion ’XTIMe:VOLTage3’", 1) ’

’

CALL Send(0, 8, "TRACe:COPY M2_1,CH1", 1)

CALL Send(0, 8, "TRACe:COPY M3_1,M2_1", 1) ’

USING THE COMBISCOPE INSTRUMENTS 3 - 59

Dimensions trace buffer

Requests for channel 1 trace

Reads the channel 1 trace

IBCNT = number of data bytes

Sends fixed command part without EOI

Sends variable <trace block> without EOI

Sends dummy string with EOI detection

3.10.3 Writing data to trace memory

The TRACe command allows you to write data from the controller into a memory register. The following possibilities are available:

Write a previously read trace using the TRACe? query.

•

Example: Send → TRACe? CH3 ’Queries for CH3 trace Read ← <trace block> ’Reads trace data block Send → TRACe M2_3,<trace block> ’Writes data block to M2_3 The result is that trace area M2_3 is filled with the acquisition trace of cha nnel 3.

Programming note:

The fixed command part (TRACe M2_3,) and the variable <trace block> must be sent separately. So, no EOI (End Or Identify) detection in between. Also the <trace block> must be sent without EOI detection and detection of the EOL (End Of Line) code, because the <trace block> could contain the EOL character, e.g., code 10 for CR

Write a trace of identical constants (range = -32767 ... 32767).

•

Example: Send → TRACe M2_4,1028 ’1028 = 1024 + 4 = 0404 hex. This command fills all memory register M2_4 locations with the constant 0404 hexadecimal for 16-bit samples, and with 04 hexadecimal for 8-bit samples.

Note: A trace can only be written to memory register space (Mi_n) and not

to acquisition space (CHn).

PROGRAM EXAMPLE:

DIM response AS STRING * 2000 ’ CALL Send(0, 8, "TRACe? CH1", 1) ’ CALL Receive(0, 8, response$, 256) ’ length = IBCNT% ’

CALL Send(0, 8, "TRACe M2_3,", 0) ’ CALL Send(0, 8, LEFT$(response$,length), 0)

CALL Send(0, 8, "", 1) ’

’

3 - 60 USING THE COMBISCOPE INSTRUMENTS

Dimensions trace buffer 1

Dimensions trace buffer 2

Requests for channel 1 trace

Reads channel 1 trace into trace1$

Input source = CH1

Enables frequency filtering; the filtered channel 1 trace is stored in M1_1

Requests for M1_1 trace

Reads M1_1 trace into trac e2$

3.10.4 Reading data from trace memory

The TRACe? query allows you to read the contents from one of the foll owing trace memory registers:

An acquisition trace from one of the input channels (CH1 to CH4).

•

Previously stored trace data from one of the memory registers (M1 to M8 or to

•

M50). This can be either an acquisition trace or a trace of constant values (refer to section 3.10.3).

The result of a post processing function; CALCulate1 in M1 and CALCulate2

•

in M2 (refer to section 3.9 "Post processing").

PROGRAM EXAMPLE:

’

*****

’Read the actual channel 1 trace into trace1$ and the filtered ’channel 1 trace into trace2$. ’

*****

DIM trace1 AS STRING * 2000 ’ DIM trace2 AS STRING * 2000 ’ CALL Send(0, 8, "TRACe? CH1", 1) ’ CALL Receive(0, 8, trace1$, 256) ’

CALL Send(0, 8, "CALCulate:FEED ’CH1’", 1) ’ CALL Send(0, 8, "CALCulate:FILTer:FREQuency:STATe ON", 1) ’

CALL Send(0, 8, "TRACe? M1_1", 1) ’ CALL Receive(0, 8, trace2$, 256) ’

USING THE COMBISCOPE INSTRUMENTS 3 - 61

Sets brightness at 0.3

3.11 Screen/Display Functions

3.11.1 Brightness control

The DISPlay:BRIGhtness command allows you to control the brightness of the trace(s) displayed on the screen of your Comb iScope instru men t on a scale from

0.0 (low) to 1.0 (high). After a PROGRAM EXAMPLE:

CALL Send(0, 8, "DISPlay:BRIGhtness .3", 1) ’

3.11.2 Display functions

The DISPlay:WINDow and DISPlay:MENU commands allow you to use the following display functions:

The WINDow1 functions use the front panel screen display of MEAS1/MEAS2,

•

CURSORS, and MATH-FFT to read measurement data from the CombiScope instrument (refer to section 3.11.2.1).

The WINDow2 function to write user-defined text on the screen (refer to

•

section 3.1 1.2.2). The MENU function to display softkey menus on the screen (refer to

•

section 3.11.2.3).

