Tektronix TDS 520A, 540A, 524A, 544A User Manual

User Manual

TDS 520A, 524A, 540A, & 544A
Digitizing Oscilloscopes

070-8710-01

Please check for change information at the rear
of this manual.

First Printing: July 1993
Revised: November 1993

Instrument Serial Numbers

Each instrument manufactured by Tektronix has a serial number on a panel insert or tag, or stamped on the
chassis. The first letter in the serial number designates the country of manufacture. The last five digits of the
serial number are assigned sequentially and are unique to each instrument. Those manufactured in the United
States have six unique digits. The country of manufacture is identified as follows:

B010000 Tektronix, Inc., Beaverton, Oregon, USA
E200000 Tektronix United Kingdom, Ltd., London
J300000 Sony/Tektronix, Japan
H700000 Tektronix Holland, NV, Heerenveen, The Netherlands

Instruments manufactured for Tektronix by external vendors outside the United States are assigned a two digit
alpha code to identify the country of manufacture (e.g., JP for Japan, HK for Hong Kong, IL for Israel, etc.).

Tektronix, Inc., P.O. Box 500, Beaverton, OR 97077
Printed in U.S.A.
Copyright E Tektronix, Inc., 1993. All rights reserved. Tektronix products are covered by U.S. and foreign

patents, issued and pending. The following are registered trademarks: TEKTRONIX, TEK, TEKPROBE, and
SCOPE-MOBILE.

Microsoft is a registered trademark of Microsoft Corporation.
IBM is a registered trademark of International Business Machines.
GPIB-PCII and GPIB-PCIIA are registered trademarks of National Instruments Corporation.
Epson is a registered trademark of Epson America, Inc.
Interleaf is a trademark of Interleaf, Inc.
PostScript is a registered trademark of Adobe Systems Incorporated.
Deskjet, Laserjet, and Thinkjet are registered trademarks of Hewlett-Packard Corporation.

WARRANTY

Tektronix warrants that this product will be free from defects in materials and workmanship for a period of three (3) years from
the date of shipment. If any such product proves defective during this warranty period, Tektronix, at its option, either will repair
the defective product without charge for parts and labor, or will provide a replacement in exchange for the defective product.

In order to obtain service under this warranty , Customer must notify Tektronix of the defect before the expiration of the
warranty period and make suitable arrangements for the performance of service. Customer shall be responsible for
packaging and shipping the defective product to the service center designated by Tektronix, with shipping charges prepaid.
Tektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the
Tektronix service center is located. Customer shall be responsible for paying all shipping charges, duties, taxes, and any
other charges for products returned to any other locations.

This warranty shall not apply to any defect, failure or damage caused by improper use or improper or inadequate
maintenance and care. Tektronix shall not be obligated to furnish service under this warranty a) to repair damage resulting
from attempts by personnel other than Tektronix representatives to install, repair or service the product; b) to repair damage
resulting from improper use or connection to incompatible equipment; or c) to service a product that has been modified or
integrated with other products when the effect of such modification or integration increases the time or difficulty of servicing
the product.

THIS WARRANTY IS GIVEN BY TEKTRONIX WITH RESPECT TO THIS PRODUCT IN LIEU OF ANY OTHER
WARRANTIES, EXPRESSED OR IMPLIED. TEKTRONIX AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. TEKTRONIX’ RESPONSIBILITY TO REPAIR OR
REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED TO THE CUSTOMER FOR
BREACH OF THIS WARRANTY. TEKTRONIX AND ITS VENDORS WILL NOT BE LIABLE FOR ANY INDIRECT,
SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES IRRESPECTIVE OF WHETHER TEKTRONIX OR THE
VENDOR HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.

German Postal Information

Certificate of the Manufacturer/Importer

We hereby certify that the TDS 520A, TDS 524A, TDS 540A, and TDS 544A Oscilloscopes and all
factory-installed options complies with the RF Interference Suppression requirements of Postal Regulation Vfg.
243/1991, Amended per Vfg. 46/1992

The German Postal Service was notified that the equipment is being marketed.
The German Postal Service has the right to re-test the series and to verify that it complies.

TEKTRONIX

Bescheinigung des Herstellers/Importeurs

Hiermit wird bescheinigt, daß der/die/das TDS 520A, TDS 524A, TDS 540A, and TDS 544A Oscilloscopes und
alle fabrikinstallierten Optionen in Übereinstimmung mit den Bestimmungen der Amtsblatt-Verfügung Vfg.
243/1991 und Zusatzverfügung 46/1992 funkentstört sind.

Der Deutschen Bundespost wurde das Inverkehrbringen dieses Gerätes angezeigt und die Berechtigung zur
Überprüfung der Serie auf Einhalten der Bestimmungen eingeräumt.

TEKTRONIX

NOTICE to the user/operator:
The German Postal Service requires that Systems assembled by the operator/user of this instrument must also

comply with Postal Regulation, Vfg. 243/1991, Par. 2, Sect. 1.
HINWEIS für den Benutzer/Betreiber:
Die vom Betreiber zusammengestellte Anlage, innerhalb derer dieses Gerät eingesetzt wird, muß ebenfalls den

Voraussetzungen nach Par. 2, Ziff. 1 der Vfg. 243/1991, genügen.

NOTICE to the user/operator:
The German Postal Service requires that this equipment, when used in a test setup, may only be operated if the

requirements of Postal Regulation, Vfg. 243/1991, Par. 2, Sect. 1.8.1 are complied with.
HINWEIS für den Benutzer/Betreiber:
Dieses Gerät darf in Meßaufbauten nur betrieben werden, wenn die Voraussetzungen des Par. 2, Ziff. 1. 8.1 der

Vfg. 243/1991 eingehalten werden.

EC Declaration of Conformity

We

Tektronix Holland N.V.
Marktweg 73A
8444 AB Heerenveen
The Netherlands

declare under sole responsibility that the

TDS 520A, 524A, 540A, & 544A Digitizing Oscilloscopes

meet the intent of Directive 89/336/EEC for Electromagnetic Compatibility.
Compliance was demonstrated to the following specifications as listed in the official

Journal of the European Communities:

EN 50081–1 Emissions:

EN 55022 Radiated
EN 55022 Conducted
EN 60555–2 Power Harmonics

EN 50082–1 Immunity:

IEC 801–2 Electrostatic Discharge
IEC 801–3 RF Radiated
IEC 801–4 Fast Transients
IEC 801–5 Surge

Welcome

Related Manuals

This is the User Manual for the

Getting Started

The
oscilloscope.

Operating Basics

These articles help you understand why your instrument works the way it
does.

Reference

The
page 3-1 for a complete list of tasks covered in that section.

Appendices

The
useful information.

The following documents are related to the use or service of the digitizing
oscilloscope.

H

H

TDS Family Digitizing Oscilloscopes Programmer Manual

The
part number 070–8709–01) describes using a computer to control the
digitizing oscilloscope through the GPIB interface.

TDS Family Option 05 Video Trigger Instruction Manual

The
part number 070–8748–00) describes use of the video trigger option (for
TDS oscilloscopes equipped with that option only).

section familiarizes you with the operation of the digitizing

covers basic principles of the operation of the oscilloscope.

section teaches you how to perform specific tasks. See

provide an options listing, an accessories listing, and other

TDS Family Digitizing Oscilloscopes

(Tektronix

(Tektronix

.

H

H

H

TDS 520A, 524A, 540A, 544A, & 644A Reference

The
number 070–8711–01) gives you a quick overview of how to operate your
digitizing oscilloscope.

TDS 520A, 524A, 540A, & 544A Performance Verification

The
part number 070–8712–01) tells how to verify the performance of the
digitizing oscilloscope.

TDS 520A, 524A, 540A, & 544A Service Manual

The
number 070–8713–01) provides information for maintaining and servicing
your digitizing oscilloscope to the module level.

(Tektronix part

(Tektronix

(Tektronix part

TDS 620A, 640A, & 644A User Manual

i

Welcome

Conventions

In the

Getting Started

dures which contain steps of instructions for you to perform. To keep those
instructions clear and consistent, this manual uses the following conventions:

H

In procedures, names of front panel controls and menu labels appear in
boldface print.

H

Names also appear in the same case (initial capitals, all uppercase, etc.)
in the manual as is used on the oscilloscope front panel and menus. Front
panel names are all upper case letters, for example, VERTICAL MENU,
CH 1, etc.

H

Instruction steps are numbered. The number is omitted if there is only
one step.

H

When steps require that you make a sequence of selections using front
panel controls and menu buttons, an arrow ( ➞

between a front panel button and a menu, or between menus. Also,
whether a name is a main menu or side menu item is clearly indicated:

Press VERTICAL MENU ➞ Coupling (main) ➞ DC (side) ➞ Band-
width (main) ➞ 100 MHz (side).

and

Reference

sections, you will find various proce-

) marks each transition

Using the convention just described results in instructions that are graphi­cally intuitive and simplifies procedures. For example, the instruction just
given replaces these five steps:

1. Press the front panel button VERTICAL MENU.

2. Press the main menu button Coupling.

3. Press the side-menu button DC.

4. Press the main menu button Bandwidth

5. Press the side menu button 100 MHz

H

Sometimes you may have to make a selection from a popup menu: Press
TRIGGER MENU ➞ Type (main) ➞ Edge (popup). In this example, you
repeatedly press the main menu button Type until Edge is highlighted in
the pop-up menu.

ii

Welcome

Getting Started

Operating Basics

Table of Contents

Safety v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Product Description 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Start Up 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Setting Up for the Examples 1-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Example 1: Displaying a Waveform 1-7. . . . . . . . . . . . . . . . . . . . . . . . . . .

Example 2: Multiple Waveforms 1-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Example 3: Automated Measurements 1-17. . . . . . . . . . . . . . . . . . . . . . . .

Example 4: Saving Setups 1-23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reference

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

At a Glance 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Triggering 2-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Acquisition 2-19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Scaling and Positioning Waveforms 2-25. . . . . . . . . . . . . . . . . . . . . . . . . .

Measurements 2-30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

Acquisition Modes 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Autoset 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Color (TDS 524A & TDS 544A) 3-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cursor Measurements 3-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Delayed Triggering 3-22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Display Modes 3-28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Edge Triggering 3-34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fast Fourier Transforms 3-38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TDS 520A, 524A, 540A, & 544A User Manual

iii

Table of Contents

File System (Optional on TDS 520A & TDS 540A) 3-55. . . . . . . . . . . . . .

Hardcopy 3-59. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Help 3-67. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Horizontal Control 3-68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Limit Testing 3-73. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Logic Triggering 3-78. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Measurement System 3-86. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Probe Accessories 3-97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Probe Cal 3-104. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Probe Compensation 3-110. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Probe Selection 3-112. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pulse Triggering 3-119. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Remote Communication 3-126. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Saving and Recalling Setups 3-130. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendices

Saving and Recalling Waveforms 3-133. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Selecting Channels 3-136. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signal Path Compensation 3-138. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Status 3-140. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Triggering 3-142. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Vertical Control 3-147. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Waveform Differentiation 3-150. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Waveform Integration 3-154. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Waveform Math 3-159. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Zoom 3-162. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix A: Options and Accessories A-1. . . . . . . . . . . . . . . . . . . . . . . .

Appendix B: Algorithms A-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix C: Packaging for Shipment A-23. . . . . . . . . . . . . . . . . . . . . . . . .

Appendix D: Factory Initialization Settings A-25. . . . . . . . . . . . . . . . . . . .

Glossary

Index

i

Contents

Safety

Please take a moment to review these safety precautions. They are provided
for your protection and to prevent damage to the digitizing oscilloscope. This
safety information applies to all operators and service personnel.

Symbols and Terms

These two terms appear in manuals:

H

statements identify conditions or practices that could result in

damage to the equipment or other property.

H

statements identify conditions or practices that could result in

personal injury or loss of life.

These two terms appear on equipment:

CAUTION

H

indicates a personal injury hazard not immediately accessible
as one reads the marking or a hazard to property including the equipment
itself.

H

DANGER

indicates a personal injury hazard immediately accessible as

one reads the marking.

This symbol appears in manuals:

TDS 620A, 640A, & 644A User Manual

Static-Sensitive Devices

These symbols appear on equipment:

DANGER

High Voltage

Protective

ground (earth)

terminal

ATTENTION

Refer to

manual

v

Safety

Specific Precautions

Observe all of these precautions to ensure your personal safety and to pre­vent damage to either the digitizing oscilloscope or equipment connected to it.

Power Source

The digitizing oscilloscope is intended to operate from a power source that will
not apply more than 250 V
either supply conductor and ground. A protective ground connection, through
the grounding conductor in the power cord, is essential for safe system
operation.

between the supply conductors or between

RMS

Grounding the Digitizing Oscilloscope

The digitizing oscilloscope is grounded through the power cord. To avoid
electric shock, plug the power cord into a properly wired receptacle where
earth ground has been verified by a qualified service person. Do this before
making connections to the input or output terminals of the digitizing oscillo­scope.

Without the protective ground connection, all parts of the digitizing oscillo­scope are potential shock hazards. This includes knobs and controls that may
appear to be insulators.

Use the Proper Power Cord

Use only the power cord and connector specified for your product. Use only a
power cord that is in good condition.

Use the Proper Fuse

To avoid fire hazard, use only the fuse specified in the parts list for your
product, matched by type, voltage rating, and current rating.

