Counting edges with dynapar encoder

[98mazdaman]

Hello,

I am very new to Labview. To kick off some experience, I am trying to count edges on a Dynapar encoder, Model E14020000303. Here is the data sheet:

 https://ecatalog.dynapar.com/downloads/E14_DS_702489_2_.pdf

I am using LabVIEW 2011, with a NI USB-6210 DAQ. My white wire on the encoder is connected to PFI0. The red and black wires are connected to my 5V voltage source. I am rotating my encoder to count the revolutions. Supposedly my encoder is a 200 PPR, and it is also quadrature. 

However, I am not understanding what I am getting when counting edges using DAQ Assistant. I am using the Edge Count on ctr0. I can set the DAQ assistant to run on 1 sample acquisition mode and count the rising edge. When I turn the encoder 100 times, the measured value on the DAQ Assistant is usually around 76500, which would mean 765 edges counted per revolution. I can also change things around and go to continuous acquisition mode. I set up PFI2 as the external clock source with a rising edge and put the green wire in PFI2. I set it to read 1 sample at 1k Hz. This usually results in counting around 820 edges.

I don't understand why I am getting these readings. The DAQ Assistant should only be counting rising edges because that is what it is set at. Why am I getting numbers so high? 

Thanks!

[mikeporter]

Does the number vary? You could have a noise problem.

Mike...

[AnalogKid2DigitalMan]

Did you connect the ground of your 5V power source to the digital ground connection on your 6210?

-AK2DM

[98mazdaman]

Yes, the number does vary. Would 800 edges counted be correct for a quadrature 200 ppr encoder when it is supposed to be counting rising edges?

[98mazdaman]

No, I did not connect the digital ground connection. I can try that tomorrow. I am learning LabVIEW for work, and I have already left for today.

[mikeporter]

The ground could easily cause this sort of behavior.

Mike....

[98mazdaman]

Hey guys,

Sorry for the late reply, I have been put on other tasks. You all were right about the ground, that indeed was the problem. With the daq grounded, the encoder measures 200 edges per revolution.

Thanks!