RST command, the brightness intensity is 0.18.

The layout of the display areas on the screen is as follows:

WINDow[1]

WINDow2

Figure 3.21 Screen layout of display functions

3 - 62 USING THE COMBISCOPE INSTRUMENTS

3.11.2.1 Readout of measurement data

The DISPlay:WINDow[1]:TEXT<n>:DATA? query allows you to acquire measured data as displayed on the upper line(s) of the screen of your CombiScope instrument. The following measured data valu es can be selected by specifying the number <n> in the query:

NUMBER <n>: MEASUREMENT VALUE: 1, 2

10, 1 1, 12, 13, 20, 21, 30, 40, 51, 52 60, 61

MEAS1/MEAS2 DA TA: The MEAS1 and MEAS2 functions must be enabled and selected via front panel control. MEAS1 data is read by sending the DISPlay:WINDow:TEXT1:DATA? query and MEAS2 data by sending the DISPlay:WINDow:TEXT2:DATA? query, followed by reading the response strings.

The format of a response string is as follows:

<meas_type>,<meas_value>,<suffix_unit>

DESCRIPTION: <meas_type> <suffix_unit>: DC voltage

AC-RMS voltage minimum voltage maximum voltage peak-to-peak voltage low level voltage high level voltage overshoot percentage preshoot percentage frequency period time pulse width rise time fall time duty cycle percentage delay time between 2 channels

MEAS1, MEAS2 data CURSORS data

MA TH - FFT frequency, amplitude

dc rms min max pkpk low high over pre freq T puls rise fall duty del

V V V V V V V % % Hz s s s s % s

USING THE COMBISCOPE INSTRUMENTS 3 - 63

Example: Send → Send → DISPlay:MENU MEASure ’Switches MEASURE menu on Send → SYSTem:KEY 2;KEY 4 ’Switches MEAS1 and MEAS2 on Send → DISPlay:WINDow:TEXT1:DATA? ’Requests MEAS1 data Read ← pkpk,6000E-04,V ’Response = peak-to-peak 0.6 volt.

CURSORS DATA: The CURSORS function offers a wide variety of voltage and time readouts. The following readout selections can be made via the CURSORS - READOUT softkey menu:

<n>: TYPE: UNIT: DESCRIPTION: 10

11 12 13 20 21 30 40

51 52

RST ’Switches MEAS1 & 2 off

dV dY V1 V2 Vdc dT F dX phase

T1-trg T2-trg

V U V V V s Hz U

s s

Voltage difference (delta-V) between the cursors. Vertical voltage (X-deflection on). Absolute voltage of cursor 1 to ground. Absolute voltage of cursor 2 to ground. DC voltage Time difference (delta-T) between the cursors. Frequency (1/dT) in Hertz. Horizontal voltage (X-deflection on). The phase between two channels in degrees Celsius.

stands for degrees ° sign)

(

The time between cursor 1 and the trigger event. The time between cursor 2 and the trigger event.

MATH - FFT DATA: The MATH1/MATH2 - FFT functions offer the readout of the relative or absolute frequency and amplitude. The following readout selections can be made via the CURSORS - READOUT and MATH - FFT - PARAM softkey menus:

<n>: TYPE: UNIT: DESCRIPTION: 6061FFT-freq

FFT-amplHzvariable

FFT frequency in Hertz.

FFT amplitude in:

- Relative FFT selected: dB

- Absolute FFT selected: dBm, dbµV, V (Vrms)

3 - 64 USING THE COMBISCOPE INSTRUMENTS

Displays MEASURE menu

Enable MEAS1 & MEAS2 and select MEAS1-DC and MEAS2-frequency

Queries for volt-dc

Reads volt-dc value

Queries for time-freq

Reads time-freq value

PROGRAM EXAMPLE: Read and print the DC and frequency characteristic of the actual signal usi ng the

MEAS1 and MEAS2 functions. The program stops to let you make the req uested MEAS selections.

DIM response AS STRING * 30 CALL Send(0, 8, "DISPlay:MENU MEASure", 1) ’ ’ ’

*****

’ PRINT ">>> Press the LOCAL key, set MEAS1 function on, and select

PRINT ">>> Set MEAS2 function on and select MEAS2-time-freq." PRINT ">>> Press any key on the controller keyboard when finished." WHILE INKEY$ = "": WEND

CALL Send(0, 8, "DISPlay:WINDow:TEXT1:DATA?", 1) ’ CALL Receive(0, 8, response$, 256) ’ PRINT "Measured volt-dc = "; LEFT$(response$, IBCNT% - 1)

CALL Send(0, 8, "DISPlay:WINDow:TEXT2:DATA?", 1) ’ CALL Receive(0, 8, response$, 256) ’ PRINT "Measured time-freq = "; LEFT$(response$, IBCNT% - 1)

MEAS1-volt-dc."

