Agilent Technologies 6000 Series FFT Measurement

Making Measurements 5

6000 Series Oscilloscope User’s Guide 223

FFT Measurement

FFT is used to compute the fast Fourier transform using analog

input channels or math functions 1 + 2, 1 – 2, or 1 * 2. FFT takes

the digitized time record of the specified source and transforms

it to the frequency domain. When the FFT function is selected,

the FFT spectrum is plotted on the oscilloscope display as

magnitude in dBV versus frequency. The readout for the

horizontal axis changes from time to frequency (Hertz) and the

vertical readout changes from volts to dB.

Use the FFT function to find crosstalk problems, to find

distortion problems in analog waveforms caused by amplifier

non-linearity, or for adjusting analog filters.

FFT Units

0 dBV is the amplitude of a 1 Vrms sinusoid. When the FFT

source is channel 1 or channel 2 (or channel 3 or 4 on 4-channel

models), FFT units will be displayed in dBV when channel units

is set to Volts and channel impedance is set to 1MΩ.

FFT units will be displayed in dBm when channel units is set to

Volts and channel impedance is set to 50Ω.

FFT units will be displayed as dB for all other FFT sources or

when a source channel’s units has been set to Amps.

DC Value

The FFT computation produces a DC value that is incorrect. It

does not take the offset at center screen into account. The DC

value is not corrected in order to accurately represent

frequency components near DC.

