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Calibration

Click the <Options><Processing Settings> menu (or press F4) and select the "Calibration" tab to access the calibration settings.  You can also click the corresponding toolbar button to access these settings.

By default, the analyzer is calibrated to units of volts. The calibration options allow you to calibrate the analyzer to a wide range of engineering units.

Enable:  if disabled the analyzer will be uncalibrated and the amplitude values will be in units of "Percent Full Scale" or "dB Full Scale" where 0 dB is the clipping point of the waveform.  Calibration is enabled by default.

Calibration File: selects which calibration file to apply.  The filenames "Volts" and "Millivolts" are reserved names and always available.  Any user created calibration files will be added to this list.

File Edit/New: allows you to create or edit a calibration file.

There are three calibration methods:

1) Directly specify transducer sensitivity - select the transducer type and then enter its actual sensitivity.  For example, 45 mV/PA for a microphone (consult your transducer calibration sheet for this information).

2) Calibrate to an external source  - this allows you to calibrate to a known external reference.  With this information we can conpute the correct scale factors.  Here is the procedure:
  • Connect a steady state reference pure tone (such as a mic calibrator) to the input of the selected channel (do not use a DC level or noise signal). 
  • Select the applicable units for the reference signal or select "Custom" and enter the axis labels to the right.
  • Enter the actual reference signal level value in the edit control (for example 94.0 dB SPL)
  • Select the reference signal type: "Peak",  "RMS" or "Peak to Peak" as appropriate (mic calibrators produce RMS values)
  • Press the "Measure External Signal" button.  The analyzer will then measure and display the voltage and frequency.  Wait for it to stabilize.  The analyzer will then compute the corresponding scale factors.  

    3) Calibrate to a Wave File containing a calibration signal - will compute the calibration scale factors from an existing wave file
  • Select the applicable units for the reference signal or select "Custom" and enter the axis labels to the right.
  • Enter the actual calibration signal level value in the edit control (for example 94.0 dB SPL)
  • Select the reference signal type: "Peak",  "RMS" or "Peak to Peak" as appropriate (mic calibrators produce RMS values)
  • Press the "Measure From Wave File" button.  The analyzer will then process the contents of the selected wave file and display the detected level (percent full scale).

    Please note that this option is intended for a situation where you are Post Processing wave files that were captured on non DT hardware and where you also have a wave file with a calibration signal of known level.  Do not use this option for recording new files as the calibration reference file recording gain is not known.

    Converting Acceleration to Velocity or Displacement:

    If you are calibrating to units of Acceleration the "Convert Acceleration To" field will activate and allow you optionally convert the spectrum to velocity or displacement.  These conversions do not apply to the time series display.

    You may customize the amplitude axis labels by directly modifying them in their respective edit boxes.  

    Channel Name:  Enter a name for the channel - this is shown on all plots and utilities to help identify the signal.


    See also:  Scaling, Transducer Compensation  Settings,