USING THE COMBISCOPE INSTRUMENTS 3 - 65

Enables display of text

Displays the text: Remote control on the screen of your CombiScope instrument

Clears the text

Displays: 1.25 k

Displays:

Displays: CH1

Displays the text: 1.25 kW CH1 on the screen of your CombiScope instrument

Selects and displays the

CURSORS menu

Switches the CURSORS menu

display off

3.11.2.2 Display of user-defined text

The DISPlay:WINDow2:TEXT commands allow you to define and clear the user text on the screen area of your CombiScope instrument. After a the display of the previously defined user text is turned off.

RST command,

PROGRAM EXAMPLE 1: (text as string data)

CALL Send(0, 8, "DISPlay:WINDow2:TEXT:STATe ON", 1) ’ CALL Send(0, 8, "DISPlay:WINDow2:TEXT:DATA ’Remote control’", 1) ’ ’

PROGRAM EXAMPLE 2: (text as block data)

CALL Send(0, 8, "DISPlay:WINDow2:TEXT:CLEar", 1) ’ CALL Send(0, 8, "DISPlay:WINDow2:TEXT:DATA #01.25 k", 0)’ CALL Send(0, 8, CHR$(25), 0) ’ CALL Send(0, 8, " CH1", 1) ’ ’ ’

Ω

Note: The ASCII character 25 (= ↓ ) is displayed as Ω on the screen of your

CombiScope instrument.

3.11.2.3 Selection of softkey menus

The DISPlay:MENU commands allow you to select and enable the display of a softkey menu. If a menu is selected via the DISPlay:MENU command, the display is automatically enabled. After a turned off.

RST command, the display of softkey menus is

PROGRAM EXAMPLE:

CALL Send(0, 8, "DISPlay:MENU CURSors", 1) ’

CALL Send(0, 8, "DISPlay:MENU:STATe OFF", 1) ’

3 - 66 USING THE COMBISCOPE INSTRUMENTS

3.12 Print/Plot Functions

The HCOPy:DEVice <TYPE> command allows you to select a hardcopy device. The following selections can be made:

DEVICE: TYPE: NOTE: Plotter

Plotter Plotter Plotter Plotter Plotter Plotter Printer Printer Printer Printer Printer Generator

The HCOPy:DATA? query allows you to request a hardcopy of the picture on the screen of your CombiScope instrument. The response data is formatted according to the current printer/plotter options, which can be selected via the front panel UTILITY menu. After a selected.

HPGL HP7440 HP7550 HP7475A HP7470A PM8277 PM8278 FX80 HP2225 LQ1500 HPLASER HP540 DUMP_M1

HPGL plot data format

Epson FX80 compatibles (9 points) ThinkJet Epson LQ150 compatibles (24 points) HP LaserJet series II & III HP DeskJet (new style protocol) Trace dump to one of the arbitrary waveform generators PM5138, PM5139, or PM5150.

RST command, the option "plotter; HPGL" is

The response data to a HCOPy:DATA? query can be sent to a connected plotter or printer to make a hardcopy. The response data is sent as block data of indefinite length and is therefore, preceded by the preamble #0 of 2 bytes. This preamble must be removed from the beginning of the block data, before sending it to a plotter or printer device.

USING THE COMBISCOPE INSTRUMENTS 3 - 67

Dimensions address array

Dimensions response string

Timeout at 10 seconds

Selects the PM8277 plotter

Requests for hardcopy data

Reads the hardcopy data

IBCNT = number of read bytes

The first 2 characters of the response block data are #0 (preamble for indefinite length)

They must not be sent to the plotter; so, send characters 3 until 3+length-2.

No End detection

End of data block

read

DSO

response data

send

HCOPy:DATA?

send plot/print data

2) data

buffer

CONTROLLER

PLOTTER

PRINTER

1) Send the query HCOPy:DATA? via the GPIB.

2) Read the block response data via the GPIB.

3) Send the print/plot data part to the printer/plotter.

ST7219

Figure 3.22 Hardcopy of screen on printer/plotter

PROGRAM EXAMPLE: Select one of the supported GPIB plotters, set its address at 22 and connect the

plotter via IEEE to the controller. Create a screen picture on the DSO that you want to plot and run the following program.

