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Tektronix TDS 684A, TDS 744A, TDS 784A Acquisition Mode, Zoom and Interpolation

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Using Features for Advanced Applications

3–154 TDS 684A, TDS 744A, & TDS 784A User Manual

Selecting the right acquisition mode can produce less noisy FFTs.

Set up in Sample. Use sample mode until you have set up and turned on your

FFT. Sample mode can acquire repetitive and nonrepetitive waveforms and does

not affect the frequency response of the source waveform.

Hi Res and Average Reduce Noise. If the pulse is repetitive, Average mode may be

used to reduce noise in the signal at a cost of slower display response. Average

operates on repetitive waveforms only, and averaging does affect the frequency

response of the source waveform.

For TDS 700A models only, after the FFT is set up and displayed, you can to

turn on Hi Res mode to reduce the effect of noise in the signal. Hi Res operates

on both repetitive and nonrepetitive waveforms; however, it does affect the

frequency response of the source waveform.

Peak Detect and Envelope Add Distortion. Peak Detect (TDS 700A models) and

Envelope mode can add significant distortion to the FFT results and are not

recommended for use with FFTs.

Once you have your waveform displayed optimally, you may magnify (or

reduce) it vertically and horizontally to inspect any feature you desire. Just be

sure the FFT waveform is the selected waveform. (Press MORE, then select the

FFT waveform in the More main menu. Then use the Vertical and Horizontal

SCALE knobs to adjust the math waveform size.)

If you wish to see the zoom factor (2X, 5X, etc.) you need to turn Zoom on:

press ZOOM ➞ On (side). The vertical and horizontal zoom factors appear on

screen.

Whether Zoom is on or off, you can press Reset Zoom Factors (side) to return

the zoomed FFT waveform to no magnification.

Zoom always uses either sin(x)/x or linear interpolation when expanding

displayed waveforms. To select the interpolation method: press DISPLAY ➞

Setting (main) ➞ Display (pop-up) ➞ Filter (main) ➞ Sin(x)/x or Linear

(side).

If the source waveform record length is 500 points, the FFT will use 2X Zoom to

increase the 250 point FFT frequency domain record to 500 points. Therefore,

FFT math waveforms of 500 point waveforms are always zoomed 2X or more

with interpolation. Waveforms with other record lengths can be zoomed or not

and can have minimum Zooms of 1X or less.

