Hi Mark:
This depends on the output impedence of the thing (sensor or whatever) transmitting the signal, and also the input inpedence of the device receiving the signal. Most NI devices, I think, have pretty high input impedence, so the line loss would probably not be a problem, unless the transmitter also has a very high impedence. If, for example the input impedence of the A/D card signal conditioner was 1 megohm, and if the output impedence of the transmitter was, for example, 50 Ohms and the cable resistance was, for example 10 Ohms, then the error due to line loss would be something like (50+10)/1 million-- All these numbers are pretty conservative guesses, so probably you'll have no problems from simple line loss.
The more serious issues are rela
ted to noise and "ground loop" errors. Depending on what other electrical equipment is in the vicinity, depending on how you ground the sensor and the A/D board, and depending on whether you use simple, shielded or coaxial cables, these can get to cause SERIOUS problems if you need great accuracy in your measurement.
Check out good discussions of this in the LabView documentation, NI's web site, and (my favorite, as someone not trained as an electrical engineer who has to sometimes commit acts of electrical engineering) Paul Horowitz & Winfield Hill "The Art of Electronics" ISBN 0-521-37095-7.
Good Luck with your measurements!
