Patent ID: 8494796

Claim:
A counting device which counts the number of signals having a linear relationship with a specific physical quantity, wherein the signals have substantially a single frequency if the specific physical quantity is constant, the device comprising: a signal counter configured to count the number of half cycles of input signals during given counting periods; a signal half cycle measurement unit configured to measure the half cycles of the input signals during the given counting periods whenever a half cycle of the signal is input; a frequency distribution generator configured to generate a frequency distribution of the half cycles of the input signals during the given counting periods, based on a measurement result from the signal half cycle measurement unit; a representative value calculator configured to calculate a representative value of a distribution of the half cycles of the input signals, based on the frequency distribution; and a correction value calculator configured to calculate, based on the measurement result from the signal half cycle measurement unit, a to number Ns and a total number Nw n so as to correct the number of the half cycles of the input signals counted by the signal counter, wherein Ns represents the total of the number of the half cycles that are less than 0.5 times the represent value, and Nw n represents the total of the number of the half cycles that are equal to or greater than 2n and less than (2n+2) times the representative value, where n is a natural number of 1 or more.