NI Elvis Read Current and Voltage Simultaneously

[gpsmith]

Greetings,

I'm trying to read voltage and current on an NI Elvis II to characterize the output of a TENS unit (currently using SignalExpress). 

What I have worked out:

Thanks to advice on another question I asked earlier today, I've now got the timing worked out so that I can produce log data at 10kHz when measuring voltage through the CH1 Scope input.

I'm now moving on to the other have, and am trying to add current in as another task.  It makes sense to me to try and read that through the DMM current input.  However, I'm getting errors that will only allow me to read the value once, instead of at the 10kHz rate I measure the voltage at (and would prefer that they are read in sync).

This seems like it should be pretty straightforward to do, but I'm just not seeing it.  It's really important (in a non-academic and non-job way) that I get this done tonight, and I really appreciate all the support this board has offered.  If there's anything I need to provide to make the issue clearer, please do not hesitate to post.!

Would it be easier to run this through LV proper instead of SignalExpress?

[Nathan-M]

The DMM that is onboard the NI ELVIS II is not specced to run at the rates you're requesting. In fact, the DMM is a software timed device, which means that it will only collect samples when your computer tells it to. I created a quick benchmarking code to see how many measurements that an ELVIS II could take per second and I came up with about 4 or 5. You can recreate the code yourself to see similar results. 

After one second, the elapsed time Express VI will output a 'true' which will stop the while loop. The DMM will be constantly acquiring and writing data into an array. When the while loop has finished, an array of DMM data will be output. The size of this array will indicate the number of samples that can be read in one second.