ASIC IMPLEMENTATION OF A DIGITAL TACHOMETER WITH HIGH-PRECISION IN A WIDE SPEED RANGE

A common method in adjustable speed drives uses an incremental shaft e ncoder and an electronic circuit for velocity estimation, The usual me thod of counting pulses coming from the encoder in a fixed period of t ime produces a high-precision velocity estimate in the high-speed rang e, High precision in the low-speed range can be achieved measuring the elapsed time between two successive pulses coming from the encoder, I n this paper a mixed method that combines the best of the two previous ly mentioned approaches has been implemented using a simple electronic circuit based on one field-programmable gate array (FPGA) and one rea d-only memory (ROM).