DIM addr(2) ’ DIM response AS STRING * 15000 ’ CALL IBTMO(0, 13) ’

CALL Send(0, 8, "HCOPy:DEVice PM8277", 1) ’ CALL Send(0, 8, "HCOPY:DATA?", 1) ’ CALL Receive(0, 8, response$, 256) ’ length = IBCNT% ’ PRINT "Number of hardcopy bytes ="; length ’

*****

’ ’ ’

*****

CALL Send(0, 22, MID$(response$, 3, length - 2), 0) ’ CALL Send(0, 22, "", 1) ’

3 - 68 USING THE COMBISCOPE INSTRUMENTS

Sets the time to 25 minutes and 36

seconds past 2 o'clock in the

afternoon.

Sets the date to 15 december 1993.

3.13 Real-Time Clock

The real-time clock keeps track of the current date and time. The date and time are stamped on acquired waveforms to be sent to a computer or to be output to a hardcopy device. The time of stamping is also the time of th e acquisition trigger .

The SYST em:TIME comman d sets the time in hours, minutes, and seconds. On ly a 24-hours time format is supported. The format of the displayed time cannot be selected.

The SYSTem:DATE command sets the date in years, months, and days. PROGRAM EXAMPLE:

CALL Send(0, 8, "SYSTem:TIME 14,25,36", 1)

CALL Send(0, 8, "SYSTem:DATE 1993,12,15", 1)

3.14 Auto Calibration

Calibration is only possible when the CombiScope instrument is warmed up. The instrument data is calibrated automatically by sending the CALibration? query. The internal calibration lasts several minutes. A "0" result is returned after correct calibration, and a "1" result is returned when the calib ration failed. Notice that the response to the calibration que ry i s on ly return ed whe n the calibration has completed.

CAL? or the

During the calibration process bit 0 "Calibrating" is set in the operation status condition register. This bit cannot be read during the execution of the CALibration? query, because these queries are sequential commands. This bit can be read after sending the CALibration command, which is an overlapped command. The completion of the CALibration command is reported in the standard Event Status Register (ESR) bit 0 (OPC bit set to 1). When the calibration is finished, bit 8 in the QUEStionable status reports a possible calibration error (if set to 1).

Note: Execute calibration only when it is needed, e.g., when a message on the

screen of your CombiScope instrument requests to do so.

CAL? or

USING THE COMBISCOPE INSTRUMENTS 3 - 69

Starts the calibration

Disables the time out mechanism

Waits for the calibration to finish and reads the result

Sets time out back to 10 seconds

0 = okay

1 = wrong

Defines "ServReq" routine call after SRQ

Enables SRQ mechanism

Sets bit 0 (Calibration) true in the case of negative transition (from 1 to 0).

Enables bit 0 for being reported in the standard status byte (STB).

Enables bit 7 (OPER) in Service Request Enable (SRE) register for generation of an SRQ.

Resets the instrument

Clears the status data

Starts auto calibration

PROGRAM EXAMPLE:

’

*****

’Calibrate the instrument and print the calibration result. ’

*****

CALL Send (0, 8, "*CAL?", 1) ’ CALL IbTMO(0, 0) ’ response$ = " " CALL Receive (0, 8, response$, 256) ’ ’ CALL IbTMO(0, 13) ’ IF LEFT$(response$, 1) = "0" THEN ’

PRINT "Calibration okay"

ELSE ’

PRINT "Calibration not successful"

ENDIF

PROGRAMMING NOTE: Status bit 0 in the operation status can be used to generate a Service Request

(SRQ) when the calibration is finished, i.e., when bit 0 becomes zero. This gives you the advantage that the program can do something else until the SRQ is generated. Therefore, program the following:

ON PEN GOSUB ServReq ’ PEN ON ’

Send → STATus:OPERation:NTRansition 1

’

Send → STATus:OPERation:ENABle 1

’

Send → *SRE 128

’

Send → *RST ’ Send → *CLS ’ Send → CALibration ’

3 - 70 USING THE COMBISCOPE INSTRUMENTS

3.15 Status Reporting

Status reporting is done via the status reporting system, which is completely described in chapter 5 "THE ST ATUS REPORTING SYSTEM" of the SCPI Users Handbook. The following figure shows the principle of the standard Status Byte (STB) register and the Service Request Generation (SRQ) mechanism:

OPERation

Status

Service

SRQ OPER

Request

Generation

Standard

Event Status

Logical OR

QUEStionable

Status

Error/ Output Queue

RQS

bit2

ESB MAV

MSS

QUES

Event

Queue

Not Used

bit0

bit1

Figure 3.23 The status reporting model for CombiScope instruments

3.15.1 Status data for the CombiScope instruments

RQS read by Serial Poll

Status Byte Reg.

