I am trying to measure time delay between two TTL pulses (rising edge of the first signal and falling edge of 2nd signal) generated by two Photo detectors (APD) . These pulses are random pulses. Pulse width is 20ns and height is 2.5 volt at 50 ohm termination. I am using NI PCI 6251 card (M series card) for this job. I have attached my program and DAQ assist settings using for this job to this mail. Problem is 6251 card couldn't detect the pulses from APD. Exactly error shown is
"Error 200474: specified operation did not complete because the specified timeout expired".
I have tried by increasing the waiting time but it didn't solve the problem. I have tested my program with 20ns pulse width TTL pulses which are generated by a function generator, in this case my program worked well and given expected result.[both the signals are from same function generator and they are synchronized so edge separation measurement gives width of the pulse ] The height (voltage) of the TTL pulse generated by the function generator is 4v at 50 ohm termination. Is this height difference creating the problem? What can be the reason ? Can anyone suggest a better way to do this job.
Thanks in advance
Regards
surya
Research student