Do Not Remove Covers or Panels

To avoid personal injury, do not operate the digitizing oscilloscope without the
panels or covers.

Electric Overload

Never apply a voltage to a connector on the digitizing oscilloscope that is
outside the voltage range specified for that connector.

Do Not Operate in Explosive Atmospheres

The digitizing oscilloscope provides no explosion protection from static dis­charges or arcing components. Do not operate the digitizing oscilloscope in
an atmosphere of explosive gases.

vi

Safety

Getting Started

Product Description

Your Tektronix digitizing oscilloscope is a superb tool for acquiring, displaying,
and measuring waveforms. Its performance addresses the needs of both
benchtop lab and portable applications with the following features:

H

500 MHz maximum analog bandwidth.

H

1 Gigasample/second maximum digitizing rate (TDS 540A & 544A);
500 Megasamples/second maximum digitizing rate (TDS 520A & 524A).

H

Four-channel acquisition — the TDS 544A & 540A offer four full-featured
channels; the TDS 520A & 524A offer two full-featured channels and two
channels with limited vertical scale selections: 100 mV, 1 V, and 10 V.

H

Waveform Math — Invert a single waveform and add, subtract, multiply,
and divide two waveforms. On instruments with Option 2F: Advanced DSP
Math (standard on the TDS 524A & 544A), integrate or differentiate a
single waveform or perform an FFT (fast fourier transform) on a waveform
to display its magnitude or phase versus its frequency.

H

Eight-bit digitizers.

H

Up to 15,000-point record length per channel (50,000-point optional).

H

Full GPIB software programmability. Hardcopy output using RS-232 or
Centronics ports (Optional on TDS 520A & 540A) and the GPIB.

H

Complete measurement and documentation capability.

H

Intuitive graphic icon operation blended with the familiarity of traditional
horizontal and vertical knobs.

H

On-line help at the touch of a button.

TDS 520A, 524A, 540A, & 544A User Manual

1Ć1

Product Description

1Ć2

Getting Started

Start Up

Before you use the digitizing oscilloscope, ensure that it is properly installed
and powered on.

Before You Begin

Operation

To ensure maximum accuracy for your most critical measurements, you
should know about signal path compensation.

Signal Path Compensation

Be sure you compensate your oscilloscope for the surrounding temperature.
This action, called
possible accuracy for your most critical measurements. See

Compensation

on this feature.

To properly install and power on the digitizing oscilloscope, do the following:

Signal Path Compensation (SPC)

on page 3-138 for a description of and operating information

, ensures maximum

Signal Path

Installation

1. Be sure you have the appropriate operating environment. Specifications
for temperature, relative humidity, altitude, vibrations, and emissions are
included in the
manual (Tektronix part number 070–8712–01).

2. Leave space for cooling. Do this by verifying that the air intake and ex­haust holes on the sides of the cabinet (where the fan operates) are free
of any airflow obstructions. Leave at least 5.1 cm (2 inches) free on each
side.

TDS 520A, 524A, 540A, & 544A Performance Verification

TDS 620A, 640A, & 644A User Manual

WARNING

To avoid electrical shock, be sure that the power cord is discon­nected before checking the fuse.

3. Check the fuse to be sure it is the proper type and rating (see Figure 1-1).
You can use either of two fuses. Each fuse requires its own cap (see
Table 1-1). The digitizing oscilloscope is shipped with the UL approved
fuse installed.

1Ć3

Start Up

Power Connector

Principal Power Switch

Fuse

4. Check that you have the proper electrical connections. The digitizing
oscilloscope requires 90 to 250 VAC

, continuous range, 47 Hz to

RMS

63 Hz, and may require up to 300 W.

5. Connect the proper power cord from the rear-panel power connector (see
Figure 1-1) to the power system.

Figure 1-1: Rear Panel Controls Used in Start Up

Table 1-1: Fuse and Fuse Cap Part Numbers

Fuse

.25 inch × 1.25 inch (UL 198.6, 3AG):

Fuse Part
Number

Fuse Cap Part
Number

159–0013–00 200–2264–00

6 A FAST, 250 V.
5 mm × 20 mm (IEC 127): 5 A (T),

159–0210–00 200–2265–00

250 V.

Front Cover Removal

Remove the front cover by grasping its left and right edges and snapping it off
of the front subpanel. (When reinstalling, align and snap back on.)

Power On

1. Check that the rear-panel principal power switch is on (see Figure 1-1).
The principal power switch controls all AC power to the instrument.

1Ć4

2. If the oscilloscope is not powered on (the screen is blank), push the
front-panel ON/STBY button to toggle it on (see Figure 1-2).

The ON/STBY button controls power to most of the instrument circuits.
Power continues to go to certain parts even when this switch is set to
STBY.

Getting Started

ON/STBY Button

Start Up

Once the digitizing oscilloscope is installed, it is typical to leave the princi­pal power switch on and use the ON/STBY button as the power switch.

Figure 1-2: ON/STBY Button

Self Test

Check the self test results. The digitizing oscilloscope automatically performs
power-up tests each time it is turned on. It will come up with a display screen
that states whether or not it passed self test. (If the self test passed, the
status display screen will be removed after a few seconds.)

If the self test fails, call your local Tektronix Service Center. Depending on the
type of failure, you may still be able to use the oscilloscope before it is serv­iced.

Power Off

Toggle the ON/STBY switch to turn off the oscilloscope.

TDS 620A, 640A, & 644A User Manual

1Ć5

Setting Up for the Examples

All the examples use the same setup. Once you perform this setup, you do
not have to change the signal connections for any of the other examples.

Remove all probes and signal inputs from the input BNC connectors along the
lower right of the front panel. Then, using one of the probes supplied with the
digitizing oscilloscope, connect from the CH 1 connector to the PROBE
COMPENSATION connectors (see Figure 1-3).

1Ć6

Figure 1-3: Connecting a Probe for the Examples

Getting Started

Example 1: Displaying a Waveform

In this first example you learn about resetting the digitizing oscilloscope,
displaying and adjusting a waveform, and using the autoset function.

Resetting the Digitizing Oscilloscope

SETUP Button

All examples in the tutorial begin by resetting the digitizing oscilloscope to a
known factory default state. Reset the oscilloscope when you begin a new
task and need to “start fresh” with known default settings.

1. Press the save/recall SETUP button to display the Setup menu (Fig­ure 1-4).

Figure 1-4: SETUP Button Location

The digitizing oscilloscope displays
screen. Figure 1-5 shows the Setup main menu.

main menus

along the bottom of the

OK Confirm Factory Init

Menu Item and Button

Recall Factory Setup

Menu Item and Button

TDS 620A, 640A, & 644A User Manual

Figure 1-5: The Displayed Setup Menu

1Ć7

Example 1: Displaying a Waveform

2. Press the button directly below the Recall Factory Setup menu item.
The display shows

side menus

along the right side of the screen. The

buttons to select these side menu items are to the right of the side menu.
Because an accidental instrument reset could destroy a setup that took a

long time to create, the digitizing oscilloscope asks you to verify the
Recall Factory Setup selection (see Figure 1-5).

3. Press the button to the right of the OK Confirm Factory Init side menu
item.

NOTE

This manual uses the following notation to represent the sequence
of selections you made in steps 1, 2 and 3:

UP ➞ Recall Factory Setup (main) ➞ OK Confirm Factory Init
(side).

Note that a clock icon appears on screen. The oscilloscope displays this
icon when performing operations that take longer than several seconds.

4. Press SET LEVEL TO 50% (see Figure 1-6) to be sure the oscilloscope
triggers on the input signal.

Press save/recall SET-

1Ć8

SET LEVEL TO 50% Button

Figure 1-6: Trigger Controls

Getting Started

Example 1: Displaying a Waveform

Display Elements

Figure 1-7 shows the display that results from the instrument reset. There are
several important points to observe:

H

trigger level bar

The

shows that the waveform is triggered at a level near

50% of its amplitude (from step 4).

H

trigger position indicator

The

shows that the trigger position of the wave-

form is located at the horizontal center of the graticule.

H

channel reference indicator

The

shows the vertical position of channel 1
with no input signal. This indicator points to the ground level for the
channel when its vertical offset is set to 0 V in the vertical menu; when

not

vertical offset is

H

trigger readout

The

set to 0 V, it points to the vertical offset level.

shows that the digitizing oscilloscope is triggering on
channel 1 (Ch1) on a rising edge, and that the trigger level is about
200–300 mV.

H

time base readout

The

shows that the main time base is set to a horizon-

tal scale of 500ms/div.

H

channel readout

The

indicates that channel 1 (Ch1) is displayed with DC
coupling. (In AC coupling, ~ appears after the volts/div readout.) The
digitizing oscilloscope always displays channel 1 at reset.

Trigger Level

Bar

Trigger Position Indicator

Channel Reference Indicator

Trigger Readout

Time Base Readout

Channel Readout

Figure 1-7: The Display After Factory Initialization

Right now, the channel, time base, and trigger readouts appear in the grati­cule area because a menu is displayed. You can press the CLEAR MENU
button at any time to remove any menus and to move the readouts below the
graticule.

TDS 620A, 640A, & 644A User Manual

1Ć9

Example 1: Displaying a Waveform

Adjusting the Waveform Display

The display shows the probe compensation signal. It is a 1 kHz square wave
of approximately 0.5 V amplitude. You can adjust the size and placement of
the waveform using the front-panel knobs.

Figure 1-8 shows the main VERTICAL and HORIZONTAL sections of the
front panel. Each has SCALE and POSITION knobs.

1. Turn the vertical SCALE knob clockwise. Observe the change in the
displayed waveform and the channel readout at the bottom of the display.

Using Autoset

Figure 1-8: The VERTICAL and HORIZONT AL Controls

2. Turn the vertical POSITION knob first one direction, then the other.
Observe the change in the displayed waveform. Then return the wave­form to the center of the graticule.

3. Turn the horizontal SCALE knob one click clockwise. Observe the time
base readout at the bottom of the display. The time base should be set to
200ms/div now, and you should see two complete waveform cycles on
the display.

When you first connect a signal to a channel and display it, the signal dis­played may not be scaled and triggered correctly. Use the autoset function
and you should quickly get a meaningful display.

When you reset the digitizing oscilloscope, you see a clear, stable display of
the probe compensation waveform. That is because the probe compensation
signal happens to display well at the default settings of the digitizing oscillo­scope.

1Ć10

Getting Started

Example 1: Displaying a Waveform

1. To create an unstable display, slowly turn the trigger MAIN LEVEL knob
(see Figure 1-9) first one direction, then the other. Observe what happens
when you move the trigger level above the highest part of the displayed
waveform. Leave the trigger level in that untriggered state.

2. Press AUTOSET (see Figure 1-10) and observe the stable waveform
display.

MAIN LEVEL Knob

Figure 1-9: TRIGGER Controls

AUTOSET Button

Figure 1-10: AUTOSET Button Location

Figure 1-11 shows the display after pressing AUTOSET. If necessary, you can
adjust the waveform now by using the knobs discussed earlier in this exam­ple.

TDS 620A, 640A, & 644A User Manual

1Ć11

Example 1: Displaying a Waveform

Figure 1-11: The Display After Pressing Autoset

NOTE

If the corners on your displayed signal look rounded or pointed (see
Figure 1-12), then you may need to compensate your probe. The

Probe Compensation

pensate your probe.

Figure 1-12: Display Signals Requiring Probe Compensation

section on page 3-110 explains how to com-

1Ć12

Getting Started

Example 2: Multiple Waveforms

In this example you learn how to display and control more than one waveform
at a time.

Adding a Waveform

The VERTICAL section of the front panel contains the channel selection
buttons. These are CH 1, CH 2, CH 3, CH 4, and MORE (Figure 1-13); on the
TDS 620A & 524A, they are CH 1, CH 2, AUX 1, AUX 2, and MORE.

TDS 620A, 640A, & 644A User Manual

Figure 1-13: The Channel Buttons and Lights

Each of the channel (CH) buttons has a light above its label. Right now, the
CH 1 light is on. That light indicates that the vertical controls are set to adjust

channel 1.
The following steps add a waveform to the display.

1. If you are not continuing from the previous example, follow the instruc­tions on page 1-6 under the heading

2. Press SETUP ➞ Recall Factory Setup (main) ➞ OK Confirm Factory
Init (side).

Setting Up for the Examples

.

1Ć13

Example 2: Multiple Waveforms

3. Press AUTOSET.

4. Press CH 2.
The display shows a second waveform, which represents the signal on

channel 2. Since there is nothing connected to the CH 2 input connector,

this waveform is a flat line.
There are several other important things to observe:

H

The channel readout on the display now shows the settings for both
Ch1 and Ch2.

H

There are two channel indicators at the left edge of the graticule.
Right now, they overlap.

H

The light next to the CH 2 button is now on, and the CH 1 light is off.
Because the knobs control only one channel at a time, the vertical
controls are now set to adjust channel 2.

H

The trigger readout still indicates that the trigger is detecting trigger
events on Ch1. The trigger source is not changed simply by adding a
channel. (You can change the trigger source by using the TRIGGER
MENU button to display the trigger menu.)

5. Turn the vertical POSITION knob clockwise to move the channel 2 wave-

form up on the graticule. You will notice that the channel reference indica­tor for channel 2 moves with the waveform.

6. Press VERTICAL MENU ➞ Coupling (main).

The VERTICAL MENU button displays a menu that gives you control
over many vertical channel parameters (Figure 1-14). Although there can
be more than one channel displayed, the vertical menu and buttons only
adjust the selected channel.