MSS read by *STB?

Service Request Enable Register *SRE <NRf> *SRE?

ST7164

The following status data applies to the CombiScope instruments:

For the meaning of the bits of the OPERation status, refer to section 3.15.1.1.

•

For the meaning of the bits of the QUEStionable status, refer to section 3.15.1.2.

•

For the meaning of the bits of the standard Event Status Register, refer to the

•

command reference for the The message output queue can contain about 250 data bytes.

•

The error/event queue can contain 20 error messages before it overflows.

•

ESR? query.

USING THE COMBISCOPE INSTRUMENTS 3 - 71

3.15.1.1 Operation status data

CALibrating

RANGing

SWEeping

wait for TRIGger

Digital mode

Pass/Fail valid

Pass/Fail status

0 0

0 0 0 0 0

CONDition filter EVENt ENABle

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15

:CONDition?STATus:OPERation :PTRansition(?)

:NTRansition(?) :EVENt? :ENABle(?)

** ** ** ** ** ** ** ** ** ** ** ** ** ** ** **

0 1 2 3 4 5 6 7 8 9

11 12 13 14 15

ST7442

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15

Figure 3.24 The Operation Status structure

BIT: MEANING:

CALibrating

This bit is set during the time that the instrument is performing a calibration.

RANGing

This bit is set during the time that the instrument is autoranging (autosetting).

SWEeping

This bit is set when the sweep (a data acquisition) is in progr ess. This bit is reset to zero when the data acquisition is finished. At the same time, the OPC bit (0) in the standard Event Status Register (ESR) is set. Only valid for multiple-shot mode (INITiate:CONTinuous OFF).

Waiting for TRIGger

This bit is set when the trigger system is initiated (INITiate) and waiting for a trigger to start an acquisition. This bit is reset to zero as soon as the instrument is triggered and the acquisition started. Only valid for single-shot and multiple-shot mode (INITiate:CONTinuous OFF).

Digital mode

This bit is set when the CombiScope instrument is in the digital mode.

Pass/Fail valid

This bit is set when the pass/fail status at bit 10 is valid.

Pass/Fail status

This bit is set if the pass/fail test has failed. If bit 9 = 1 and bit 10 = 0, the test has passed. If bit 9 = 1 and bit 10 = 1, the test has failed.

Table 3.3 The Operation Status bits

3 - 72 USING THE COMBISCOPE INSTRUMENTS

3.15.1.2 Questionable status data

EVENt

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15

ENABle

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15

VOLTage

TEMPerature

CALibration

Overload 50Ω

CONDition filter

0 0 0 0

0 0 0

0 0 0 0 0 0

10 11 12 13 14 15

** ** ** ** ** ** ** ** ** ** ** ** ** ** ** **

STATus:QUEStionable:CONDition?

:PTRansition(?) :NTRansition(?)

:EVENt? :ENABle(?)

ST7157

Figure 3.25 The Questionable Status structure

BIT: MEANING:

VOLTage

This bit is set if a digital sample value is clipped at the maximum or minimum value while a FETCh? query is done on the sample array. This bit is also set if a FETCh? query did not succeed because the shape of the waveform did not match the measure function request. Example: FETCh:FREQuency? in the case of only half a sine wave.

TEMPerature

This bit is set by the instrument if the difference between the current temperature and the temperature at the moment of the last calibration exceeds a certain level. This is an indication that the instrument must be calibrated. The temperature is sensed internally about half an hour after power on. This bit is reset after power on and after calibrating.

CALibration

This bit is set by the instrument when an internal calibration did not complete successfully . This bit is reset after power on and after successful calibration.

Overload 50

Ω

This bit is set by the instrument when any 50Ω input terminator is overloaded. This bit is reset after power on, or if none of the input terminators is overloaded.

Table 3.4 The Questionable Status bits

USING THE COMBISCOPE INSTRUMENTS 3 - 73

Clears the event registers + error/event queue

Presets the enable register + filters

3.15.2 How to reset the status data

The

CLS command allows you to clear the following status data structures:

All event status registers, such as the following:

•

- standard event status register (ESR)

- status byte register (STB)

- operation event status register (STATus:OPERation:EVENt)

- questionable event status register (STATus:QUEStionable:EVENt) The Error/event queue.

•

The STATus:PRESet command presets the filters and enable register of the operation and questionable status data in such a way that device-dependent events are reported. The result is as follows:

STATUS REGISTER DATA STRUCTURE PRESET VALUE OPERation

QUEStionable

ENABle register PTRansition filter NTRansition filter ENABle register PTRansition filter NTRansition filter

0000 hex. 7FFF hex. 0000 hex. 0000 hex. 7FFF hex. 0000 hex.

