I am trying to measure a differential voltage with a NI9205. I created a very simple scan mode VI to measure AI5 10 times a second and display the measurements in a waveform chart. No matter what I hook up to the NI 9205 module, the measurement is always zero.
I have tested AI5 with a voltage divider that outputs 0 to 10 volts. The voltage is seen at the NI 9205 card because the voltage can be measured with a multimeter at the module header where the signal wires are attached. I have also tried another sensor outputting 26mV into AI1 and still have no measurement.
The module is set up in my project as measuring a differential +/- 10V signal yet I still see a zero measurement on my VI's front panel. What might I be doing wrong?
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What do you have connected to the negative side? Did you connect the COM to your ground?
You might want to post your code. When you say zero, you mean 0.0000000000000 right? Make sure you're checking for errors.
I have the negative side (channel) connected to my negative signal output from my sensor. I have not connected my COM terminal to ground. Does the 9205 need the COM connected to the voltage supply ground in order to produce a measurement?
Thank you for the help.
I have always received 0 no matter the data type. I know the 9205 outputs values in fixed point when running an FPGA application and double in a scan mode application.
I am testing out two different voltage ranges when trying to collect a measurement: one at 26mV and another closer to 10V. Even with my +-10V range, there should be some non-zero measurement for 26mV.
You didn't answer my question about if it was 0.000000000000 or just something small. Also, you don't have an error indicator on your scan read node. Lastly, it might be nice to have a minimal project so that the nodes don't break when we open the code.
I received an error from the shared variable input (voltage measurement) stating that there is a shared variable in the VI and an error occurred when reading the shared variable. The error code is -65536 and I could not find any information about this code.
I have created a new project and now the 9205 module works. I think I may ditch my current project, create a new project and transfer all the "good" VI's.
Thank you for all the help.
I found your error:
It looks like maybe you are using hybrid mode in the "bad" project. If you don't need hybrid features, then I think you're good to go.
Awesome, the article nanocyte has above is most likely my error. My project is a hybrid mode project. I will read up on initializing the FPGA code before the scan mode code. Thank you for the help!