how to damp the flucating voltage

[Dost]

I am using labview 7.1 with E series card . i made a VI that acquires data from the card. i have used AI sample channel.vi to acquire data in a while loop . I am getting flucating voltage at the out put . what could be the possible remedy to acquire the stable out put.

[altenbach]

What is your definition of "fluctuating": Random noise or slow drifts.

How are your wires connected? Do you use any termination resistors? Differential or Single ended? What is your typical voltage range?

[Dost]

I do nt understand what do u mean by terminal resitors .I am using diffential mode my voltage range is 0 to 5 volts. when i test it with MAX i found it gives me 1.24 to 1.25 not changining very much but when i tested it with my developed VI using AI sample channel it gives me voltages from 1.21 to 1.25 channgine very rapidy i checked it voltage using volt meter it gives me 1.24 or 1.25 .

looking forward for any suggestion

[LV_Pro]

When you checked with MAX were the settings for sampling, etc. the same as in your program? There really shouldn't be any difference if the settings are the same. As to measuring with a meter, they have very slow response times compared with most data acquisitions, so they effectively average out noise, unless it is really big and really slow. Most, if not all, measurement fluctuations like you mention are traceble to noise on the input signal. The difference between MAX and a program may be in the sampling rate, gain settings (full scale definition), whether autoscaling is turned on in one or the other. I've seen the reverse, where I saw what looked like really big "noise" swings in MAX, only to realize that I had autoscaling turned on and the graph's scale was from 4.9 to 5.1 and what looked like a big swing was a few mV. The same can happen if you are looking at the output of your DAQ on a graph, be sure to check how the scaling is set. If the sampling rate is really high for the DAQ vs MAX, MAX may effectively "average" the readings, as it doesn't seen a rapidly changing value, where the DAQ, sampling at a higher frequency, may catch every noise fluctuation.

P.M