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Remote velocity detection

Remote velocity detection

Remote velocity detection

(OP)
I would like to measure the velocity of a surface 0-150mm/s with a non contact sensor and a high refresh rate, 10kHz.  I would like to output signal to oscilloscope or PC, pulse or analogue signal would do.  
Sensor can be close to surface and I can can mark the surface with lines like an encoder track.  Lines would have to be <0.2mm.
I have tried a high speed contrast laser sensor but it was too slow even at 0.05ms switching time.
I thought of high speed opto-switch with microscope and even optical mouse sensor technology.
I cant find reflective encoder technology that doesn't require really high accuracy between surface and sensor.

Know of any suppliers in the industry that may have a solution?


RE: Remote velocity detection

Your specs imply that you need a speed resolution of 1.5E-9 m/sec.

Really?

RE: Remote velocity detection

(OP)
How do you work that out?

RE: Remote velocity detection

To get velocity with a high update rate, you will need a much finer encoder resolution.  In general, you need two position transitions per update cycle to calculate delta position/ delta time.  Any chance that you could attach a high resolution encoder to some drive shaft?

RE: Remote velocity detection

Well, possibly incorrectly.  Ran out of coffee this morning.

RE: Remote velocity detection

I think what MJ was trying to calculate was the encoder resolution; assuming a minimum speed of 1 mm/s and a 10 kHz sample rate, the platform will have only moved 0.1 micrometers.  Assuming a 10:1 test accuracy ratio, you'd need 10 encoder lines, or 20 lines/spaces in that interval.  This means the lines and spaces on the encoder would need to be 5 nm wide, which is pretty darn small.

Perhaps you need to consider something like a linear velocity transducer: http://www.transtekinc.com/linear_vel.htm

TTFN

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RE: Remote velocity detection

Yeah, yeah, that's what I was trying to do smile

RE: Remote velocity detection

Or if you can connect to a shaft that drives the belt, you could possibly run an encoder on a jackshaft at 10x speed (or some other multiple) to gain the resolution. The negative would be possible backlash issues.
ISZ

RE: Remote velocity detection

If you have the ability to take your measurement parallel to the surface rather than normal (get ahead of / behind your object) a displacment laser could work.  They can output analog signals with resolutions down to single digit nanometers.

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