Measuring RPM of a small motor

[bluenoted]

Hi!~

It's too small to measure RPM with a optical tachometer.

Is there any method to get RPM of a small motor?

Thanks in advance...

 

[dgallagher]

Depends upon your definition of small. Is there an exposed shaft? What is the diameter?
Link to a variety of small hand held tachometers and tach sensors:

http://www.reliabilitydirect.com/tachometerproducts/tachindex.htm

 

[GregLocock]

You can get the surface speed of a shaft with a laser velocimeter. Whether it could focus on such a small shaft is an interesting question.

Perhaps you could look at the drive current with a scope, or analyse the nosie it makes?



Cheers

Greg Locock

 

[hacksaw]

if it is really small and turning slowly, use a stop watch...

 

[strokersix]

How about a small mark on the shaft and a strobe light?

 

[Timelord]

Bluenoted,

I've got a mechanical rotation counter in my toolbox. It is made by Starrett. It comes with several different sized small rubber couplings that you hold against the shaft. Run it for a fixed amount of time and do the division and you get the speed. You can probably find one at a tool dealer.

Timelord

 

[m777182]

Your motor is probably fastened onto a drive.Perhaps it would be easier to measure the RPM somewhere on the drive. With a tinny color strip on a rotating part of the drive you can measure rotational frequency and calculate the RPM of the motor.
m777182

 

[Rob45]

You can always put an accelerometer on it or nearby, and find the rotational frequency.
If it's not clear from that, unbalance it slightly, then try again!

 

[Emmet]

If it's a commutated motor, we have two products that measure motor speed from commutation current. The first product is older technology, model CRSM1, but we have a new, not-yet-announced product that can track motor speed well enough to allow it to do time-domain averaging of vibration caused by the motor's imbalance.... Contact me for more info if your motor is commutated.... eraftery@cdasys.com

 

[dubi123]

I don't know what kind of motor it is.
May be you can try this software, it works 30 days in demo mode.

http://www.esser.u-net.com/rpm.htm

It uses sound card and microphone.