Aliasing

When using FFTs, it is important to be aware of frequency

aliasing. This requires that the operator have some knowledge

as to what the frequency domain should contain, and also

consider the sampling rate, frequency span, and oscilloscope

Contents

Main Notices Manual Part Number Edition Warranty Technology Licenses In This Users Guide Page 6000 Series Oscilloscope Users Guide 5 Tabl e 1 Model Numbers, Bandwidths, and Sampling Rates Tabl e 2 Secure Environment Mode Option 6 6000 Series Oscilloscope Users Guide Tabl e 3 Memory Depth Option Numbers Tabl e 4 Upgrade Options Page Page Contents Page Page Page Page Page Page Page Page Page A 1 Getting Started Page Page To inspect package contents 6000 Series Oscilloscope Users Guide 23 Figure 1 Package contents for 6000A Series AC-powered oscilloscopes 6000A Series Oscilloscope 24 6000 Series Oscilloscope Users Guide 1Getting Started Figure 2 Package contents for 6000A Series battery-powered oscilloscopes (Option BAT) 6000A Series Option BAT Oscilloscope Page 26 6000 Series Oscilloscope Users Guide 1Getting Started Tabl e 6 Accessories available Page To adjust the 6000A Series handle To mount the oscilloscope in a rack To mount the 6000A Series oscilloscope in a rack To mount the 6000L Series oscilloscope in a rack Tools required (not supplied) Page NOTE Ventilation requirements 6000A Ventilation Requirements 6000L Ventilation Requirements 6000 Series Oscilloscope Users Guide 33 To power-on the oscilloscope 54684e82 Stop XY Z Digital WARNING Page Charging the Battery Operating with the Automotive Power Adapter Cable Replacing the Battery CAUTION result if an improper AC adapter is used. NOTE Page The remote interface To establish a LAN connection (6000A Series) NOTE To establish a LAN connection (6000L Series) Hostname NOTE To establish a point-to-point LAN connection Stand-alone connection to a PC To use the Web interface Controlling the oscilloscope using a Web browser Operating the oscilloscope using a Web browser NOTE Setting a password Page Page Scrolling and Monitor Resolution Identify Function Printing the oscilloscopes display from a web browser To connect the oscilloscope probes CAUTION To verify basic oscilloscope operation WARNING CAUTION Page To compensate the oscilloscope probes To calibrate the probes Passive Probes Supported NOTE Active Probes Supported By 300 MHz, 500 MHz, and 1 GHz Bandwidth Models By 100 MHz Bandwidth Models Using Quick Help Quick Help Languages Page Page 62 6000 Series Oscilloscope Users Guide 2 Front-Panel Controls 6000L Series Oscilloscope Controls Rear Panel Front and Rear Panel Controls and Connectors 1. Power Switch 2. Power Indicator 3. LAN Status Indicator 4. Reset Switch 5. Intensity Control Page Page 6000A Series Oscilloscope Front-Panel Controls NOTE Conventions Graphic Symbols in Softkey Menus 68 6000 Series Oscilloscope Users Guide 2 Front-Panel Controls Figure 6 6000A Series 4-Channel Oscilloscope Front Panel 4-Channel 6000A Series Oscilloscope Front Panel Front Panel Controls Page 14. Utility Key 15. Trigger Controls 16. Run Controls 17. Waveform Keys 18. Horizontal Position Control 19. Horizontal Menu/Zoom Key 20. Horizontal Sweep Speed Control 21. Measure Keys 22. Display 23. Entry Knob Page 2-Channel 6000A Series Oscilloscope Front Panel (differences only) Interpreting the display Status line Display area Measurement line Softkeys 6000A Series Front-Panel Operation To adjust the waveform intensity To adjust the display grid (graticule) intensity To start and stop an acquisition NOTE To make a single acquisition Auto Single To pan and zoom Choosing Auto trigger mode or Normal trigger mode Using AutoScale To set the probe attenuation factor Passive Probes Active Probes Manually Setting the Probe Attenuation Factor Using the analog channels Vertical sensitivity Vernie r Vertic al ex pans ion Ground level Vertic al po siti on NOTE Page Page To set up the Horizontal time base Main mode Page Page Zoom mode Page Roll mode XY mode To make cursor measurements NOTE To make automatic measurements Using Labels To turn the label display on or off To assign a predefined label to a channel To define a new label To load a list of labels from a text file you create To reset the label library to the factory default To print the display CAUTION To set the clock To set up the screen saver NOTE To set the waveform expansion reference point Expand About Ground Expand About Center To perform service functions User Calibration To perform User Cal User Cal Status Self Test About Oscilloscope Installed licenses: To restore the oscilloscope to its default configuration 3 Viewing and Measuring Digital Signals To connect the digital probes to the circuit under test CAUTION Page Page Acquiring waveforms using the digital channels To display digital channels using AutoScale Example Page Interpreting the digital waveform display Activity indicator To switch all digital channels on or off To switch groups of channels on or off To switch a single channel on or off To change the displayed size of the digital channels To reposition a digital channel To change the logic threshold for digital channels To display digital channels as a bus Using cursors to read bus values Page Bus values are displayed when using Pattern trigger Page 4 Triggering the Oscilloscope Triggering Features NOTE Selecting Trigger Modes and Conditions To select the Mode and Coupling menu Trigger modes: Normal and Auto Auto mode Normal mode To select trigger Coupling To select trigger Noise Rejection and HF rejection To s et H ol do ff Triggering the Oscilloscope 4 6000 Series Oscilloscope Users Guide 135 The External Trigger input 2-Channel oscilloscope External Trigger input External Trigger Probe Settings Probe Attenuation CAUTION 4-Channel oscilloscope External Trigger input CAUTION Trigger Types To use Edge triggering Trigger level adjustment NOTE To use Pulse Width triggering Page < qualifier time set softkey > qualifier time set softkey To use Pattern triggering Page Hex Bus Pattern Triggering NOTE To use CAN triggering NOTE Page Page Page To use Duration triggering Page < qualifier time set softkey > qualifier time set softkey To use FlexRay triggering Modes of VPT1000 Control/Operation Oscilloscope Controls the VPT1000, Asynchronous Mode Monitoring NOTE Oscilloscope Controls the VPT1000, Synchronous Mode Monitoring Setting Up the Oscilloscope and the VPT1000 Connecting the Oscilloscope and the VPT1000 Accessing the VPT1000 Menu Specifying the VPT1000 LAN Address Selecting the VPT1000 Control/Operating Mode In PC Mode In Asynchronous Mode