Fluke CombiScope PM3370B, CombiScope PM3384B, CombiScope PM3394B, CombiScope PM3380B, CombiScope PM3390B User Manual

Download

$XWRUDQJLQJ &RPEL6FRSH



,QVWUXPHQW

30%30%30% 30%30%

SCPI Users Manual

02/- Nov-1998

TRADEMARKS

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

 is a trademark of Fluke Corporation.

PCIIA is a trademark of National Instruments Corporation.

HPGL is a trademark of Hewlett-Packard Company.

Printed in the Netherlands

III

CONTENTS Page

1 ABOUT THIS MANUAL

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

1.1 What this Manual Contains

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

2 GETTING STARTED WITH SCPI PROGRAMMING

. . 2-1

2.1 Preparations for SCPI Programming

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

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

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

2.2 Initializing the CombiScope Instrument

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

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

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

2.4 Acquiring Traces

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

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

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

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

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

3 USING THE COMBISCOPE INSTRUMENTS

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

3.1 Introduction

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

3.2 Fundamental Programming Concepts

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

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

3.2.2 Single function programming using the instrument model . . 3-5

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

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

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 chara cteristics from memory tr aces . . . . . . . . . . 3-17

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

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

3.4.1.1 Triggering

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

3.4.1.2 Video triggering

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

3.4.1.3 The trigger modes

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

3.4.1.4 Pre- and post-triggering

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

3.4.1.5 External triggering

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

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

3.4.2.1 Single-shot acquisition

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

3.4.2.2 Repetitive acquisitions

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

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

3.4.3.1 Conversion of 8- bit samples to integer

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

3.4.3.2 Conversion of 16-bit samples to integer

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

3.4.3.3 Conversion to voltage values

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

. . . 3-45

3.9.1.2 Specify the settings of the post processing function.

. . 3-46

3.9.1.3 Enable the post processing function.

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

3.9.1.4 Check the result of the post processing function.

. . . . . 3-47

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 memo ry . . . . . . . . . . . . . . . . . . . . . . . . . 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

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

3.11.2.2 Display of user-defined text

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

3.11.2.3 Selection of softkey menus

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

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

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

3.15.1.2 Questionable status data

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

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)

. . . . . . . 3-74

3.15.3.2 Program example using a service request (SRQ)

. . . . 3-75

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

3.15.4.1 Error-reporting routine

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

3.15.4.2 Error-repor tin g usin g th e SRQ me ch an ism

. . . . . . . . . 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

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

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

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

B.1 Cross Reference Front Panel Keys / Commands

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

B.2 Cross Reference Softkey Menus / Commands

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

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

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

C MANUAL CONVENTIONS

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

C.1 Abbreviations Used

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

C.2 Glossary of Symbols Used

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

C.3 List of Tables

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

C.4 List of Figures

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

C.5 Documents Referenced

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

D STANDARDS INFORMATION

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

D.1 SCPI Conformance Information

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

D.2 List of Implemented IEEE-488.2 Syntactical Elements

. . . . . . D-2

E SUMMARY OF SYSTEM SETTINGS

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

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 abbreviatio ns and symb ols are 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. Th ese program e xamples 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 unde r

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 manua l have been 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 manua l have been 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 followin g drive rs and pa rameters 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 d evice becomes 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 = 0).

•

<address> IEEE instrument address (default CombiScope instrument

address = 8).

•

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

constant -1 (FFFF hex.).

•

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

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

•

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

GETTING STARTED WITH SCPI PROGRAMMING 2 - 3

•

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

query .

•

<eot> An "end of text" indication:

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

•

<term> A "terminate" indication:

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

•

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

13 = 10 seconds.

PROGRAM EXAMPLE:

’

*****

’Initial program statements: ’

*****

REM $INCLUDE:’c:\pc-gpib\488driv\QBDECL.BAS’ ’

Includes GPIB drivers

CLS ’

Clears text from PC screen

CALL SendIFC(0) ’

Clears the GPIB interface

CALL IbTMO(0, 13) ’

Sets time out at 10 seconds

PROGRAMMING NOTE:

The variable IBCNT% contains the number of response bytes (including NL

)

after reading a response messag e using th e Rece ive driver.

2 - 4 GETTING STARTED WITH SCPI PROGRAMMING

2.2 Initializing the CombiScope Instrument

2.2.1 How to reset the CombiScope instrument

The instrument itself can be reset by sending the

RST command. This sets the instrument to a fixed setup optimized for remote operation. The status and error data of the instrument can be cleared by sending the

CLS command.

PROGRAM EXAMPLE:

’

*****

’Reset the instrument and clear the status data: ’

*****

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

CALL Send(0, 8, "*CLS", 1) ’

Clears the status data

2.2.2 How to identify the CombiScope instrument

The identity of the instrument can be queried by sending the

IDN? query, followed by reading the instrument response message. The options of the instrument can be queried by sending the

OPT? query, followed by reading the

instrument response message. PROGRAM EXAMPLE:

’

*****

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

*****

response$ = SPACE$(65) CALL Send (0, 8, "*IDN?", 1) ’

Requests for identification

CALL Receive (0, 8, response$, 256) ’

Reads the ident string

PRINT "Ident: "; LEFT$(response$, IBCNT%) ’

Prints the ident string

CALL Send (0, 8, "*OPT?", 1) ’

Requests for options

CALL Receive (0, 8, response$, 256) ’

Reads the options string

PRINT "Options: "; LEFT$(response$, IBCNT%) ’

Prints the options string

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

RST command the digital mode is selected. The INST rument subsystem 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) ’

Switches to analog mode

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

Switches back to digital mode

GETTING STARTED WITH SCPI PROGRAMMING 2 - 5

2.3 Error Reporting

Instrument errors are usually caused by programming or setting errors. They are reported by the instrument during the executi on 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 SYSTem:ERRor? query or the ST ATus:QUEue? query to the instrument, followed by reading the response message. However , through this practice the same "error reporting" statements must be repeated after se nding each SCPI command. Th is is not always practical. Therefore, one of the following app roaches 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) ’

Requests for error

CALL Receive(0, 8, er$, 256) ’

Reads error message

PRINT "Response to error query = "; PRINT LEFT$(er$, IBCNT%-1) ’

Displays error message

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 INIT iate 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:

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

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

Example:

# 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

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

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

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 tra ce sample bytes 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 trigger level to e.g., 0.1 volts.

PREP ARA TIONS:

•

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) ’

Formats 8-bits sample

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

Formats 8192 sample points

CALL Send(0, 8, "TRIGger:SOURce INTernal1", 1) ’

Trigger-source = channel 1

CALL Send(0, 8, "TRIGger:LEVel 0.1", 1) ’

Trigger-level = 0.1

CALL Send(0, 8, "INITiate", 1) ’

Single shot initiation

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) ’

Waits for previous commands

to finish

CALL Send(0, 8, "TRACe? CH1", 1) ’

Queries for channel 1trace

CALL Receive(0, 8, tracebuf$, 256) ’

Reads channel 1 trace

’ ’

The contents of the tracebuf$ string is as follows:

’

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

’ 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% ’

IBCNT% = number of bytes

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

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) ’

Resets the instrument

’ ’After *RST a trace acquisition is defined at 512 samples of 16 bits ’(2 bytes). ’ CALL Send(0, 8, "CONFigure:AC (@2)", 1) ’

Configures channel 2

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

Switches channel 2 on

OPEN "O",#1,"TRACE5.DAT" ’

Opens file TRACE5.DAT

FOR i=1 TO 5

CALL Send(0, 8, "INITiate", 1) ’

Single initiation

CALL Send(0, 8, "*WAI;TRACe? CH2", 1) ’

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.

’ CALL Receive(0, 8, tracebuf$, 256) ’

Reads channel 2 trace

PRINT #1, "Trace buffer:"; i ’

Writes trace header to file

PRINT #1, LEFT$(tracebuf$, IBCNT%) ’

Writes trace buffer to file

NEXT i

CLOSE ’

Closes file TRACE5.DAT

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

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. Th e following levels of measurement instructions can be used:

The highest level:

MEASure?

