Apparatus and method for measuring the frequency of a pulse signal

摘要

An apparatus for measuring the frequency of a pulse train signal and method therefor applicable to a speedometer of a vehicle are disclosed in which a count value C of at least one counter which counts number of pulses in the pulse train signal for predetermined counting intervals of time DELTA T (=T/n, wherein T denotes a frequency measuring time interval and n denotes a calculation constant) is updated to a value related to the count value for each predetermined counting interval of time DELTA T and stored and outputted for each predetermined counting interval of time DELTA T so that the same or better performance as that using a stagger ring method can be achieved. The value is expressed by (C-C/ alpha ) in a first preferred embodiment (wherein alpha denotes the calculation constant preferably equal to n), by (C-Cxm/ alpha +D) in a second preferred embodiment (wherein m denotes the number of counters and D denotes the latest count values of the m counters during DELTA T at the time of update), by (C-M1xC/ alpha +M2 D) in a third preferred embodiment (wherein M1 and M2 denotes values determined according to a change rate of the count value C of the counter with respect to time and D denotes the latest count value of the counter for DELTA T at the time of update), and by (C-C/M) in a fourth preferred embodiment (wherein M denotes a value determined according to a change rate of the count value C of the counter with respect to time).