Each menu item in the Vertical menu displays a side menu. Right now,
the Coupling item in the main menu is highlighted, which means that the
side menu shows the coupling choices. At the top of the side menu, the
menu title shows the channel affected by the menu choices. That always
matches the lighted channel button.

7. Press W (side) to toggle the selection to 50 W. That changes the input

coupling of channel 2 from 1 MW to 50 W. The channel readout for chan­nel 2 (near the bottom of the graticule) now shows an W indicator.

1Ć14

Getting Started

Ch2 Reference Indicator

Side Menu Title

Example 2: Multiple Waveforms

Changing Controls to Another Channel

Figure 1-14: The Vertical Main Menu and Coupling Side Menu

Pressing a channel (CH) button sets the vertical controls to that channel. It
also adds the channel to the display if that waveform is not already displayed.

1. Press CH 1.
Observe that now the side menu title shows Ch1 (Figure 1-15), and that

the light above CH 1 is lighted. The highlighted menu item in the side
menu has changed from the 50W channel 2 setting to the 1MW imped­ance setting of channel 1.

2. Press CH 2 ➞ W (side) to toggle the selection to 1MW. That returns the
coupling impedance of channel 2 to its initial state.

TDS 620A, 640A, & 644A User Manual

1Ć15

Example 2: Multiple Waveforms

Side Menu Title

Removing a Waveform

Figure 1-15: The Menus After Changing Channels

Pressing the WAVEFORM OFF button removes the waveform for the current-
ly selected channel. If the waveform you want to remove is not already se­lected, select that channel using the channel (CH) button.

1. Press W AVEFORM OFF (under the vertical SCALE knob).
Since the CH 2 light was on when you pressed the WAVEFORM OFF

button, the channel 2 waveform was removed.
The channel (CH) lights now indicate channel 1. Channel 1 has become

the selected channel. When you remove the last waveform, all the CH
lights are turned off.

2. Press W AVEFORM OFF again to remove the channel 1 waveform.

1Ć16

Getting Started

Example 3: Automated Measurements

In this example you learn how to use the automated measurement system to
get numeric readouts of important waveform characteristics.

Displaying Automated Measurements

To use the automated measurement system, you must have a stable display
of your signal. Also, the waveform must have all the segments necessary for
the measurement you want. For example, a rise time measurement requires
at least one rising edge, and a frequency measurement needs at least one
complete cycle.

1. If you are not continuing from the previous example, follow the instruc­tions on page 1-6 under the heading

2. Press SETUP ➞ Recall Factory Setup (main) ➞ OK Confirm Factory
Init (side).

3. Press AUTOSET.

4. Press MEASURE to display the Measure main menu (see Figure 1-16).

Setting Up for the Examples

.

TDS 620A, 640A, & 644A User Manual

Figure 1-16: Measure Main Menu and Select Measurement Side Menu

1Ć17

Example 3: Automated Measurements

5. If it is not already selected, press Select Measrmnt (main). The readout
for that menu item indicates which channel the measurement will be
taken from. All automated measurements are made on the selected
channel.

The Select Measurement side menu lists some of the measurements that
can be taken on waveforms. There are many different measurements
available; up to four can be taken and displayed at any one time. Press­ing the button next to the –more– menu item brings up the other mea­surement selections.

6. Press Frequency (side). If the Frequency menu item is not visible, press

–more– (side) repeatedly until the Frequency item appears. Then press
Frequency (side).

Observe that the frequency measurement appears within the right side of
the graticule area. The measurement readout includes the notation Ch1,
meaning that that measurement is taken on the channel 1 waveform. (To
take a measurement on another channel, select that channel, and then
select the measurement.)

7. Press Positive Width (side) ➞ –more– (side) ➞ Rise Time (side) ➞
Positive Duty Cycle (side).

All four measurements are displayed. Right now, they cover a part of the
graticule area, including the displayed waveforms.

8. To move the measurement readouts outside the graticule area, press
CLEAR MENU (see Figure 1-17).

1Ć18

Getting Started

Example 3: Automated Measurements

Press here to

remove menus

from screen.

Removing Measurement Readouts

Changing the Measurement Reference Levels

Figure 1-17: Four Simultaneous Measurement Readouts

The Measure menu lets you remove measurements you no longer want
displayed. You can remove any one measurement, or you can remove them
all with a single menu item.

Press MEASURE ➞ Remove Measrmnt (main) ➞ Measurement 1, Mea-
surement 2, and Measurement 4 (side) to remove those measurements.
Leave the rise time measurement displayed.

By default, the measurement system will use the 10% and 90% levels of the
waveform for taking the rise time measurement. You can change these values
to other percentages or change them to absolute voltage levels.

To examine the current values, press Reference Levels (main) ➞ High Ref
(side).

The General Purpose Knob

TDS 620A, 640A, & 644A User Manual

The general purpose knob, the large knob, is now set to adjust the high
reference level (Figure 1-18).

1Ć19

Example 3: Automated Measurements

General Purpose Knob

Setting and Readout

General Purpose

Knob Icon

Highlighted Menu Item with

Boxed Readout Value

Figure 1-18: General Purpose Knob Indicators

There are several important things to observe on the screen:

H

The knob icon appears at the top of the screen. The knob icon indicates
that the general purpose knob has just been set to adjust a parameter.

H

The upper right corner of the screen shows the readout High Ref: 90%.

H

The High Ref side menu item is highlighted, and a box appears around
the 90% readout in the High Ref menu item. The box indicates that the
general purpose knob is currently set to adjust that parameter.

Turn the general purpose knob left and right, and then use it to adjust the high
level to 80%. That sets the high measurement reference to 80%.

Hint: To make large changes quickly with the general purpose knob, press the
SHIFT button before turning the knob. When the light above the SHIFT button
is on and the display says

Coarse Knobs

in the upper-right corner, the

general purpose knob speeds up significantly.

The Numeric Keypad

Any time the general purpose knob is set to adjust a numeric parameter, you
can enter the value as a number using the keypad instead of using the knob.

Always end the entry of a number by pressing the ENTER (

).

1Ć20

The numeric keypad also provides multipliers for engineering exponents, such
as m for milli, M for mega, and m for micro. To enter these multiplier values,
press the SHIFT button, then press the multiplier.

Getting Started

1. Press Low Ref (side).

Example 3: Automated Measurements

Displaying a Snapshot of Automated Measurements

2. On the numeric keypad, press the 2, the 0, and the ENTER (
tons, which sets the low measurement reference to 20%. Observe that
the rise-time value has changed.

3. Press Remove Measrmnt (main) ➞ All Measurements (side). That
returns the display to its original state.

You have seen how to display up to four individual automated measurements
on screen. You can also pop up a display of almost all of the automated
measurements available in the Select Measrmnts side menus. This snap­shot of measurements is taken on the waveform currently selected using the
channel selection buttons.

As when displaying individual measurements, you must have a stable display
of your signal, and that signal must have all the segments necessary for the
measurement you want.

1. Press Snapshot (main) to pop up a snapshot of all available single
waveform measurements. (See Figure 1-19).

) but-

TDS 620A, 640A, & 644A User Manual

Figure 1-19: Snapshot of Channel 1

The snapshot display includes the notation Ch 1, meaning that the mea­surements displayed are taken on the channel 1 waveform. You take a
snapshot of a waveform in another channel by first selecting that channel
using the channel selection buttons.

1Ć21

Example 3: Automated Measurements

The snapshot measurements do not continuously update. Snapshot
executes a one-time capture of all measurements and does not update
those measurements unless it is performed again.

2. Press Again (side) to do another snapshot and update the snapshot
measurements.

3. Press Remove Measrmnt (main) to remove the snapshot display. (You
can also press CLEAR MENU, but a new snapshot will be executed the
next time you display the Measure menu.)

1Ć22

Getting Started

Example 4: Saving Setups

This example shows you how to save all the settings of the digitizing oscillo­scope and how to recall the setup later to quickly re-establish the previously
saved state. The oscilloscope provides several storage locations where you
can save the setups. With the file system (optional on the TDS 620A &
TDS 640A), you can also save setups to a floppy disk.

Besides being able to save several complete setups, the digitizing oscillo­scope remembers all the parameter settings when you power it off. That
feature lets you power on and continue where you left off without having to
reconstruct the state of the digitizing oscilloscope.

Saving a Setup

First, you need to create an instrument setup you want to save. The next
several steps establish a two-waveform display with a measurement on one
waveform. The setup created is complex enough that you might prefer not to
go through all these steps each time you want that display.

1. If you are not continuing from the previous example, follow the instruc­tions on page 1-6 under the heading

2. Press SETUP ➞ Recall Factory Setup (main) ➞ OK Confirm Factory
Init (side).

3. Press ➞ AUTOSET.

4. Press MEASURE ➞ Select Measrmnt (main) ➞ Frequency (side).
(Press the –more– side menu item if the Frequency selection does not
appear in the side menu.)

5. Press CH 2 ➞ CLEAR MENU.

6. Press SETUP ➞ Save Current Setup (main) to display the Setup main
menu (see Figure 1-20).

Note that the setup locations shown in the side menu are labeled
either

user

or

factory.

user

labeled
there. If you work in a laboratory environment where several people
share the digitizing oscilloscope, check with the other users before
you overwrite their setup. Setup locations labeled
factory setup stored as a default and can be used to store current
setups without disturbing previously stored setups.

, you will overwrite the user setup previously stored

If you save your current setup in a location

Setting Up for the Examples

factory

.

have the

TDS 620A, 640A, & 644A User Manual

1Ć23

Example 4: Saving Setups

Recalling a Setup

Figure 1-20: Save/Recall Setup Menu

7. Press one of the To Setup side menu buttons to store the current instru-
ment settings into that setup location. Remember which setup location
you selected for use later.

There are more setup locations than can be listed at one time in the side
menu. The –more– side menu item gives you access to all the setup
locations.

Once you have saved a particular setup, you can change the settings as
you wish, knowing that you can come back to that setup at any time.

8. Press MEASURE ➞ Positive Width (side) to add that measurement to
the display.

To recall the setup, Press SETUP ➞ Recall Saved Setup (main) ➞ Recall
Setup (side) for the setup location you used in the last exercise. The positive

width measurement is now removed from the display because you selected it
after you saved the setup.

This completes the tutorial. You can restore the default settings by pressing
SETUP ➞ Recall Factory Setup (main) ➞ OK Confirm Factory Init (side).

1Ć24

Getting Started

Operating Basics

Overview

This section describes the basic concepts of operating the digitizing oscillo­scope. Understanding the basic concepts of your digitizing oscilloscope will
help you use it much more effectively.

The first part,
nized and gives some very general operating instructions. It also contains an
overview of all the main menus. This part includes:

H

Front Panel Map

H

Rear Panel Map

H

Display Map

H

Basic Menu Operation

H

Menu Map

The second part explains the following concepts:

H

The triggering system, which establishes conditions for acquiring sig­nals. Properly set, triggers can convert displays from unstable jumbles or
blank screens into meaningful waveforms. See

H

The acquisition system, which converts analog data into digital form.
See

H

The waveform scaling and positioning system, which changes the
dimensions of the waveform display. Scaling waveforms involves increas­ing or decreasing their displayed size. Positioning means moving them
up, down, right, or left on the display. See

forms

At a Glance

Acquisition

on page 2-25.

, quickly shows you how the oscilloscope is orga-

Triggering

on page 2-19.

Scaling and Positioning Wave-

on page 2-13.

TDS 620A, 640A, & 644A User Manual

H

The measurement system, which provides numeric information on the
displayed waveforms. You can use graticule, cursor, and automated
measurements. See

At the end of each topic,
more information can be found.

To explore these topics in more depth and to read about topics not covered in
this section, see

Reference.

Measurements

For More Information

Page 3-1 lists the topics covered.

on page 2-30.

will point you to sources where

2Ć1

Overview

2Ć2

Operating Basics

Front Panel Map —
Left Side

At a Glance

The

At a Glance

panels, and the menu system. These will help you understand and operate
the digitizing oscilloscope. This section also contains a visual guide to using
the menu system.

section contains illustrations of the display, the front and rear

File System,
page 3-55
(Optional on
TDS 640A &
TDS 620A)

ON/STBY Switch,

page 1-3

Main Menu Buttons,

page 2-7

Side Menu
Buttons,
page 2-7

CLEAR MENU
Removes Menus
from the Display

TDS 620A, 640A, & 644A User Manual

2Ć3

At a Glance

Front Panel Map —
Right Side

Cursor Measurements, page 3-17

Saving and Recalling

Waveforms, page 3-133

File System, page 3-55 (Optional

on TDS 620A & TDS 640A)

Saving and Recalling Setups,

page 3-130

Autoset, page 3-10

Help, page 3-67

Status, page 3-140

Selecting Channels,

page 3-136

Measurement System,

page 3-86

Hardcopy, page 3-59

File System, page 3-55

Color, page 3-12 (TDS 644A & TDS 524A)
Display Modes, page 3-28
Remote Communication, page 3-126

Acquisition Modes,
page 3-3

Cursor Measurements,
page 3-17

2Ć4

Waveform Math,

page 3-159

Vertical Control,

page 3-147

Zoom,

page

3-162

Horizontal Control,

Ground

page 3-68

Probe Compensation,

page 3-110

Triggering, page 3-142

Operating Basics

Rear Panel Map

Principal Power Switch,

page 1-3

Centronics Connector

(Optional on TDS 620A

& TDS 640A)

RS-232 Connector

(Optional on TDS 620A

& TDS 640A)

At a Glance

GPIB

Connector

page 3-126

Fuse,

page 1-3

Serial Number

Power Connector,

page 1-3

(Color with TDS 524A

VGA Output

& TDS 644A,

Monochrome with

TDS 620A &

TDS 640A)

Rear Panel

Connectors

(on TDS 540A &

544A only)

SIGNAL OUTPUT –

(Provides CH3 analog signal output)

AUX TRIGGER INPUT –

(Provides auxiliary trigger signal input)

MAIN TRIGGER OUTPUT –

(Provides main trigger (TTL) output)

DELAYED TRIGGER OUTPUT –

(Provides delayed trigger (TTL) output)

Security

Bracket

TDS 620A, 640A, & 644A User Manual

2Ć5

At a Glance

Display Map

The acquisition

status, page 3-3

Indicates position of

vertical bar cursors in

the waveform record,

page 3-147

Trigger position (T),

page 3-142

Shows what part of the waveform

record is displayed, page 3-68

The value entered with

the general purpose

knob

The waveform
record icon

When present, the general

purpose knob makes coarse

adjustments; when absent,

fine adjustments

Trigger level on

waveform (may be

an arrow at right

side of screen

instead of a bar)

Channel level

and waveform

source

Vertical scale,

page 3-147

The main menu with

choices of major

actions

Cursor
measurements,
page 3-17

The side menu
with choices of
specific actions

Trigger
parameters,
page 3-144

Horizontal scale
and time base
type, page 3-68

2Ć6

Operating Basics

To Operate a Menu

1. Press front-panel menu button.
(Press SHIFT first if button

label is blue.)

At a Glance

2. Press one of these buttons to

3. Press one of these buttons to

select from main menu.

select from side menu (if

displayed).

4. If side menu item has an ad­justable value (shown in re-

verse video), adjust it with the

general purpose knob or

keypad.

TDS 620A, 640A, & 644A User Manual

2Ć7

At a Glance

To Operate a Pop-Up Menu

Press

to display pop-ups.

Press it again

to make selection.

Alternatively, press

SHIFT first to make

selection in the opposite

direction.

A pop-up selection changes the

other main menu titles.

Press here to

remove menus

from screen.

2Ć8

At a Glance

Menu Map

At a Glance

Acquire Menu

(see page 3-3)

Application Menu

(see the Programmer
manual for more details)

Cursor Menu

(see page 3-17)

Delayed Trigger Menu

(see page 3-22)

Press these but­tons:

To bring up these menus:

Display Menu – Color

(TDS 524A & TDS 544A)
(see page 3-12 )

Display Menu – Display

(TDS 524A & TDS 544A)
(see page 3-28)

Display Menu – Display

(TDS 520A & TDS 540A)
(see page 3-28)

Horizontal Menu

(see page 3-68)

TDS 520A, 524A, 540A, & 544A User Manual

2Ć9

At a Glance

Hardcopy Menu

(TDS 620A & TDS 640A)
(see page 3-59)

Hardcopy Menu

(TDS 644A & TDS 524A)
(see page 3-59)

Main Trigger Menu – Edge

(see page 3-34)

Main Trigger Menu – Logic

(see page 3-78)

Main Trigger Menu –Pulse

(see page 3-119)

Press these buttons:

To bring up these menus:

Measure Menu

(see page 3-86)

More Menu

(see page 3-159)

Save/Recall Setup Menu

(see page 3-130)

Save/Recall Waveform Menu

(see page 3-133)

Status Menu

(see page 3-140)

2Ć10

Operating Basics

At a Glance

Utility Menu – Calibration

see page )

(

Utility Menu – Config

(see pages )

Utility Menu – Diagnostics

see the Service manual)

(

Utility Menu – I/O

(see page 3-126)

– GPIB

Press these buttons:

To bring up these menus:

Utility Menu – I/O

(optional on TDS 620A &
TDS 640A) (see page 3-126)

– RS232

Vertical Channel Menu

see page 3-147)

(

Zoom Menu

see page 3-162)

(

TDS 620A, 640A, & 644A User Manual

2Ć11

At a Glance

2Ć12

Operating Basics

Triggering

This section describes the edge trigger of the main trigger system and ex­plores, in a general sense, the topic of triggering. This oscilloscope also has
logic and pulse triggers in the main trigger system and a delayed trigger
system. They are described in Section 3.

Triggers determine when the digitizing oscilloscope starts acquiring and
displaying a waveform. They help create meaningful waveforms from unsta­ble jumbles or blank screens (see Figure 2-1).

Triggered Waveform Untriggered Waveforms

Trigger Sources

Figure 2-1: Triggered Versus Untriggered Displays

The trigger event establishes the time-zero point in the waveform record, and
all points in the record are located in time with respect to that point. The
digitizing oscilloscope continuously acquires and retains enough sample
points to fill the pretrigger portion of the waveform record (that part of the
waveform that is displayed
screen).

When a trigger event occurs, the digitizing oscilloscope starts acquiring
samples to build the posttrigger portion of the waveform record (displayed

after,

or to the right of, the trigger event). Once a trigger is recognized, the
digitizing oscilloscope will not accept another trigger until the acquisition is
complete.

The basic trigger is the edge trigger. An edge trigger event occurs when the

source

trigger
specified voltage

You can derive your trigger from various sources.

H

Input channels — the most commonly used trigger source is any one of
the four input channels. The channel you select as a trigger source will
function whether it is displayed or not.

(the signal that the trigger circuit monitors) passes through a

level

before,

in a specified direction (the trigger

or to the left of, the triggering event on

slope

).

TDS 620A, 640A, & 644A User Manual

2Ć13

Triggering

H

AC Line Voltage — this trigger source is useful when you are looking at
signals related to the power line frequency. Examples include devices
such as lighting equipment and power supplies. Because the digitizing
oscilloscope generates the trigger, you do not have to input a signal to
create the trigger.

H

Auxiliary Trigger — this trigger source is useful in digital design and
repair. For example, you might want to trigger with an external clock or
with a signal from another part of the circuit. To use the auxiliary trigger,
connect the external triggering signal to the Auxiliary Trigger input con­nector on the oscilloscope rear panel (TDS 640A & TDS 644A only).

Types

The digitizing oscilloscope provides three standard triggers for the main
trigger system: edge, pulse, and logic. Option 05 provides a video trigger. The
standard triggers are described in individual articles found in the
section. A brief definition of each type follows:

H

Edge — the “basic” trigger. You can use it with both analog and digital
test circuits. An edge trigger event occurs when the trigger
signal the trigger circuit is monitoring) passes through a specified voltage

level

in the specified direction (the trigger

H

Pulse — special trigger primarily used on digital circuits. Three classes of
pulse triggers are
the main trigger only.

H

Logic — special trigger primarily used on digital logic circuits. You select
Boolean operators for the trigger sources. Triggering occurs when the
Boolean conditions are satisfied. There are two kinds of logic triggers,

state

and

pattern.

only.)

H

Video — (with option 05) special trigger used on video circuits. It helps
you investigate events that occur when a video signal generates a hori­zontal or vertical sync pulse. Supported classes of video triggers include

NTSC, PAL, SECAM

width, runt,

(Logic triggers are available on the main trigger system

, and high definition TV signals.

and

glitch

slope

).

. Pulse triggering is available on

Reference

source

(the

Trigger Modes

2Ć14

The trigger mode determines how the oscilloscope behaves in the absence of
a trigger event. The digitizing oscilloscope provides two different trigger
modes,

H

normal

Normal — this trigger mode lets the oscilloscope acquire a waveform
only when it is triggered. If no trigger occurs, the oscilloscope will not
acquire a waveform. (You can push FORCE TRIGGER to force the
oscilloscope to make a single acquisition.)

and

automatic

.

Operating Basics

Triggering

H

Automatic — this trigger mode (auto mode) lets the oscilloscope acquire
a waveform even if a trigger does not occur. Auto mode uses a timer that
starts after a trigger event occurs. If another trigger event is not detected
before the timer times out, the oscilloscope forces a trigger anyway. The
length of time it waits for a trigger event depends on the time base set­ting.

Be aware that auto mode, when forcing triggers in the absence of valid trig­gering events, does not sync the waveform on the display. In other words,
successive acquisitions will not be triggered at the same point on the wave­form; therefore, the waveform will appear to roll across the screen. Of course,
if valid triggers occur the display will become stable on screen.

Since auto mode will force a trigger in the absence of one, auto mode is
useful in observing signals where you are only concerned with monitoring
amplitude level. Although the unsynced waveform may “roll” across the
display, it will not freeze as it would in normal trigger mode. Monitoring of a
power supply output is an example of such an application.

Holdoff

When a trigger event is recognized, the oscilloscope disables the trigger
system until acquisition is complete. In addition, the trigger system remains
disabled during the holdoff period that follows each acquisition. You can set
holdoff time to help ensure a stable display.

For example, the trigger signal can be a complex waveform with many possi­ble trigger points on it. Though the waveform is repetitive, a simple trigger
might get you a series of patterns on the screen instead of the same pattern
each time.

Digital pulse trains are good examples (see Figure 2-2). Each pulse looks like
any other, so many possible trigger points exist. Not all of these will result in
the same display. The holdoff period allows the digitizing oscilloscope to
trigger on the correct edge, resulting in a stable display.

TDS 620A, 640A, & 644A User Manual

2Ć15

Triggering

Trigger Points

Trigger Level

Acquisition

Interval

Holdoff Holdoff

Triggers are Not Recognized During Holdoff Time

Acquisition

Interval

Holdoff

Figure 2-2: Trigger Holdoff Time Ensures Valid Triggering

Holdoff is settable from 0% (minimum holdoff available) to 100% (maximum
available). To see how to set holdoff, see

Mode & Holdoff

minimum and maximum holdoff varies with the horizontal scale. See

Variable, Main Trigger
Verification Manual

in the TDS 520A, 524A, 540A, & 544A

, Section 2 on

Specification, T ypical Characteristics

on page 3-37. The

Holdoff,

Performance

for

typical minimum and maximum values.

Coupling

Trigger coupling determines what part of the signal is passed to the trigger
circuit. Available coupling types include AC, DC, Low Frequency Rejection,
High Frequency Rejection, and Noise Rejection:

DC coupling

H

passes all of the input signal. In other words, it passes both

AC and DC components to the trigger circuit.

AC coupling

H

passes only the alternating components of an input signal.
(AC components above 10 Hz are passed if the source channel is in
1 MW coupling; above 200 kHz are passed in 50 W coupling.) It removes
the DC components from the trigger signal.

High frequency rejection

H

removes the high frequency portion of the trig­gering signal. That allows only the low frequency components to pass on
to the triggering system to start an acquisition. High frequency rejection
attenuates signals above 30 kHz.

Low frequency rejection

H

does the opposite of high frequency rejection.

Low frequency rejection attenuates signals below 80 kHz.

Noise Rejection

H

lowers trigger sensitivity. It requires additional signal
amplitude for stable triggering, reducing the chance of falsely triggering
on noise.

2Ć16

Operating Basics

Triggering

Trigger Position

Slope and Level

The adjustable

trigger position

defines where on the waveform record the

trigger occurs. It lets you properly align and measure data within records. The

before

part of the record that occurs

after

part that occurs

the trigger is the posttrigger portion.

the trigger is the pretrigger portion. The

To help you visualize the trigger position setting, the top part of the display
has an icon indicating where the trigger occurs in the waveform record. You
select in the Horizontal menu what percentage of the waveform record will
contain pretrigger information.

Many users find displaying pretrigger information a valuable troubleshooting
technique. For example, if you are trying to find the cause of an unwanted
glitch in your test circuit, it may prove valuable to trigger on the glitch and
make the pretrigger period large enough to capture data before the glitch. By
analyzing what happened before the glitch, you may uncover clues about the
source of the glitch.

The slope control determines whether the oscilloscope finds the trigger point
on the rising or the falling edge of a signal (see Figure 2-3).

You set trigger slope by selecting Slope in the Main Trigger menu and then
selecting from the rising or falling slope icons in the side menu that appears.

Trigger Level Can be

Adjusted Vertically

The level control determines where on that edge the trigger point occurs (see
Figure 2-3).

Positive-Going Edge Negative-Going Edge

Trigger Slope Can be Positive or Negative

Figure 2-3: Slope and Level Controls Help Define the Trigger

The digitizing oscilloscope lets you set the main trigger level with the trigger

MAIN LEVEL knob.

TDS 620A, 640A, & 644A User Manual

2Ć17

Triggering

Delayed Trigger

For More Information

As mentioned earlier in this section there is also a delayed trigger system that
provides an edge trigger (no pulse or logic triggers). When using the delayed
time base, you can also delay the acquisition of a waveform for a user-speci­fied time or a user-specified number of delayed trigger events (or both) after a
main trigger event.

Delayed Triggering

See

Edge Triggering

See

Horizontal Controls

See

Logic Triggering

See

Pulse Triggering

See

Triggering

See

, on page 3-142.

, on page 3-22.

, on page 3-34.

, on page 3-68.

, on page 3-78.

, on page 3-119.

2Ć18

Operating Basics

Acquisition

Acquisition is the process of sampling the analog input signal, converting it
into digital data, and assembling it into a waveform record. The oscilloscope
creates a digital representation of the input signal by sampling the voltage
level of the signal at regular time intervals (Figure 2-4).

