Frequency measuring method and frequency measuring system

Abstract

The invention discloses a frequency measuring method and a frequency measuring system. The frequency measuring method includes: latching pulse edges of input signals by means of clock signals to acquire pulse number Np and clock number Nc in sampling time, and computing pulse frequency P according to P=(NpxC) / Nc, wherein relative error by the frequency measuring method is + / -1 / Nc. When in low frequency, the relative error + / -1 / Np corresponding to + / - pulse signals in existing frequency measuring method is converted into + / -1 / Nc equivalently, while the clock number Nc is much higher than the pulse number Np, namely + / -1 / Nc is much smaller than + / -1 / Np, and accordingly, accuracy is improved. When in high frequency, by setting reasonable unit timing time and being compared with existing period measuring method, the Nc is increased along with prolonging of periods of input signals in the unit timing time, while + / - / Nc is reduced, and accuracy is improved as well. Therefore, when in high frequency and low frequency, the frequency measuring method is higher in measuring accuracy as compared with the existing measuring method.

Description

technical field [0001] The invention belongs to the field of electronic technology, in particular to a frequency measurement method and system. Background technique [0002] At present, on-site control systems, data acquisition and communication systems, and equipment monitoring systems have been widely used in various industries. For example, in the steam turbine speed control system, the accuracy and real-time performance of the steam turbine speed acquisition are very high. There are two commonly used acquisition methods: the measurement frequency method and the measurement period method. [0003] The measurement frequency method is to count the pulses of the input signal within the unit timing time; the measurement cycle method is to count a certain reference pulse within the input signal cycle time. When counting in the above two methods, for a counting process, there is a counting error of ±1 counted pulse. That is to say, for the measurement frequency method, there...

AI Technical Summary

Problems solved by technology

That is to say, for the measurement frequency method, there is a counting error of ±1 input signal within the unit timing time, so the relative error generated by it is about ±1 / N, where N is the measured input signal within the unit timing time It can be seen that the measurement accuracy of this method is poor at low frequencies; for the measurement cycle method, correspondingly, within the cycle time of the input signal, there is a counting error of ±1 reference pulse used, so the relative The error is about ±1 / M, where M is the number of reference pulses measured within the period of the input signal. It can be seen that this method has poor measurement accuracy at high frequencies

[0004] To sum up, both methods have the problem of poor accuracy in some cases, so it is necessary to provide a frequency measurement method with high measurement accuracy regardless of high frequency or low frequency

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