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cFP-QUAD-510 won't read encoder inputs > 5V

I have a cFP-1808 ethernet interface with 7 modules attached.  One is a cFP-QUAD-510.  When I hook an encoder to this module and view velocity/position measurements in MAX, I only get valid results if I use the module's 5VDC regulator to power the encoder.  The encoder itself can take 5-24VDC, but when I try giving it 12VDC or 24VDC, I get no new updates in MAX (i.e. the status is successful, the velocity reads zero, and the time stamp doesn't change from when I first started the task).  While powering the encoder with these external supplies, I put a scope on the encoder outputs and verified that they are 90 deg offset square waves (with amplitudes at 11V and 22V respectively) as expected.    When I use the 12VDC or 24VDC power supply as input to the 5VDC regulator and power the encoder off that, everything seems to work perfectly.   The only difference between the two cases is the voltage level given to the encoder.  The manual for the cFP-QUAD-510 claims that it can accept encoder levels as high as 30V.   I'm testing now for a future application where I won't have the option of powering an encoder with the 5V regulator.  What could be causing this problem?

Thanks,
Jeff
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Hi Jeff,

That seems peculiar that your device is not reading counts for the higher voltages.

You may want to check out the following KB first:
My FP-QUAD-510 Will Not Count




Otis
Training and Certification
Product Support Engineer
National Instruments
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ahh, I missed a key part of the sentence:  The FP-QUAD-510 requires the use of an 8–30 VDC, 5 W external power supply for the input channels and the +5 V outputs.

Even if the encoder doesn't use the provided 5V regulator, I still need to attach the external power supply. I tried it, and it works. Thanks!
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