11-19-2009 11:46 AM
Dear All,
After scanning through examples and threads I still do not manage to set up my task. Therefore I would be greatful for any help or example.
The task:
Counting pulses (from a photodetector). The pulses are TTL type and about 15ns long randomly spaced in time. The arrival frequency depends on the light level and varies strongly between 100Hz and 5MHz. Gated means in my case that I am interested in the count rate, i.e. number of count events per time period (usually 0.1-1s). Continuously means that the pulse rate shall be detected continuously and displayed over very long periods (hours).
At final stage I want two read 3 channels synchronosly.
The hardware used is a NI USB-6210 (two devices for 3 channels). Software Labview v8.6.
Using the provided examples like Count Dig events , I manage to count pulses but the counter is simply adding up the count events. I cannot figure out how to reset the counter to zero after a certain integration time without restarting the whole counter each time.
marc
11-19-2009 03:01 PM
Hello Marc,
Just to make sure you are aware, the input bandwidth of the USB-6210 is 20 MHz per the specifications. Any signals smaller than 50 ns are unlikely to be detected properly. Whenever your signal varies above 20 MHz, you will start missing counts and the farther above 20 MHz you go, the more counts you will miss. I'd honestly be surprised if you are able to count a 15 ns pulse reliably at all.
Regards,