FFT Measurement Hints | Agilent Technologies 41A, 54621D, 24A, 42A

Making Measurements

FFT Measurement

4To make other measurements, press the Quick Meas key and set the

Source softkey to Math.

You can make peak-to-peak, maximum, minimum, and average dB measurements on the FFT waveform. You can also find the frequency value at the first occurrence of the waveform maximum by using the X at Max measurement.

The following FFT spectrum was obtained by connecting the front panel Probe Comp signal (~1.2 kHz from 54620-series) to channel 1. Set sweep speed to 10 ms/div, vertical sensitivity to 1 V/div, Units/div to 10 dB, Offset to -28.0 dB, Center frequency to 5.00 kHz, frequency Span to 10.0 kHz, and window to Hanning.

FFT measurements

FFT Measurement Hints

It is easiest to view FFTs with Vectors set to On. The Vector display mode is set in the Display menu.

The number of points acquired for the FFT record 2048 and when frequency span is at maximum, all points are displayed. Once the FFT spectrum is displayed, the frequency span and center frequency controls are used much like the controls of a spectrum analyzer to examine the frequency of interest in greater detail. Place the desired part of the waveform at the center of the screen and decrease frequency span to increase the display resolution. As frequency span is decreased, the number of points shown is reduced, and the display is magnified.

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Agilent Technologies 41A, 54621D, 24A, 42A, 54621A, 22A manual FFT Measurement Hints

