Example VI? AO channel as power supply for transucer while simultaneously acquiring data from transducer

[CarolynM]

Hi,

I want to output a 5 V signal to my transducer via an AO channel on a NI BNC board while simultaneously measuring data from the transducer on the board via an AI channel. The concept is simple and I can do it in a simple VI very ungracefully.  Is there example code anyone knows of that does something similar? If not, would you suggest running the AI channel nested inside a while loop for the AO power supply channel?  Syncing is not a huge issue, I just want power to be on or off during the whole time I am collecting data from the AI channel.

Thanks

[nathand]

Do not use an AO channel as a supply voltage; it's not designed for that and may not supply enough current.  Most NI boards supply 5V on a dedicated pin - which hardware are you using?  If you need to turn the 5V on and off, consider a relay triggered by a digital IO line.  It's possible a digital IO channel on its own will work for you, but again, the IO pins are designed for signaling and not as a power supply.

[CarolynM]

Okay, thanks for the advice.  I am using a BNC 2090 board and was using a D/A Converter Out channel for the power supply. Is there another way I can figure this on the 2090 board or should I get a separate power supply?

[nathand]

What device is connected to the 2090?  Most likely there's a +5V supply on one of the screw terminals.

EDIT: How much current does the transducer draw?

[CarolynM]

The DAQ device is a DAQCard 6036E. It looks like it has a couple +5 V pins.  How can I figure out how to connect my device to the output of that pin on the 2090?

I believe the transducer draws a current of 1-6 mA. 

[nathand]

If you look at the specs for the 6036E, you'll see that the analog outputs can drive a maximum of 5mA, and the digital outputs are good to 24mA.  So, if you need to switch the supply on and off, the digital output will probably work.  If you don't need to switch it, I'd connect it directly to the +5V source.  I don't have either a 6036E or a BNC-2090 in front of me, but from the manual for the 2090 it appears that the outputs - including +5V - are labeled appropriately.  You'll have to figure out how to make the physical connections since I know nothing about your device, the connectors it uses, and what electrical resources you have available.

[CarolynM]

Are you implying that the digital output is better than the analog output when switching on and off? Or better than the pin?

If I do use the AO or DO, back to my original question, do you have any suggestions for running it simultaneously with AI? Know any good examples?

[nathand]

The digital output is better for supplying power than the analog output.  The constant +5V source is the best choice if you do not need to turn it on and off (it stays on constantly).

There's nothing complicated about the digital IO, look at any of the examples.  It maintains state, so you just need to turn it on when you want it on and turn it off when you want it off.  No need to do anything simultaneously.  If you can't figure it out, attach your code so it will be easier to provide comments specific to your situation.