Note: A *RST command does not affect the contents of:

- event registers

- event enable registers

- output queues

- transition filters

PROGRAM EXAMPLE:

CALL Send(0, 8, "*CLS", 1) ’ CALL Send(0, 8, "STATus:PRESet", 1) ’

3 - 74 USING THE COMBISCOPE INSTRUMENTS

Timeout at 10 seconds

Resets the instrument

Enables OPC-bit (0) in ESE

OPeration Completed" is reported in bit 5 (ESB) of the STB after sending

OPC

Automatic configuration

This command forces the instrument to set the OPC bit

when all pending operations have been finished

Single initiation

Requests for the STB

Reads the STB

ESB = bit 5 (value 32)

Operation completed

Fetches AC-RMS value

Reads AC-RMS value

Prints AC-RMS value

3.15.3 How to enable status reporting

The principle of using the status reporting mechanism is explained by showing two program examples. In the first example the standard Status Byte (STB) is checked to signal "operation completed". In the second example the SRQ mechanism is used to signal "operation completed" by generating a Service Request.

3.15.3.1 Program example using the status byte (STB)

PROGRAM EXAMPLE: In this example the standard status byte (STB) is checked to detect whether or

not a "CONFigure:AC" + "INITiate" operation is completed. If completed, the program continues by fetching and printing the AC-RMS value.

CALL IBTMO(0, 13) ’ CALL Send(0, 8, "*RST", 1) ’ CALL Send(0, 8, "*ESE 1", 1) ’ ’" ’ CALL Send(0, 8, "CONFigure:AC", 1) ’ CALL Send(0, 8, "*OPC", 1) ’ ’ ’ CALL Send(0, 8, "INITiate", 1) ’ ESB.bit.set = 0 result$ = SPACE$(3) WHILE ESB.bit.set = 0

CALL Send(0, 8, "*STB?", 1) ’ CALL Receive(0, 8, result$, 256) ’ IF (VAL(result$) AND 32) THEN ’

ESB.bit.set = 1 ’

END IF WEND CALL Send(0, 8, "FETCh:AC?", 1) ’ result$ = SPACE$(30) CALL Receive(0, 8, result$, 256) ’ PRINT "AC-RMS value = "; result$ ’

USING THE COMBISCOPE INSTRUMENTS 3 - 75

Defines SRQ-routine

Enables SRQ-routine

Timeout at 10 seconds

Resets the instrument

Sets OPC-bit in ESR

OPeration Completed" is reported in bit 5 (ESB) of STB after sending

OPC

Sets ESB-bit in SRE-register

SRQ generation after "OPeration Completed" is enabled

Automatic configuration

Single initiation

This command forces the instrument to set the OPC bit in the STB

when all pending operations have been finished

Do something else while waiting for SRQ; continue when SRQ.detected = 1

Fetches AC-RMS value

Reads AC-RMS value

Prints AC-RMS value

Serial polls for the status byte to reset the SRQ-mechanism

Queries for the contents of the Event Status Register to clear the OPC-bit

3.15.3.2 Program example using a service request (SRQ)

PROGRAM EXAMPLE: In this example the "Service Request" mechanism is used to detect whether or

not a "CONFigure:AC" + "INITiate" oper ation is completed. If completed , an SRQ is generated to continue with fetching and printing the AC-RMS value.

SRQ.detected = 0 ON PEN GOSUB ServReq ’ PEN ON ’ CALL IBTMO(0, 13) ’ CALL Send(0, 8, "*RST", 1) ’ CALL Send(0, 8, "*ESE 1", 1) ’ ’" ’ CALL Send(0, 8, "*SRE 32", 1) ’ ’ ’ CALL Send(0, 8, "CONFigure:AC", 1) ’ CALL Send(0, 8, "INITiate", 1) ’ CALL Send(0, 8, "*OPC", 1) ’ ’ ’ WHILE SRQ.detected = 0 ’ WEND CALL Send(0, 8, "FETCh:AC?", 1) ’ result$ = SPACE$(30) CALL Receive(0, 8, result$, 256) ’ PRINT "AC-RMS value = "; result$ ’ END ’ ServReq:

PRINT "Service request generated because of Operation Completed." CALL ReadStatusByte(0, 8, sbyte%) ’ ’ PRINT "STB byte ="; sbyte% CALL Send(0, 8, "*ESR?", 1) ’ ’ resp$ = " "

CALL Receive(0, 8, resp$, 256)

PRINT "ESR byte = "; resp$ SRQ.detected = 1

RETURN

3 - 76 USING THE COMBISCOPE INSTRUMENTS

Configures for AC-RMS

Performs 20 measurements

Reads the AC-RMS value

Prints the AC-RMS value

Checks for instrument errors

Queries for a system error

Reads the instrument error

Prints the instrument error

3.15.4 How to report errors

Instrument errors usually caused by programming or setting errors, can be reported by the instrument during the execution of each command. To make sure that a program is running properly, you should 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, followe d 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 SYSTem:ERRor? or STATus:QUEue? query and read the instru-

ment 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 3.16.4.1.

