The microprocessor module measures the RF power by means of the A/D converter, measures the temperature and controls the input amplifier sensitivity. Using this data, the software calculates the true RF input power by interpolating in calibration tables.
During the in house commissioning each power sensor individually gets calibrated at several temperatures over the whole dynamic range. The calibration tables derived from this are stored on the power sensor. During operation, the power sensor interpolates in these tables to evaluate the true measured power from the raw ADC value and the temperature reading.