Differential optical encoder with PXI 6281

[gkp]

Hello, I am trying to measure linear motion using Renishaw's signum (5nm resolution) differential optical encoder. The NI hardware is:

BNC 2110 (breakout board)

PXI 6281 (DAQ)

PXI 8106 (Controller)

The encoder has A+,A-,B+,B- signals. But the counter only has A,B,Gnd input terminals. How do I connect Differential encoder to the single ended DAQ input?

I have tried using this circuit given on NI website (http://digital.ni.com/public.nsf/allkb/30B7D84EEA53A6E98625692F00640B9B?OpenDocument) but I see noise in the position signal of the order of 30nm.

Is there any other way this could be done. Is there some third party circuitry which I can try out?

Thanks for reading

Gaurav

[ManLongAtNI]

Helo Gaurav,

How Do I Use a Quadrature Encoder with My Data Acquisition Board?

Depending on how noisy the environment is, you can typically ignore the inverse line and only wire the A, B, Z lines as indicated in the above KnowledgeBase article. Keep in mind that your device may be on a different ground so you will have to make sure the ground of your encoder device is reference to the digital ground of the DAQ device. 

If you are still  having issues, can you verify what you mean by noise in the position by providing a screenshot of the encoder signal. I imagine the same external noise influencing both lines and that shouldn't make a difference in mesaurement since A, B are compared relative one anotherr to make the position measurment.