Tektronix TDS-200 User Manual

User Manual

TDS 200-Series Digital Real-Time Oscilloscope

071-0398-03

This document supports firmware version FV:v1.00 and above.

www.tektronix.com

pending. Information in this publication supercedes that in all previously published material. Specifications and price change privileges reserved.

Tektronix, Inc., P.O. Box 500, Beaverton, OR 97077 TEKTRONIX and TEK are registered trademarks of Tektronix, Inc.

WARRANTY SUMMARY

(TDS 200-Series Digitizing Oscilloscope)

T ektronix warrants that the products that it manufactures and sells will be free from defects in materials and workmanship for a period of three (3) years from the date of shipment from an authorized Tektronix distributor. If a product or CRT proves defective within the respective period, T ektronix will provide repair or replacement as described in the complete warranty statement.

To arrange for service or obtain a copy of the complete warranty statement, please contact your nearest Tektronix sales and service office.

EXCEPT AS PROVIDED IN THIS SUMMARY OR THE APPLICABLE WARRANTY STATEMENT, TEKTRONIX MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL TEKTRONIX BE LIABLE FOR INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES.

WARRANTY SUMMARY

(P2100 Probe)

T ektronix warrants that the products that it manufactures and sells will be free from defects in materials and workmanship for a period of one (1) year from the date of shipment. If a product proves defective within the respective period, Tektronix will provide repair or replacement as described in the complete warranty statement.

To arrange for service or obtain a copy of the complete warranty statement, please contact your nearest Tektronix sales and service office.

General Safety Summary v. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contacting Tektronix vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Product End-of-Life Handling viii. . . . . . . . . . . . . . . . . . . . . . . .

Getting Started 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General Features 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Installation 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Power Cord 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Security Loop 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Extension Modules 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Functional Check 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Probe Compensation 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Self Calibration 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Probe Safety 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Probe Attenuation Setting 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Basic Concepts 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Triggering 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Source 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Types 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Modes 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Holdoff 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Coupling 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Position 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Slope and Level 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Acquiring Data 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Acquisition Modes 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Time Base 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Scaling and Positioning Waveforms 16. . . . . . . . . . . . . . . . . . . . .

Vertical Scale and Position 17. . . . . . . . . . . . . . . . . . . . . . . . . .

Horizontal Scale and Position; Pretrigger Information 17. . . .

T aking Measurements 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Graticule 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cursors 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Automated 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Setting Up the Oscilloscope 21. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Using Autoset 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Saving a Setup 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Recalling a Setup 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Defaults (Factory Setup) 22. . . . . . . . . . . . . . . . . . . . . . . . . . .

TDS 200-Series Digital Oscilloscope User Manual

Table of Contents

Operating Basics 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Display Area 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Using the Menu System 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Circular List Menu Boxes 26. . . . . . . . . . . . . . . . . . . . . . . . . .

Action Button Menu Boxes 27. . . . . . . . . . . . . . . . . . . . . . . . .

Radio Button Menu Boxes 27. . . . . . . . . . . . . . . . . . . . . . . . . .

Page Selection Menu Boxes 27. . . . . . . . . . . . . . . . . . . . . . . . .

Waveform Displays 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Vertical Controls 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Horizontal Controls 31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Trigger Controls 32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Menu and Control Buttons 33. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Connectors 35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Application Examples 37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T aking Simple Measurements 38. . . . . . . . . . . . . . . . . . . . . . . . . .

Using Autoset 38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T aking Automatic Measurements 39. . . . . . . . . . . . . . . . . . . .

Measuring Two Signals 40. . . . . . . . . . . . . . . . . . . . . . . . . . . .

T aking Cursor Measurements 42. . . . . . . . . . . . . . . . . . . . . . . . . .

Measuring Pulse Width 42. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Measuring Rise Time 43. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Measuring Ring Frequency 45. . . . . . . . . . . . . . . . . . . . . . . . .

Measuring Ring Amplitude 46. . . . . . . . . . . . . . . . . . . . . . . . .

Analyzing Signal Detail 47. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Looking at a Noisy Signal 47. . . . . . . . . . . . . . . . . . . . . . . . . .

Separating the Signal from Noise 48. . . . . . . . . . . . . . . . . . . .