(easy to use) The middle level:

CONFigure

READ?

(equivalent to MEASure?)

(gives more programming flexibility) The lowest level:

INITiate

FETCh?

(equivalent to READ?)

(to acquire more signal characteristics) The following table shows which measurement tasks are executed by the

measurement instructions:

MEASure?

CONFigure

READ?

INITiate

FETCh?

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

2 - 10 GETTING STARTED WITH SCPI PROGRAMMING

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) ’

Measures the AC-RMS value

CALL Receive (0, 8, response$, 256) ’

Reads the AC-RMS value

PRINT "AC-RMS value : "; LEFT$(response$, IBCNT% -1) CALL Send (0, 8, "FETCh:PTPeak?", 1) ’

Fetches the Peak-To-Peak value

CALL Receive (0, 8, response$, 256) ’

Reads the PTP value

PRINT "Peak-To-Peak value: "; LEFT$(response$, IBCNT% - 1) CALL Send (0, 8, "FETCh:AMPLitude?", 1) ’

Fetches the amplitude value

CALL Receive (0, 8, response$, 256) ’

Reads the amplitude value

PRINT "Amplitude value : "; LEFT$(response$, IBCNT% - 1)

2.5.2 How to make repeated measurements

The measurement instructions allow you to make repea ted measurements. The CONFigure command allows you to configure the instrument, the READ? query allows you to make a measurement, and the FETCh? query a llows 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) ’

Configures for AC-RMS

FOR i = 1 TO 5 ’

Performs 5 measurements

CALL Send (0, 8, "READ:AC?", 1) ’

Initiates AC-RMS reading

CALL Receive (0, 8, response$, 256) ’

Reads the AC-RMS value

PRINT "AC-RMS: "; LEFT$(response$, IBCNT%-1); CALL Send (0, 8, "FETCh:PTPeak?", 1) ’

Fetches the Peak-T o -Peak value

CALL Receive (0, 8, response$, 256) ’

Reads the PTP value

PRINT " / Peak-To-Peak: "; LEFT$(response$, IBCNT%-1); CALL Send (0, 8, "FETCh:AMPLitude?", 1) ’

Fetches the amplitudevalue

CALL Receive (0, 8, response$, 256) ’

Reads the amplitude value

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 envir onm ent. Fo r tha t pu rpo se, 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, there was no standard for the remote operation of instruments. A wide range of different command sets existed. Each set h ad its own te rminolo gy 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 programming concepts w ere introduced. 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 Stand ard Co mman ds for Pr ogra mm abl e In strum ents, 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 mai nly achieved by the consistent programming envir onment for instrument control and data usag e 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 query MEASure:FREQuency? acquires the frequency characteristic of the input signal, regardless of whether the instrument is a freque ncy 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 considerab ly 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 i nterface differs in some as pects from the front panel operation. This is becaus e the lo cal fron t panel ope ra 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 g uide towards the 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 allo ws for easy progra mming 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 instrument can be accessed using different programming concepts. The concept to be chosen 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 r equired 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:

MEASure:FREQuency?

Measures the frequency of the signal at channel 1.

2) Single function programming using the instrument model Advantage: Allows you to program individual functions separa tely through

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

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

functions.

Example:

TRACe? CH1

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:

SAV 3

Saves actual instrument settings to internal memory 3.

RCL 3

Recalls instrument settings from internal memory 3.

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

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

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 req uested result. 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:FREQuen cy? 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 functions of the oscilloscope separately.

- start the acquisition of the data.

- position the cursor markers.

- calculate the frequency from the acquired data.

- read the calculated 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 confi gure 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 instruction s 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 instrument 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 tr aditionally 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 in strument that 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.

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.

INPut SENSe

TRIGger

DISPlay

TRACe CALCulate

ST7155

Figure 3.1 The Instrument Model for CombiScope instruments

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 yo ur 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 used to program instrument functions that cannot be directly accessed usin g individual program instru ctions. 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 an d from which it can be restored.

Send

→

SAV 3 Saves the current set up into memory 3.

Send

→

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

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.

Example for the complete instrument settings: Send

→ SYSTem:SET? Queries the oscilloscope for the complete

instrument setup.

Read

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

contains the requested instrument setup, from the oscilloscope.

Send

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

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.

Read

← <settings> Reads the cursor settings.

. . 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 n o 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 te dious process, it is certainly not recomm ended 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 SENS e:AVERage ON is much better.

To select function s that cannot be 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 then 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 instructi ons refer to the signal char acteristics 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 instructions 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 an d 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 ( measure 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 time, 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 instr uctions.

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

(HIGH - LOW)

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)

TMINimum

MINimum

FALL

OVERshoot

RISE PREShoot

AMPLitude

PTPeak

NWIDthPWIDth

PERiod

LOW

HIGH

FALL TIME

FALL PREShoot

MAXimum

TMAXimum

RISE TIME

RISE OVERshoot

REFerence HIGH

REFerence MIDDle

REFerence LOW

ST7154

Figure 3.2 Pulse characteristics

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

- :FTIMe = 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 measurements 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 i nstrum ent 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 functio n 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 min d that the instrument 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 corresponding C ONFigure instructions. But, these sets only serve to specify the desired result. They are ignored as far as they affect instrument setting s. 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 mu ltiple READ? queries 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 result. 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 sh ould always be explicitly 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

TRG command or the GET (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 possible 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

TRG.

INITiate Starts the measurement process.

TRG Triggers the acquisition.

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

USING THE COMBISCOPE INSTRUMENTS 3 - 17

3.3.8 Fetching characteristics from memory traces

The FETCh? query not only allows you to determine a cha racteristic 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) ’

Configures for channel 2

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

Switches channel 2 on

CALL Send(0, 8, "INITiate", 1) ’

Single initiation

CALL Send(0, 8, "TRACe:COPY M1_2,CH2", 1) ’

Copies CH2-trace to M1_2

’ ’

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

’ CALL Send(0, 8, "FETCh:AC? (@M1_2)", 1) ’

Fetches AC-RMS of M1_2

CALL Receive(0, 8, response$, 256) ’

Enters AC-RMS value

PRINT "AC-RMS value : "; response$ ’

Prints AC-RMS value

CALL Send(0, 8, "FETCh:PTPeak? (@M1_2)", 1) ’

Fetches Peak-To- Peak of M1_2

CALL Receive(0, 8, response$, 256) ’

Enters Peak-To-Peak value

PRINT "Peak-To-Peak value: "; response$ ’

Prints Peak_to_peak value

CALL Send(0, 8, "FETCh:AMPLitude? (@M1_2)", 1) ’

Fetches amplitude of M1_2

CALL Receive(0, 8, response$, 256) ’

Enters amplitude value

PRINT "Amplitude value : "; response$ ’

Prints amplitude value

3 - 18 USING THE COMBISCOPE INSTRUMENTS

3.4 Acquisition

3.4.1 Acquisition control

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

The trigger model shows that after a

RST command, the instrumen t is in the IDLE state. An acquisition doesn’t start until an INITiate command is receive d. Initiation of the oscilloscope occurs by sending the INITiate[:IMMediate] command

INIT

INIT:CONT ON

*RST

ABORt

power on

Yes

IDLE state

INITiated state

INIT:CONT ON

Yes

Wait for complete

Wait for TRIGger state

Wait for trigger

Acquisition

Acquisition completed

Start acquisition

TRIGger

:LEVel :SLOPe

TRIGger

:SOURce

BUS IMMediate INTernal LINE

ST7186

Figure 3.3 The Trigger Model for acquisitions

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

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

RST is received. The ABORt

command distinguishes from

RST in that *RST also resets the instrument settings, whereas, ABORt does not. For example, when INITiate:CONTinuous is set to ON, a

RST command not only aborts the pending acquisition and forces 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.

When the instrument is in the IDLE state, the "no-pending operation" flag that is associated with the acquisition is set T rue. The

OPC and *OPC? commands use 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.

