05-02-2007 12:27 PM
I am having trouble designing a VI to do what I need. I am trying to find the time difference between two digital pulses on two separate channels but the VI that I currently have only has a precision of more than a millisecond. I needs it to be under 0.1 ms.
Exactly what I am doing:
I have two optical sensors that give a digital pulse on two separate channels when an object passes by them. They are separated by a known distance (about 8 inches) and I am passing an object by them at a relatively high velocity (about 17 feet/sec). I need to use the time difference between them to find an exact velocity. The input is normally high and becomes low when an object interupts the field. I need the time difference between the falling edges and it needs to be within 0.1 ms.
My equipment:
M Series 6250 PCI DAQ
BNC 2120 connector block
I suspect that I need to use LabVIEW realtime but I am not familiar with it. If anyone can think of a good way to do this or even has a VI that I can take a look at then it would be very helpful.
05-02-2007 12:32 PM
I've only got seconds to reply now, but you should look into examples for "two signal edge separation" measurements using one of the on-board counter/timers. You can easily get sub-microsecond resolution!
-Kevin P.
05-02-2007 12:35 PM
05-02-2007 02:03 PM
05-02-2007 02:19 PM
Two-edge separation measures 2 different signals coming in on 2 different pins, but only 1 counter "channel" is used to perform the measurement. The M-series allow very flexible signal routing, so you can very likely map almost any physical PFI pin to almost any functional counter usage (timebase, sample clock, gate, trigger).
-Kevin P.
05-02-2007 02:52 PM
Thanks Kevin,
That does exactly what I need.
05-02-2007 05:26 PM
05-02-2007 07:55 PM
03-16-2010 09:17 AM