ADC noise in different delay time in DAQmx

[labmaster]

My DAQ read two voltage through the two channels by using USB-6215 of maximum speed 250 kS/s.

For this work, I use the timed loop with a proper delay time(20~50 ms) and Analog N channel 1 sample.vi.

The loop will be alive for 10 sec.

For 20 ms delay, the noise is greater than that in 50 ms.

 What should I check to resolve this critical problem?

메시지가 05-28-2008 11:27 PM에 labmaster에 의해 편집되었음

[mallorim]

Hi labmaster,

It is curious that you are seeing this noise just with two different timing schemes. There are a few things we can test to see if the noise is an issue with the program, or with your hardware connections. Do you see these same noise conditions introduced when you use a test panel in Measurement and Automation Explorer (MAX), set to continuous Mode and a rate of 20 Hz or 50 Hz? Make sure that the test panel also has the correct grounding configuration: differential, referenced single-ended, etc. If you do not see the noise on the test panel, then your connections are most likely fine.

You can also try the LabVIEW example program Cont Acq&Graph Voltage-Int Clk.vi which you can use to acquire voltage on both channels. You can also set the sample rate, to either 20 or 50 Hz, which you mentioned, or you can set the sample rate to 250 kHz.

Regards, Mallori