Contents

Agilent 54621D/22D/41D/42D Mixed-Signal Oscilloscopes Horizontal Controls select sweep speed and delay parameters Display shows current input signalsSoftkeys extend the functionality of command keys Utilities This Book Page Contents Trigger Types Contents Run/Stop/Single/Infinite Persistence Operation Using Labels on the Mixed-Signal Oscilloscope Capturing Data Saving and Recalling Traces and SetupsMath Functions Cursor Measurements Utilities Contents-6 Getting Started Getting Started Getting Started Setting up the Oscilloscope To inspect package contents To inspect package contents Package contents for 54620/40-Series Oscilloscopes To inspect options and accessories To inspect options and accessories Model Description To inspect options and accessories Accessories available Plug Type Cable Part Number To inspect options and accessories Power Cords To clean the oscilloscope To clean the oscilloscopeDisconnect power from the instrument To adjust the handle To adjust the handle To power-on the oscilloscope To power-on the oscilloscopePress the power switch To adjust the waveform intensity To adjust the waveform intensity To connect the oscilloscope analog probes To connect the oscilloscope analog probes Press Autoscale To compensate your analog probeTo compensate your analog probe To use the digital probes mixed-signal oscilloscope only To use the digital probes mixed-signal oscilloscope only Connect the clip to a node in the circuit you want to test Signal Lead Ground Lead Clip Signals Ground To connect a printer To connect a printerTo connect an RS-232 cable To verify basic oscilloscope operation To verify basic oscilloscope operationPress the Autoscale key on the front panel Getting started using the oscilloscope interface To verify basic oscilloscope operation Using Quick Help Getting Started Loading an updated language file from floppy disk Loading an updated language file from floppy diskPage Front-Panel Overview Front-Panel Overview Using Auto trigger mode versus Normal trigger mode Using Single versus Run/StopViewing signal detail with acquire mode Important Oscilloscope Considerations Important Oscilloscope Considerations Using Vectors Display menu Post Acquisition Processing Delayed Sweep 54620/40-series Oscilloscope Front Panels 54620/40-series Oscilloscope Front Panels 54624A 4-Channel Oscilloscope Front Panel Entry knob Autoscale key Softkeys 54621D, 54622D D, and 54642D digital channels Front-Panel Operation Interpreting the display Interpreting the display Example To use analog channels to view a signalTo use analog channels to view a signal To use digital channels to view a signal To use digital channels to view a signal To display signals automatically using Autoscale To display signals automatically using AutoscaleHow Autoscale Works Undo Autoscale To apply the default factory configuration To apply the default factory configuration Center the signal on the display using the position knob To adjust analog channel vertical scaling and positionTo adjust analog channel vertical scaling and position Measurement Hints Expand About Center To set the vertical expand reference for the analog signalTo set analog channel probe attenuation factor To display and rearrange the digital channels To display and rearrange the digital channels To operate the time base controls Press the Main/Delayed, then press the Vernier softkeyTo operate the time base controls To start and stop an acquisition First set trigger Mode/Coupling Mode softkey to NormalTo make a single acquisition To start and stop an acquisition Press the Delayed softkey To use delayed sweepTo use delayed sweep Press Main/Delayed To make cursor measurements To make cursor measurements To make automatic measurements To make automatic measurementsChoose what measurement you want on that source by pressing To modify the display grid To modify the display gridTo print the display Triggering the Oscilloscope Triggering the Oscilloscope Trigger Out connector Selecting Trigger Modes and Conditions To select the Mode and Coupling menu Auto Level and Auto modes To select a trigger mode Normal, Auto, Auto LevelTo select a trigger mode Normal, Auto, Auto Level Normal mode To select trigger Coupling To select trigger CouplingTo select Noise Reject and HF Reject To set holdoff To set holdoff To set holdoff Holdoff Operating Hints External Trigger Input External Trigger Probe SettingsExternal Trigger Input Previous menu MegaZoom Technology Simplifies Triggering Trigger Types To use Edge triggering To use Edge triggeringSelect 1, 2, Ext, or Line as the trigger source To use Edge triggering To use Pulse Width triggering To use Pulse Width triggering Press the qualifier softkey to select the time qualifier Qualifier time set softkey Qualifiers can be set as follows To use Pattern triggering To use Pattern triggering Specifying an Edge in a Pattern To use can triggering To use can triggering Press the Trigger softkey to select the trigger condition Press the Baud softkey to set the can signal baud rate To use Duration triggering To use Duration triggering To use Duration triggering When the duration trigger occurs To use I2C triggering To use I2C triggering Ack Data Stop Start Address R/W Condition Frame Start Addr7 Read Ack Data or Condition 26th clock edge To use I2C triggering To use Sequence triggering To use Sequence triggering Sequence Selected Edge Pattern 1 and Edge Press the Stage softkey and select FindPress the Find softkey and select the Find stage condition Edge Pattern 2 and Edge Nth Edge Press the Stage softkey and select Trigger on Edge 1 or Pattern 1 and Edge Timeout Press the Stage softkey and select Reset on To use Sequence triggering To use SPI triggering To use SPI triggering Resetting all bits in the serial data string to one value Assign source channels to the clock, data, and frame signals To use SPI triggering To use SPI triggering To use TV triggering To use TV triggering To use TV triggering Provide Correct Matching Press the Mode softkey to select the TV triggering mode TV standard Field Alt Field Alternate Triggering To trigger on a specific line of video Line Number Represents Count Line Numbers per Field for Each TV Standard To trigger on all TV line sync pulses To trigger on a specific field of the video signal To trigger on all fields of the video signal To trigger on odd or even fields Holdoff Settings To use USB triggering To use USB triggering To use USB triggering Trigger Out connector MegaZoom Concepts and Oscilloscope Operation MegaZoom Concepts and Oscilloscope Operation MegaZoom Concepts Memory depth values Deep MemoryDeep Memory MegaZoom Technology Oscilloscope ResponsivenessOscilloscope Responsiveness Display Update Rate Display Update Rate Turning channels off To setup the Analog channelsTo setup the Analog channels To setup the Analog channels Press the Invert softkey to inverted the selected channel Press the Imped impedance softkeyPress the BW Limit softkey to turn on bandwidth limiting Press the Probe softkey to display the channel probe menu Press the Main softkey to select Main horizontal mode To setup the Horizontal time baseTo setup the Horizontal time base Main mode Press the Vernier softkey to turn on the time base vernier To setup the Horizontal time base Delayed mode To setup the Horizontal time base XY mode Roll mode Acquisition Modes Acquisition ModesPress the Acquire key to display the Acquire menu Peak Detect All points displayed after Single or Stop Smoothing # Avgs=1 or High-resolution mode Average Mode Realtime Mode Press the