rpm monitoring with micrologix 1100

Im using a micrologix 1100 BBB, and i want to have a real time rpm monitoring on a motor shaft using an inductive sensor.Ill be using the HSC input I 0/0, but ill need your help for the rest.( im a brand new electrician)

thanx

neomad said:

Im using a micrologix 1100 BBB, and i want to have a real time rpm monitoring on a motor shaft using an inductive sensor.Ill be using the HSC input I 0/0, but ill need your help for the rest.( im a brand new electrician)

thanx

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Welcome to the Forum!

There are a number of examples in Chapter 5 of the ML1100 Instruction Reference Manual. Start there, and get to know what the HSC can do, and the different Parameters. Basically, you will want to Count Pulses over a Time Period. One minute is the obvious choice, however, that means you will have to wait a full minute for an updated value, so you might want to use a shorter time, and then multiply. However, this does add some error.

Instruction Reference:

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1763-rm001_-en-p.pdf

Stu....

Welcome to the Forum !

This is a good exercise in basic math and sensor theory, too.

To measure the speed of a motor shaft with an inductive sensor, typically you either count teeth on a sprocket or you count a key or other feature that is prominent from the shaft.

Let's say you're counting a shaft key. For the sake of argument, it's a 1/4" key on a 1" motor shaft, so it sticks up 1/8" above the shaft.

A the typical speed of an industrial induction motor, 1800 RPM, the key will be passing the sensor 30 times a second.

So as an exercise, figure this out: for the above assumptions, for how many milliseconds will the input be true ?

Can a standard MicroLogix input reliably count that signal ? Can a high-speed MicroLogix input reliably count that signal ?

And will the proximity sensor you chose reliably detect the key if it's only present for that number of milliseconds ?