cDAQ module to module timing

[jeff_scharpf]

Hello,

I'm using a CompactDAQ 9178 with a 9237 (strain) and 9411 (HS digital) module(s).

The strain module has two load cells attached and the 9411 as a rotary encoder configured with X4 quadature input.

I created two tasks, one with the two load cells and one with the rotary encoder position. I set the sample rate to 10KHZ and both tasks are timed off of the analog sample clock.

My question is, how do I determine how much delay there is (if any) between readings from the 9237 and the encoder position? I have them both running continously in a while loop and I'm just collecting the data as if they were simultanous.

How do I determine the module to module delay? The read commands are both in the same loop but they run "parallel" so I don't know if either one runs first. I have it set up to read 100 readings per loop iteration and I append them to a chart. I'm trying to understand if there is any delay or offset from the strain readings to the encoder position reading.

I hope this is clear.

Thanks,

Jeff

[Mockingbird · Accepted solution]

Hi Jeff,

there would not really be a delay from module to module with what you have. However, there is a filter delay that you would have to account for since you are using a 9237. The links below talk about this more and how you can adjust for the filter delay:

http://zone.ni.com/reference/en-XX/help/370466V-01/mxdevconsid/filterdelay/

http://digital.ni.com/public.nsf/allkb/F989B25FF6CA55C386256CD20056E27D?OpenDocument

[jeff_scharpf]

Thank you! I will look at those.

[jeff_scharpf]

Gabriel does this only apply to digital trigger? Is it the same if I'm using the cDAQ ai sample clock as my timebase? 

I see from your link that the 9237 shows 40/Fs so at a 10KHZ sample rate I would see a 4 ms delay.. is this correct?

I'm not sure if I'm interpreting that correctly.