Digital Tachometer with Fast Dynamic Response Implemented by a Microprocessor

A digital tachometer consists of an incremental shaft encoder and an electronic circuit to evaluate the digital or analog speed signal. The method of evaluation and the design of the electronic circuit determine the dynamic performance and the accuracy of the tachometer. The usual method of counting pulses coming from the shaft encoder normally provides a poor dynamic performance, particularly if high accuracy and a wide speed range are required. A method is suggested which provides a good dynamic response combined with good accuracy over a wide speed range. Though the process is very fast, it is possible to use this method in an electronic circuit based on a microprocessor and other highly integrated programmable chips. This implementation is discussed, and it is shown how using a microprocessor-controlled circuit affects the achievable accuracy of the tachometer.