Changing analogue input value based on trigger level

[mrendell]

I have a cRIO chassis that outputs a digital signal on a NI9402 card, and this card is connected to a PXI6683H input, so that I can generate a trigger onto the PXI card using the cRIO.

I want the PXI RT controller to generate a current on a PXIe4322 channel based on this digital signal. i.e. if the NI9402 card has generated a 'high' signal then the PXIe4322 should generate 0mA, and if it generates a 'low' signal then the PXIe4322 should generate 12mA.

Can anyone lend some advice on how I might achieve this in LabVIEW, if indeed it's possible! I'm wondering if it might involve creating a software trigger from edge detection in some way.

[NPowl]

Hi Mrendell,

I want to ask for some more info here if that's OK:

What sort of latency are you looking for here? You could set up DAQ triggers in the typical fashion to detect a falling/rising edge and then analyse the signal in software to determine whether to output a current or not, but this would result in some latency as you would be using software timing.

There may be ways to do it in hardware but I'm not sure how to do it right now and I expect it would involve more work than normal

Thanks,

Nick

[mrendell]

Thanks for the query Nick.

Ideally it would be hardware-timed as everything else in the system is hardware-timed, ideally I'd want it on the 1ms level of latency. Would software timing be able to achieve that?

I'm going to have a further dig around to see if I can find hardware methods.

[NPowl]

In terms of software timing - you can find an estimate of latency here: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P9QiSAK&l=en-US but you may experience jitter. I think the use of software timing will depend on how deterministic you need the response to be.