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 ca n be ignored d uring a specific holdoff time, which can be programmed using the TRIGger:HOLDoff command. During the hold-off time the eve nt 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 (r efer to section 3.4.1.2 "Video triggering"), LOGic, or GLITch triggering. After a

RST

command, the trigger type is EDGE.

Note: Logic state, pattern, or g litch 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

TRG serves as the trigger event when BUS is selected as

trigger source. The trigger event is determined by the AC line voltage when L INE is selected, and

is derived from the input signal when INTernal is programmed as trigger source. For the 2-channel CombiScope instruments, EXTernal 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, a n acquisition does not wait for a trigger event. So, an INITiate command causes the acquisition to begin immediately. After a

RST

command, the trigger source is IMMediate, which means no trigger is re quired.

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-p eak, deactivates the trigger level . After a

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

peak is switched off.

USING THE COMBISCOPE INSTRUMENTS 3 - 21

Trigger Slope

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

RST command

the TRIGger:SLOPe is set to POSitive. PROGRAM EXAMPLE:

CALL Send(0, 8, "CONFigure:PTPeak (@2)", 1) ’

Configures channel 2

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

Sets channel 2 ON

CALL Send(0, 8, "TRIGger:SOURce INTernal2", 1) ’

Trigger source = channel 2

CALL Send(0, 8, "TRIGger:LEVel 0.2", 1) ’

Trigger level = 0.2 V

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

CALL Send(0, 8, "TRIGger:SLOPe NEGative", 1) ’

Trigger slope = negative

CALL Send(0, 8, "INITiate", 1) ’

Single initiation

CALL Send(0, 8, "FETCh:PTPeak? (@2)", 1) ’

Queries for peak-to-peak

response$ = " " CALL Receive(0, 8, response$, 256) ’

Enters peak-to-peak

PRINT "Measured peak-to-peak = "; response$ ’

Prints peak-to-peak

Trigger Coupling

The TRIGger:LPASs and TRIGger:HPASs commands allow you to select the Main Time Base ( MTB) trigger coupling b y programmin g a fixed cu tof f freque ncy. The possible trigger coupling options

AC coupling, DC coupling, Low Frequency

reject

, and

High Frequency reject

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

RST

command, the cutoff frequency is 10 Hertz, wh ich selects trigger coupling AC.

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

DC COUPLING (0 Hz cutoff frequency):

DC coupling causes the signal to be passed over the full bandwidth (from 0 Hz to 60/100/200 MHz).

PROGRAM EXAMPLE:

*** *** Select DC coupling on input signal channel 2. SENSe:FUNCtion:ON "XTIMe:VOLTage2"

Sets CH2 on.

INPut2:COUPling DC

Sets CH2 input signal DC coupled.

TRIGger:SOURce INTernal2

Sets trigger source = CH2.

*** *** Select DC coupling on MTB triggering. TRIGger:FILTer:LPASs:STATe ON

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

this selects MTB trigger DC coupling.

AC COUPLING (10 Hz cutoff frequency):

AC coupling causes the signal to be passed from 10 Hz to the full bandwidth frequency (60/100/200 MHz).

PROGRAM EXAMPLE:

*** *** Select AC coupling on input signal channel 3. SENSe:FUNCtion:ON "XTIMe:VOLTage3"

Sets CH3 on.

INPut3:COUPling AC

Sets CH3 input signal AC coupled.

TRIGger:SOURce INTernal3

Sets trigger source = CH3.

*** *** Select AC coupling on MTB triggering. TRIGger:FILTer:LPASs:STATe ON

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

this selects MTB trigger DC coupling.

TRIGger:FILTer:LPASs:FREQuency 10

Sets cutoff frequency = 10 Hz; this selects

MTB trigger AC coupling.

Figure 3.4 DC Coupling

FULL BANDWIDTHDC

DC COUPLING-3dB

0dB

FREQ.

T7427

Figure 3.5 AC Coupling

FULL BANDWIDTH10Hz

AC COUPLING-3dB

0dB

FREQ.

ST7426

USING THE COMBISCOPE INSTRUMENTS 3 - 23

LF-REJECT (30 KHz cutoff frequency):

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

PROGRAM EXAMPLE:

TRIGger:FILTer:LPASs:STATe ON

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

(DC coupling).

TRIGger:FILTer:LPASs:FREQuency 3E+4

Sets cutoff frequency = 30 KHz;

this selects MTB trigger LF-reject.

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).

PROGRAM EXAMPLE:

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

Sets High-Pass filter on;

this selects MTB trigger HF-reject.

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 programme d on signals wi th a po sitive or negative si gnal polarity using the TRIGger:VIDeo:SSIGnal command.

Figure 3.6 LF Reject

FULL BANDWIDTH30kHz

LF -REJECT

-3dB

0dB

FREQ.

ST7428

Figure 3.7 HF Reject

FULL BANDWIDTH30kHz

HF-REJECT

-3dB

0dB

FREQ.

ST7429

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 : 1050/1125/1250 lines per frame

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

Selects

TV video

triggering.

TRIGger:VIDeo:FORMat:TYPE SECAM

Selects the

SECAM

standard with 625 lines per frame.

TRIGger:VIDeo:FORMat:LPFRame 1125

Selects the

HDTV

standard with

1125

lines per frame.

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

Selects the video

lines

trigger mode.

TRIGger:VIDeo:LINE 512

Selects video line number

512

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

Selects video

field

triggering.

TRIGger:VIDeo:FIELd:NUMBer 2

Selects the video

field2

trigger mode.

TRIGger:VIDeo:FORMat:TYPE PAL

Selects the

PAL

standard with 625 lines per frame.

TRIGger:VIDeo:LINE 123

Selects video line number

123

. As a result the video mode is

automatically switched to

field1

(field1 = lines 1 .. 312).

TRIGger:VIDeo:LINE 325

Selects video line number

325

. As a result the video mode is

automatically switched to

field2

(field2 = lines 313 .. 625).

TRIGger:VIDeo:FIELd:NUMBer 1

Selects the video

field1

trigger mode. As a result the video

line number is automatically switched to

(= 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:

Table 3.1 The TRIGger modes

Trigge r mode:

INITiate :CONTinuous

TRIGger :SOURce

>>>Single-shot<<< Generates one sweep, regardless of any trigger settings (valid after

RST).

OFF IMMediate

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

OFF

INTernal<n> or LINE

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

OFF EXTernal

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

ON IMMediate

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

INTernal<n> or LINE

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

ON EXTernal

>>>Single-Shot<<< Generates one sweep triggered by

TRG

or GET, regardless of any trigger settings.

ON or OFF

BUS

3 - 26 USING THE COMBISCOPE INSTRUMENTS

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.

OPERATION STATUS BITS:

STATE DESCRIPTION:

bit 5

Wait for TRIG

bit 3

SWEeping

OPC

idle state (after

RST)

000

Wait 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)

000

Wait for trigger state (INIT received)

1 00

= armed

Wait for complete (triggered)

010

= busy

Finished with acquisition

001

= ready

USING THE COMBISCOPE INSTRUMENTS 3 - 27

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. Tri ggering occurs when the trigger cond itions 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.

Pre- and post-triggering are p rogra mmed wi th the SENSe:SWEe 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

RST value of the total acquisition time (SENSe:SWEep:TIME) is 10 ms, the trigger point is positioned in the middle of the trace.

PROGRAM EXAMPLE:

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

1 ms post-trigger

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

1 ms pre-trigger

Trace

begin

end

time axis

total acquisition time

pre trigger

trigger moment

SENSe:SWEep:TIME

SENSe:SWEep:OFFSet:TIME

ST7190

Trace

begin

end

time axis

total acquisition time

post trigger

trigger moment

SENSe:SWEep:TIME

SENSe:SWEep:OFFSet:TIME

ST7191

Figure 3.9 Post-triggering

Figure 3.8 Pre-triggering

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:

- attenuator 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:

• EXTerna l 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.