Capturing a Single-Shot Signal 49. . . . . . . . . . . . . . . . . . . . . . . . .

Optimizing the Acquisition 50. . . . . . . . . . . . . . . . . . . . . . . . .

Measuring Propagation Delay 51. . . . . . . . . . . . . . . . . . . . . . . . . .

Triggering on a Video Signal 53. . . . . . . . . . . . . . . . . . . . . . . . . . .

Triggering on Video Fields 54. . . . . . . . . . . . . . . . . . . . . . . . .

Triggering on Video Lines 54. . . . . . . . . . . . . . . . . . . . . . . . . .

Using the Window Function to See Waveform Details 55. . . .

Triggering on Odd or Even Video Fields 57. . . . . . . . . . . . . . .

Analyzing a Differential Communication Signal 60. . . . . . . . . . .

TDS 210 and TDS 220 (Firmware V 2.00 and Above), and

TDS 224 (All Versions) Oscilloscopes 61. . . . . . . . . . . . . . . .

TDS 210 and TDS 220 Oscilloscopes (Firmware Below

V 2.00) without a TDS2MM 62. . . . . . . . . . . . . . . . . . . . . . . .

TDS 210 and TDS 220 Oscilloscopes (Firmware Below

V 2.00) with a TDS2MM 62. . . . . . . . . . . . . . . . . . . . . . . . . . .

Viewing Impedance Changes in a Network 63. . . . . . . . . . . . . . . .

TDS 200-Series Digital Oscilloscope User Manual

Table of Contents

Reference 65. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Acquire 66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Autoset 70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cursors 71. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Display 72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Horizontal 74. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Math 76. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TDS 210 and TDS 220 (Firmware V 2.00 and Above) and

TDS 224 (All Versions) Oscilloscopes , 76. . . . . . . . . . . . . . . .

TDS 210 and TDS 220 Oscilloscopes (Firmware Below

V 2.00) without a TDS2MM 77. . . . . . . . . . . . . . . . . . . . . . . .

TDS 210 and TDS 220 Oscilloscopes (Firmware Below

V 2.00) with a TDS2MM 77. . . . . . . . . . . . . . . . . . . . . . . . . .

Measure 79. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Save/Recall 81. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Trigger Controls 83. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Utility 87. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Vertical 89. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hard Copy 90. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix A: Specifications 91. . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix B: Accessories 103. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix C: General Care and Cleaning 107. . . . . . . . . . . . . . .

Glossary 109. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Index 115. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TDS 200-Series Digital Oscilloscope User Manual

iii

Table of Contents

TDS 200-Series Digital Oscilloscope User Manual

General Safety Summary

Review the following safety precautions to avoid injury and prevent damage to this product or any products connected to it. To avoid potential hazards, use this product only as specified.

Only qualified personnel should perform service procedures.

To Avoid Fire or Personal Injury

Use Proper Power Cord. Use only the power cord specified for this

product and certified for the country of use.

Connect and Disconnect Properly. Do not connect or disconnect probes

or test leads while they are connected to a voltage source.

Ground the Product. This product is grounded through the grounding

conductor of the power cord. To avoid electric shock, the grounding conductor must be connected to earth ground. Before making connections to the input or output terminals of the product, ensure that the product is properly grounded.

Connect the Probe Properly. The probe ground lead is at ground

potential. Do not connect the ground lead to an elevated voltage.

Observe All Terminal Ratings. To avoid fire or shock hazard, observe all

ratings and marking on the product. Consult the product manual for further ratings information before making connections to the product.

Do Not Operate Without Covers. Do not operate this product with

covers or panels removed.

Use Proper Fuse. Use only the fuse type and rating specified for this

product.

Avoid Exposed Circuitry. Do not touch exposed connections and

components when power is present.

Do Not Operate With Suspected Failures. If you suspect there is damage

to this product, have it inspected by qualified service personnel.

Provide Proper Ventilation. Refer to the manual’s installation

instructions for details on installing the product so it has proper ventilation.

TDS 200-Series Digital Oscilloscope User Manual

General Safety Summary

Do Not Operate in Wet/Damp Conditions. Do Not Operate in an Explosive Atmosphere. Keep Product Surfaces Clean and Dry.

