Signal Conditioning

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Why would I be Getting RPM variation from encoder input

Our machine reads RPM from encoder. Either 2500  RPM or 3500 RPM with some variation. Recently we get variation of 2000 to 3000 RPM which is not possible from the motor. What should I have the techs look for that could be causing this ? It looks to me like it is interference. The optical Isolator went bad recently and was replaced. Now the RPM channel works again but it is not always stable. Usually is a flat line with +/- 5 RPM variation. At times we get several thousand RMP variatiion.  Any suggestions ?

 

The techs keep working with the lab view program. I think it is a loose wire or possibly a calibration issue. I am new to the cRIO environment. Many years A-B 500 experience and analog I-O. I have not read encoder pulses before though. It may be going to a 9401 card. I'm guessing though. Wanting to get more familiar with the cards and the uses.

 

Crio 9037  9474  9381  9208  9219  9230  9401 8ch high speed i-o

 

 

 

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Hook up a scope at the inputs to see how the signals look like?

 

Line hum on the inputs? Isolation faults?   Replaced the optoisolator with a to slow one? 

 

Check the DAQ: Use a signal generator (or the soundcard 😉 ) or a spare encoder with a drilling MC to simulate the inputs ...

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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