speed estimation using low resolution encoders


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I am working on a report that looks at the estimation of speed when a low resolution encoder is in use. I just wanted help on the areas of application of the low resolution encoder, its advantages & disadvantages, its comparison with the high resolution encoders as well as links that could guide me on my work.

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I've used low resolution encoders on a SLC (pulse rate ~300hz), sometimes in conjunction with an interrupt subroutine, so that I could simply take the input to a fast discrete input card vs. using a true HSC card, when that resolution was adequate for control of speed. The module was much cheaper, ladder programming as easy or easier than a HSC card, and I got 14 other inputs I could use as general purpose DI's.

Eric Ratliff

I agree with Steve Myres. Using a low resolution encoder means you can use a lower cost counter. For example, this device, http://www.icpdas-usa.com/products.php?PID=285 , has 14 input channels that each have a built in software counter. But, the limit is 100 Hz, pulses must be at least 5 ms in duration. So, a high resolution encoder could over run this device if the RPM or liner velocity were too high.