Select a channel amongst the channels for which DC calibration has been selected on the main tab
Shows the current status of the channel, calibrated or uncalibrated
You can edit the amplitude response (EU vs ADC counts) or the frequency response (multiplier against frequency).
For amplitude response, ADC counts will be either bipolar (signed integer) or unipolar (unsigned integer)
Tick this check box to define the amplitude response as a breakpoint table (see 6). If unticked, the response will be defined as a polynomial.
The breakpoint table (at least 2 points) for the amplitude response
In the breakpoint table, specify ADC counts of millivolts
In the breakpoint table, the power factor of the EU specified (Peak, Peak-to-Peak or RMS).
To add a new point in the breakpoint table
Shows amplitude response as defined in the break point table. The green curve is built by linear interpolation between the points. The dash red trace is the polynomial fitting to the values.
When any values are added, removed or updated in the grid, the GUI will attempt to match a fifth order polynomial to the values. The coefficients of the polynomial are displayed in a grid; the error from the original values to the polynomial is displayed as three figures:
Root Mean Squared (RMS) Error
Peak Error
Peak Error minus RMS Error The graph on the bottom of the polynomial box displays error squared through the range of values. The user may modify the up-sample factor with the up down arrows in the polynomial box. This value represents the factor by which the signal (built from the user values) is up-sampled before fitting a polynomial; this helps to smooth the resulting polynomial since the fitting method used is a least squares approximation to minimise the squared error at points (as opposed to minimising the error along a line).
Calibration may be saved in the configuration file as the breakpoint table defined in 6), or the fitted polynomial displayed in 11). Note that if the configuration is saved as breakpoint table, linear interpolation will be used when the cal is applied in real-time.
Amplitude response is defined as a polynomial
Specify the polynomial coefficients in the grid (up to the 5th order).
Frequency response (multiplier vs frequency) can be defined as a breakpoint table or a polynomial. Frequency calibration is applied in frequency domain, on each FFT bin.