Sampling and Digitizing

+5.0 V

0 V 0 V 0 V 0 V

Input Signal Sampled

Points

–5.0 V

Digital

Values

+5.0 V

–5.0 V

Figure 2-4: Acquisition: Input Analog Signal, Sample, and Digitize

The sampled points are stored in memory along with corresponding timing
information. You can use this digital representation of the signal for display,
measurements, or further processing.

You specify how the digitizing oscilloscope acquires data points and as­sembles them into the waveform record.

The trigger point marks time zero in a waveform record. All record points
before the trigger event make up the pretrigger portion of the the waveform
record. Every record point after the trigger event is part of the posttrigger
portion. All timing measurements in the waveform record are made relative to
the trigger event.

TDS 620A, 640A, & 644A User Manual

Each time it takes a sample, the oscilloscope digitizer produces a numeric
representation of the signal. The number of samples may be larger than the
number of points in your waveform record. In fact, the oscilloscope may take
several samples for each record point (Figure 2-5).

Interval for One Waveform Record Point

Samples For a

Record Point

Figure 2-5: Several Points May be Acquired for Each Point Used

2Ć19

Acquisition

The digitizer can use the extra samples to perform additional processing,
such as averaging or looking for minimum and maximum values.

The digitizing oscilloscope creates a waveform record containing a user-spe­cified number of data points. Each record point represents a certain voltage
level that occurs a determined amount of time from the trigger event.

Record Length

The number of points that make up the waveform record is defined by the
record length. You can set the record length in the Horizontal menu. The
digitizing oscilloscope provides record lengths of 500, 1000, 2500, 5000, and
15000 points.

You can order option 1M that provides a maximum record length of 50,000
points. That option is available only at the time of original purchase; it cannot
be installed later.

Sampling

Sampling is the process of converting the analog input signal to digital data
for display and processing (see Figure 2-6). The two general methods of
sampling are

real-time

and

equivalent-time

.

Real-Time Sampling — In real-time sampling, the oscilloscope digitizes all

the points it acquires after one trigger event (see Figure 2-6). Use real-time
sampling to capture single-shot or transient events.

Record Points

Sampling Rate

Figure 2-6: Real-Time Sampling

Two factors that affect real-time sampling on the digitizing oscilloscope are

interleaving
Interleaving

digitizing speeds by combining the efforts of several digitizers. For example, if
you want to digitize on all channels at one time (four on the TDS 644A and
TDS 640A and two on the TDS 524A and TDS 620A), each of those channels
can digitize at a maximum real-time speed of 250 Megasamples/second (per
channel).

If you use two channels, the TDS 644A and TDS 640A oscilloscopes can
combine the efforts of two digitizers to each channel and acquire at 500
Megasamples/second (per channel).

and

interpolation

refers to the ability of the digitizing oscilloscope to attain higher

.

2Ć20

Operating Basics

Acquisition

If you focus on only one channel at the maximum possible real-time rate, the
TDS 524A and TDS 620A oscilloscopes can acquire at 500 Megasamples/
second using both its digitizers, while the TDS 644A and TDS 640A oscillo­scopes can combine all four digitizers and acquire at 1 Gigasample/second.

Depending on how many channels you are using and the speed of the time
base, at some point the digitizing oscilloscope
samples to create a waveform record. (See the discussion on page 2-22 for
more details about when that happens.) At that point, the digitizing oscillo­scope will create the waveform record in one of two ways depending on
whether you have limited the oscilloscope to real-time sampling or enabled
equivalent-time sampling (you make that choice in the Acquisition menu).

If you have restricted it to real-time sampling, the digitizing oscilloscope uses
a process called interpolation to create the intervening points in the waveform
record. There are two options for interpolation: linear or sin(x)/x.

will not be able to get enough

Linear interpolation

by using a straight line fit. It assumes all the interpolated points fall in their
appropriate point in time on that straight line. Linear interpolation is useful for
many waveforms such as pulse trains.

Sin(x)/x interpolation

actual values acquired. It assumes all the interpolated points fall along that
curve. That is particularly useful when acquiring more rounded waveforms
such as sine waves. Actually, it is appropriate for general use, although it may
introduce some overshoot or undershoot in signals with fast rise times.

computes record points between actual acquired samples

computes record points using a curve fit between the

NOTE

When using either type of interpolation, you may wish to set the
display style so that the real samples are displayed intensified
relative to the interpolated samples. The instructions under

on page 3-28 explain how to turn on intensified samples.

Style

Display

Equivalent-Time Sampling — The digitizing oscilloscope only uses

equivalent-time sampling if you have enabled the equivalent-time option in the
Acquisition menu
which to create a waveform record.

and the oscilloscope is not able to get enough samples with

TDS 620A, 640A, & 644A User Manual

In equivalent-time (ET) sampling the oscilloscope acquires samples over
many repetitions of the event (Figure 2-7). It should only be used on repetitive
signals.

2Ć21

Acquisition

Record Points

1st Acquisition Cycle

2nd Acquisition Cycle

3rd Acquisition Cycle

nth Acquisition Cycle

Figure 2-7: Equivalent-Time Sampling

The oscilloscope takes a few samples with each trigger event and eventually
constructs a waveform record using the samples from multiple acquisitions.
That feature lets you accurately acquire signals with frequencies much higher
than the digitizing oscilloscope real-time bandwidth.

Selecting Sampling Mode

The digitizing oscilloscope uses a type of equivalent-time sampling called

random equivalent-time sampling

. Although the samples are taken sequential­ly in time, they are random with respect to the trigger. That is because the
oscilloscope sample clock runs asynchronously with respect to the input
signal and the signal trigger. The oscilloscope takes samples independent of
the trigger position and displays them based on the time difference between
the sample and the trigger.

The sampling speeds and the number of channels you choose affect the
mode the digitizing oscilloscope uses to sample waveforms. Basically, if the
time base is 200 ns or slower, the digitizing oscilloscope uses real-time sam­pling for creating waveform records when Fit to Screen is off.

When the time base is faster than 50 ns, the digitizing oscilloscope creates
waveform records using equivalent-time sampling or interpolation. For speeds
between 200 ns and 20 ns, the digitizing oscilloscope creates waveform
records differently depending on the number of input channels and type of
oscilloscope you are using (see Table 2-1).

2Ć22

Operating Basics

Table 2-1: Sampling Mode Selection —

100 ns/Div to 50 ns/Div (When Fit to Screen is Off)

Acquisition

Acquisition Modes

Instrument and
Number of Channels

TDS 544A & 540A,
any 1 channel

TDS 544A & 540A,
any 2 channels

TDS 544A & 540A,
3 or more channels

TDS 524A & 520A,
any 1 channel

TDS 524A & 520A, any
2 channels

The digitizing oscilloscope supports five acquisition modes.

Sample

H

H

Peak Detect

H

Hi Res

100 ns/Div 50 ns/Div

Real-time Real-time

Real-time Equivalent-time or

interpolated real-time

Equivalent-time or
interpolated real-time

Real-time Equivalent-time or

Equivalent-time or
interpolated real-time

Equivalent-time or
interpolated real-time

interpolated real-time
Equivalent-time or

interpolated real-time

Bandwidth

Coupling

H

Envelope

H

Average

Sample acquisition mode, which acquires in real time, is the mode most
commonly used. You can read about Sample and the other acquisition modes

Acquisition Modes,

in

Bandwidth

and display accurately (that is, with less than 3 dB attenuation).
You can set different bandwidths with the digitizing oscilloscope. Lower band-

width settings let you eliminate the higher frequency components of a signal.
The TDS 600A series offers Full (500 MHz), 100 MHz, and 20 MHz band­width settings.

You can couple your input signal to the digitizing oscilloscope three ways. You
can choose between AC, DC, or Ground (GND). You can also set the input
impedance.

H

H

refers to the range of frequencies that an oscilloscope can acquire

DC coupling shows both the AC and DC components of an input signal.
AC coupling shows only the alternating components of an input signal.

beginning on page 3-3.

TDS 620A, 640A, & 644A User Manual

2Ć23

Acquisition

For More Information

H

Ground (GND) coupling disconnects the input signal from the acquisition.

H

Input impedance lets you select either 1 MW or 50 W impedance.

NOTE

If you select 50 Wimpedance with AC coupling, the digitizing oscillo­scope will not accurately display frequencies under 200 kHz.

See

Scaling and Positioning Waveforms
Acquisition Modes

See

, on page 3-3.

, on page 2-25.

2Ć24

Operating Basics

Scaling and Positioning Waveforms

Record View

Channel Reference Icon

Scaling and positioning waveforms means increasing or decreasing their
displayed size and moving them up, down, right, and left on the display.

Two display icons, the channel reference indicator and the record view, help
you quickly see the position of the waveform in the display (see Figure 2-8).
The channel reference icon points to the ground of the waveform record when
offset is set to 0 V. This is the point about which the waveform contracts or
expands when the vertical scale is changed. The record view, at the top of the
display, indicates where the trigger occurs and what part of the waveform
record is displayed.

Original Position Positioned Vertically Positioned Horizontally

Original Scale Scaled Horizontally

Figure 2-8: Scaling and Positioning

Scaled

Vertically

TDS 620A, 640A, & 644A User Manual

2Ć25

Scaling and Positioning Waveforms

Vertical System

You can adjust the vertical position of the selected waveform by moving it up
or down on the display. For example, when trying to compare multiple wave­forms, you can put one above another and compare them, or you can overlay
the two waveforms on top of each other. To move the selected waveform turn
the vertical POSITION knob.

You can also alter the vertical scale. The digitizing oscilloscope shows the
scale (in volts per division) for each active channel toward the bottom left of
the display. As you turn the vertical SCALE knob clockwise, the value de­creases resulting in higher resolution because you see a smaller part of the
waveform. As you turn it counter-clockwise the scale increases allowing you
to see more of the waveform but with lower resolution.

Besides using the position and scale knobs, you can set the vertical scale and
position with exact numbers. You do that with the Vertical menu Fine Scale
and Position selections and the general purpose knob and/or the keypad.

Offset

Vertical offset changes where the channel reference indicator is shown with
respect to the graticule. Offset adds a voltage to the reference indicator
without changing the scale. That feature allows you to move the waveform up
and down over a large area without decreasing the resolution.

Offset is useful in cases where a waveform has a DC bias. One example is
looking at a small ripple on a power supply output. You may be trying to look
at a 100 mV ripple on top of a 15 V supply. The range available with offset
can prove valuable as you try to move and scale the ripple to meet your
needs.

Horizontal System

2Ć26

Adjusting the horizontal position of waveforms moves them right or left on the
display. That is useful when the record length of the waveform is so large
(greater than 500 points) that the digitizing oscilloscope cannot display the
entire waveform record at one time. You can also adjust the scale of the
waveform. For example, you might want to see just one cycle of a waveform
to measure the overshoot on its rising edge.

You adjust the horizontal scale of the displayed waveform records using the
horizontal SCALE knob and the horizontal position using the horizontal
POSITION knob.

The digitizing oscilloscope shows the actual scale in the bottom right of the
display. The scale readout shows the time per division used. Since all live
waveforms use the same time base, the digitizing oscilloscope only displays
one value for all the active channels.

Operating Basics

Actual High-Frequency Waveform

Apparent Low-Frequency

Waveform Due to Aliasing

Sampled Points

Scaling and Positioning Waveforms

Aliasing

When

aliasing

actual waveform being input or a waveform is not stable even though the light
next to TRIG’D is lit. Aliasing occurs because the oscilloscope cannot sample
the signal fast enough to construct an accurate waveform record (Figure 2-9).

happens, you see a waveform with a frequency lower than the

Figure 2-9: Aliasing

One simple way to check for aliasing is to slowly change the horizontal scale
(time per division setting). If the shape of the displayed waveform changes
drastically, you may have aliasing.

In order to represent a signal accurately and avoid aliasing, you must sample
the signal more than twice as fast as the highest frequency component. For
example, a signal with frequency components of 500 MHz would need to be
sampled at a rate faster than 1 Gigasamples/second.

There are various ways to prevent aliasing. Try adjusting the horizontal scale,
or simply press the AUTOSET button. You can also counteract some aliasing
by changing the acquisition mode in the Acquisition menu. For example, if
you are using the sample mode and suspect aliasing, you may want to
change to the peak detect mode. Since the peak detect mode searches for
samples with the highest and lowest values, it can detect faster signal compo­nents over time.

Delayed Time Base

You can set a main time base and a delayed time base. Each time base has
its own trigger. There are two types of delayed time base acquisitions. Each
type is based on its triggering relationship to the main time base. These are
delayed runs after main and delay triggerable (after time, events, or both)
acquisitions.

TDS 620A, 640A, & 644A User Manual

The delayed time base is useful in displaying events that follow other events.
See

Triggering

on page 2-13 for more information on the delayed trigger.

2Ć27

Scaling and Positioning Waveforms

Real Time

Fast Frame

FastFrame

You can define and enable FastFrameTM (also called “segmented memory”)
on the TDS 600A. This feature lets you capture multiple acquisitions in the
acquisition memory of a single channel. Figure 2-10 shows how FastFrame
combines the desired captured records into one larger record. For example,
FastFrame would let you store 10 records of 500 samples each into one
record with a 5000 sample length.