In Synchronous Mode In Asynchronous or Synchronous Mode NOTE Triggering on FlexRay Frames, Times, or Errors Accessing the FlexRay Trigger Menu Triggering on FlexRay Frames Triggering on the FlexRay Time Schedule NOTE Triggering on FlexRay Errors NOTE To use I2C triggering NOTE Page Page Page Page Page To use Nth Edge Burst triggering Trigger Idle Time Page To use LIN triggering NOTE Page Page To use Sequence triggering Page Define the Find: stage falling edge. All other channels will be defaulted to dont care (X). Define the Trigger on: stage falling edge. All other channel edges will be defaulted to dont care. Define the optional Reset on: stage falling edge. All other channel edges will be defaulted to dont care. Adjust the trigger level To use SPI triggering NOTE Triggering the Oscilloscope 4 6000 Series Oscilloscope Users Guide 183 Assign source channels to the clock, data, and frame signals Page Page Set up the number of bits in the serial data string and set values for those data bits Resetting all bits in the serial data string to one value To use TV triggering The Page Page Example exercises To trigger on a specific line of video Page To trigger on all 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 Page Page To use UART/RS232 triggering NOTE Page Page Page Page To use USB triggering Page The Trigger Out connector Triggers Source frequency Source frequency/8 5 Making Measurements To use the XY horizontal mode Page Page Page Page Math Functions Math scale and offset Multiply Page Subtract Page Differentiate Page Integrate Page FFT Measurement FFT Units DC Value Aliasing Page Spectral Leakage FFT Operation Page Page FFT Measurement Hints Page Square Root Page Cursor Measurements To make cursor measurements Page Page Page Page Page Page Automatic Measurements Time Measurements Phase and Delay Voltage Measurements Preshoot and Overshoot To make an automatic measurement To set measurement thresholds Page Time Measur ements Counter Duty Cycle Frequency To isolate an event for frequency measurement Period Fall Time Rise Time + Width Width X at Max Delay and Phase Measurements Delay Phase Voltage Measurements Page Amplitude Average Base Maximum Minimum RMS Std Deviation Page Top To isolate a pulse for Top measurement Overshoot and Preshoot Measurements Preshoot Overshoot 6 Displaying Data Pan and Zoom To pan and zoom a waveform To set the waveform expansion reference point Expand About Ground Expand About Center To set the waveform expansion reference point Antialiasing Using the XGA video output Display Settings Infinite persistence To use infinite persistence to display multiple repetitive events Grid intensity Vectors (connect the dots) Using Vectors (Display menu) Varying the intensity to view signal detail Page Acquisition Modes At Slower Sweep Speeds Selecting the Acquisition mode Normal Mode Peak Detect Mode High Resolution Mode Averaging M ode To use the Averaging mode Realtime Sampling Option Realtime Sampling and Oscilloscope Bandwidth Using Serial Decode To decode I2C data NOTE Interpreting Decoded I2C Data Page To decode SPI data NOTE Page Interpreting Decoded SPI Data Page To decode CAN data Page NOTE Interpreting Decoded CAN Data Page CAN Totalizer Type s o f F ram es Counters Page To decode LIN data NOTE Displaying Data 6 6000 Series Oscilloscope Users Guide 289 3Specify the LIN signal: aPress the Settings softkey to access the LIN Signals Menu. Page NOTE Page Page To decode FlexRay data NOTE Interpreting Decoded FlexRay Frame Data Frame Decoding Interpreting Decoded FlexRay Time Data Global Time-Schedule Decoding FlexRay Totalizer Counters To decode UART/RS232 data Page Page NOTE Interpreting Decoded UART/RS232 Data Page UART/RS232 Totalizer To reduce the random noise on a signal HF Reject LF Reject Noise rejection Page Using peak detect mode to find a glitch Page How AutoScale Works Undo AutoScale Specifying the Channels Displayed After AutoScale Preserving the Acquisition Mode During AutoScale Page 7 Saving and Printing Data Printing the oscilloscopes display Print options NOTE Selecting print options Palette Supported Printers Saving and Printing Data 7 6000 Series Oscilloscope Users Guide 319 Saving oscilloscope data NOTE Selecting a destination for your saved data NOTE Selecting a file name Overwriting a file Creating a new file name Page Waveform Trace and Oscilloscope Setup Display Image and Waveform Data Files Display Image and Waveform Data File Formats Choosing save settings Palette Length Control To s ave a w av ef or m an d/ or setup to a USB device To save a waveform and/or setup to the oscilloscopes internal memory To recall waveform trace and/or oscilloscope setup File explorer File system Internal memory USB devices NOTE To use the file explorer Secure Environment Mode Option 332 6000 Series Oscilloscope Users Guide 7 Saving and Printing Data Tabl e 1 8 Ordering the Secure Environment Mode Option 8 Reference Upgrading to an MSO or adding memory depth Software and firmware updates To set up the I/O port Using the 10 MHz reference clock Sample clock and frequency counter accuracy the rear panel or damage to the instrument may occur. Supplying an external timebase reference To supply a sample clock to the oscilloscope Page To synchronize the timebase of two or more instruments To check warranty and extended services status To return the instrument To clean the oscilloscope Digital channel signal fidelity: Probe impedance and grounding Input Impedance Page Probe Grounding Page Best Probing Practices To replace digital probe leads Binary Data (.bin) Binary Data in MATLAB Versio n Binary Header Format File Header Wavefor m Heade r Header Size Wavefor m Type Number of Waveform Buffers Points X Display Range X Display Origin X Increment X Origin X Units Page Wavefor m Data H eader Waveform Data Header Size Buffer Type Bytes Per Point Example Program for Reading Binary Data Reference 8 6000 Series Oscilloscope Users Guide 351 Examples of Binary Files Single Acquisition Multiple Analog Channels The following picture shows a binary file of a single acquisition with multiple analog channels. 352 6000 Series Oscilloscope Users Guide 8 Reference Single Acquisition All Pods Logic Channels Minimum and Maximum Values in CSV Files Page 9 Power and Environmental Conditions Power Requirements Measurement Category Measurement Category measurement category. Measurement Category Definitions WARNING Transient Withstand Capability CAUTION Environmental Conditions Specifications Acknowledgements Contact us Page Index Symbols Numerics A B D E F G H I L M N O P Q R S T U V W X Y