analog channel noise

[escski 0]

I hope someone can help me out here....I have a system 5/03 of which is connected an analog card 1746-NI8 on one of the channels I am measuring resistance the range is 1- 10 ohms, however when I try to scale the input through the SCP instr... the counts are not stable at all ,,, I then measure the input voltage coming in from the resistance meter and its rock solid.... I thought I was picking up noise on the analog input but as I stated the voltage is solid..... I don't know where the noise would be coming from..... any ideas would be greatly appreciated.... note: the other channels are noisy as well...

[TimWilborne 108]

Can you post a sketch of how you have your modules wired? These are 4-20mA

[Mickey 71]

Looks like there dip switch selectable voltage or current. (see pdf below) But you are right, how he has it connected or what he has connected is confusing. A drawing would help. 1746NI8VoltageOrCurrent.pdf

[TimWilborne 108]

Mickey, what PDF creator do you use, for some reason I can only open up about half the PDFs you post. But you are correct, my mistake

[escski 0]

all inputs are connected as differential, and are config as 0-10v, there is one channel that is not connected and is not Jumpered , I wonder if that would have any effect.

[TimWilborne 108]

So where are you getting your power from? What do you have hooked to the + and -? Provide a sketch if you can. Also, if you put a voltmeter across the + and - of a particular channel, do you see this fluctuation? Is the reading what you expect?

[Mickey 71]

The one above was created by PDF995. But sometimes I use CutePDF writer. I have had complaints about CutePDF though. Edited 1 Oct 2008 by Mickey

[finfin 0]

How much are the counts varying? all meters have dampening or filtering. Maybe you need to add filtering. You might try putting a scope on it if one is available. A capacitor in your circuit might help also.