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 3.16.4.2.

3.15.4.1 Error-reporting routine

Send the SYSTem:ERRor? or STATus:QUEue? query and read the instrument response after every group of commands that functionally belong to each other, by calling an error-reporting routine after each gro up of commands.

PROGRAM EXAMPLE:

DIM response AS STRING * 30 CALL Send (0, 8, "CONFigure:AC (@1)", 1) ’ FOR i = 1 TO 20 ’

CALL Send (0, 8, "READ:AC?", 1)

CALL Receive (0, 8, response$, 256) ’

PRINT "AC-RMS: "; response$ ’

GOSUB ErrorCheck ’ NEXT i ’

*****

’

REST OF THE APPLICATION

*****

’

*****

END ErrorCheck:

CALL Send (0, 8, "SYSTem:ERRor?", 1) ’

CALL Receive (0, 8, response$, 256) ’

PRINT "Error: "; response$ ’ RETURN

USING THE COMBISCOPE INSTRUMENTS 3 - 77

Loop until 0, ’No error

Sends error query

Reads error string

Displays error string

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

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

PROGRAM EXAMPLE:

ON PEN GOSUB ErrorCheck PEN ON ’

*****

’

APPLICATION PROGRAM

*****

’

*****

END ’

***************************************************

’ Subroutine reading all errors from the error queue. ’

***************************************************

SUB ErrorCheck

er$ = SPACE$(1) WHILE LEFT$(er$, 1) <> "0" ’

CMD$ = "SYSTem:ERRor?" CALL Send(0, 8, CMD$, 1) ’ er$ = SPACE$(60) CALL Receive(0, 8, er$, 256) ’ PRINT "Error = "; er$ ’

WEND

END SUB

3 - 78 USING THE COMBISCOPE INSTRUMENTS

Resets the instrument (for reset values, refer to the

RST command in the command reference)

Saves the complete instrument setup into memory 3

Recalls the complete instrument setup from memory 3

Reserves space for instrument settings

Queries for the complete instrument setup

'(no <node> parameter specified)

Reads the instrument settings

IBCNT% = number of settings bytes

Sends the command header (note the space)

EOI checking disabled (0)

Sends the instrument settings

EOI checking enabled (1)

3.16 Saving/Restoring Instrument Setups

This level of programming involves all functions in the CombiScopes instrumen ts, i.e., complete instrument setups are processed. This allows you to program one or more functions that are not individually programmable. The following possibilities can be programmed:

Restoring initial settings.

•

Saving/restoring complete setups via internal memory.

•

Saving/restoring complete or partical setups via the GPIB controller.

•

3.16.1 How to restore initial settings

Initial settings can be restored by sending the instrument-specific functions to a default state and selects the digital mode.

PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’

3.16.2 How to save/restore a setup via instrument memory

Complete instrument setups can be stored and recalled via one of the internal memories of the CombiScope instrument. Th e settings in recall memo ry 0 are the initial settings. The settings in the recall memories 1 through 10 are user programmable.

PROGRAM EXAMPLE:

CALL Send(0, 8, "*SAV 3", 1) ’ CALL Send(0, 8, "*RCL 3", 1) ’

3.16.3 How to save/restore a setup via the GPIB controller

Complete instrument setups or a part of the setup (node) can be stored and recalled via the external memory of the controller using the SYSTem:SET? <node> query (store setup) and SYSTem:SET command (recall setup).

PROGRAM EXAMPLE:

DIM settings AS STRING * 350 ’ CALL Send(0, 8, "SYSTem:SET?", 1) ’

CALL Receive(0, 8, settings$, 256) ’ length = IBCNT% ’ CALL Send(0, 8, "SYSTem:SET ", 0) ’

CALL Send(0, 8, LEFT$(settings$, length), 1) ’

RST command. This resets the

’

USING THE COMBISCOPE INSTRUMENTS 3 - 79

3.17 Front Panel Simulation

The use of "front panel simulation" commands must be restricted to special applications or front panel functions that are not supported by SCPI commands. Bear in mind the differences between different instruments from the same family, as described in the beginning of this chapter.