Display key to view the Display menu Display modesInfinite Persistence Clear display Vectors On/Off Zoom Pan and ZoomPan and Zoom To pan and zoom a waveform To pan and zoom a waveform Run/Stop/Single/Infinite Persistence Operation Single versus Run/Stop Acquiring DataAcquiring Data Memory Depth/Record Length Memory Depth/Record LengthRun/Stop versus Single Single To take a single trace To run and stop an acquisitionPress the Single key To run and stop an acquisition To capture a single event Connect a signal to the oscilloscope Set up the triggerTo capture a single event Operating Hints Clearing stored infinite persistence waveforms To use infinite persistenceTo use infinite persistence To clear the waveform display To clear the waveform displayPress the Display key, then press the Clear Display softkey To display digital channels using Autoscale Configuring the Mixed-Signal Oscilloscope Interpreting the digital waveform display Activity indicatorInterpreting the digital waveform display List of stacked channels To turn individual channels on and off To turn individual channels on and off To change the display size of the digital channels To force all channels on or all channels offPress the Turn on or Turn off softkey Displayed To change the logic threshold for digital channels To change the logic threshold for digital channels Input Impedance Using Digital Channels to Probe CircuitsUsing Digital Channels to Probe Circuits High-Frequency Probe Equivalent Circuit Probe Grounding Best Probing Practices Using Labels on the Mixed-Signal Oscilloscope To turn the label display on or off To turn the label display on or off To assign a predefined label to a channel To assign a predefined label to a channelPress the Label key To define a new label Label Assignment Auto-Increment FeaturesTo define a new label To define a new label Label List Management Press the Default Library softkey To reset the label library to the factory defaultTo reset the label library to the factory default Defaulting labels without erasing the default library Making a hardcopy print Saving and Recalling Traces and SetupsPress the Save/Recall key to display the Save/Recall menu To Autosave traces and setups To Autosave traces and setups MegaZoom Concepts and Oscilloscope Operation To create a new file name, press the New File softkey To save traces and setups to a new file on the floppy diskTo save traces and setups to a new file on the floppy disk Recalling overwrites current settings To recall traces and setupsTo recall traces and setups Saving printing screen images to floppy disk Saving printing screen images to floppy diskPress the CSV, TIF, or BMP softkey Recalling the factory default setup Recalling the factory default setup Making Measurements Concepts about the 54620/40-series Oscilloscopes Making Measurements Capturing Data Main and Delayed Sweep Making Measurements To use delayed sweep To reduce the random noise on a signal To reduce the random noise on a signal LF Reject Press the Acquire key, then press the Averaging softkey Use averaging to reduce noise on the displayed waveform Smoothing # Avgs=1 or High-resolution mode Making Measurements Characterize the glitch with delayed sweep To use the Roll horizontal mode To use the Roll horizontal modePress the Main/Delayed key, then press the Roll softkey To use the XY horizontal mode To use the XY horizontal mode Signal centered on the display Calculate the phase difference using the formula below Signals are 90 out of phase Signals are in phase Math Operating Hints Math Functions Math Scale and Offset are Set Automatically Math Scale and OffsetMath Scale and Offset Multiply Multiply Subtract Subtract Differentiate Differentiate Figure below shows an example of differentiate Integrate Integrate Integrate and Signal Offset FFT Measurement FFT Measurement Aliasing FFT Operation Scale and offset considerations FFT Measurement Hints FFT Measurement FFT Measurement Hints Cursor Measurements To make cursor measurements Select the X and Y softkeys to make a measurement Cursor Examples Cursors measure frequency of pulse ringing Measuring pulse width with cursors Automatic Measurements Phase DelayAverage Amplitude Base Maximum Minimum Peak-to-Peak RMS Top Preshoot Overshoot Making automatic measurements Making automatic measurements Making time measurements automatically Making time measurements automaticallyFFT measurements Digital channel time measurements Duty Cycle CounterFrequency Period Rise Time Making time measurements automatically Fall Time+ Width Width Isolating an event for frequency measurement Making time measurements automatically At Min Making Delay and Phase Measurements Making Delay and Phase MeasurementsDelay Digital channel measurements Phase Measurement Math Measurements and Units Making voltage measurements automaticallyMaking voltage measurements automatically Measurement definitions Top Using delayed sweep to isolate a pulse for Top measurement Preshoot Making overshoot and preshoot measurementsMaking overshoot and preshoot measurements Making overshoot and preshoot measurements Overshoot Page Utilities Utilities To configure Quick Help languages To configure Quick Help languages Language Info softkey Loading an updated language file from floppy disk To update your instrument to the latest application software Press the Format softkey to select the print format To configure a printerTo configure a printer Scale factors CSV lengthGray scale printing Form feed To use the floppy disk Deleted files cannot be recoveredTo use the floppy disk To set up the I/O port to use a controller To set up the I/O port to use a controllerPress the XON DTR softkey to set the RS-232 handshake Press the Baud softkey to set the RS-232 baud rate RS-232 Connections Pin Number Signal To set the clock To set the clock Press the Saver softkey to select the screen saver type To set up the screen saverTo set up the screen saver To set up the screen saver To perform service functions To perform service functionsPress Start User Cal to start the routine User Cal About Oscilloscope User Cal StatusSelf test To set other options Default Library softkey mixed-signal oscilloscopes onlyTo set other options Expand softkey Performance Characteristics Performance Characteristics Acquisition Digital Channels on 54621D and 54622D only Agilent 54620-series Performance CharacteristicsAcquisition Analog Channels Vertical System Analog Channels Agilent 54620-series Performance Characteristics Accuracy = ±2.0%80 mV + 0.4%80 mV = ±1.92 mV Vertical System Digital Channels 54621D and 54622D only Sample rate of 200/400 MSa/s Horizontal Can Trigger System External EXT Triggering Analog Channel TriggeringDigital D15 D0 Channel Triggering 54621D and 5462 2D Display System Measurement Features Storage FFT Installation categories General CharacteristicsPower Requirements Agilent 54620-series Performance Characteristics Acquisition Digital Channels on 54641D and 54642D only Agilent 54640-series Performance Characteristics Agilent 54640-series Performance Characteristics Vertical System Digital Channels 54641D and 54642D only Range Ns/div to 50 s/div Resolution Vernier Minimum pulse width setting 2 ns Digital D15 D0 Channel Triggering 54641D and 54642D Display System Window Rectangular, Flattop, Hanning Noise Floor General Characteristics Page Numerics Index Missing acknowledge condition, I2C trigger Index Index-3 Index-4 Declaration of Conformity EMC Product Regulations Declaration of Conformity Product Regulations Safety Agilent Technologies, Inc Document Warranty