TM

Figure 2-10: Fast Frame

Zoom

Autoset

You can use zoom to see more detail without changing the acquired signal.
When you press the ZOOM button, a portion of the waveform record can be
expanded or compressed on the display, but the record points stay the same.

Zoom is very useful when you wish to temporarily expand a waveform to
inspect small feature(s) on that waveform. For example, you might use zoom
to temporarily expand the front corner of a pulse to inspect its aberrations.
Use zoom to expand it horizontally and vertically. After you are finished, you
can return to your original horizontal scale setting by pressing one menu
button. (The zoom feature is also handy if you have acquired a waveform
while using the fastest time per division and want to further expand the wave­form horizontally.)

Autoset lets you quickly obtain a stable waveform display. It automatically
adjusts a wide variety of settings including vertical and horizontal scaling.
Other settings affected include trigger coupling, type, position, slope, and
mode and display intensities.
autoset does.

Autoset

on page 3-10 describes in detail what

2Ć28

Operating Basics

For More Information

See

Autoset
Delayed Triggering

See

, on page 3-10.

Scaling and Positioning Waveforms

, on page 3-22.

Horizontal Control

See

Vertical Control

See

Zoom

See

, on page 3-162.

, on page 3-68.

, on page 3-147.

TDS 620A, 640A, & 644A User Manual

2Ć29

Measurements

The digitizing oscilloscope not only displays graphs of voltage versus time, it
also can help you measure the displayed information (see Figure 2-11).

Measurement Sources

Automated

Measurements

Ch 1

Frequency

100 MHz

Ch 1 Period

10 ns

Graticule

Cursors

Cursor

Readouts





 

Figure 2-11: Graticule, Cursor and Automated Measurements

The oscilloscope provides three measurement classes. They are: automated,
cursors, and graticule measurements.

2Ć30

Automated Measurements

You make automated measurements merely by pressing a few buttons. The
digitizing oscilloscope does all the calculating for you. Because these mea­surements use the waveform record points, automated measurements are
more accurate than cursor or graticule measurements.

Press the MEASURE button for the automated measurement menus. These
menus let you make

amplitude

(typically in seconds or hertz), and
can select and display up to four measurements at a time. (See Table 3-5 on
page 3-86 for a list of all the automatic measurements and their definitions.)

You can make automated measurements on the entire waveform record or
just on a specific part. The gating selection in the Measurement menu lets
you use the vertical cursors to limit the measurement to a section of the
waveform record.

(typically in volts; sometimes in %),

area

(in volt-seconds) measurements. You

Operating Basics

time

Measurements

The snapshot selection in the Measurement menu lets you display almost all
of the measurements at once. You can read about snapshot under

of Measurements,

on page 3-95.

Snapshot

Automated measurements use readouts to show measurement status. These
readouts are updated as the oscilloscope acquires new data or if you change
settings.

Cursor Measurements

Cursors are fast and easy-to-understand measurements. You take measure­ments by moving the cursors and reading their numeric values from the on
screen readouts, which update as you adjust the position of the cursors.

active

Cursors appear in pairs. One cursor is

and the other
move the active cursor (the solid line) using the general purpose knob. The
SELECT button lets you select (toggle) which cursor bar is active or inactive.
The inactive cursor is a dashed line on the display.

To get the cursor menu, press the CURSOR button. There are three kinds of
cursors available in that menu:

inactive

. You

Independent Mode

H

H

H

There are also two modes for cursor operation available in the cursor me­nu —

Only Selected Cursor

Moves

Horizontal bar cursors
Vertical bar cursors

measure vertical parameters (typically volts).

measure horizontal parameters (typically time or

frequency).

Paired cursors

measure both vertical parameters (typically volts) and

horizontal parameters (typically time or frequency).

independent

and

tracking

Tracking Mode

(See Figure 2-12).

Both Cursors Move

in Tandem

Figure 2-12: Cursor Modes

TDS 620A, 640A, & 644A User Manual

Independent mode

H

one

move

cursor at a time (the active cursor) using the general purpose

cursors operate as was earlier described; that is, you

knob, and you use the SELECT button to toggle which cursor is active.

2Ć31

Measurements

H

Tracking mode

same time using the general purpose knob. To adjust the solid cursor
relative to the dashed cursor, you push the SELECT button to suspend
cursor tracking and use the general purpose knob to make the adjust­ment. A second push toggles the cursors back to tracking.

cursors operate in tandem: you move

both

cursors at the

You can read more detailed information about how to use cursors in

Measurements,

beginning on page 3-17.

Cursor

Graticule Measurements

Graticule measurements provide you with quick, visual estimates. For exam­ple, you might look at a waveform amplitude and say “it is a little more than
100 mV.”

You can perform simple measurements by counting the number of major and
minor graticule divisions involved and multiplying by the scale factor.

For example, if you counted five major vertical graticule divisions between the
minimum and maximum values of a waveform and knew you had a scale
factor of 100 mV/division, then you could easily calculate your peak-to-peak
voltage:

5 divisions × 100 mV/division = 500 mV.

NOTE

AUX 1 and AUX 2 (TDS 524A & TDS 620A) can not be set to the
volts per division needed to match video graticules.

For More Information

When you select the NTSC graticule, the volts per division of all selected
channels is set to 143 mV/div (152 mV/div for PAL) where the divisions are
those of the conventional graticule, not the divisions of the video graticules.
For NTSC, the actual grid lines represent 10 IRE, and for PAL the lines are
100 mV apart.

Appendix B: Algorithms

See
oscilloscope calculates each automatic measurement.

Cursor Measurements

See
measurements.

Measurement System

See
measurements.

Tutorial Example 3: Automated Measurements

See
information on automatic measurements.

Waveform Math

See
waveforms.

, on page 3-159, for using cursors to measure math

, on page A-9, for details on how the digitizing

, on page 3-17, for more information on cursor

, on page 3-86, for more information on automatic

, on page 1-17, for more

2Ć32

Operating Basics

Reference

Overview

This section describes the details of operating the digitizing oscilloscope. It
contains an alphabetical list of tasks you can perform with the digitizing
oscilloscope. Use this section to answer specific questions about instrument
operation. These tasks include:



Acquisition Modes



Autoset



Color



Cursor Measurements



Delayed Triggering



Display Modes



Edge Triggering



Fast Fourier Trans-

forms



File System



Hardcopy



Help



Horizontal Control



Limit Testing



Logic Triggering



Measurement System

H Probe Cal



Probe Compensation



Probe Selection



Pulse Triggering



Remote Communication



Saving and Recalling Setups



Saving and Recalling Wave-

forms



Selecting Channels



Signal Path Compensation



Status



Triggering



Vertical Control



Waveform Differentiation



Waveform Integration



Waveform Math

TDS 620A, 640A, & 644A User Manual



Zoom

Many of these tasks list steps you perform to accomplish the task. You should

Conventions

read

on page ii of

Welcome

before reading about these tasks.

3Ć1

Overview

3Ć2

Reference

Acquisition Modes

The acquisition system has several options for converting analog data into
digital form. The Acquisition menu lets you determine the acquisition mode,
whether or not to permit equivalent time sampling, and how to start and stop
acquisitions.

Description of Modes

The digitizing oscilloscope supports five acquisition modes.

Sample

H

H

Peak Detect

H

Hi Res

H

Envelope

H

Average

The Sample, Peak Detect, and Hi Res modes operate in real-time on a single
trigger event, provided the digitizing oscilloscope can acquire enough samples
for each trigger event. Envelope and Average modes operate on multiple
acquisitions. The digitizing oscilloscope averages or envelopes several wave­forms on a point-by-point basis.

Figure 3-1 illustrates the different modes and lists the benefits of each. It will
help you select the appropriate mode for your application.

Sample Mode

In Sample mode, the oscilloscope creates a record point by saving the first
sample (of perhaps many) during each acquisition interval. (An acquisition
interval is the time covered by the waveform record divided by the record
length.) This is the default mode.

TDS 620A, 640A, & 644A User Manual

Peak Detect Mode

Peak Detect mode alternates between saving the highest sample in one
acquisition interval and lowest sample in the next acquisition interval. Peak
Detect mode only works with real-time, non-interpolated sampling.

If you set the time base so fast that it requires real-time interpolation or
equivalent-time sampling, the mode automatically changes from Peak Detect
to Sample, although the menu selection will not change.

3Ć3

Acquisition Modes

Single Waveform Acquisition

Samples Acquired in Four

Acquisition Intervals

Interval 1 2 3 4

Use to reveal aliasing and for glitch detection.

Provides the benefits of enveloping with the

Provides the benefits of averaging

with the speed of a single acquisition.

Acquisition

Mode

Sample

Uses first sample

in interval

Use for fastest acquisition rate.

This is the default mode.

Peak Detect

Uses highest and lowest
samples in two intervals

speed of a single acquisition.

Hi Res

Calculates average of all

samples in interval

Use to reduce apparent noise.

Displayed

Record Points

Waveform

Drawn on CRT

Three Acquisitions from One Source

Acquisition

1

Uses Peak Detect Mode for Each Acquisition

Uses Sample Mode for Each Acquisition

23

Figure 3-1: How the Acquisition Modes Work

Multiple Waveform Acquisitions

Acquisition

Mode

Envelope

Finds highest and

lowest record points over

many acquisitions

Use to reveal variations

in the signal across time.

Average

Calculates average value for
each record point over many

acquisitions

Use to reduce apparent noise

in a repetitive signal.

Waveform

Drawn on CRT

3Ć4

Reference

Acquisition Modes

Hi Res Mode

In Hi Res mode, the digitizing oscilloscope averages all samples taken during
an acquisition interval to create a record point. That average results in a
higher-resolution, lower-bandwidth waveform.

This mode only works with real-time, non-interpolated sampling. If you set the
time base so fast that it requires real-time interpolation or equivalent-time
sampling, the mode automatically becomes Sample, although the menu
selection will not change.

A key advantage of Hi Res is its potential for increasing resolution regardless
of the input signal. Table 3-1 and the equations shown below illustrate how
you can obtain up to 15 significant bits with Hi res mode. Note that the resolu­tion improvements are limited to speeds slower than 400 ns/div. Also, resolu­tions above 15 bits are not allowed by internal hardware and computation
limitations.

Si = Sampling Interval for TDS 500A = 4ns

ą

D

t = Sample Interval

=

TimeńDiv

Number Of Points/Div

Nd = Number of points per decimation interval
Resolution Enhancement (bits) =

Table 3-1: Additional Resolution Bits

Time Base Speed

400 ns and faster 8 bits
1 ms to 2 ms 9 bits

5 ms to 10 ms 10 bits
20 ms to 50 ms 11 bits
100 ms to 200 ms 12 bits
500 ms 13 bits
1 ms to 2 ms 14 bits
5 ms and slower 15 bits

0.5 LOG2(Nd)

Bits of Resolution

= = 100

D

t

=

Si

ns

= 25

2 extra bits

TDS 620A, 640A, & 644A User Manual

Envelope Mode

Envelope mode lets you acquire and display a waveform record that shows
the extremes in variation over several acquisitions. You specify the number of
acquisitions over which to accumulate the data. The oscilloscope saves the
highest and lowest values in two adjacent intervals similar to the Peak Detect
mode. But Envelope mode, unlike Peak Detect, gathers peaks over many
trigger events.

3Ć5

Acquisition Modes

After each trigger event, the oscilloscope acquires data and then compares
the min/max values from the current acquisition with those stored from pre­vious acquisitions. The final display shows the most extreme values for all the
acquisitions for each point in the waveform record.

Average Mode

Average mode lets you acquire and display a waveform record that is the
averaged result of several acquisitions. This mode reduces random noise.
The oscilloscope acquires data after each trigger event using Sample mode.
It then averages the record point from the current acquisition with those
stored from previous acquisitions.

Acquisition Readout

Acquisition Readout

The acquisition readout at the top of the display (Figure 3-2) shows the state
of the acquisition system (running or stopped). The “running” state shows the
sample rate and acquisition mode. The “stopped” state shows the number of
acquisitions acquired since the last stop or major change.

3Ć6

Figure 3-2: Acquisition Menu and Readout

Reference

Acquisition Modes

Operation

To bring up the acquisition menu (Figure 3-2) press SHIFT ACQUIRE MENU.

Acquisition Mode

To choose how the digitizing oscilloscope will create points in the waveform
record:

Press SHIFT ACQUIRE MENU ➞ Mode (main) ➞ Sample, Peak Detect, Hi
Res, Envelope, or Average (side).

When you select Envelope or Average, you can enter the number of wave­form records to be enveloped or averaged using the keypad or the general
purpose knob.

NOTE

If you selected the longest record length available in the Horizontal
menu, then you cannot select Hi Res as your acquisition mode. This
is because Hi Res mode uses twice the acquisition memory that the
other acquisition modes use. If Hi Res and the longest horizontal
record length were allowed to be selected at the same time, the
oscilloscope would run out of memory.

Repetitive Signal

To limit the digitizing oscilloscope to real-time sampling or let it choose be­tween real-time or equivalent-time sampling:

Press SHIFT ACQUIRE MENU ➞ Repetitive Signal (main) ➞ ON or OFF
(side).

H

ON (Enable ET) uses both the real time and the equivalent time features
of the digitizing oscilloscope.

H

OFF (Real Time Only) limits the digitizing oscilloscope to real time
sampling. If the digitizing oscilloscope cannot accurately get enough
samples for a complete waveform, the oscilloscope will use the interpola­tion method selected in the display menu to fill in the missing record
points. That is, it will use either the linear or sin(x)/x interpolation algo­rithm.

