Non Contact Digital RPM Meter

[D45]

Who has a digital non contact rpm meter?

Reliable? Accurate?

I tinker with small engines alot and am considering one for a diagnostic tool

 

[gizardlizard]

I have one. Used it a few times on old school skid loaders. It works good. Forgot I even still have it lol.

 

[GeoBruin]

I picked one up on Amazon Warehouse Deals. I wasn't sure if it was broken because it was not reliably reading most things. I starting reading and ended up essentially painting a white, high contrast stripe on the shafts/spindles I was trying to measure. It then kind of worked better. I ultimately ended up wrapping the shaft in dark colored tape, and then painting a white stripe on the tape. Then it mostly worked.

I don't know if this is typical behavior, or if this is the intended function/behavior. Perhaps others will chime in with their experiences.

 

[BrandonV]

I picked one up on Amazon Warehouse Deals. I wasn't sure if it was broken because it was not reliably reading most things. I starting reading and ended up essentially painting a white, high contrast stripe on the shafts/spindles I was trying to measure. It then kind of worked better. I ultimately ended up wrapping the shaft in dark colored tape, and then painting a white stripe on the tape. Then it mostly worked.

I don't know if this is typical behavior, or if this is the intended function/behavior. Perhaps others will chime in with their experiences.

Pretty much every one I've ever run into says to apply some form of reflective tape onto the object being measured so that makes sense.

 

[wyb2]

I picked one up on Amazon Warehouse Deals. I wasn't sure if it was broken because it was not reliably reading most things. I starting reading and ended up essentially painting a white, high contrast stripe on the shafts/spindles I was trying to measure. It then kind of worked better. I ultimately ended up wrapping the shaft in dark colored tape, and then painting a white stripe on the tape. Then it mostly worked.

I don't know if this is typical behavior, or if this is the intended function/behavior. Perhaps others will chime in with their experiences.

That’s how they work - shines a light on the shaft and has a sensor that looks for the frequency of light/dark transitions. Mine came with a little “starter pack” of reflective tape, I just assumed they all did seeing as how it’s basically required for operation.

My contribution to the thread: mine was reliable until one of the AA batteries leaked and rotted out the spring that makes contact on the negative side. So I say it’s a great little tool to have around, but (like probably anything that is used infrequently) worth popping the batteries out each time you are done with it.

Actually, mine is still reliable, it just requires a little wad of aluminum foil to install the 3rd battery.

 

[BTL-A4]

I have the Harbor Freight one. It comes with reflective tape that seems to work well. I had to put dark tape on my mill to get it to work on that.

 

[richfinn]

I've got a GTC (it's not exactly non contact, it works by touching an HT lead or ignition Coil).

You would want the GTC 505 M kit with the extra adapters.

GTC505 Engine Ignition Analyzer

Finding dead or malfunctioning coils and plugs can be hard work. The GTC505 makes ignition troubleshooting quick, easy, and painless.

gtc.ca

 

[timgunn1962]

I have had maybe 3 over the last 20-odd years. All have used reflective tape and have worked well with it.

At work, the main hassle with using them is shutting down the machine, removing the guarding and sticking on the tape before restarting and taking a measurement. Our equipment is mostly wedge-belt driven and the belt dust gets on the tape so, even if the tape stays on long enough, the next time you need to measure the speed, it doesn't reflect.

Optical tachos and Infra-Red thermometers are the two instruments that some folk (mostly desk-jockey managers) expect to magically produce precise and accurate readings with no more effort than the press of a button. They can certainly do that, but there's usually a fair amount of preparatory work to get to that stage.

 

[johninct]

I bought a cheap one off Ebay or Amazon and it works good unless there is a lot of daylight/ sunshine on the tape.

 

[RPH]

I have the harbor freight model. Used to verify rpm’s on machine tools during build and programming. Worked well for what I needed.