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 "Cop ying traces to m emory" 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.

INPut[1]

INPut

INPut2

INPut3

INPut4

:VOLTage[1]

:VOLTage2

:VOLTage3

:VOLTage4

:SWEep

Main Time Base

ST7160

SENSe

TRACe

CH 1

CH 2

CH 3

CH 4

memory

Figure 3.10 The trace acquisition flow

3 - 30 USING THE COMBISCOPE INSTRUMENTS

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 ’

Dimensions trace buffer

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

’

Trigger source becomes IMMediate

’

Number of trace sa mples becomes 512

’

Number of trace sa mple bits becomes 16

CALL Send(0, 8, "CONFigure:AC", 1) ’

Configures for optimal AC-RMS settings

CALL Send(0, 8, "INITiate", 1) ’

Initiates single acquisition

CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’

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.

’ CALL Receive(0, 8, response$, 256) ’

Reads the channel 1 trace data

3.4.2.2 Repetitive 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$. Th e 1 0 trace bu ffers are written to the file TRACE10 on the hard disk. T riggering is done via the GPIB by sending the

TRG command.

DIM response AS STRING * 1033 ’

Dimensions trace buffer

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

’

Trigger source becomes IMMediate

’

Number of trace samples becomes 512

’

Number of trace sample bits becomes 16

CALL Send(0, 8, "CONFigure:AC (@1)", 1) ’

Configures for optimal AC-RMS settings.

CALL Send(0, 8, "TRIGger:SOURce BUS", 1) ’

Trigger source = GPIB

OPEN "O",#1,"TRACE10" ’

Opens file TRACE10

FOR i=1 TO 10 ’

10 sequential trace acquisitions

CALL Send(0, 8, "INITiate", 1) ’

Initiates an acquisition

CALL Send(0, 8, "*TRG", 1) ’

Triggers via the GPIB

CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’

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.

’ CALL Receive(0, 8, response$, 256) ’

Reads the channel 1 trace

PRINT #1, response$ ’

Writes the trace buffer to file

NEXT i ’

Next trace acquisition

CLOSE ’

Closes file TRACE10

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

RST the samples are sent as 2 byte codes. When samples are formatted as tw o bytes, the most significant b yte (msb) is sent 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.

The value of the trace points relate to the vertical position of the corresponding sample on the screen of the CombiScope in strument. As the figure 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 vertica l scr een boundaries. T race 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.

top

mid

bottom

screen

range

32767

(127)

25600 (100)

1(1) 0(0)

-1 (-1)

-25600

(-100)

-32768

(-128)

32767 (127)

25600 (100)

1(1) 0(0)

65535

(255)

39936

(156)

32768

(128)

trace range

Decimal value

of byte code

Trace sample

value (Ts)

Screen

position (Ps)

ST7187

Note: Numbers between parenthesis apply to single byte format.

Figure 3.11 Relation between screen position and trace value

3 - 32 USING THE COMBISCOPE INSTRUMENTS

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:

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

data is read and converted to integer samples in the arr ay "trace", and the number of trace bytes and trace samples is printed. The conversion from sin gle byte value to integer is done as follows (refer to figure 3.12): If byte

≥ 128 then integer = byte - 256.

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

DIM trace(512) ’

Array of 512 integers

DIM response AS STRING * 520 ’

Trace response buffer

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

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

Data format of 8-bits samples

CALL Send(0, 8, "INITiate", 1) ’

Single shot initiation

CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’

Queries for channel 1 trace

CALL Receive(0, 8, response$, 256) ’

Reads the channel 1 trace

PRINT "Number of read bytes ="; IBCNT% ’

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

’ 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

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

USING THE COMBISCOPE INSTRUMENTS 3 - 33

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:

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

data is read and converted to integer samples in the arr ay "trace", and the number 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

256 + byte2.

If byte1

≥ 128 then integer = (byte1 - 256)

256 + byte2.

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

256 + 32 = - 224.

DIM trace(512) ’

Arra

y of 512 i

ntegers

DIM response AS STRING * 1033 ’

Trace response buffer

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

’

Sets 16 bit sample data format

CALL Send(0, 8, "INITiate", 1) ’

Single shot initiation

CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’

Queries for channel 1 trace

CALL Receive(0, 8, response$, 256) ’

Reads the channel 1 trace

PRINT "Number of trace bytes ="; IBCNT% ’

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>

J = 2 * i + 2 + nr.of.digits ’

Pointer to next sample

byte1 = ASC(MID$(response$, J, 1)) ’

Most Significant Byte

byte2 = ASC(MID$(response$, J + 1, 1)) ’

Least Significant Byte

IF byte1 < 128 THEN

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

NEXT i

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

3 - 34 USING THE COMBISCOPE INSTRUMENTS

3.4.3.3 Conversion to voltage values

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

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

Vs = (Ps

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

Vs = (Ps

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

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

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

100 = Ts / 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)

PTPeak - OFFSet (for 8-bit sample traces)

Vs = (Ts / 51200)

PTPeak - OFFSet (for 16-bit sample traces)

PTPeak

Trace sample

value (Ts)

Screen

position (Ps)

Amplitude value (Vs)

ST7188

OFFSet

0Volt

-OFFSet+PTPeak/2

-OFFSet

-OFFSet-PTPeak/2

top

100%

mid

bottom

-100%

32767

(127)

25600

(100)

(0)

-25600 (-100)

-32768 (-128)

Figure 3.12 Relation between screen position and amplitude value

USING THE COMBISCOPE INSTRUMENTS 3 - 35

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) ’

Array of sample voltages

DIM response AS STRING * 1033 ’

Trace data response string

DIM peaktop AS STRING * 10 ’

Peak-to-peak response string

DIM offs AS STRING * 10 ’

Offset response string

’ CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

CALL Send(0, 8, "CONFigure:AC (@1)", 1) ’

Configures for optimal AC-RMS settings

’

Signal-offset also becomes zero

CALL Send(0, 8, "INITiate", 1) ’

Initiates single acquisition

CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’

Requests channel 1 trace

CALL Receive(0, 8, response$, 256) ’

Reads channel 1 trace

’ 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) ’

Queries ptp

CALL Receive(0, 8, peaktop$, 256) ’

Reads ptp

ptpeak = VAL(LEFT$(peaktop$, IBCNT%)) ’

IBCNT% = length

CALL Send(0, 8, "SENSe:VOLTage:RANGe:OFFSet?", 1) ’

Queries offset

CALL Receive(0, 8, offs$, 256) ’

Reads offset

offset = VAL(LEFT$(offs$, IBCNT%)) ’

IBCNT% = length

IF sample.length = 1 THEN

FOR i = 1 TO nr.of.samples ’

1-byte 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 ’

2-byte samples

J = 2 * i + 2 + nr.of.digits ’

Pointer to next sample

byte1 = ASC(MID$(response$, J, 1)) ’

M.S.B.

byte2 = ASC(MID$(response$, J + 1, 1)) ’

L.S.B.

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

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:

In the expressio n, 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: Send

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

16, which means 16 sequential acquisitions are averaged.

Send

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

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 suf ficient 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 ’

Dimensions trace string

DIM amplitude AS STRING * 10 ’

Dimensions amplitude string

DIM frequency AS STRING * 10 ’

Dimensions frequency string

CALL Send(0, 8, "CONFigure:AC (@1)", 1) ’

Configures for AC-RMS

CALL Send(0, 8, "SENSe:AVERage:COUNt 4", 1) ’

Average factor = 4

CALL Send(0, 8, "SENSe:AVERage ON", 1) ’

Averaging is turned on

CALL Send(0, 8, "INITiate", 1) ’

Initiates the averaging acquisition

CALL Send(0, 8, "*WAI;TRACe? CH1", 1) ’

Queries for channel 1 trace

CALL Receive(0, 8, trace$, 256) ’

Enters channel 1 trace

’

The trace samples are averaged over 4 sequential trace acquisitions.

