How to externally time data acquisition rate

[thw2]

I have Lab-PC-1200 card and Labview 5.1. I will like to read the signals from a Hamamatsu linear detector array that has 1024 pixels on it. The trigger (or sample) rate of the detector can be modified over a range covering 1 MHz to 15.625 kHz.

I use the 'Acquire N Scans ExtScanClk D-Trig.vi' (written by a NI staff member) downloaded from the web. If I set the trigger rate of the detector to 15.625 kHz (the slowest possible), the program runs without any problem. However, if I use a faster trigger rate (say, 31.25 kHz) no data is collected. According to the specs, the maximum data acquisition rate of the Lab-PC-1200 card is supposed to be 100 kS/s. How do I solve this problem?

[thw2]

I've answered my own question. The solution lies in disabling the internal channel clock and connecting the triggering clock to the EXTCONV* port of Lab-PC-1200 card to fire the channel clock. The scan clock should be timed with an even faster external clock from the detector. Ultimately, it is the channel clock that is important, not the scan clock. The lab-PC card uses the channel clock in conjunction with the number of channels to set up internal gating pulses which of course become the limiting factor. The external triggering clock connected to the channel clock cannot be faster than the speed of the card (in my case, it's 100 kHz).