Acquisition ModeZoom and Interpolation

Contents

Main Page WARRANTY Certificate of the Manufacturer/Importer German Postal Information Bescheinigung des Herstellers/Importeurs EC Declaration of Conformity Page Table of Contents Getting Started Operating Basics Reference Appendices Glossary Index List of Figures Page Page Page List of Tables Page General Safety Summary Injury Precautions Product Damage Precautions Safety Terms and Symbols Certifications and Compliances Page Preface Related Manuals Conventions Default Model Page TDS 684A, TDS 744A, & TDS 784A User Manual 11 Product Description Product Specification Start Up Preparation Input Coupling Signal Path Compensation Recommended Probes Probe Usage Putting into Service Installation Front Cover Removal Power On Self Test Power Off Page Overview Page Operating Interface Maps Front Panel Map Left Side 24 TDS 684A, TDS 744A, & TDS 784A User Manual Front Panel Map Right Side TDS 684A, TDS 744A, & TDS 784A User Manual 25 Rear Panel Map 26 TDS 684A, TDS 744A, & TDS 784A User Manual Display Map To Operate a Menu To Operate a Pop-Up Menu Tutorial Setting Up for the Examples Connect the Input Signal Reset the Oscilloscope Examine the Display Elements Page Example 1: Displaying a Waveform Adjust the Waveform Display Autoset the Oscilloscope Example 2: Displaying Multiple Waveforms Add a Waveform Page Assign Controls to Another Channel Remove a Waveform Example 3: Taking Automated Measurements Display Measurements Automatically Remove Measurement Readouts Change the Measurement Reference Levels Page Displaying a Snapshot of Automated Measurements Example 4: Saving Setups Save a Setup Recall a Setup Page Page Overview Acquiring and Displaying Waveforms Page Acquiring and Displaying Waveforms Coupling Waveforms to the Oscilloscope To Compensate Passive Probes Page Setting up Automatically: Autoset and Reset Input Impedance Considerations To Autoset the Oscilloscope List of Autoset Defaults Selecting Channels To Reset the Oscilloscope To Identify the Selected Channel To Select and Remove Waveforms Scaling and Positioning Waveforms Waveform Priority To Check Position To Check the Vertical Scale To Change Vertical Scale and Position Page To Change Vertical Parameters To Check the Horizontal Status To Change Horizontal Scale and Position To Change Horizontal Parameters Page Choosing an Acquisition Mode To Select the Delayed Time Base Sampling and Digitizing Real-time Sampling Equivalent-Time Sampling Interpolation Interleaving The Acquisition Modes Acquiring and Displaying Waveforms Multiple Waveform Acquisitions Figure 313: How the Acquisition Modes Work TDS 684A, TDS 744A, & TDS 784A User Manual 321 Single Waveform Acquisition Page Page Selecting Repetitive Sampling Stop After Preventing Aliasing Customizing the Display Change Display Settings Select the Display Style Adjust Intensity Set Display Readout Options Page Select Interpolation Filter Select the Graticule Type Select the Format Page Customizing the Display Color Change the Display Color Choose a Palette Change the Palette Colors Set Math Waveform Color Set Reference Waveform Color Select Options Restore Colors Zooming on Waveforms Using with Waveforms Interpolation and Zoom Checking the Zoom Factor Zoom a Waveform Page Set Interpolation Reset Zoom Using Dual Window Mode (TDS 700A Models Only) Dual Zoom a Waveform (TDS 700A Models Only) To Set Dual Zoom Offset Page Using InstaVu Acquisition Mode (TDS 700A Models Only) Waveform Capture Rate To Use InstaVu Mode Acquiring and Displaying Waveforms 344 TDS 684A, TDS 744A, & TDS 784A User Manual Normal DSO Mode Figure 326: Normal DSO Acquisition and Display Mode Versus InstaVu Mode InstaVu Mode Page Using FastFrameT (TDS 700A Models Only) Page Page Triggering on Waveforms Triggering Concepts The Trigger Event Trigger Sources Trigger Types Trigger Modes Trigger Holdoff Trigger Coupling Trigger Position Triggering from the Front Panel Slope and Level Delayed Trigger System To set MAIN LEVEL To Set to 50% To Force a Trigger To Single Trigger To Check Trigger Status Page Triggering on a Waveform Edge Trigger Menu To Check Edge Trigger Status To Select Edge Triggering To Select a Source To Specify Coupling To Set Mode & Holdoff Triggering Based on Logic To Set Slope To Set Level Pattern and State Classes Setup and Hold Class Triggering on Waveforms TDS 684A, TDS 744A, & TDS 784A User Manual 363 To Check Logic Trigger Status To Trigger on a Pattern Page To Define a Time Qualified Pattern Trigger To State Trigger To Trigger on Setup/ Hold Time Violations Page Triggering on Pulses Page To Trigger on a Glitch Page To Trigger on a Runt Pulse Page Trigger Based on Pulse Width To Trigger Based on Slew Rate Page Page Delayed Triggering Page Triggering on Waveforms 