How do I calculate the accuracy of the NI 9239 AI module

Hello all,
I am in the market for an AI module that can help me resolve angles to an accuracy of 1/10 of a degree. I am going to have a resolver and I want to do the work of a resolver to linear converter by reading in the signals and doing the math with an NI 9239. I am just trying to figure out if I can get the accuracy I need out of it. How do I go about figuring this out. I don't want someone to do it for me just some help to step through it.
The 9239 has 24 bit resolution and I am using it from +/- 10V, so a 20 volt range. This should give me an accuracy of
20/((2^24)-1) = 1.19x10^-6 V/bit
Is this correct, so I should be able to get an accuracy of a 1/10 of a degree?
Solved!
Go to Solution.

You could also use an encoder wheel and the counter input on the DAQ device. To gain additional accuracy you could then gear the encoder by 10:1 or 100:1
Measuring very small voltages often results in erroneous values being read from induced currents or nearby interference. If you still want to use the analog input, then you could still gear up your measuring device, which would decrease your potential error ratio
*EDIT - Spacebar went all strange and posted the unfinished message O_o
Message Edited by yenknip on 10-14-2008 04:09 PM
- Cheers, Ed

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