following is an example of Amplitude Calibration procedure.
desired amplitude level must be entered in the Input Level
field of the Settings/Calibration window.
Next, the Calibrate INTERNAL source level or Calibrate
EXTERNAL source level button must be pressed.
If the Calibrate EXTERNAL source level is pressed, an
external pure tone generator (microphone calibrator or other
similar device) is supposed to be used.
If the Calibrate INTERNAL source level is pressed, the
soundcard must be connected in loopback (input connected to
starting the procedure, be sure that the input level (and
output level in case of internal calibration) of the
soundcard are correctly set. Check this with some test measurements,
in the Scope window.
this procedure, the amplitude values have been calibrated.
this example an SPL (dB) calibration procedure with a pure tone
of 94 dB is shown. The same can be done with other types of
calibration (Volts or mVolts).
NOTE: the Transfer Function Measurement option
in the Settings/FFT window must be disabled in order
to show amplitude values of data according with the above calibration
Also, FFT length and buffer length must be the same and all
scope data must be selected, in order to have the better accuracy
of the FFT peak amplitude value, according with FFT and Signal
This is done automatically when data are measured and analyzed
in the RTA window.
check the correct calibration, for example in case of internal
calibration, a 1 kHz signal can be set as internal signal
source in the Settings/General window.
a measurement can be performed. Open the Scope window, select
all data and open the FFT of scope Data window.
the below picture the Rectangular data weighting window is used.
The amplitude of the 1 kHz tone peak will be now 94 dB.
calibration can be verified also in the RTA window.
Narrow band spectrum:
1/3 Octave bands: