Different value from DAQ USB Device on different computers?

[zupp]

Hello,

I didn't find an answer to this one so I am opening a new question. Here is the problem:

I have a NI USB 6003 card and I am reading some analog signal from a pressure sensor with a framerate of 1000 Hz (I actually use 4 analog input channels for 4 sensors). I created a VI and everything works fine on my computer. I then created a standalone application (.exe) and installer that includes LabView Runtime Environment and drivers for DAQ device. When I install everything on a target computer the program works, but the readings from sensor are weird! For example: I get a readout of 1 bar with a deviation of 0.02 bar on my original computer. When I plug the device on host computer I get an average readout of 1 bar with a deviation of 0.5 bar, which is a lot! This deviation could be seen as some high frequency disturbance - like a noise. What could be the problem? Is this even related with LabView or is it hardware problem?

OS information:

Win 7, 64 bit (my computer)

Win 7, 32 bit (host computer)

LabView info:

LabVIew 2013 , version 13.0f2 (32-bit)

NI MAX version 14.0.0f0

Installer includes:

NI LabView Run-Time Engine 2013 f2

NI-DAQmx Runtime 14.0

Thanks in advance about this one!

Best regards,

Matevz

[Sam_Sharp · Accepted solution]

If you run the NI MAX Test Panel on each computer, do you get the same reading? How do you specify which device to use in your code (e.g. MAX Tasks? Project Tasks? DAQmx configuration VIs?) and do the devices have the same configuration? Are you using the exact same USB 6003 device or are you using a different one on each PC?

Is one computer a Desktop and the other a Laptop? The low-cost DAQ devices are not isolated so you could get noise from your PC's power supply.

[zupp]

Hey Sam!

Thanks for this one. Meanwhile, I figgured out that the noise is exacly 50 HZ, so this is definitely from the PC's power supply as you mentioned. By the way, both computers are laptops. Mine is HP ProBook and the other one some low cost Fujitsu computer. So we found who to blame 🙂

Best regards,

Matevz

[Sam_Sharp]

If you disconnect the laptop charger, you'll probably find the noise disappears 😉

Either get a USB isolator, an isolated DAQ device, or a mains suppression filter.