PURPOSE: To improve the input tracking performance by setting a sampling period in response to an instantaneous quantity in a pulse input processing unit processing the instantaneous quantity of a pulse input.

CONSTITUTION: A pulse of prescribed interval is inputted to an input terminal 1 one by one every time detected information quantity reaches a unit quantity. A sampling device 2 counts the input pulse number at each sampling period, the instantaneous quantity is obtained by dividing the pulse number by the sampling period and the result is fed to a sampling period setting device 3 and a data smoothing processing unit 4. The sampling period setting device 3 decides the sampling period in inverse proportion to the inputted pulse number and gives a command to the sampling device 2. The data smoothing processing unit 4 applies data smoothing processing such as moving average processing and weighted filtering processing and outputs a final instantaneous amount from an output terminal 5.