Configuring Differential Ports?

[Jimbo76]

Hi,

I've a sbRio (9636) device with analog inputs which I'm using to acquire data. In my Labview project I have the Chassis and FPGA listed, as well as the connectors. If I click on, say, AI0, I can set the voltage sensitivity (1, 5, 10 volts) and whether it is a differential or referenced single ended connection. All very nice ...

The question is this - for a differential measurement you need two ports. The manual for the sbRio helpfully informs me that those would be port AI0 and AI7 on my device. BUT if I configure AI0 to be differential, AI7 does not automatically become differential. In other words, I could quite happily set AI0 to be differential and when I look at the configuration of AI7 it still says reference single ended.

So, do I have to change each pair of ports to be differential or is that automatic (despite what the properties tells me)? What happens if I set AI0 to 5 volts, differential and AI7 to 1 volt RSE? Which I could do but shouldn't be able to! Am I *really* changing the configuration of the ports in the properties tab. There's also no option under MAX to configure the whole board for either RSE or Differential!

Can anyone explain?

[NabilahF · Accepted solution]

Hi Jimbo76,

I am an Applications Engineer from National Instruments. When configuring an sbRIO for differential analog input, you must right-click the appropriate positive channel (AI0-AI7) in Project Explorer and select Properties. From here you can customize the configuration of the channel, which you can then save by clicking OK.

It is important to note that although the complementary differential channel is still visible (AI(n+8) for any AI(n)), it is not active and should be ignored. I hope this helps.

Regards,

[Jimbo76]

Thanks very much for that!

It all works!! 🙂