Non-Contact Hand Tachometer

Hi Fellas -

Does anyone know if there is some sort of non-contact hand tach available that does measurement in ft/min? All the ones I've found are in RPM and measuring some of the lengths or diameters of these driven parts would be almost impossible.

Thanks guys....Jay

The non-contact velocimeters I have worked with fall into two categories:

1. Photocell looking at a reflector on a spinning shaft and some math. These are common and cheap, but you have ruled them out.

2. High tech (read expensive) CCD or lasers that measure the velocity directly from a surface. All those like this I have worked with are fixed mount units and must be carefully adjusted for a limited range. I have never seen one that is handheld.

Wish I knew of one myself, and if you find something new let us know...

Unless you are using an actual doppler laser guage, surface velocity is not going to be measurable with a standard optical hand tach... Well, unless you are printing a high contrast mark of your target ever foot.

http://www.betalasermike.com/length/default.aspx

For an example of a typical non-contact velocity/length measuring device.

I didn't know if there was a company out there that sold these things with a pre-printed piece of tape that would have alternating pieces of material every inch or two. Have it be a foot or two feet long. I'm just getting sick of speed tracking gigantic drums that are warmed up to 400 degrees going 1000+ fpm.

I guess I wasn't exactly looking for something handheld as I was looking for something portable. Something I could mount would be ideal since that would my the "oh **** this thing is flying" nervous hand tremors out of the equation.

What about a speed probe? We use speed probes quite successfully on some of our compressors here. A proximitor with the probe installed just off the shaft should do the trick quite nicely. Admittedly, the speed readout is in RPM, but if you are willing to mount a unit, getting the outside diameter (there must be design spec sheets somewhere) and placing a conversion factor in the control system shouldn't be much of a hassle. Only drawback is the probe needs to be relatively close to the shaft (max about 1,5 cm, model dependent) in order to interrupt the EMF sufficiently to produce a reading, and I'm not sure what clearances you're dealing with here. You'll also have to have some sort of recess or extrusion in order to produce a Hz frequency the proximitor can convert into a useable reading.

Not sure if this helps.

Alternatively, if you cannot mount a permanent unit (I'd convince management that monitoring high temperature, high speed machinery at the range necessary to get an accurate tachometer reading is HIGHLY dangerous), and definitely need something portable, it looks like this might do the trick for you...

http://www.eztechinstruments.com/vt8204.htm