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

Reads the amplitude

CALL Receive(0, 8, amplitude$, 256) ’

Enters the amplitude

CALL Send(0, 8, "FETCh:FREQuency?", 1) ’

Fetches the frequency

CALL Receive(0, 8, frequency$, 256) ’

Enters the frequency

’

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

AVG

.. X

()n⁄

∑

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.

Figure 3.13 The Trigger Model during acquisition averaging

INIT

INIT:CONT ON

*RST

ABORt

power on

Yes

IDLE state

INITiated state

INIT:CONT ON

Yes

Wait for completeWait for trigger

acquisition

averaging

TRIGger

:LEVel :SLOPe

TRIGger

:SOURce

LINE INTernal IMMediate

ST7189

SENSe:AVERage:COUNt

Wait for AVERage state

Yes

3 - 38 USING THE COMBISCOPE INSTRUMENTS

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

RST command, channel 1 is turned on and the

other channels off (including the EXTernal input for PM33x0A). Addition of two channels can be selected by specifying the "XTIMe:VOL Tage:SUM"

parameter as follows: > Addition of CH1 and CH2: "XTIMe:VOL Tage:SUM 1,2" > Addition of CH3 and CH4: "XTIMe:VOL Tage: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

PROGRAM EXAMPLE:

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

’

Sets CH1+CH2 on

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

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

INPut[1]

INPut

INPut2

INPut3

INPut4

:VOLTage[1]

:VOLTage2

:VOLTage3

:VOLTage4

:OFF

[:ON]

:OFF

[:ON]

:OFF

[:ON]

:OFF

[:ON]

:FUNCtion

"XTIMe:VOLTage1"

"XTIMe:VOLTage2"

"XTIMe:VOLTage3"

"XTIMe:VOLTage4"

:SWEep

Main Time Base

ST7158

SENSe

TRACe

CH 1

CH 2

CH 3

CH 4

memory

Figure 3.14 Input channel control

USING THE COMBISCOPE INSTRUMENTS 3 - 39

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.

3.7.1 AC/DC/ground coupling

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

RST command,

all input channels are DC coupled. PROGRAM EXAMPLE:

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

Sets channel 1 AC coupled

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

Sets channel 2 ground coupled

INPut[1]

INPut

INPut2

INPut3

INPut4

:VOLTage[1]

:VOLTage2

:VOLTage3

:VOLTage4

:OFF

[:ON]

:OFF

[:ON]

:OFF

[:ON]

:OFF

[:ON]

:FUNCtion

"XTIMe:VOLTage1"

"XTIMe:VOLTage2"

"XTIMe:VOLTage3"

"XTIMe:VOLTage4"

:SWEep

Main Time Base

ST7159

SENSe

Figure 3.15 Signal conditioning

3 - 40 USING THE COMBISCOPE INSTRUMENTS

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) ’

Turns the filter on

CALL Send(0, 8, "INPut:FILTer:FREQuency?", 1) ’

Requests for the filter frequency

response$ = " " CALL Receive(0, 8, response$, 256) ’

Reads the filter frequency

PRINT "Filter freq. = "; response$ ’

Prints: Filter freq. = 2.00E+07

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

RST

command, the impedance of each input channel is 1 M

Ω.

PROGRAM EXAMPLE:

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

Sets channel 4 impedance at 50

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) or INV erted (inverted signal).

PROGRAM EXAMPLE:

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

Sets INV CH2 off

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

Sets INV CH4 on

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

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

complies to a vertical sensitivity of 200 mV.

USING THE COMBISCOPE INSTRUMENTS 3 - 41

Because the programmed PTPeak and OFFSet values directly affect the trace values, they can be used to calculate the voltage amplitude of the corresp onding trace samples. As explained in section 3.4.3.3 "Conversion to voltage values", the voltage amplitude of a trace sample can be calculated from the equati ons:

Vs = (Ts / 200)

PTPeak - OFFSet (for 8-bit sample traces)

Vs = (Ts / 51200)

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

RST command, the vertical offset

for each input channel is zero. PROGRAM EXAMPLE:

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

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

’

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

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

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

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 divisions 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 maximu m 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) ’

Auto triggering

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

Sets CH2 on

CALL Send(0, 8, "SENSe:VOLTage2:RANGe:AUTO ON", 1) ’

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

3 - 42 USING THE COMBISCOPE INSTRUMENTS

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 num ber of samples is 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) ’

Acquisition length = 512 samples.

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

Acquisition lengthd = 8192 samples .

3.8.2 Time base speed

The SENSe:SWEep:TIME command specifies the time b ase 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

PROGRAM EXAMPLE:

CALL Send(0, 8, "SENSe:SWEep:TIME?, 1) ’

Requests sweep time

CALL Receive(0, 8, STIME$, 256) ’

Reads sweep time

CALL Send(0, 8, "TRACe:POINts? CH1, 1) ’

Requests number of trace points

CALL Receive(0, 8, TPOINTS$, 256) ’

Reads number of trace points

SWETIM = VAL(STIME$) ’

Converts string to variable

TRAPOI = VAL(TPOINTS$) ’

Converts string to variable

MTB = 50 * SWETIM / (TRAPOI-1) ’

Calculates the MTB

PRINT "Main Time Base ="; MTB ’

Prints the 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 samp le 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 tech niques, where points in the requested trace 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) ’

Real time mode off

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

Real time mode on

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

Sets peak detection on.

3 - 44 USING THE COMBISCOPE INSTRUMENTS

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 si x wavefo rm peri ods a re displ ayed on the scr een . 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.

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) ’

Auto triggering

CALL Send(0, 8, "TRIGger:SOURce INTernal1", 1) ’

Sets CH1 trigger source

CALL Send(0, 8, "SENSe:SWEep:TIME:AUTO ON", 1) ’

Sets auto time base on

Figure 3.16 Definition of a signal period

PERI

D LEN

THPERI

D LEN

ST7430

HYSTERESIS

TRIGGER LEVEL

X3X1

USING THE COMBISCOPE INSTRUMENTS 3 - 45

3.9 Post Processing

3.9.1 How to do post processing

The post processing functions CALCulate1 and CALCulate2 com ply 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.

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: Send

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

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 CALCu late1 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.

SENSe

CH 1 CH 2 CH 3 CH 4

TRACe

M1_1 M1_2 M1_3 M1_4

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

Figure 3.17 Post processing control

3 - 46 USING THE COMBISCOPE INSTRUMENTS

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:

Send

→CALCulate2:TRANsform:FREQuency:WINDow HAMMing

’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

- int eg ra tin g traces :INTegral

- differentiating traces :DERivative (al ias :DIFFerential) Example:

Send

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

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.

SENSe

CH 1 CH 2 CH 3 CH 4

TRACe

M1_1 M1_2 M1_3 M1_4

M2_1 M2_2 M2_3 M2_4

M3_1 M3_2 M3_3 M3_4

M50_1 M50_2 M50_3 M50_4

CALCulate[1]

CALCulate2

ST7162

CALCulate

CALCulate:FEED "M3_2"

CALCulate2:FEED "M2_4"

Figure 3.18 Post processing feed definition

USING THE COMBISCOPE INSTRUMENTS 3 - 47

3.9.1.4 Check the result of the post proce ssing 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 trac e for CALCula te2, the result is placed in M2_n (n = 1, 2, 3, 4).

Example: Send

→ CALCulate2:FEED "CH3"

Send

→ CALCulate2:INTegral:STATe ON

’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

→ TRACe? M2_1 ’Requests for M2_1 trace

Read

← <trace_buffer> ’Reads M2_1 trace

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

CALCulate block, but not

as source for the same CALCulate block.

