Quadrature Encoder measurements with PXI-6143 S-Series DAQ

[Bentup]

Has anyone used a S-series PXI-6143 DAQ to take encoder position measurements? I believe there are 2 counters available, if you have any examples of how to access and read from these counters it would be greatly appreciated.

[lab_boy]

Hey,

Check out this DF, it should not be different than regular M-Series board. Along with this article1 and article2 I am assuming you are using LabVIEW (as LabVIEW ROCKS )

Good luck !

-lab

[Bentup]

Thanks. Another question. I tried using the quadratureencoderm-series.vi in the link you gave me. When I run this vi I get the error message "physical channel does not support the measurement type required by the virtual channel you are creating". Does this mean that my S-Series DAQ does not support the angular encoder measurement?

[John_P1]

Hi Bentup,

Measuring a quadrature encoder on your device is actually going to be a bit different than on an M series device.  The STC-2 chip, which is used in the M series, allows for A and B inputs specifically for encoder signals (used in the Angular Encoder task).  The original STC-1 chip which is used in E series and most S series boards (including your 6143) does not have these same inputs.  Instead, you may must a Count Digital Events task (taking advantage of the up/down line of the counter).  The Angular Encoder task is not supported on STC-1 devices.

The article that lab_boy linked earlier actually mentions how to use an encoder with an E series device once you scroll down a bit (here's the link again).  This same procedure should apply to your S series--connect the A output of your encoder to the source of the Counter (this is the signal that you are counting).  Connect B to the up/down line of the counter (P0.6 and P0.7 for counter 0 and 1 respectively). 

The downside with this method is that it is more susceptible to vibrations or noise on the encoder lines. If this is a problem for you, you can look into an external encoder conditioner like the one mentioned in the article.  I hope this helps!

Best Regards,

John

[Bentup]

Thanks John. I have connected the Channel A to PFI8 (Pin 37) and Channel B to P0.6(PIN 16). I still have no output being registered from the encoder. It may be a problem with the encoder. I created a count edges task in the measurement and automation explorer but recieve no edge count when rotating the shaft of the encoder back and forth. Any other suggestions for checking encoder functionality?

[AnalogKid2DigitalMan]

Did you connect the ground of the power supply powering the encoder to the digital ground of your DAQ card?

What is the make/model of the encoder you are using?

-AK2DM

[Bentup]

I have connected the ground of the power supply to PIN36 on my SCB-68. I still recieve no counter feedback when rotating the encoder shaft. I have created a task using the DAQ-MX to count edges with the acquisition mode set to on demand. The encoder is from koyo and series TRDA-2E. Any other ideas?

[AnalogKid2DigitalMan]

bentup:

Need the full part number, since that model offers open collector or line driver outputs, which may or may not be the cause of no counts. If you have a voltmeter handy, probe the outputs while slowly rotating the shaft, hopefully you see 0-5V transitions.

http://www.electromate.com/db_support/downloads/Section1.pdf

-AK2DM

[Bentup]

Full part number is TRDA-2E2500A.

[AnalogKid2DigitalMan]

That model is an open collector. What voltage are you powering the encoder with?

If using 5V for power, try adding a 1Kohm resistor to each encoder output, connect the other end of the resistors to +5V.

-AK2DM