 

[rmanrman]

I have one for 3 years bought on amazon
Works great. I use it when I do annual maintenance on my whole house generator
The speed is very important for the generator to stay on 60Hz. Do need to attach a white strip before checking with non contact sensor

 

[jmarkwolf]

HF. Had one of these for years. Works well.

https://www.harborfreight.com/search?q=photo%20tachometer

 

[Snip's]

I just bought this one a couple of weeks ago to set the Repulsion / Induction switch over speed on my Delta motor rebuild...
Had to use black electrical tape on the shiny jacobs chuck on the drill press I was using for RPM setting...
As usual, the Amazon description is inaccurate... Top speed is 99,999 RPM not 99 RPM
It was repeatable and worked well for what I needed...

 

[Motown]

Get one of these, they work perfectly fine.

Amazon.com

 

[Steve_P]

For small engine use, I have one similar to the one Motown linked to above that I bought off Ebay 5+ years ago; it shipped from China, and I don't remember the price, but <$20 total. I haven't used it in 6 months, but it still worked then, which was far longer than I expected. I'll buy another one just like it when it dies.

When I worked at a small engine shop, we had a Stihl digital tach. This was in the 1980s, so it was a huge deal at that time as it probably cost $300+. We used it to set max RPM on saws and trimmers, and we found that prior to getting that tach that we were consistently tuning engines too lean, and thus fast, when adjusting by ear. We didn't blow anything up prior to this, but it's always nice to do things right.

 

[alfadan]

Does anyone else think the little handheld ones are also confused by fluorescent/LED lighting? I get some erratic readings sometimes in the shop. Not a big deal, but could be something to consider.

 

[rlitman]

Does anyone else think the little handheld ones are also confused by fluorescent/LED lighting? I get some erratic readings sometimes in the shop. Not a big deal, but could be something to consider.

Fluorescent absolutely yes. LED, maybe, it depends on the driver. But sunlight washes them out too.

 

[GeoBruin]

Fluorescent absolutely yes. LED, maybe, it depends on the driver. But sunlight washes them out too.

Hadn't even considered LED PWM.

 

[jayemm]

 

[seber]

I used an optical unit when I was working. It worked fine as long as the user put reflective tape on the part. I now use a Stihl electronic that also works very well. I think it was $20.

 

[darkzero]

I've got an old Monarch & a Reed. Both use reflective tape to measure RPM. The Reed can also do counts.

My Monarch is old, long discontinued, newer models available. Uses an incan bulb for light, while it worked fine I replaced it with a red LED just for the heck of it. Monarchs are expensive, I got this one a long time ago on ebay.

The Reed is modern/current model, LED, laser pointer, backlit LCD. Normally cost just over $100. I got it for $44 on Amazon Warehouse. It was brand new, even the box looked fine.

They sell the reflective tape for optical tachometers but it's expensive if you buy it that way. I got a roll of reflective tape from work that they were gonna toss out, it's enough to last 3 or 4 lifetimes.

 

[D45]

Interesting. I guess I was not aware reflective tape had to be used to get readings

Is this true for all of these digital meters?

 

[jayemm]

I bought one of these and it came with reflective tape. Couldn't get steady readings. Found out that in addition to peeling off the paper on the adhesive side, there's a clear plastic that needs to be peeled off of the reflective side. "Locks on " good now.
**** Edited to add: it's pretty lightweight, not horrible, but kinda cheapy feeling but OK for my home purposes. For constant shop use I'd get something built a bit heavier that might take a few knocks better.
After researching these I avoided the real cheapies and settled on this one. It cost ~$32 incl. tax delivered. I found youtube reviews on these tachometers were helpful in choosing one but obviously a hands on would be great too.

 

[alfadan]

That aluminum duct tape seems to work ok.

 

[Damon L.]

We always used strobe tachometers at a former employer. Think a timing light that you adjust the frequency of the light flashing. When the shaft (or reciprocating assembly) stands still, you have the rpm.

It wouldn't work well for changing RPMS, but if you have steady state things that you need the RPM from they are the ticket, and require no reflective tape or other prep.