Run-out measurement on live commutator 1

[Skogsgurra]

Hello all,

I needed to measure run-out of the commutator on a number of running DC motors the other week.

A contacting transducer could not be used for several reasons, so I used a Telemecanique inductive sensor with a 4-20 mA output and a 5 mm linear range. I terminated the sensor with resistors to have a 1 V/mm sensitivity and this made a measurement with 1 micron resolution easy.

I am quite happy with this arrangement and the band-width (checked on a lathe) is well above 200 Hz, which makes measurement on machines running at 1500 - 2000 RPM an easy matter. But, there is a problem: The mechanics guys do not think that this method is reliable, They cannot say why, they just do not think that it works. The reason is probably that they never have seen it used before. Not used to it, you could say.

What I need is some supporting evidence or comments. Have you used this set-up? What is your experience? Are there any circumstances that say that it cannot be used?

Any comment is welcome.

 

[ScottyUK]

Hi Skogsgurra,

Ask your mechanical friends if they have ever heard of Bently Nevada or CSI. Both these companies use inductive sensors as part of their vibration monitoring equipment. This type of equipment is is commonly used to monitor and protect very high capital value items of rotating plant such as turbines and generators. The turbine and generator manufacturers trust the technology to protect these large and expensive machines: it sounds to me like you have made the front end of one of these systems from your own materials. Well done!



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Start each new day with a smile.

Get it over with.

 

[Skogsgurra]

Scotty,

Just what I needed! I will have a look at their home-pages.

Thx