Safety Terms and Symbols

Terms in This Manual. These terms may appear in this manual:

WARNING. Warning statements identify conditions or practices that could result in injury or loss of life.

CAUTION. Caution statements identify conditions or practices that could result in damage to this product or other pr operty.

Terms on the Product. These terms may appear on the product:

DANGER indicates an injury hazard immediately accessible as you read the marking.

WARNING indicates an injury hazard not immediately accessible as you read the marking.

CAUTION indicates a hazard to property including the product.

Symbols on the Product. These symbols may appear on the product:

Protective Ground

(Earth) Terminal

Measurment

Ground Terminal

CAUTION

Refer to Manual

Measurment

Input Terminal

TDS 200-Series Digital Oscilloscope User Manual

Contacting Tektronix

Product support

Service support

For other information

For questions about using Tektronix measurement products, call toll free in North America: 1-800-833–9200 6:00 a.m. – 5:00 p.m. Pacific time

Or contact us by e-mail: support@tektronix.com

For product support outside of North America, contact your local Tektronix distributor or sales office.

Tektronix offers extended warranty and calibration programs as options on many products. Contact your local Tektronix distributor or sales office.

For a listing of worldwide service centers, visit our web site.

In North America: 1-800–833–9200 An operator can direct your call.

To write us Tektronix, Inc.

P.O. Box 500 Beaverton, OR 97077-0001 USA

Web site www.tektronix.com

TDS 200-Series Digital Oscilloscope User Manual

vii

Contacting Tektronix

Product End-of-Life Handling

Components that Contain Mercury. The cold cathode fluorescent tube

located in the liquid crystal display backlight contains trace elements of mercury. When you are ready to reclaim the instrument, you must properly transfer it according to local regulations concerning mercury-containing equipment or ship the instrument to the Tektronix Recycling Operations (RAMS). You can contact Tektronix for the RAMS shipping address and instructions.

viii

TDS 200-Series Digital Oscilloscope User Manual

Getting Started

TDS 200-Series Digital Oscilloscopes are small, lightweight, benchtop packages that you can use to take ground-referenced measurements. The TDS 210 and TDS 220 oscilloscopes have two-channels; the TDS 224 has four channels.

In addition to the list of general features, this section covers the following topics:

H How to install your product H How to add extended functions H How to perform a brief functional check H How to compensate probes H How to use the self calibration routine H How to match your probe attenuation factor

NOTE. To select a display language, push the UTILITY menu button, and then push the Language menu box item to select the appropriate language.

TDS 200-Series Digital Oscilloscope User Manual

Getting Started

General Features

H 100 MHz (TDS 220 or TDS 224) or 60 MHz (TDS 210)

bandwidth with selectable 20 MHz bandwidth limit

H 1 GS/s sample rate and 2,500 point record length for each

channel

H Cursors with readout H Five automated measurements H High-resolution, high-contrast LCD display with temperature

compensation and replaceable back light

H Setup and waveform storage H Autoset for quick setup H Waveform averaging and peak detection H Digital real-time oscilloscope H Dual time base H Video trigger capability H RS-232, GPIB, and Centronics communication ports easily added

with optional extension modules

H Variable persistence display H User interface available in ten user-selectable languages

TDS 200-Series Digital Oscilloscope User Manual

Installation

Power Cord

Use only power cords designed for your oscilloscope. Use a power source that delivers 90 to 264 VAC page 105 for a list of available power cords.

Use the power cord notch to help route the cord to the rear of the instrument and avoid inadvertently disconnecting the power source.

, 45 to 440 Hz. Refer to

RMS

Power cord

notch

Getting Started

Securing cable

Security Loop

Use the built-in cable channels to secure both your instrument and extension module to your location.

TDS 200-Series Digital Oscilloscope User Manual

Getting Started

Extension Modules

You can increase the feature set of your oscilloscope by inserting an extension module. Refer to page 103 for information about the available modules.

CAUTION. Electr ostatic discharge (ESD) can damage components in the extension module and the oscilloscope. Do not operate your instrument with the extension module connector exposed.

Modules slide

in and out

TDS 200-Series Digital Oscilloscope User Manual

Functional Check

Perform this quick functional check to verify that your instrument is operating correctly .

