Electrical Calculations All about calculations How is power factor calculated? We calculate power factor off of real power (P) and apparent power (S). Where pf = P/S. Real power is calculated from the product of the Instantaneous Voltage and Current. Apparent power is calculated from the product of the RMS values for Voltage and Current.AC (RMS) / DC (Mean) / Frequency values The Channel Checker shows 4 values for each channel input: AC+DC (RMS) Geometric sum of the AC and DC values. May not match the numerical sum of the AC and DC values. AC (RMS) AC-only RMS value of the signal input. DC (Mean) DC-only value of the signal input. Frequency The frequency count of the signal. Firmware v4.0.5 and above calculates this based on the zero-crossing of the signal, firmware prior to v4.0.5 calculates frequency based around the mean-value of the signal.