The MVR Feedback Card is calibrated at the factory at both the 10-Volt and 30-Volt Settings.
The plot above shows a calibration curve that is typical of what would be observed at 10 Volts. At 30 Volts, the curve would be similar except that it would show about 20-25 milligals of range corresponding to 3-4 volts range in the Feedback Voltage output.
To perform the calibration, the raw Feedback voltage is measured at a number of points over the feedback range. A linear fit to the points is used to determine the slope of the calibration curve. The calibration factor is then expressed in units of Volts per Dial Turn. Typical calibration factor values are in the range of 1.2 to 1.5 Volts per Dial Turn with the 10-volt supply to the MVR card.
Note that the voltage range measured is NOT always symmetrical about zero volts. This is normal, and may be related to slight asymmetry in the geometry of the capacitor plates inside the gravity meter.