See

Acquisition

on page 2-19 for details about sampling.

Stop After

You can choose to acquire exactly one waveform sequence or to acquire
waveforms continuously under manual control.

Press SHIFT ACQUIRE MENU ➞ Stop After (main) ➞ RUN/STOP button
only, Single Acquisition Sequence, or Limit Test Condition Met (side)
(see Figure 3-3).

TDS 620A, 640A, & 644A User Manual

3Ć7

Acquisition Modes

Figure 3-3: Acquire Menu — Stop After

H

RUN/STOP button only (side) lets you start or stop acquisitions by
toggling the RUN/STOP button. Pressing the RUN/STOP button once will
stop the acquisitions. The upper left hand corner in the display will say
Stopped and show the number of acquisitions. If you press the button
again, the digitizing oscilloscope will resume taking acquisitions.

H

Press Single Acquisition Sequence (side). That selection lets you run a

single sequence of acquisitions by pressing the RUN/STOP button. In
Sample, Peak Detect, or Hi Res mode, the digitizing oscilloscope will
acquire a waveform record with the first valid trigger event and stop.

In Envelope or Average mode, the digitizing oscilloscope will make the
specified number of acquisitions to complete the averaging or enveloping
task.

If the oscilloscope is in equivalent-time mode and you press Single
Acquisition Sequence (side), it will continue to recognize trigger events
and acquire samples until the waveform record is filled.

Hint: To quickly select Single Acquisition Sequence without displaying the
Acquire and Stop After menus, press SHIFT FORCE TRIG. Now the

RUN/STOP button operates as just described. (You still must display the

Acquire menu and then the Stop After menu to leave Single Acquisition

Sequence operation.)

3Ć8

Reference

Acquisition Modes

H

Limit Test Condition Met (side) lets you acquire waveforms until wave-

form data exceeds the limits specified in the limit test. Then acquisition

stops. At that point, you can also specify other actions for the oscillo-

scope to take, using the selections available in the Limit Test Setup

main menu.

NOTE

In order for the digitizing oscilloscope to stop an acquisition when
limit test conditions have been met, limit testing must be turned
using the

Setting up limit testing requires several more steps. You can create the

template waveform against which to compare incoming waveforms, using

the Create Limit Test Template main menu item. You can then specify

that the comparison is to be made, and the channel to compare against

the template, using the Limit Test Sources main menu item.

Limit Test Setup

main menu.

ON

,

For More Information

Acquisition

See
See

Limit Testing

, on page 2-19.

, on page 3-73.

TDS 620A, 640A, & 644A User Manual

3Ć9

Autoset

The autoset function lets you quickly obtain and display a stable waveform of
usable size. Autoset automatically sets up the front panel controls based on
the characteristics of the input signal. It is much faster and easier than a
manual control-by-control setup.

Autoset makes adjustments in these areas:

H

Acquisition

H

Display

H

Horizontal

H

Trigger

H

Vertical

NOTE

Autoset may change vertical position in order to position the wave­form appropriately. It always sets vertical offset to 0 V.

Operation

Autoset Defaults

1. Press the Channel Selection button (such as CH 1) corresponding to your
input channel to make it active.

2. Press AUTOSET.

If you use autoset when one or more channels are displayed, the digitizing
oscilloscope selects the lowest numbered channel for horizontal scaling and
triggering. Vertically, all channels in use are individually scaled.

If you use autoset when no channels are displayed, the digitizing oscilloscope
will turn on channel one (CH 1) and scale it.

Table 3-2 on the following page lists the autoset defaults.

3Ć10

Reference

Table 3-2: Autoset Defaults

Autoset

Control

Changed by Autoset to

Selected channel Numerically lowest of the displayed

channels

Acquire Mode Sample
Acquire Repetitive Signal On
Acquire Stop After RUN/STOP button only
Display Style Vectors
Display Intensity — Overall

If less than 50%, set to 75%

(TDS 640A & TDS 620A)
Display Format YT
FastFrame

TM

Off
Horizontal Position Centered within the graticule window
Horizontal Scale As determined by the signal frequency
Horizontal Time Base Main Only
Horizontal Record Length Unchanged
Limit Test Off
Trigger Position Unchanged
Trigger Type Edge
Trigger Source Numerically lowest of the displayed

channels (the selected channel)
Trigger Level Midpoint of data for the trigger source
Trigger Slope Positive
Trigger Coupling DC
Trigger Holdoff 0
Vertical Scale As determined by the signal level
Vertical Coupling DC unless AC was previously set.

AC remains unchanged.
Vertical Bandwidth Full
Vertical Offset 0 volts
Zoom Off

TDS 620A, 640A, & 644A User Manual

3Ć11

Color (TDS 524A & TDS 644A)

The TDS 524A & TDS 644A can display information in different colors. The
Color menu lets you choose palettes of colors and decide what colors to
assign to what pieces of information.

Operation

To bring up the Color menu:

1. Press DISPLAY to show the Display menu.

2. Press Settings in the main menu until you select Color from the pop-up
menu (see Figure 3-4).

3Ć12

Figure 3-4: Display Menu — Setting

Color lets you alter color settings for various display components such as

waveforms and text. Display lets you adjust the style, intensity level, grati­cule, and format features. For more information on display, see
page 3-28.

Display

on

Reference

Color

Choose Palette

You can choose a palette of 13 colors from a menu of pre-set palettes.

1. Choose the starting palette by selecting Palette from the main menu.

2. Select one of the available palettes in the side menu. Choose from Nor-
mal, Bold, Hardcopy Preview or Monochrome.

3. If you are using a persistence display and wish to vary the color of each
point depending on its persistence, choose Persistence Palettes. Then
choose Temperature, Spectral, or Gray Scale from the resulting side
menu. Choose View Palette to preview your selection on the display.
Press Persistence Palette to quit preview mode. Press Clear Menu to
return to the Palette menu.

NOTE

Use at higher room temperatures or with higher intensity display
formats, such as the white fields in the Hardcopy Preview palette,
can temporarily degrade display quality.

You can select the Hardcopy Preview palette when using certain
color hardcopy formats. The default colors in the hardcopy preview
palette comprise a white background and fully saturated primary
colors which generally produce the best result.

Change Palette Colors

You can change the current palette colors. You do this by selecting a color
and varying its hue, lightness, and saturation. Hue is the wavelength of light
reflected from the surface. It varies continuously along the color spectrum as
produced by a rainbow. Lightness refers to the amount of light reflected from
the surface. It varies from black, to the nominal color, to white. Saturation is
the intensity of color. Completely desaturated color is gray. Completely satu­rated color of any hue is that color at its most intense level.

1. Select the main menu Change Colors item (see Figure 3-5).

TDS 620A, 640A, & 644A User Manual

3Ć13

Color

ScrTxt

Figure 3-5: Display Menu — Palette Colors

2. Select one of the 13 colors by pressing (repeatedly) Color in the side
menu.

3. If you want to use the factory default for this color, press the side menu
Reset to Factory Color.

4. Choose Hue from the side menu and use the general purpose knob or
keypad to select the desired hue. Values range from 0 to 359. Sample
values are: 0 = blue, 60 = magenta, 120 = red, 180 = yellow, 240 = green,
and 360 = cyan.

5. Choose Lightness from the side menu and use the general purpose
knob or keypad to select the lightness you desire. A value of 0 results in
black. A value of 50 provides the nominal color. A value of 100 results in
white.

6. Choose Saturation from the side menu and use the general purpose
knob or keypad to select the saturation you desire. A value of 100 pro­vides a pure color. A value of 0 provides gray.

Set Math Waveform Color

3Ć14

To define math waveform colors:

1. Choose to define math waveform colors by selecting the main menu Map
Math item.

2. Select one of the three math waveforms by pressing Math in the side
menu.

Reference

Color

3. If you want to assign the selected math waveform to a specific color,
press Color and cycle through the choices.

4. If you want the selected math waveform to be the same color as the
waveform it is based on, select Color Matches Contents. If the math
waveform is based on dual waveforms, the math waveform will use the
color of the first constituent waveform.

To return to the factory defaults, select Reset to Factory Color.

Set Reference Waveform Color

To define reference waveform colors:

1. Press Map Reference in the main menu (see Figure 3-6).

2. Select one of the four reference waveforms by pressing Ref in the side
menu.

3. To assign the selected reference waveform to a specific color, press
(repeatedly) Color and choose the value.

4. To make the selected reference waveform the same color as the wave­form it is based on, select Color Matches Contents.

To return to the factory defaults, select Reset to Factory Color.

TDS 620A, 640A, & 644A User Manual

Figure 3-6: Display Menu — Map Reference Colors

3Ć15

Color

Select Options

To define what color to show where a waveform crosses another waveform:

1. Press the Options main menu item.

2. Select that you wish to use a special color to mark collision zones by
toggling Collision Contrast in the side menu to ON.

Restore Colors

To restore colors to their factory default settings:

1. Press the main menu Restore Colors item (see Figure 3-7).

2. Select what you wish to restore by pressing Reset Current Palette To

Factory, Reset All Palettes To Factory or Reset All Mappings To
Factory in the side menu.

For More Information

3Ć16

Display Modes,

See

Figure 3-7: Display Menu — Restore Colors

on page 3-28.

Reference

Cursor Measurements

Use the cursors to measure the difference (either in time or voltage) between
two locations in a waveform record.

Description

Horizontal Bar Cursors Vertical Bar Cursors

Cursors are made up of two markers that you position with the general pur­pose knob. You move one cursor independently or both cursors in tandem,
depending on the cursor mode. As you position the cursors, readouts on the
display report measurement information.

There are three cursor types:
ure 3-8).

Horizontal bar cursors
Vertical bar cursors

cy).

Figure 3-8: Cursor Types

horizontal bar, vertical bar,

measure vertical parameters (typically volts).

measure horizontal parameters (typically time or frequen-

and

paired

Paired Cursors

(Fig-

TDS 620A, 640A, & 644A User Manual

Paired cursors

tal parameters (typically time) simultaneously.
Look at Figure 3-8. Note that each of the two paired cursors has a long

vertical bar paired with an
volts); the long vertical bars measure horizontal parameters (typically time or
frequency). (See

measure both vertical parameters (typically volts) and horizon-

X

. The Xs measures vertical parameters (typically

Cursor Readouts

on page 3-18 for more information.)

3Ć17

Cursor Measurements

NOTE

When cursors measure certain math waveforms, the measurement
may not be of time, frequency, or voltage. Cursor measurement of
those math waveforms that are not of time, frequency, or voltage is
described in Waveform Math, which begins on page 3-159.

Independent Mode

There are two cursor modes:

Only Selected Cursor

Moves

In independent mode you move only one cursor at a time using the general
purpose knob. The active, or selected, cursor is a solid line. Press SELECT
to change which cursor is selected.

In tracking mode you normally move both cursors in tandem using the general
purpose knob. The two cursors remain a fixed distance (time or voltage) from
each other. Press SELECT to temporarily suspend cursor tracking. You can
then use the general purpose knob to adjust the distance of the solid cursor
relative to the dashed cursor. A second push toggles the cursors back to
tracking.

independent

Tracking Mode

Figure 3-9: Cursor Modes

and

tracking

(see Figure 3-9).

Both Cursors Move

in Tandem

Cursor Readouts

3Ć18

The cursor readout shows the absolute location of the selected cursor and the
difference between the selected and non-selected cursor. The readouts differ
depending on whether you are using H Bars or V Bars.

H

H Bars:

the value after D shows the voltage difference between the
cursors. The value after @ shows the voltage of the selected cursor
relative to ground (see Figure 3-10). With the video trigger option, you
can also display the voltage in IRE units.

H

V Bars:

the value after

D shows the time (or frequency) difference be-

tween the cursors. The value after @ shows the time (frequency) of the
selected cursor relative to the trigger point. With the video trigger option,
you can also display the line number.

Reference

Cursor Readout (H Bars)

Non-selected Cursor

(Dashed Line)

Cursor Measurements

In FastFrame mode, the @ shows the time position of the selected cursor
relative to the trigger point of the frame that the selected cursor is in. The

D

shows the time difference between the two cursors only if both cursors

are in the same frame.

H

Paired: the value after one D shows the voltage difference between the

X

the two

s; the other

D shows the time (or frequency) difference between

the two long vertical bars. The value after @ shows the voltage at the
of the selected cursor relative to ground (see Figure 3-11).

In FastFrame mode, the D shows the time difference between the two
cursors only if both cursors are in the same frame.

X

Operation

Selected Cursor

(Solid Line)

Figure 3-10: H Bars Cursor Menu and Readouts

Paired cursors can only show voltage differences when they remain on
screen. If the paired cursors are moved off screen horizontally, Edge will
replace the voltage values in the cursor readout.

To take cursor measurements, press CURSOR to display the Cursor menu
(Figure 3-10).

TDS 620A, 640A, & 644A User Manual

Function

Select the type of cursors you want using the Function menu item:
Press CURSOR ➞ Function (main) ➞ H Bars, V Bars, Paired, or Off (side).

3Ć19

Cursor Measurements

Position of Vertical Bar Cursors

(Useful for Locating Cursors

Outside the Display)

Cursor Readout (Paired)

Non-selected Cursor

(Dashed Vertical Bar)

(Solid Vertical Bar)

Selected Cursor

Figure 3-11: Paired Cursor Menu and Readouts

Mode

Select the cursor mode you want using the Mode menu item.

