Troubleshooting a tach generator

[bfrankin]

It is  my understanding that a tach generator is nothing more than a mini generator. Is it possible to verify proper tach operation simply by spinning the tach and monitoring voltage? Is there anything else I should look for when troubleshooting a tach gen?

Thanks in advance for any help on this...

[admino]

A cordless drill is an excellent means of checking a tach generator. You can calculate the voltage based on the speed of the cordless drill.

You can also megger each lead to ground and check for resistance.

You can also pull the brushes and inspect them while you're at it. Also shine a flashlight in at the commutator and see what it looks like.

Other than that, I'm not sure what else you can check.

[stantheman]

Troubleshooting a tach generator for an electric motor

I've seen tach generator end bearings go bad. It isn't an electrical issue but it becomes noisy for a time before it stops working. The bad tach bearings will lead to an electrical failure at some point.

Also, in my experience as an electrician in an industrial plant, the noisy tach generator bearings are not always easy to hear, so most of the time you will find the bearings gone bad after it's too late.

[travis]

Tach generators can take plenty of abuse, but sooner or later they become the source of your shop floor woes. They can be tested with an analog voltmeter and a cordless drill in a quiet area of your shop.

The test is simple, the faster the drill turns, the higher the output voltage. It should also be fairly stable voltage.