AI-Single Scan Problem

[Paul_2003]

I've written a little routine that measures voltage from a potentiostat that has 2 outputs from it:

1. Output with Gain control
2. Output without Gain control

My routine measures the voltage (current) until the current reaches a specific value then performs an output to the potentiostat. Now the output current from the potentiostat is very low, so I have to use the gain output.

My routine is comprised of 2 nested loops:

1. Switches the potentiostat output x amount of times i.e. between high current and low current.
2. Records the input using AI-Single Scan until specified current is reached.

I've tried to include some sort of case structure in my second loop that changes the channel for the AI-Single Scan but it seems that it does
n't change at all.

Any ideas?

Cheers,

Paul

[Matthew C]

Hello Paul,

Thank you for contacting National Instruments.

If I understand your application correctly, you are monitoring one of the outputs of your potentiostat using AI-Single Scan. Once that output reaches a specified value, you want your application to begin acquiring data from a different analog input channel, namely, one that is wired to the second output of your potentiostat.

One possible solution is to use the "Greater?" function to continuously monitor the first input's value. Once it reaches your specified value, use the boolean output of the "Greater?" function to halt the current acquisition and close the session. Then wire that same boolean output to your case structure to reinitialize data acquisition on the second channel. I have w
ritten a small VI that illustrates what I am talking about. My VI uses DAQmx, but you can certainly use Traditional DAQ in the same way.

I hope this helps! If you have additional questions, let me know.

Matthew C
Applications Engineer
National Instruments