PROGRAM EXAMPLE:

DIM response AS STRING * 1033 ’

Dimensions trace buffer

CALL Send(0, 8, "CALCulate2:FEED ’CH3’", 1) ’

Channel 3 = source CALC2

CALL Send(0, 8, "CALCulate2:TRANsform:FREQuency:WINDow HAMMing", 1) CALL Send(0, 8, "CALCulate2:TRANsform:FREQuency:STATe ON", 1)

’

Enables FFT-Hamming

CALL Send(0, 8, "TRACe? M2_1", 1) ’

Requests for M2_1 trace

CALL Receive(0, 8, response$, 256) ’

Reads the M2_1 trace

3 - 48 USING THE COMBISCOPE INSTRUMENTS

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 MATH1 and MA TH2 respectively . The calcul ation can be an addition (+), a subtraction (-), or a multiplication (

). The attenuation of the resulting trace is automatically set higher than the sum of the attenuations of the individual traces.

PROGRAM EXAMPLE:

CALL Send(0, 8, "CALCulate:MATH (CH1+CH2)", 1) ’

Channel 1 + channel 2

CALL Send(0, 8, "CALCulate:MATH:STATe ON", 1) ’

Math function enabled

’

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

CALL Send(0, 8, "CALCulate2:MATH (M1_1 - CH2)", 1) ’

M1_1 - channel 2

’

The resulting trace (which is the CH1 trace) is stored in M2_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) ’

Channel 3 = input source

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

Channel 3 + channel 2

CALL Send(0, 8, "CALCulate:MATH:STATe ON", 1) ’

Math function enabled

’

The resulting trace (CH3 + CH2) is stored in M1_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 corresponding 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

RST command, the number of

points is 5.

USING THE COMBISCOPE INSTRUMENTS 3 - 49

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

PROGRAM EXAMPLE:

CALL Send(0, 8, "CALCulate:INTegral:STATe ON", 1) ’

Integral CALC1 on

CALL Send(0, 8, "CALCulate2:DERivative:POINts 35", 1)’

35 differential points

CALL Send(0, 8, "CALCulate2:DERivative:STATe ON", 1) ’

Differential CALC2 on

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 frequ en cy (Hz) and an ampli tu de 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 FFT RECTangular function transforms a repetitive time amplitude trace into its power spectrum.

•

The FF T 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.

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 re sponse to a TRACe? query are shifted 4 divisions up wards. The va lues of the r esulting FFT trace points are between -0 dB and -80 dB. This results in the following relation between screen position and sample valu e:

3 - 50 USING THE COMBISCOPE INSTRUMENTS

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

25 = 100

- for 16-bit samples: 4

6400 = 25600

•

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

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)

0.4

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

0.0015625

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 freq uency components. The component with the highest amplitude is taken as the reference level, referred to as the 0 dB level.

When absolute FF T 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 (reference = 1 mW) with REFerence IMPedance of 50Ω

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

-dBµV (reference = 1 µV)

- Vrms (reference = RMS signal amplitude)

Trace sample value Trace point

8-bits

16-bits value

screen range

top - - - - - 1 00 25600 - 0 dB

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

trace range

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

- - - - - - - 25 6 40 0 - 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

USING THE COMBISCOPE INSTRUMENTS 3 - 51

Absolute FF T amplitude s are calculated from the true signa l 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 for the a bsolute 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:

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:

Examples: At 20mV/div. : 2.24

20 ≈ 44.8 mVrms

At 100mV/div.: 2.24

100 ≈ 224 mVrms

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

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:

This can be calculated as a signal level of:

V rms offset calculation:

A signal of 1 mW at 50Ω impedance is ta ken as voltag e r eference at 100 mV/d iv. From this signal the RMS voltage is calculated as follows:

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

Urms

Example for attenuator setting 0.5 V/div.:

6,34 2⁄ 2 2,24≈

2,24 * <number of millivolts per divisions>

P 0,224()

50⁄ 0,001 W 1 mW≈≈=

P0,224()

600⁄ 0,0000836 W 83,6 µW≈≈=

10 * log

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

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

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:

Example for attenuator setting 0.5 V/div.:

dBm - 600Ω offset calculation:

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

Example for attenuator setting 0.5 V/div.:

dBµV offset calculation:

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

Example for attenuator setting 0.5 V/div.:

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

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

Note:

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

13,9794==

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

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

Note:

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

3,1875874==

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

Note: 0 dBµV = 1 µV (1.0E-6 V) at 50Ω impedance.

dBµV offset 20 * 1,118034 1E-6⁄()log

120,9691==

USING THE COMBISCOPE INSTRUMENTS 3 - 53

SUMMARY OF CALCULATED OFFSET VALUES:

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>

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

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 m emory where the post processing trace is stored.

A TTENUATOR

SETTING:

Vrms:

dBm-50

Ω

dBm-600

Ω

dBµV:5V/div

,, 1 ,,+1 1.18034

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

1 13.0103

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

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 "rectang". > MA TH - PARAM - READOUT "rel" to select relative FFT. > MA TH - 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

50) / (acquisition_length - 1). The calculation factor to determine the sample point frequencies is determined as follows: calc = 1250 / (acquisition_length

MTB * 50).

> 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 .

•

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

•

Convert and print the frequency and ampli tude values of the FF T 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

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 histogram 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)

’

This turns the histogram function on

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

RST command, the number of points is 19.

PROGRAM EXAMPLE:

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

’

35 filter points

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

’

Filter CALC1 on

3 - 56 USING THE COMBISCOPE INSTRUMENTS

3.10 Trace Memory

The trace memory of the CombiScopes instruments consists o f space for channel acquisition traces (CH1 to CH4) and m emory register 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 programmed:

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

RST command, the number of trace samples is 512.

- 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.

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.

SENSe

CH 1 CH 2 CH 3 CH 4

TRACe

M1_1 M1_2 M1_3 M1_4

M2_1 M2_2 M2_3 M2_4

M3_1 M3_2 M3_3 M3_4

M50_1 M50_2 M50_3 M50_4

ST7163

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

USING THE COMBISCOPE INSTRUMENTS 3 - 57

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

Table 3.2 Relation between acquisition length and available trace memory

Note: Delayed Time Base (DTB) acquisition traces a re only saved in the CH1

to CH4 memory, when the acquisition le ngth 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

RST 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.

PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’

Length of trace samples = 16 bits

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

Length of trace samples = 8 bits

TRACe:POINts CHANNELS: MEMORY REGISTERS: STANDARD:

512 2K 4K 8K

EXTENDED:

512 8k 16K 32K

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

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

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

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

3 - 58 USING THE COMBISCOPE INSTRUMENTS

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 memo ry 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) ’

Channel 1 on

’

Channel 2, 3, 4 off

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

Channel 3 also on

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

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

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

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

USING THE COMBISCOPE INSTRUMENTS 3 - 59

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 acqui sition trace of channel 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 blo ck> 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 n ot

to acquisition space (CHn).

PROGRAM EXAMPLE:

DIM response AS STRING * 2000 ’

Dimensions trace buffer

CALL Send(0, 8, "TRACe? CH1", 1) ’

Requests for channel 1 trace

CALL Receive(0, 8, response$, 256) ’

Reads the channel 1 trace

length = IBCNT% ’

IBCNT = number of data bytes

CALL Send(0, 8, "TRACe M2_3,", 0) ’

Sends fixed command part without EOI

CALL Send(0, 8, LEFT$(response$,length), 0)

’

Sends variable <trace block> without EOI

CALL Send(0, 8, "", 1) ’

Sends dummy string with EOI detection

3 - 60 USING THE COMBISCOPE INSTRUMENTS

3.10.4 Reading data from trace memory

The TRACe? query allows you to read the contents from o ne of the following 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 ’

Dimensions trace buffer 1

DIM trace2 AS STRING * 2000 ’

Dimensions trace buffer 2

CALL Send(0, 8, "TRACe? CH1", 1) ’

Requests for channel 1 trace

CALL Receive(0, 8, trace1$, 256) ’

Reads channel 1 trace into trace1$

CALL Send(0, 8, "CALCulate:FEED ’CH1’", 1) ’

Input source = CH1

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

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

CALL Send(0, 8, "TRACe? M1_1", 1) ’

Requests for M1_1 trace

CALL Receive(0, 8, trace2$, 256) ’

Reads M1_1 trace into trace2$

USING THE COMBISCOPE INSTRUMENTS 3 - 61

3.11 Screen/Display Functions

3.1 1.1 Brightness control

The DISPlay:BRIGhtness command allows you to control the brightness of the trace(s) displayed on the screen o f you r C ombiSco pe instrumen t on a scale fro m

0.0 (low) to 1.0 (high). After a

RST command, the brightness intensity is 0.18.