Getting Started

ON/OFF

button

PASSED

PROBE COMP

CH 1

1. Turn on the instrument.

Wait until the display shows that all self tests passed. Push the SAVE/RECALL button, select Setups in the top menu box and push the Recall Factory menu box. The default Probe menu attenuation setting is 10X.

2. Set the switch to 10X on the P2100 probe

and connect the probe to channel 1 on the oscilloscope. To do this, align the slot in the probe connector with the key on the CH 1 BNC, push to connect, and twist to the right to lock the probe in place.

Attach the probe tip and reference lead to the PROBE COMP connectors.

3. Push the AUTOSET button. Within a few

seconds, you should see a square wave in the display (approximately 5 V at 1 kHz peak-to-peak).

Push the CH 1 MENU button twice to turn off channel 1, push the CH 2 MENU button to turn on channel 2, repeat steps 2 and 3. For TDS 224, repeat for CH 3 and CH 4.

TDS 200-Series Digital Oscilloscope User Manual

Getting Started

Probe Compensation

Perform this adjustment to match your probe to the input channel. This should be done whenever you attach a probe for the first time to any input channel.

PROBE

COMP

Overcompensated

Undercompensated

AUTOSET

button

CH 1

1. Set the Probe menu attenuation to 10X.

Set the switch to 10X on the P2100 probe and connect the probe to channel 1 on the oscilloscope. If you use the probe hooktip, ensure a proper connection by firmly inserting the tip onto the probe.

Attach the probe tip to the PROBE COMP 5V connector and the reference lead to the PROBE COMP Ground connector, turn on the channel, and then press AUTOSET.

2. Check the shape of the displayed

waveform.

Compensated correctly

3. If necessary, adjust your probe.

Repeat as necessary .

TDS 200-Series Digital Oscilloscope User Manual

Self Calibration

The self calibration routine lets you quickly optimize the oscilloscope signal path for maximum measurement accuracy. You can run the routine at anytime but you should always run the routine if the ambient temperature changes by 5_ C or more.

To compensate the signal path, disconnect any probes or cables from the input connectors. Then, press the UTILITY button and select Do Self Cal to confirm that you are ready to proceed.

Probe Safety

A guard around the probe body provides a finger barrier for protection from electric shock.

Getting Started

Finger guard

WARNING. To avoid electric shock when using the probe, keep fingers behind the guard on the probe body.

To avoid electric shock while using the probe, do not touch metallic portions of the probe head while it is connected to a voltage source.

Connect the probe to the instrument and connect the ground terminal to ground before you take any measurements.

TDS 200-Series Digital Oscilloscope User Manual

Getting Started

Probe Attenuation Setting

Probes are available with various attenuation factors which affect the vertical scale of the signal.

To change (or check) the probe attenuation setting, press the VERTICAL MENU button (of the channel you are using), and then press the menu selection next to Probe until the correct setting is displayed.

This setting remains in effect until changed again.

NOTE. The default Probe menu attenuation setting is 10X when the oscilloscope is shipped.

Be sure that the Attenuation switch on the P2100 probe is set to match the Probe menu selection in the oscilloscope. The probe switch settings are 1X and 10X.

Attenuation switch

NOTE. When the Attenuation switch is set to 1X, the P2100 probe limits the bandwidth of the oscilloscope to 7 MHz. To use the full bandwidth of the oscilloscope, be sure to set the switch to 10X.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

To use your oscilloscope effectively, you must understand the following basic concepts:

H Triggering H Acquiring data H Scaling and positioning waveforms H Measuring waveforms H Setting Up the oscilloscope

The figure below shows a block diagram of the various functions of an oscilloscope and their relationship to each other .

Each

channel

Ext

AC Line

Vertical:

gain and

position

Trigger

Acquire data:

mode and time base

Waveform

record:

2500 points

Display

Computer interface (TDS2CM)

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

Triggering

The trigger determines when the oscilloscope starts to acquire data and display a waveform. When a trigger is set up properly, it can convert unstable displays or blank screens into meaningful waveforms.

