Simultaneous acquisition (continuous & N Samples) of a single signal by forking to two DAQ inputs?

[DoctorAutomatic]

I don't know enough about electrical engineering or data acquisition to know if this is fine or a big no-no.

Essentially I'm acquiring a 0-2000 mV analog signal using a USB DAQ (USB 6001). I have a need to acquire the signal continuously, and also N Samples when a user triggers something. Now I know I could just do the continuous acquisition and implement my own logic to simulate the native DAQmx N Samples from my continuous data. However, my architecture, and all the things going on, would really benefit from just having a second channel acquiring N Samples via native DAQmx functions. I'm sure someone will think it's so easy to just index some samples from my continuous data but I would really prefer to not have to do that for circumstances that are beyond explaining on this forum. 

Is it kosher for me to simply use a jumper wire from the input on the DAQ that is acquiring continuously to a second input that I can setup with an N Samples DAQmx task? Would this harm the fidelity of my signal in any way (qualitative or quantitative)? Does this go against any best practices or in some way considered to be a terrible idea? 

[Bob_Schor]

What an interesting question!  Where I think you will "go astray" with a single USB-6001 is configuring the DAQmx Timing for two A/D Tasks, each with a different set of Input channels and each needing a different "clock" configuration.  I've never considered trying to do this, so I must confess that I don't know if this is not possible, but suspect it might be the case.

However, the USB-6001 is a relatively inexpensive device.  Plug in a second one, and write your Continuous task for one, your N-Sample task for the other.  You shouldn't have too much of a problem branching your input wire (again, I don't recall the input impedance of the 6001 Analog Input), but you can simply try it and see if sampling with two USB-6001s gives you the same reading as you get with Continuous Sampling with a single 6001.

Bob Schor

[Kevin_Price]

I *do* know that it's not possible to run 2 distinct AI tasks needing different clock configs simultaneously on a USB-6001.  (But in fairness, it's also not possible on a whole lot of other much more expensive DAQ devices).

You can't do it the way you were hoping.  You either have to deal with indexing from the continuous task or take Bob's advice to add a 2nd inexpensive USB-6001.

-Kevin P

[Henrik_Volkers]

The 6001 is 20kSPS max (If I got the datasheet rigth) ... continously capture the data (producer consumer), capture the user trigger timestamp (BTW what type of trigger?) and cut out the data?