PROGRAM EXAMPLE:

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

Sets brightness at 0.3

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 3.11.2.2).

•

The MENU function to display softkey menus on the screen (refer to section 3.11.2.3).

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 measur ed data values can be sel ected by specifying the number <n> in the query:

MEAS1/MEAS2 DATA: 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>

NUMBER <n>: MEASUREMENT VALUE: 1, 2

10, 11, 12, 13, 20, 21, 30, 40, 51, 52 60, 61

MEAS1, MEAS2 data CURSORS data

MATH - FFT frequency, amplitude

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

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 →

RST ’Switches MEAS1 & 2 off 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:

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: 10

11 12 13 20 21 30 40

51 52

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. V ertical 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.

<n>: TYPE: UNIT: DESCRIPTION: 60

FFT-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

PROGRAM EXAMPLE: Read and print the DC and frequency ch aracteristic of the actual signal u sing the

MEAS1 and MEAS2 functions. The program stops to l et you make the requeste d MEAS selections.

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

Displays MEASURE menu

’ ’

*****

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

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

MEAS1-volt-dc." 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) ’

Queries for volt-dc

CALL Receive(0, 8, response$, 256) ’

Reads volt-dc value

PRINT "Measured volt-dc = "; LEFT$(response$, IBCNT% - 1)

CALL Send(0, 8, "DISPlay:WINDow:TEXT2:DATA?", 1) ’

Queries for time-freq

CALL Receive(0, 8, response$, 256) ’

Reads time-freq value

PRINT "Measured time-freq = "; LEFT$(response$, IBCNT% - 1)

USING THE COMBISCOPE INSTRUMENTS 3 - 65

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

RST command,

the display of the previously defined user text is turned off. PROGRAM EXAMPLE 1: (text as string data)

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

Enables display of text

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

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

PROGRAM EXAMPLE 2: (text as block data)

CALL Send(0, 8, "DISPlay:WINDow2:TEXT:CLEar", 1) ’

Clears the text

CALL Send(0, 8, "DISPlay:WINDow2:TEXT:DATA #01.25 k", 0)’

Displays: 1.25 k

CALL Send(0, 8, CHR$(25), 0) ’

Displays:

Ω

CALL Send(0, 8, " CH1", 1) ’

Displays: CH1

’ ’

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

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

RST command, the display of softkey menus is

turned off. PROGRAM EXAMPLE:

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

Selects and displays the

CURSORS menu

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

Switches the CURSORS menu

display off

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:

The HCOPy:DATA? que ry 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 optio ns, which can be selected via the front panel UTILITY menu. After a

RST command, the option "plotter; HPGL" is

selected. 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.

DEVICE: TYPE: NOTE: Plotter

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

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.

USING THE COMBISCOPE INSTRUMENTS 3 - 67

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) ’

Dimensions address array

DIM response AS STRING * 15000 ’

Dimensions response string

CALL IBTMO(0, 13) ’

Timeout at 10 seconds

CALL Send(0, 8, "HCOPy:DEVice PM8277", 1) ’

Selects the PM8277 plotter

CALL Send(0, 8, "HCOPY:DATA?", 1) ’

Requests for hardcopy data

CALL Receive(0, 8, response$, 256) ’

Reads the hardcopy data

length = IBCNT% ’

IBCNT = number of read bytes

PRINT "Number of hardcopy bytes ="; length ’

*****

’

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.

’

*****

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

No End detection

CALL Send(0, 22, "", 1) ’

End of data block

Figure 3.22 Hardcopy of screen on printer/plotter

1) Send the query HCOPy:DA T A? via the GPIB.

2) Read the block response data via the GPIB.

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

DSO

data

buffer

CONTROLLER

send

HCOPy:DATA?

PLOTTER

read response

data

send plot/print data

PRINTER

ST7219

3 - 68 USING THE COMBISCOPE INSTRUMENTS

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 a lso the time of the acquisition trigger.

The SYSTem:TIME command sets the time in hours, minutes, and seconds. Only 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, month s, and days. PROGRAM EXAMPLE:

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

Sets the time to 25 minutes and 36

seconds past 2 o'clock in the

afternoon.

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

Sets the date to 15 december 1993.

3.14 Auto Calibration

Calibration is only possible when the CombiScope instrument is warmed up. The instrument data is calibrated automatically by sending the

CAL? or the CALibration? query. The internal calibration lasts several minutes. A "0" result is returned after correct calibration, and a "1" result is return ed when the ca libration failed. Notice that the response to the calib ratio n query i s only re turned whe n the calibration has completed.

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

CAL? or 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.

USING THE COMBISCOPE INSTRUMENTS 3 - 69

PROGRAM EXAMPLE:

’

*****

’Calibrate the instrument and print the calibration result. ’

*****

CALL Send (0, 8, "*CAL?", 1) ’

Starts the calibration

CALL IbTMO(0, 0) ’

Disables the time out mechanism

response$ = " " CALL Receive (0, 8, response$, 256) ’

Waits for the calibration to finish and reads the result

. ’ CALL IbTMO(0, 13) ’

Sets time out back to 10 seconds

IF LEFT$(response$, 1) = "0" THEN ’

0 = okay

PRINT "Calibration okay"

ELSE ’

1 = wrong

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 ’

Defines "ServReq" routine call after SRQ

PEN ON ’

Enables SRQ mechanism

Send → STATus:OPERation:NTRansition 1

’

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

Send → STATus:OPERation:ENABle 1

’

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

Send → *SRE 128

’

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

Send → *RST ’

Resets the instrument

Send → *CLS ’

Clears the status data

Send → CALibration ’

Starts auto 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 STATUS 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 (SR Q) mechanism:

3.15.1 Status data for the CombiScope instruments

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

ESR? query.

•

The message output queue can contain about 250 data bytes.

•

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

OPERation

Status

Standard

Event Status

QUEStionable

Status

Output Queue

Error/ Event

Queue

Service

Request

Generation

SRQ OPER

RQS

MSS

ESB MAV

QUES

bit2

bit1

bit0

Logical OR

RQS read by Serial Poll

MSS read by *STB?

Status Byte Reg.

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

ST7164

Not Used

Figure 3.23 The status reporting model for CombiScope instruments

USING THE COMBISCOPE INSTRUMENTS 3 - 71

3.15.1.1 Operation status data

BIT: MEANING: 0

CALibrating

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

RANGing

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

SWEeping

This bit is set when the sweep (a data acquisitio n) is in pr ogress. 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

Figure 3.24 The Operation Status structure

CONDition filter EVENt ENABle

1 2 3 4 5 6 7 8 9

11 12 13 14 15

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

0 1 2 3 4 5 6 7 8 9

11 12 13 14 15

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15

:CONDition?STATus:OPERation

CALibrating

RANGing

SWEeping

wait for TRIGger

0 0

Digital mode

Pass/Fail valid

Pass/Fail status

0 0 0 0 0

:PTRansition(?) :NTRansition(?)

:EVENt? :ENABle(?)

ST7442

3 - 72 USING THE COMBISCOPE INSTRUMENTS

3.15.1.2 Questionable status data

BIT: MEANING: 0

VOLTage

This bit is set if a digital sample value is clipped at the maxim um 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 co mplete successfully . This bit is reset after power on and after successful calibra tion.

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

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15

VOLTage

0 0 0

TEMPerature

0 0 0

CALibration

Overload 50Ω

0 0 0 0 0 0

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

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15

STATus:QUEStionable:CONDition?

:PTRansition(?) :NTRansition(?)

:EVENt? :ENABle(?)