Triggered waveform Untriggered waveforms

When the oscilloscope starts to acquire a waveform, it collects enough data so that it can draw the waveform to the left of the trigger point. The oscilloscope continues to acquire data while waiting for the trigger condition to occur. After it detects a trigger, the oscilloscope continues to acquire enough data so that it can draw the waveform to the right of the trigger point.

Source

You can derive your trigger from various sources: Input channels, AC Line, and External.

Input. The most commonly used trigger source is any one of the input

channels. The channel you select as a trigger source will function whether it is displayed or not.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

AC Line. You can use this trigger source when you want to look at

signals related to the power line frequency, such as lighting equipment and power supply devices. The oscilloscope generates the trigger, so you do not have to input a trigger signal.

External (TDS 210 and TDS 220 Only). You can use this trigger source

when you want to acquire data on two channels and trigger from a third. For example, you might want to trigger from an external clock or with a signal from another part of the test circuit.

The EXT and EXT/5 trigger sources both use the external trigger signal connected to the EXT TRIG connector . EXT uses the signal directly; you can use EXT on signals with a trigger level range of +1.6 V to – 1.6 V.

The EXT/5 trigger source divides the signal by 5 which extends the trigger level range from + 8 V to – 8 V. This allows the oscilloscope to trigger on a larger signal.

Types

The oscilloscope provides two types of triggers: Edge and Video.

Edge. You can use the edge trigger with analog and digital test

circuits. An edge trigger occurs when the trigger input passes through a specified voltage level in the specified direction.

Video. You can use the video trigger on fields or lines of standard

video signals. Refer to T riggering on a Video Signal on page 53.

Modes

The trigger mode determines how the oscilloscope behaves in the absence of a trigger event. The oscilloscope provides three trigger modes: Auto, Normal, and Single.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

Auto. This trigger mode allows the oscilloscope to acquire a

waveform even when it does not detect a trigger condition. If no trigger condition occurs while the oscilloscope waits for a specific period (as determined by the time-base setting), it will force itself to trigger.

Refer to T ime Base on page 16 for more information on time bases. When forcing invalid triggers, the oscilloscope cannot synchronize

the waveform, and the waveform seems to roll across the display. If valid triggers occur, the display becomes stable on the screen.

You can use Auto mode to monitor an amplitude level, such as a power supply output, which may cause the waveform to roll across the display .

Normal. The Normal mode allows the oscilloscope to acquire a

waveform only when it is triggered. If no trigger occurs, the oscilloscope will not acquire a new waveform, and the previous waveform, if any, will remain on the display.

Single. The Single mode allows the oscilloscope to acquire one

waveform each time you press the RUN button, and the trigger condition is detected.

The data that the oscilloscope acquires depends on the acquisition mode. Refer to Acquisition Modes on page 15 for more information on the type of data each acquisition mode will acquire.

NOTE. When you use the Single trigger mode with the Average acquisition mode, the number of waveforms specified in the number of averages are acquired befor e the acquisition stops.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

Holdoff

Triggers are not recognized during holdoff time (the period that follows each acquisition). For some signals, you need to adjust the holdoff period to produce a stable display.

The trigger signal can be a complex waveform with many possible trigger points on it, such as a digital pulse train. Even though the waveform is repetitive, a simple trigger might result in a series of patterns on the screen instead of the same pattern each time.

Acquisition

interval

Trigger level

Indicates

trigger points

Holdoff

Triggers are not recognized during holdoff time.

Acquisition

interval

Holdoff

Acquisition

interval

Holdoff

For example, you could use the holdoff period to prevent triggering on any other pulse except the first one in a pulse train. This way, the oscilloscope would always display the first pulse.

To access the Holdoff control, press the HORIZONTAL Menu button, select Holdoff, and use the HOLDOFF knob to change the amount of time in the holdoff period.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

Coupling

Trigger coupling determines what part of the signal passes on to the trigger circuit. Coupling types include DC, AC, Noise Rejection, High Frequency Rejection, and Low Frequency Rejection.

DC. DC coupling passes both AC and DC components. AC. AC coupling blocks DC components. Noise Rejection. Noise Reject coupling lowers the trigger sensitivity

and requires more signal amplitude for stable triggering. This reduces the chance of falsely triggering on noise.

High Frequency Rejection. HF Reject coupling blocks the high

frequency portion and passes on only the low frequency components.

