Assuming you're using the AbsoluteEncoderCounters example:
1. Yeah that's what I had intended--the specs you gave included a possible 10- or 12- bit configuraiton so I wanted to accommodate both. Keep in mind I don't have the encoders to actually try it out for myself though...
2. I had configured it this way to keep it a little simpler for test purposes. You can manually turn the encoder slowly and check the value as you do it to make sure the acquired data matches reality. To get the task to sample the encoder data at a fixed rate you should just need to modify the ctr0 task to run continuously:
a. Add a DAQmx Timing VI to the task (before committing/starting)--configure it to "Implicit", and make the sample mode "Continuous Samples".
b. Modify the high time for your task depending on your desired sample rate (sample rate= 1/(high time + low time)).
c. Move the DAQmx Start to before the loop, but after all the other tasks have started (wire the error out from the Merge Errors function to the input of the DAQmx Start to achieve this). Remove the DAQmx Stop.
d. You no longer need to commit the task explicitly.
e. Remove the event structure and the acquire button (or if you're feeling up to it replace it with a dynamic DAQmx Every N Samples Event...)--you could instead just read every loop iteration and poll the stop button in your loop to keep it simple.
f. Depending on your sample interval (in part b), you may need to read back more than 1 "sample" per loop (keep in mind a single "sample" is really 12 samples of the digital input line). You'll have to parse the array accordingly.
3. Before following the steps in #2, try just manually rotating the shaft if possible and keeping it stationary through several reads for troubleshooting, then slightly turn the axis and repeat, and keep doing this. You'd only expect a large jump when the measurement transitions between 4095 and 0.
Once the shaft is rotating on its own, you could run into seemingly random measurements if the sample rate is not enough (at the point where you are uncertain about the number of rollovers that have occurred). If you know the direction of movement, the sample rate must be greater than (not equal to) the rate that the shaft is turning. If you don't know the direction of motion, the sample rate needs to be greater than (not equal to) twice the rate the shaft is turning.
Best Regards,
John Passiak
