Hi,
I am attaching a vi that we've been working on to do a gated photon counting task. The main vi is the "double photon counting" vi, which calls the data_taker subVi. We developed much of it with help from the forum! To start, we have 2 pci 6229 cards and 4 counters overall and we're using labview 2009.
We use a trigger ttl and one counter to generate a delayed gate for for the purpose of photon counting. We then use that gate to count ttl pulses coming from two photodetectors. This process consumes 3 of 4 of our counters (1 for each of two photodetectors, 1 to generate a gate). We would like to implement a background counting task for one of our photodetectors using the 4th and final counter. Ideally we would have an additional gate which would be the same length as our original gate but somewhat later in time after our trigger. I think this would require 2 additional counters, one to generate the gate and one to do the counting, though I'd love to be wrong and hear that it can be accomplished with PFIs ... and I have a nagging feeling that it can, though I don't know how.
As a work-around, we thought we might be able to configure a 3rd counting task that counts when our gate is not on (when the gate signal is low, or after the falling the falling edge of our gate) so that we could use the same gate for all 3 counting tasks. I have configured a vi that I thought would work, but the counter still appears to be very sensitive to our signal (which is large by comparison to the background and is only occurring during the gate). I have tried making the gate very large to be sure that the the signal is not leaking outside of our gate, but that doesn't seem to have been the problem. It really appears that the counter is still counting during the gate.
Is there something apparently wrong with the idea that I can configure the counter to count at all other times except during the TTL pulse that represents our gate? Is there a better way to do accomplish this or an apparent error in my vi?
I would appreciate any insight or suggestions of other threads to follow that I may have missed in my searches!
Thanks !
Meg
