unreferenced measurement in FPGA-mode

[ThomasV]

Hi,

We have a NI 9205 C-series module (32x analog input -10..10V). If we use this module in CompactDAQ (with DAQmx), we can config the measurement to be referenced to AI_Sense (via unreferenced measurement, vs single ended (= referenced to GND).

Now we are using this module in a CompactRIO, in FPGA mode (not scan engine). Here we can only drag the module input node in the FPGA-VI and select the channel. However we cannot config the measurement. In FPGA mode it always seems to be configured as single ended. We want to use AI_Sense as reference.

There is also no AI_sense input node to measure (to subtract the measurement values from).

Can somebody explain if we can use the AI_sense pin on the NI 9205, when using it on a cRIO in FPGA-mode?

Thx,

Thomas.

[MaxJoseph]

Could you just make two single ended measurements of both and do the subtraction yourself on the FPGA? Measure your AI channel and AI_Sense then do the subtraction and output this value to another pin.

Alternatively, can you configure your measurement on the project? FPGAs are not dynamic, they are hardwired. Sure, they are reconfigurable, but this is not the same as dynamic! Your description of the problem indicates that you expect to be able to configure the measurement 'on the fly' on the FPGA. This is dynamic programming and might not be possible! In this case LabVIEW usually provides a method on the project window.

Else you have to reframe the problem like I did in the first paragraph.

[ThomasV]

Hi,

I think there is a misunderstanding : we just want to measure referenced to AI_Sense in FPGA mode. Nothing dynamic.

Als, as I mentioned i don't think we can measure the AI_Sense input and then subtract. There is only the FPGA channel 0 to 31 input node (so 32 values referenced to GND. We have no AI-sense value. So nothing to subtract from.

Kind regards,

Thomas.

[MaxJoseph]

Hi,

The action of reconfiguring the measurement could be dynamic, like you describe. If CLIP is required to change the measurement type the FPGA will have to be stopped, reflashed and then started again. I do not know whether this is the case for your measurement. If it is then you would usually configure the measurement in the project window.

It sounds like you are unable to select the AI_sense input on your block diagram. I am unfortunately not familiar with the 9205 and cannot comment on how to make this pin available. There might be a way to do that on the project window too.