External clocking of PXI-5122

[Azazel]

Hello all,

I am using LV 8.2, PXI-5122, PXI chassis PXI-1042Q, Windows XP

I am trying to drive the PXI-5122 DAQ card with an external clock and it seems to work when the clock is a continuous signal.  Unfortuneatly for my application I require the clock signal to be very similar to a burst as I only need to acquire data in a periodic matter with a very short "no clk signal" down time (<1e-6s) between successive burts. More exactly, I need to send 512 cycles of a 43MHz signal (can be sine or square) and acquire data on the rising edge of each cycle, then wait until the next series of 512 cycles.  I know that this could be accomplished with the internal clk, but unfortunetly my clk signal will eventually need to be chirped (ie. 46MHz to 40Mhz over the 512 cycles).  When I try this I get the following error "The error (BFFA49D9 or -1074116135 or DAQmx -200550) message reports a hardware clocking error." I guess my first question is, Does the external clk funtion for the PXI-5122 have to be continusous or can it be set up like a burst? Secondly, has anyone out there used a chirped signal with any of the NI digitizers as a clk to drive there data acquisition?  Thirdly, is my solution the right approach or do any of you cleaver people have a different method of acquiring data with the PXI-5122 where the clock is not set to a constant frequency but in fact can be slightly chirped?  Any help would be greatly appreciated.

Thanks,

Azazal

[Azazel]

I forgot to mention that the external clk is for a sample - timebase clk, not a reference clk.

Azazal

[David L.]

Hi Azazal,

The scope does require a continuous & free running clock, so the chirped clock will not work. One suggestion is to try stopping and starting the task in between changing clock frequencies. Since the amount of time to do this is system dependant, there is no guarantee if it will work or not.