Analogue input voltages railing to +/-32768

[adamar]

Adam

Hi,

I recently bought a RIO-7833R PCI card and am having weird problems with it.

I would like to use it to measure analogue voltages. However, even when nothing is connected to the card, the analogue input channels are railing to +/- 32768. I've written a very simple program to measure these voltages and it’s hard to see how there could be a bug in this code (see attached image). So, I'm thinking it has to be something with the driver of the card or some other bug in LabVIEW, or perhaps a setting on the card that needs to be changed.

Complicating things is that I actually had another card that was doing the same thing that I returned. When they sent me this brand new card it also gave the same values, so I do not think it is a hardware problem with the card. In addition, I've also changed the computer the card was installed in, and again, I get the same values.

Has anybody seen this before? Could there be a bug in the labview driver? I've tried changing the setup of the card in MAX so that the measurements are "differential” or “single ended,” but this does not appear to solve the problem.

Thanks,

[Jack._W]

Hi Adam,

I understand you are getting some strange readings from the analogue inputs on your NI PCI-7833R.

From what you say I agree that it is unlikely to be a problem with your specific piece of hardware. I have had a search to see if there are any known hardware faults for this device fitting your description and didn't get any results.

I don't believe the driver will be creating a problem for such a simple task as long as you have the correct one for your hardware and OS installed. You can check that it shows up in the software section in MAX.

I would suggest then that you try using the known working analogue input project for your device in the LabVIEW example finder which can be found on the start up screen.

In the example finder Select the Browse tab>>>Open the hardware folder>>>R Series>>> Basic IO>>>Analogue Input - R Series.lvproj. This has the FPGA VI to deploy to your hardware and a test Host VI. See if you can then get the expected 0 input when unconnected and test with a signal input on the graph.

Hope this helps

[rickford66]

I don't know about the specific hardware you mention, but it has been my experience that analog inputs that are not loaded, will either float around, or will float to the place that their input design causes.  If you aren't applying a voltage, and you expect to see zero, then ground the input.  Also, if the input is differential, it is not enough to just connect them together.  There needs to be a reference to ground somewhere, so ground both inputs.

[AnalogKid2DigitalMan]

I believe rickford66's assessment of the issue is correct.

-AK2DM

[adamar]

I attempted to run the software you suggested and I am getting an error: -61024

Possible reason(s):

Labview FPGA: The device type that has been configured in this function does not match the actual type of device

This error seem odd so I switched the drivers to match the 7831R that the sample expects...does not work. Again I then switched the driver back to the org 7833R that matches the device. This is a strange issue any help???

Thanks