Tachometer

[gas]

I've been asked to add a speed readout to an existing machine, 1200 RPM.
Is there an easier way than cutting a hole in a small box, installing a meter, mounting a power supply etc. etc.?
1.5 dia shaft, limited machine tools at the worksite.

Any comments would be appreciated.

 

[JLand]

How does the shaft spin? I think knowing what drives the shaft and what sort of gearing (or the like) that sits between the source of energy and the shaft may give you enough information.

E.g. the shaft is driven via an EIP VFD. The 4-pole motor spins a 5:1 gearbox. The line frequency is 60hz. This means your shaft is rotating at 5 * (Hz/60) * 1800 * optional slip factor.

If this exact method isn't possible, I bet some variation of it is possible with some key assumptions.

 

[gas]

Thank you
It's for a test machine so I have to look at the shaft itself, the VFD thing didn't fly. I already asked them.

 

[doctord]

can it be a hand held device?

 

[gas]

I suggested that they buy a hand tach but that was also rejected.

 

[JLand]

That leaves the obvious optical tachometer, but you could also do a hall effect or a vibration tachometer. I am sure there are other methods as well. I have experience with neither, but I know they exist. Either way, a handheld tachometer to validate results would probably be a good idea. A quick search indicates they are very inexpensive.

 

[goghie]

You can try inductive, contactless encoders.
https://www.turck.de/en/productgroup/Sensors/Encoders

 

[gas]

Thanks all.
I'm just going to go with a big number and maybe that will convince them to go with a hand held.

 

[Snyd1]

It is not really clear to me what you have to work with other than a motor and a shaft. They said no to VFD, is there a PLC/HMI available inputs. If an input is available that can handle 20hz then a simple prox and flag on the shaft could give you a read out on the HMI if not something like this is cheap. What is the point though if they are not controlling speed, just wanting to see if the motor is failing?

https://www.amazon.com/DIGITEN-Digi...ocphy=9023746&hvtargid=pla-569356064328&psc=1

 

[Tom Jenkins]

I've used photoelectric switches with reflective tape on the shaft successfully. You will need the mounting, power, and display materials you mention. Check with Red Lion - they have a lot of options.

 

[mylespetro]

I've used photoelectric switches with reflective tape on the shaft successfully. You will need the mounting, power, and display materials you mention. Check with Red Lion - they have a lot of options.

I've done this as well, if I recall correctly in our application, it did require a bit of stickhandling in the logic to account for if the shaft stops with the tape under (or partially under) the sensor.