382 TDS 684A, TDS 744A, & TDS 784A User Manual Delayed Triggerable By Events Figure 349: How the Delayed Triggers Work Delayed Triggerable By Time To Run After Delay To Trigger After Delay Page Page Page Measuring Waveforms Taking Automated Measurements Measurement List Measuring Waveforms TDS 684A, TDS 744A, & TDS 784A User Manual 389 Table 39: Measurement Definitions (Cont.) Measurement Readouts Display Measurements Remove Measurements Gate Measurements Define High-Low Setup Define Reference Levels Take a Delay Measurement Take a Snapshot of Page Taking Cursor Measurements Cursor Types Cursor Modes Cursor Readouts Select the Cursor Function Set Mode and Adjust the Cursors Taking Graticule Measurements Select Cursor Speed Select Time Units Select Amplitude Units Optimizing Measurement Accuracy: SPC and Probe Cal Measure Waveform Amplitude Measure Waveform Time Signal Path Compensation Page Probe Cal Page Page Page Page Page Page Saving Waveforms and Setups Saving and Recalling Setups To Save a Setup To Recall a Setup Page Saving and Recalling Waveforms To Save a Waveform Page To Recall a Waveform From Disk To Enable Autosave Managing the File System To Run the File Utilities To Access the File Utilities To Delete To Rename To Copy To Print To Create a Directory Printing a Hardcopy To Set Confirm Delete To Set Overwrite Lock To Format Supported Formats To Set Up for Making Hardcopies Page Page To Print Directly to a Hardcopy Device To Save to a Floppy Disk To Print Using a Controller Communicating with Remote Instruments To Prepare for Remote Operation To Set Up for Remote Operation Page Page Determining Status and Accessing Help Displaying Status Displaying the Banner Page Displaying Help Page Using Features for Advanced Applications Limit Testing To Create Limit Test Template Page To Select a Limit Test Source To Specify the Limit Test Response Single Waveform Comparisons Multiple Waveform Comparisons Waveform Math To Use Single Wfm Math To Use Dual Wfm Math Fast Fourier Transforms To Average a Math S To Create an FFT Page Page To Take Cursor Measurements of an FFT To Take Automated Measurements of an FFT The FFT Frequency Domain Record Page Page Record Length Acquisition Mode Zoom and Interpolation Undersampling (Aliasing) Considerations for Phase Displays Page FFT Windows Page Page Waveform Differentiation To Create a Derivative of a Page Page Waveform Integration Using Zoom To Create a Integral Math To Take Cursor Page To Take Automated DC Offset Using Zoom Page Page Appendix A: Options and Accessories Options Appendix A: Options and Accessories A2 TDS 684A, TDS 744A, & TDS 784A User Manual Table A1: Options (Cont.) Standard Accessories Optional Accessories Accessory Probes Accessory Software Warranty Information Service Assurance Page Appendix B: Algorithms Measurement Variables High, Low HighRef, MidRef, LowRef, Mid2Ref Other Variables MCross Calculations Page Measurement Algorithms Amplitude Area Burst Width Cycle Area Cycle Mean Frequency High Low Maximum Mean Minimum Negative Duty Cycle Negative Overshoot Negative Width Peak to Peak Period Phase Positive Duty Cycle Positive Overshoot Positive Width Rise Time RMS: Measurements on Envelope Waveforms Integration Algorithm Page Missing or Out-of-Range Samples Appendix C: Packaging for Shipment Page TDS 684A, TDS 744A, & TDS 784A User Manual D1 Appendix D: Factory Initialization Settings D2 TDS 684A, TDS 744A, & TDS 784A User Manual TDS 684A, TDS 744A, & TDS 784A User Manual D3 D4 TDS 684A, TDS 744A, & TDS 784A User Manual TDS 684A, TDS 744A, & TDS 784A User Manual D5 Page Appendix E: Probe Selection Passive Voltage Probes General Purpose (High Input Resistance) Probes Low Impedance (ZO) Probes High Voltage Probes Active Voltage Probes High Speed Active Probes Differential Probes Fixtured Active Probes Current Probes Optical Probes Time-to-Voltage Converter Page Page Glossary Page Page Page Page Page Page Page Page Page Page Page Page TDS 684A, TDS 744A, & TDS 784A User Manual Index1 Index Numbers A Index2 TDS 684A, TDS 744A, & TDS 784A User Manual B C TDS 684A, TDS 744A, & TDS 784A User Manual Index3 D Index4 TDS 684A, TDS 744A, & TDS 784A User Manual TDS 684A, TDS 744A, & TDS 784A User Manual Index5 E F G Index6 TDS 684A, TDS 744A, & TDS 784A User Manual H TDS 684A, TDS 744A, & TDS 784A User Manual Index7 I K L M Index8 TDS 684A, TDS 744A, & TDS 784A User Manual TDS 684A, TDS 744A, & TDS 784A User Manual Index9 N Index10 TDS 684A, TDS 744A, & TDS 784A User Manual O P TDS 684A, TDS 744A, & TDS 784A User Manual Index11 Q R Index12 TDS 684A, TDS 744A, & TDS 784A User Manual S TDS 684A, TDS 744A, & TDS 784A User Manual Index13 T Index14 TDS 684A, TDS 744A, & TDS 784A User Manual U V W TDS 684A, TDS 744A, & TDS 784A User Manual Index15 X Y Z