Hi Everyone, I basically need to measure the time between the rising edges of the encoder B pulse. I am running an engine at 600rpm and acquire pressure data from it for each CAD(crank angle degree). My encoder gives me a pulse at every 0.5 CAD so I have 720 pulses each revolution. I use the Z pulse which is the exhaust top dead center pulse as the trigger to start data acquisition. I need to measure the time between each CAD pulse and write that time into a separate column of a spread sheet. The reason I need to do this is because I record high speed videos of the combustion and the camera generates a precise time stamp for every image after it receives the trigger to start recording. I need to be able to find the the corresponding CAD and pressure value to each image and the only way to accurately do it is to compare the time. I really hope someone can advise me on this as this mod is very important for me right now and I can't complete my thesis experiment till I do this and I'm facing a time crunch. Would be very grateful for any help and guidance. I've also attached my pressure program VI. It does not have a while loop and needs to be run continuously and I know that's really bad but I've just been using what the guy before me did and haven't had time to modify it. Reuven.

Here's a slightly modified example that adds in the use of an "Arm Start" trigger. Counter input tasks need to be triggered this way as the standard start trigger isn't supported. Note that the very first value buffered by this task will measure the time from the trigger edge to the 1st encoder edge. It is *NOT* a full period. It can still be useful though if you plan to calculate timestamps for each encoder edge relative to the initial trigger signal. (Note: newer X-series NI boards made an ill-considered decision where they don't give you this option. The first buffered value comes at the 2nd encoder edge after the trigger. It really messes up trying to sync with an AI task that samples on *every* encoder edge.) -Kevin P

LabVIEW

Time Elapsed between encoder pulses

Solved!

The only thing I see is the trigger config for the AI task. It's block-diagram-wired to be a signal from the other board. Since you've already screwdriver-wired from the counter output to the AI board PFI0, you just need to block-diagram-wire "/Dev1/PFI0" as the trigger signal for the AI task.

-Kevin P

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