Acquired DC signal from the power meter with BNC2110 and PCI6052E is not stable !!!!!

[Nok]

Hello,,, everyone,
I connect DC-output(0-1 V) from the power meter to the BNC-2110 with DAQ card(PCI6052E) and the signal is oscillate.

I measure the signal with the Fluke Digital multimeter and the measurement value is work fine and stable. Normally, we connect this power meter to the ploter in order to record the power value and the result also work fine.

I guess that may be the noise problem and I try to apply the window filter but it's still not work properly as multimeter.

Anybody has the experience about how to handle this kind of application... Pls help me !!!!

Thank you for any help.

[Nok]

Hi... again everybody

I forget to post my program ..!!!

[JoshuaP]

Hey Nok,

I took a look at you program and that is not a very good way to continuously acquire data. In this case the device is acquiring the data at a very slow rate and this makes it almost impossible to use the filter VIs. In order to filter out higher frequency noise you need to sample much faster than the noise.

I would recommend the Cont Acq&Graph(buffered).vi shipping example that comes with LabVIEW as a starting point for your program. Just make sure you change the limits to 0-1V so your card can adjust its gain settings to help reduce noise. This example uses the hardware clock in the device to sample at a specified rate that you set in the program. The default should be around 1000 samples/second. You can then setup a filter in the software to
remove any 60Hz noise that might be introduced by room lighting or power supplies.

It�s also possible that you are using the incorrect grounding. Try switching between differential and RSE mode. It should be documented in the BNC user manual on how to switch.

http://www.ni.com/pdf/manuals/321860e.pdf

I hope this helps out.

Joshua P.
Application Engineering
National Instruments