1. Press CURSOR ➞ Mode (main) ➞ Independent or Tracking (side):

H

Independent makes each cursor positionable without regard to the
position of the other cursor.

H

Tracking makes both cursors positionable in tandem; that is, both
cursors move in unison and maintain a fixed horizontal or vertical
distance between each other.

2. Use the general purpose knob to move the selected (active) cursor if
Independent was selected in step 1. Press SELECT to change which
cursor is active and moves. A solid line indicates the active cursor, and a
dashed line the inactive cursor.

or
Use the general purpose knob to move both cursors in tandem if Track-

ing was selected in step 1. Press SELECT to temporarily suspend cursor
tracking; then use the general purpose knob to adjust the distance of the
solid cursor relative to the dashed cursor. Press SELECT again to re-
sume tracking. A solid line indicates the adjustable cursor and a dashed
line the fixed cursor.

3Ć20

Reference

Cursor Measurements

Time Units

You can choose to display vertical bar cursor results in units of time or fre­quency. If you have Option 5 Video, you can also display the results in terms
of video line number.

Press CURSOR ➞ Time Units (main) ➞ seconds or 1/seconds (Hz) or,
with Option 5, video line number (side).

Amplitude Units

If you are measuring NTSC signals, you can choose to display vertical read­ings in IRE units. If you are trying to do this, you should have option 05 Video
Trigger installed as it would be difficult to trigger on composite video wave­forms without option 05.

Press CURSOR ➞ Amplitude Units (main) ➞ IRE (NTSC)

To return to normal:
Press CURSOR ➞ Amplitude Units (main) ➞ Base

For More Information

Cursor Speed

You can change the cursors speed by pressing SHIFT before turning the
general purpose knob. The cursor moves faster when the SHIFT button is
lighted and the display reads

Measurements

See

Waveform Math

See
multiplied waveforms.

Fast Fourier Transforms

See
page 3-150, and
equipped with Option 2F Advanced DSP Math (standard on the TDS 524A &
TDS 644A), for information on cursor units with integrated, differentiated, and
FFT waveforms.

See the
equipped with the video trigger option, for information on cursor units with
video waveforms.

TDS Family Option 05 Video Trigger Interface,

, on page 2-30.

, on page 3-159, for information on cursor units with

Waveform Integration

Coarse Knobs

on page 3-38,

in the upper right corner.

Waveform Differentiation

on page 3-154, if your oscilloscope is

if your oscilloscope is

on

TDS 620A, 640A, & 644A User Manual

3Ć21

Delayed Triggering

The TDS 600A Series oscilloscopes provide a main time base and a delayed
time base. The delayed time base, like the main time base, requires a trigger
signal and an input source dedicated to that signal. You can only use delay
with respect to the main edge trigger and certain classes of main pulse trig­gers.

Delayed Triggerable

After Time

There are two different ways to delay the acquisition of waveforms:

runs after main

delayed triggerable

. Only delayed triggerable uses the

and

delayed trigger system.

Delayed runs after main

looks for a main trigger, then waits a user-defined

time, and then starts acquiring (see Figure 3-12).

Wait for
Main
Trigger

Wait
User-Specified
Time

Acquire
Data

Figure 3-12: Delayed Runs After Main

Delayed triggerable

looks for a main trigger and then, depending on the type
of delayed trigger selected, makes one of the three types of delayed trigger­able mode acquisitions listed below (see Figure 3-13).

Wait for
Main
Trigger

Wait
User-Specified
Time

Wait for
Delayed
Trigger
Event

delayed

Acquire
Data

3Ć22

Delayed Triggerable

After Events

Delayed Triggerable

After Events/Time

Wait the
User-Specified
Number of Delayed
Trigger Events

Wait the
User-Specified
Number of Delayed
Trigger Events

Wait
User-Specified
Time

Figure 3-13: Delayed Triggerable

Reference

H

After Time

trigger event, and then acquires.

waits the user-specified time, then waits for the next delayed

Delayed Triggering

After Events

H

then acquires.

After Events/Time

H

events, then waits the user-specified time, and then acquires.

The digitizing oscilloscope is always acquiring samples to fill the pretrigger
part of the waveform record. When and if delay criteria are met, it takes
enough posttrigger samples to complete the delayed waveform record and
then displays it. Refer to Figure 3-14 for a more detailed look at how delayed
records are placed in time relative to the main trigger.

waits for the specified number of delayed trigger events and

waits for the specified number of delayed trigger

NOTE

When using the delayed triggerable mode, the digitizing oscillo­scope provides a conventional edge trigger for the delayed time
base. The delayed time base will not trigger if the main trigger type
(as defined in the Main Trigger menu) is logic, if the main trigger
type is edge with its source set to auxiliary (not available on the
TDS 524A & TDS 620A), or if the main trigger type is pulse with the
runt trigger class selected.

Operation

You use the Horizontal menu to select and define either delayed runs after
main or delayed triggerable. Delayed triggerable, however, requires further
selections in the Delayed Trigger menu.

Delayed Runs After Main

1. Press HORIZONTAL MENU ➞ Time Base (main) ➞ Delayed Only

(side) ➞ Delayed Runs After Main (side). Use the general purpose knob
or the keypad to set the delay time.

If you press Intensified (side), you display an intensified zone on the
main timebase record that shows where the delayed timebase record
occurs relative to the main trigger. For Delayed Runs After Main mode,
the start of the intensified zone corresponds to the start of the delayed
timebase record. The end of the zone corresponds to the end of the
delayed record.

TDS 620A, 640A, & 644A User Manual

3Ć23

Delayed Triggering

Pretrigger Record

Delayed Runs After Main

Main Trigger Point

Main

Trigger

Source

Delayed Triggerable By Events

Main Trigger Point

Main
Trigger
Source

Delayed

Trigger
Source

Delayed Triggerable By Time

Time Delay

(From Horiz Menu)

Waiting for nth Event

(Where n=5)

Posttrigger Record

Delayed Trigger Waveform Record

Start Posttrigger Acquisition

Delayed Trigger Waveform Record

Start Posttrigger

Acquisition (Trigger on nth

Delayed Trigger Event)

Main Trigger Point

Main

Trigger

Source

Delayed

Trigger

Source

Delayed Triggerable By Events/Time

Main Trigger Point

Main
Trigger
Source

Delayed

Trigger
Source

Waiting for nth Event

(Where n=4)

Time Delay

Time Delay

(From Delay Trig Menu)

(From Delay Trig Menu)

Time Delay

(From Delay Trig Menu)

Delayed Trigger Waveform Record

Start Posttrigger Acquisition

(First Trigger After Delay)

Delayed Trigger Waveform Record

Start Posttrigger Acquisition

3Ć24

Figure 3-14: How the Delayed Triggers Work

Reference

Delayed Triggering

Delayed Triggerable

You must make sure that the Main Trigger menu settings are compatible with
Delayed Triggerable.

1. Press TRIGGER MENU.

2. If Type is set to Logic, press Type (main) to change it to either Edge or
Pulse as fits your application. Logic type is incompatible with Delayed
Triggerable.

3. If Source is set to Auxiliary (not available on the TDS 524A &
TDS 620A), press Source (main). Select any source other than Auxiliary

from the side menu according to your application.

4. Press HORIZONTAL MENU ➞ Time Base (main) ➞ Delayed Only
(side) ➞ Delayed Triggerable (side).

NOTE

The Delayed Triggerable menu item is not selectable unless incom­patible Main Trigger menu settings are eliminated. (See the steps at
the beginning of this procedure.) If such is the case, the Delayed
Triggerable menu item is dimmer than other items in the menu.

By pressing Intensified (side), you can display an intensified zone that
shows where the delayed timebase record
trigger event must be received) relative to the main trigger on the main
time base. For Delayed Triggerable After mode, the start of the intensified
zone corresponds to the possible start point of the delayed time base
record. The end of the zone continues to the end of main time base, since
a delayed time base record may be triggered at any point after the delay
time elapses.

To learn how to define the intensity level of the normal and intensified
waveform, see

Now you need to bring up the Delayed Trigger menu so you can define
the delayed trigger event.

5. Press SHIFT DELAYED TRIG ➞ Delay by (main) ➞ Triggerable After
Time, Events, or Events/Time (side) (Figure 3-15).

6. Enter the delay time or events using the general purpose knob or the
keypad. If you selected Events/Time, use Time (side) and Events (side)
to switch between setting the time and the number of events.

Hint: You can go directly to the Delayed Trigger menu (see step 5). By
selecting one of Triggerable After Time, Events, or Events/Time, the
oscilloscope automatically switches to Delayed Triggerable in the Hori­zontal menu. You will still need to display the Horizontal menu if you wish
to leave Delayed Triggerable.

Display Modes

on page 3-28.

may

occur (a valid delay

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3Ć25

Delayed Triggering

The Source menu lets you select which input will be the delayed trigger
source.

7. Press Source (main) ➞ Ch1, Ch2, Ch3 (Ax1 on the TDS 524A &
TDS 620A), Ch4 (Ax2 on the TDS 524A & TDS 620A), or Auxiliary (not

available on the TDS 524A & TDS 620A) (side).

Figure 3-15: Delayed Trigger Menu

8. Press Coupling (main) ➞ DC, AC, HF Rej, LF Rej, or Noise Rej (side)
to define how the input signal will be coupled to the delayed trigger. For
descriptions of these coupling types, see

Triggering

on page 2-13.

9. Press Slope (main) to select the slope that the delayed trigger will occur
on. Choose between the rising edge and falling edge slopes.

When using Delayed Triggerable mode to acquire waveforms, two trigger
bars are displayed. One trigger bar indicates the level set by the main
trigger system; the other indicates the level set by the delayed trigger
system.

10. Press Level (main) ➞ Level, Set to TTL, Set to ECL, or Set to 50%
(side).

H

Level lets you enter the delayed trigger level using the general pur­pose knob or the keypad.

H

Set to TTL fixes the trigger level at +1.4 V.

H

Set to ECL fixes the trigger level at –1.3 V.

3Ć26

Reference

Delayed Triggering

NOTE

When you set the Vertical SCALE smaller than 200 mV, the oscillo­scope reduces the Set to TTL or Set to ECL trigger levels below
standard TTL and ECL levels. That happens because the trigger
level range is fixed at
next smaller setting after 200 mV) the trigger range is
is smaller than the typical TTL (+1.4 V) or ECL (–1.3 V) level.

H

Set to 50% fixes the delayed trigger level to 50% of the peak-to-peak
value of the delayed trigger source signal.

center. At 100 mV (the

V which

For More Information

Triggering

See

Triggering

See

, on page 2-13.
, on page 3-142.

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3Ć27

Display Modes

The digitizing oscilloscope can display waveform records in different ways.
The Display menu lets you adjust the oscilloscope display style, intensity
level, graticule, and format.

Operation

To bring up the Display menu:

1. Press DISPLAY to show the Display menu.

2. On the TDS 644A & TDS 524A, press Setting in the main menu until you
select Display from the pop-up menu.

Display lets you adjust the style, intensity level, graticule, and format features
described below. Color (TDS 644A & TDS 524A) lets you alter color settings
for various display components such as waveforms and text. For more in-

Color

formation on color, see

on page 3-12.

Display Style

Press DISPLAY ➞ Style (main) ➞ Vectors, Intensified Samples, Dots,
Infinite Persistence, or Variable Persistence (side) (Figure 3-16).

3Ć28

Figure 3-16: Display Menu — Style

Reference

Display Modes

H

Vectors has the display draw vectors (lines) between the record points.

H

Dots display waveform record points as dots.

H

Intensified Samples also displays waveform record points as dots.
However, the points actually sampled are displayed in the Zone color
(TDS 644A & TDS 524A) or intensified relative to the interpolated points.

In addition to choosing Intensified Samples in the side menu, the oscilloscope
must be interpolating (equivalent time must be off) or Zoom must be on with
its horizontal expansion greater that 1X. See interpolation on page 2-21; see
Zoom beginning on page 3-162.

H

Variable Persistence lets the record points accumulate on screen over
many acquisitions and remain displayed only for a specific time interval.
In that mode, the display behaves like that of an analog oscilloscope. You
enter the time for that option with the keypad or the general purpose
knob. On color instruments, record points are also displayed with colors
that vary depending on the points persistence. See Choose Palette on
page 3-13.

H

Infinite Persistence lets
some control (such as scale factor) causing the display to be erased.

the record points accumulate until you change

Intensity

Intensity lets you set text/graticule and waveform intensity (brightness) levels.
To set the intensity:

Press DISPLAY ➞ Intensity (main) ➞ Overall (TDS 640A & TDS 620A),
Text/Grat, Waveform, or Contrast (TDS 640A & TDS 620A) (side). Enter the
intensity percentage values with the keypad or the general purpose knob.

All intensity adjustments operate over a range from 20% (close to fully off) to
100% (fully bright).

Contrast (TDS 640A & TDS 620A) operates over a range from 100% (no
contrast) to 250% (intensified portion at full brightness).

NOTE

The Intensified setting for Timebase in the horizontal menu causes
a zone on the waveform to be

(TDS 644A & TDS 524A) or

waveform. If the contrast is set to 100%, you won’t be able to
distinguish the intensified portion from the rest of the waveform
because both are the same brightness.

displayed in the Zone color

intensified relative to the rest of the

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