Proximity sensor capable of sensing flat spots on shaft?
Proximity sensor capable of sensing flat spots on shaft?
(OP)
Hi, my question is if a proximity sensor would be capable of sensing flat spots ground into a rotating shaft. For example, if the proximity sensor (rated at 8mm max air gap) were mounted so that the face of the shaft were 7mm away, would a flat spot ground to a depth of 6mm be enough to switch the sensor (meaning this low spot would be out of range to the sensor)? For reference, the shaft is about 4-5/8" in diameter, made of 4140 steel, and is rotating at 2100 RPM. With 4 flat spots (for balancing) that would be a pulse frequency of 140Hz. I was looking at inductive senors but with it being 4140 I believe my air gap would be too small after the correction factor.
This would by the cleanest way for me to sense the RPM of the shaft, otherwise I would need to sense the attached gearbelt via another setup.
Thanks,
Lee
This would by the cleanest way for me to sense the RPM of the shaft, otherwise I would need to sense the attached gearbelt via another setup.
Thanks,
Lee





RE: Proximity sensor capable of sensing flat spots on shaft?
RE: Proximity sensor capable of sensing flat spots on shaft?
RE: Proximity sensor capable of sensing flat spots on shaft?
RE: Proximity sensor capable of sensing flat spots on shaft?
Cheers
Greg Locock
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RE: Proximity sensor capable of sensing flat spots on shaft?
It will probably work perfectly when adjusted perfectly before you ship.
It will be a maintenance nightmare and unreliable in the real world.
If shaft speed is important, then it's important enough to deserve a dedicated system to measure.
RE: Proximity sensor capable of sensing flat spots on shaft?
Why not set a laser beam perpendicular to the shaft and just outside the radius to the flat spot on the shaft, with the source on one side of the shaft and the target on the other. You would get an indication every time the flat spot matched the laser beam line. And, if you set the laser warm enough you would ultimately trim the shaft to that length too.
RE: Proximity sensor capable of sensing flat spots on shaft?
- the typically short sensing range
- whether your control system can handle the frequency, response time, and signal hysteresis
- sufficiently discriminate the displacement change
- electrical interference issues
- and probably a few other things I haven't remembered
These things only work well on ferrous metals, though.The resolution is typically less, but another option may be ultrasonic sensors (try Banner Engineering, SICK, others). I got a very nice little ultrasonic analog-output sensor from Baumer (Swiss, I think) that was designed for sensing the liquid level inside test tubes. I was surprised at the resolution (+/-0.1mm if I recall).
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com
RE: Proximity sensor capable of sensing flat spots on shaft?
However, there are sensors that can detect that level of change: http://www.omron-ap.com/product_info/E2C-EDA/index.asp supposedly can resolve down to 1um.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Proximity sensor capable of sensing flat spots on shaft?
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