# Other Questions and Information # 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. # Ratings, certifications, etc # AIC or short-circuit rating
AIC (ampere interrupting capacity) is the maximum short-circuit current that a circuit breaker can safely interrupt. The eGauge is not a circuit so it does not have an AIC rating.
Socket-meters (or any type of in-line meter) will have a maximum current that they can safely carry and such meters usually have a short-circuit current rating. For safe operation, the short-circuit current rating has to be higher than the maximum short-circuit current that could occur at a given installation location.
eGauge EG3xxx and EG4xxx meters are not inline-meters and as such do not have a short-circuit current rating. Instead, the CT sensors of the eGauge meters clamp around existing wires, so as long as those wire have suitable current rating, the installation will be safe.