Different sampling rates for PXI-5152?

[bravedonxiote]

LabVIEW gurus,

I have a PXI-5152 and I'm acquiring acoustic data at 1 GS/s using the NI-Scope express VI. I recently received a Thorlabs pyroelectric pulsed energy meter with the hopes of using it to measure the laser energy in order to normalize my photoacoustic response by taking the peak to peak voltage of my acoustic signal and dividing by the peak to peak voltage of my pyroelectric sensor. Unfortunately, I realized that while my acoustic signal gives me an acoustic peak within a few microseconds of the trigger (the laser's trigger electrical pulse which is plugged into the trigger on the PXI-5152), the pyroelectric sensor gives me a long (millisecond) time frame before it responds with it's peak.

I would prefer to sample my acoustic signal at 1 GS/s, however, I won't be able to gather enough signals (and the LabVIEW will run very slowly) in an acquisition to gather the pyroelectric peak to peak voltage in this case. Is there a way I can sample a 1 GS/s for Ch0 and 10MS/s on Ch1 in LabVIEW, or is this limited by the digitizer since it's simultaneously sampled? If it is a limitation of the hardware, what are my options?

[Nathan-P]

You are correct, this is a hardware limitation, because the devices are simultaniously sampled.  Though after the data is acquired and sent to LabVIEW, you can manipulate it to get what you want.  If the CH1 sample rate you want is a multiple of the sample rate of CH0, then you could just decimate the data using "Decimate arrays.vi" (in the arrays palette).  

For example, if you sample both channels at 1GS/s, then CH1 you just decimate by a factor of 100, or in other words, only keep 1 out of 100 samples.  This then gives CH1 an effective sample rate of 10MS/s.  

The only other options would be getting another digitizer, and running them at the same time with different sample rates.  There is an example that shows how to do this in the LabVIEW Example Finder.  niscope EX TClk syncronization with multiple sample rates.vi or something like that.

I hope this helps!

-Nathan