Low Frequency Rejection. LF Reject coupling does the opposite of high

frequency rejection.

Position

The horizontal position control establishes the time between the trigger and the screen center. Refer to Horizontal Scale and Position; Pretrigger Information on page 17 for more information on how to use this control to position the trigger .

Slope and Level

The Slope and Level controls help to define the trigger. The Slope control determines whether the oscilloscope finds the

trigger point on the rising or the falling edge of a signal. To access the trigger slope control, press the TRIGGER Menu button, select Edge, and use the Slope button to select Rising or Falling.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

The Level control determines where on the edge the trigger point occurs. To access the trigger level control, press the HORIZONTAL Menu button, select Level, and use the LEVEL knob to change the value.

Positive-going

edge

Trigger level can be

adjusted vertically

Trigger slope can be

positive or negative

Negative-going

edge

Acquiring Data

When you acquire analog data, the oscilloscope converts it into a digital form. You can acquire data using three different acquisition modes. The timebase setting affects how rapidly data is acquired.

Acquisition Modes

There are three acquisition modes: Sample, Peak Detect, and Average.

Sample. In this acquisition mode, the oscilloscope samples the signal

in evenly spaced intervals to construct the waveform. This mode accurately represents analog signals most of the time.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

However, this mode does not acquire rapid variations in the analog signal that may occur between samples. This can result in aliasing (described on page 18) and may cause narrow pulses to be missed. In these cases, you should use the Peak Detect mode to acquire data.

Peak Detect. In this acquisition mode, the oscilloscope finds the

highest and lowest values of the input signal over a sample interval and uses these values to display the waveform. In this way, the oscilloscope can acquire and display narrow pulses, which may have otherwise been missed in Sample mode. Noise will appear to be higher in this mode.

Average. In this acquisition mode, the oscilloscope acquires several

waveforms, averages them, and displays the resulting waveform. You can use this mode to reduce random noise.

Time Base

The oscilloscope digitizes waveforms by acquiring the value of an input signal at discrete points. The time base allows you to control how often the values are digitized.

To adjust the time base to a horizontal scale that suits your purpose, use the SEC/DIV knob.

Scaling and Positioning Waveforms

You can change the display of waveforms by adjusting their scale and position. When you change the scale, the waveform display will increase or decrease in size. When you change the position, the waveform will move up, down, right, or left.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

The channel reference indicator (located on the left of the graticule) identifies each waveform on the display. The indicator points to the ground level of the waveform record.

Vertical Scale and Position

You can change the vertical position of waveforms by moving them up or down on the display. To compare data, you can align a waveform above another or you can align waveforms on top of each other.

You can change the vertical scale of a waveform. The waveform display will contract or expand about the ground level.

Horizontal Scale and Position; Pretrigger Information

You can adjust the Horizontal Position control to view waveform data before the trigger, after the trigger, or some of each. When you change the horizontal position of a waveform, you are actually changing the time between the trigger and the center of the display. (This appears to move the waveform to the right or left on the display.)

For example, if you want to find the cause of a glitch in your test circuit, you might trigger on the glitch and make the pretrigger period large enough to capture data before the glitch. You can then analyze the pretrigger data and perhaps find the cause of the glitch.

You change the horizontal scale of all the waveforms by using the SEC/DIV knob. For example, you might want to see just one cycle of a waveform to measure the overshoot on its rising edge.

TDS 200-Series Digital Oscilloscope User Manual

Basic Concepts

The oscilloscope shows the time per division in the scale readout. Since all active waveforms use the same time base, the oscilloscope only displays one value for all the active channels, except when you use a Window Zone.

Aliasing. Aliasing occurs when the oscilloscope does not sample the

signal fast enough to construct an accurate waveform record. When aliasing happens, you see a waveform with a frequency lower than the actual waveform being input or a waveform that is not stable even though the oscilloscope triggered.

Actual high-frequency

Apparent low-frequency

waveform due to aliasing

waveform

Sampled points

One way to check for aliasing is to slowly change the horizontal scale with the SEC/DIV knob. If the shape of the waveform changes drastically, you may have aliasing.

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 5 MHz would need to be sampled at 10 Megasamples per second or faster .

TDS 200-Series Digital Oscilloscope User Manual

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