It is possible to simulate the pressing of a key on the front panel by using the SYSTem:KEY command. It is also possible to detect whether or not a key has been pressed. This is done via bit 6 (URQ) of the Event Status Register ( query). The last key pressed can be queried by using the SYSTem:KEY? query.

Furthermore, it is better to use the DISPlay:MENU command to switch a softkey menu ON or OFF. The pressing of a softkey can be simulated with the SYSTem:KEY 1 to 6 command. Since the role of each softkey is determined by a previously selected menu, this will be a tedious and cumbersome process. Still it might be of interest for simple applications.

Example: The command sequence the instrument (e.g., digital mode on and peak detection of f), switches the softkey menu ACQUIRE on, and simulates the pressing of softkey 2, which causes peak detection to be switched on.

RST;DISPlay:MENU ACQuire;:SYSTem:KEY 2 resets

ESR?

3.17.1 How to simulate the pressing of a front panel key

The SYSTem:KEY commands allow you to simulate the pressing of a front panel key. The front panel key numbering (not the rotary knobs) is roughly divided into the following matrix of rows and columns.

column: 1 2 3 13 row 1

row 2 row 3

row 4

row 7 row 8 801 802 803 813

101 201

102

103

202

203

302

303

402

304

702

703

113

213 313

413

. .

713

Note: The number positions 1 to 6 represent the softkeys.

3 - 80 USING THE COMBISCOPE INSTRUMENTS

Resets the instrument

Enables the UTILITY softkey menu

Selects the PROBE option

Selects the PROBE CORR option

Selects the 10:1 option

Disables the UTILITY softkey menu

In this example the probe correction factor for input channel 1 is set at 10:1

via softkey menu UTILITY

Simulates

Autoset

Resets the instrument

Enables the UTILITY softkey menu

Selects the PROBE + PROBE CORR + 10:1 options

Disables the UTILITY softkey menu

In this example the probe correction factor for input channel 1 is set at 10:1 via softkey menu UTILITY

PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’ CALL Send(0, 8, "SYSTem:KEY 104", 1) ’ CALL Send(0, 8, "SYSTem:KEY 2", 1) ’ CALL Send(0, 8, "SYSTem:KEY 5", 1) ’ CALL Send(0, 8, "SYSTem:KEY 4", 1) ’ CALL Send(0, 8, "SYSTem:KEY 104", 1) ’ ’

AUTOSET SIMULA TION:

CALL Send (0, 8, "SYSTem:KEY 101", 1) ’

3.17.2 How to simulate the operation of a softkey menu

The MEASure:MENU command allows you to enable or disable the display of the softkey menus. The "SYSTem:KEY 1 to 6" command allows you to simulate the pressing of one of the softkeys 1 to 6.

PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’ CALL Send(0, 8, "DISPlay:MENU UTIL", 1) ’ CALL Send(0, 8, "SYSTem:KEY 2;KEY 5;KEY 4", 1) ’ CALL Send(0, 8, "DISPlay:MENU:STATe OFF", 1) ’ ’

USING THE COMBISCOPE INSTRUMENTS 3 - 81

3.18 Functions not Directly Programmable

Not all front panel functions are individually pro grammable with SCPI commands. However, the SYSTem:SET and the following functions:

- Cursor functions see CURSORS menu (appendix B.2.2)

- Logic Triggering see TRIGGER menu (appendix B.2.10)

- Event functions see TB MODE menu (appendix B.2.9)

- DTB functions see DTB (DEL’D TB) menu (appendix B.2.6)

- X pos see X POS button

- Display menu functions see DISPLAY menu (appendix B.2.3)

- Pass/Fail functions see MATHPLUS MATH menu

Other functions and keys that are not individually programmable with SCPI commands are accessible using the SYSTem:KEY command. They are:

- Roll mode DISPlay:MENU TBMode;:SYSTem:KEY 3 toggles on/off

- Trigger noise DISPlay:MENU TRIGger;:SYSTem:KEY 4 toggles on/off

- TEXT OFF key SYSTem:KEY 801 selects next option

- STATUS key SYSTem:KEY 201 toggles on/off

- MAGNIFY keys SYSTem:KEY 210/211 selects previous/next step

- ENVELOPE DISPlay:MENU ACQuire;:SYSTem:KEY 3 toggles on/off

- MULT iple-shot DISPlay:MENU TBMode;:SYSTem:KEY 1 (u p)or 2 (down) (after INITiate:CONTinuous OFF)

SAV/*RCL commands can be used to access

(appendix A5 and B.2.4.)

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