two edge separation measurement

[DAQ_Newbie]

Hey there,

Ive got 2 optical switches (TTL signals) which I use to measure the velocity of an object. One opto is connected to the AUX (signal 1) and the other to the GATE. The object goes thru opto1 first and then opto2. The object then bouces back through opto 2 and opto1. I also want to calculate the rebound velocity but cannot use the same two edge separation measurement technique as opto2 (which is now signal 1 upon rebound) is connected to the GATE and opto1 (signal 2 after rebound) is connected to the AUX.

cheers

don

[Kevin_Price]

One simple idea is to parallel wire the opto signals to 2 different counters.  Let one measure the forward time and the other one measure the rebound time.

If the edge sequence goes 1-2-2-1 (with two discrete pass-through events on opto2), you may need to set up the 2nd counter to use the trailing edge of the

opto2 pulse as an "Arm Start" trigger.

If you're using an M-series multifunction board, it may be easier to create a hardware-timed digital task and then figure out the timing with some post-processing.

-Kevin P.