CONDition filter

EVENt

ENABle

ST7157

Figure 3.25 The Questionable Status structure

USING THE COMBISCOPE INSTRUMENTS 3 - 73

3.15.2 How to reset the status data

The

CLS command allows you to clear the following status data structu res:

•

All event status registers, such as the following:

- standard event status register (ESR)

- status byte register (STB)

- operation event status register (ST ATus: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:

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) ’

Clears the event registers + error/event queu e

CALL Send(0, 8, "STATus:PRESet", 1) ’

Presets the enable register + filters

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.

3 - 74 USING THE COMBISCOPE INSTRUMENTS

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 m echanism 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) ’

Timeout at 10 seconds

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

CALL Send(0, 8, "*ESE 1", 1) ’

Enables OPC-bit (0) in ESE

’"

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

OPC

. ’ CALL Send(0, 8, "CONFigure:AC", 1) ’

Automatic configuration

CALL Send(0, 8, "*OPC", 1) ’

This command forces the instrument to set the OPC bit

’

when all pending operations have been finished

. ’ CALL Send(0, 8, "INITiate", 1) ’

Single initiation

ESB.bit.set = 0 result$ = SPACE$(3) WHILE ESB.bit.set = 0

CALL Send(0, 8, "*STB?", 1) ’

Requests for the STB

CALL Receive(0, 8, result$, 256) ’

Reads the STB

IF (VAL(result$) AND 32) THEN ’

ESB = bit 5 (value 32)

ESB.bit.set = 1 ’

Operation completed

END IF WEND CALL Send(0, 8, "FETCh:AC?", 1) ’

Fetches AC-RMS value

result$ = SPACE$(30) CALL Receive(0, 8, result$, 256) ’

Reads AC-RMS value

PRINT "AC-RMS value = "; result$ ’

Prints AC-RMS value

USING THE COMBISCOPE INSTRUMENTS 3 - 75

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" + "INIT iate" operation 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 ’

Defines SRQ-routine

PEN ON ’

Enables SRQ-routine

CALL IBTMO(0, 13) ’

Timeout at 10 seconds

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

CALL Send(0, 8, "*ESE 1", 1) ’

Sets OPC-bit in ESR

’"

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

OPC

. ’ CALL Send(0, 8, "*SRE 32", 1) ’

Sets ESB-bit in SRE-register

’

SRQ generation after "OPeration Completed" is enabled

. ’ CALL Send(0, 8, "CONFigure:AC", 1) ’

Automatic configuration

CALL Send(0, 8, "INITiate", 1) ’

Single initiation

CALL Send(0, 8, "*OPC", 1) ’

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

’

when all pending operations have been finished

. ’ WHILE SRQ.detected = 0 ’

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

. WEND CALL Send(0, 8, "FETCh:AC?", 1) ’

Fetches AC-RMS value

result$ = SPACE$(30) CALL Receive(0, 8, result$, 256) ’

Reads AC-RMS value

PRINT "AC-RMS value = "; result$ ’

Prints AC-RMS value

END ’ ServReq:

PRINT "Service request generated because of Operation Completed." CALL ReadStatusByte(0, 8, sbyte%) ’

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

. ’ PRINT "STB byte ="; sbyte% CALL Send(0, 8, "*ESR?", 1) ’

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

. ’ resp$ = " "

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

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

RETURN

3 - 76 USING THE COMBISCOPE INSTRUMENTS

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 o f 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 SYSTem:ERRor? query or the ST ATus:QUEue? query to the instrument, followed by reading the response message. However , through this practice the same "error reporting" statements must be repeated after se nding each SCPI command. Th is is not always practical. Therefore, one of the following approaches is advised:

1) Send the SYSTem:ERRor? or STATus: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 3.16.4.1.

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 ro utine after each group of commands.

PROGRAM EXAMPLE:

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

Configures for AC-RMS

FOR i = 1 TO 20 ’

Performs 20 measurements

CALL Send (0, 8, "READ:AC?", 1) CALL Receive (0, 8, response$, 256) ’

Reads the AC-RMS value

PRINT "AC-RMS: "; response$ ’

Prints the AC-RMS value

GOSUB ErrorCheck ’

Checks for instrument errors

NEXT i ’

*****

’

*****

REST OF THE APPLICATION

’

*****

END ErrorCheck:

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

Queries for a system error

CALL Receive (0, 8, response$, 256) ’

Reads the instrument error

PRINT "Error: "; response$ ’

Prints the instrument error

RETURN

USING THE COMBISCOPE INSTRUMENTS 3 - 77

3.15.4.2 Error-repor tin g usin g 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" ’

Loop until 0, ’No error

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

Sends error query

er$ = SPACE$(60) CALL Receive(0, 8, er$, 256) ’

Reads error string

PRINT "Error = "; er$ ’

Displays error string

WEND

END SUB

3 - 78 USING THE COMBISCOPE INSTRUMENTS

3.16 Saving/Restoring Instrument Setups

This level of programming involves all functions in the Com biScopes instruments, 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

RST command. This resets the

instrument-specific functions to a default state and selects the digita l mode. PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument (for reset values, refer to the

RST command in the command reference)

3.16.2 How to save/restore a setup via instrument memory

Complete instrument setups can be stored and recalled via one of the inter nal memories of the CombiScope instr ument. The settings in re call memory 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) ’

Saves the complete instrument setup into memory 3

CALL Send(0, 8, "*RCL 3", 1) ’

Recalls the complete instrument se tup from memory 3

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 ’

Reserves space for instrument settings

CALL Send(0, 8, "SYSTem:SET?", 1) ’

Queries for the complete instrument setup

’

'(no <node> parameter specified)

CALL Receive(0, 8, settings$, 256) ’

Reads the instrument settings

length = IBCNT% ’

IBCNT% = number of settings bytes

CALL Send(0, 8, "SYSTem:SET ", 0) ’

Sends the command header (note the space)

’

EOI checking disabled (0)

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

Sends the instrument settings

’

EOI checking enabled (1)

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 betwe en different instruments from the sa me 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 (

ESR?

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

RST;DISPlay:MENU ACQuire;:SYSTem:KEY 2 resets the instrument (e.g., digital mode on and peak detectio n off), switches the softkey menu ACQUIRE on, and simulates the pressing of softkey 2, which causes peak detection to be switched on.

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.

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

column: 1 2 3 13 row 1

row 2

101 201

102 202

103 203

113 213

row 3 row 4

row 7

1 2 . . 6

302 402

. .

702

303 304

. .

703

313 413

. .

713

row 8 801 802 803 813

3 - 80 USING THE COMBISCOPE INSTRUMENTS

PROGRAM EXAMPLE:

CALL Send(0, 8, "*RST", 1) ’

Resets the instrument

CALL Send(0, 8, "SYSTem:KEY 104", 1) ’

Enables the UTILITY softkey menu

CALL Send(0, 8, "SYSTem:KEY 2", 1) ’

Selects the PROBE option

CALL Send(0, 8, "SYSTem:KEY 5", 1) ’

Selects the PROBE CORR option

CALL Send(0, 8, "SYSTem:KEY 4", 1) ’

Selects the 10:1 option

CALL Send(0, 8, "SYSTem:KEY 104", 1) ’

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

AUTOSET SIMULATION:

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

Simulates

Autoset

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) ’

Resets the instrument

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

Enables the UTILITY softkey menu

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

Selects the PROBE + PROBE CORR + 10:1 options

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

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

USING THE COMBISCOPE INSTRUMENTS 3 - 81

3.18 Functions not Directly Programmable

Not all front panel functions are ind ividually programmable with SCPI commands. However, the SYSTem:SET and

SAV/*RCL commands can be used to access

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

(appendix A5 and B.2.4.)

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;:SYST em:KEY 1 (up)or 2 (down)

(after INITiate:CONTinuous OFF)

Fluke CombiScope PM3370B, CombiScope PM3384B, CombiScope PM3394B, CombiScope PM3380B, CombiScope PM3390B User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual