beginner question - 3 sensors

I have 3 optical sensors, placed vertically.
My conveyor transports a "box" past these 3 sensors, to measure height, depending on how many of the sensors that see the box (1, 2 or 3)
My question is, how do I limit my program to only trigger once when measurering?
I expect sensor 1 going high, would trigger my program to think the box had a certain height, before sensor 2 could go high, hence give me a wrong height.

Apparently the timing of the sensors is not always the same? I would suggest that you add a short time delay from the lowest sensor before you decide what height you actually have and interlock the three sizes so that only the highest sensor seen can be true. (example: lowest size = sensor1 AND NOT sensor2 AND NOT sensor3)

You could try basing it something like the attached albeit this is quite simplistic.

Steve

It sounds like you’re triggering a process to look at all three sensors by sensor 1 going high. If so then what’s happening is that when sensor 1 goes high the process starts by looking at the status of all of the sensors but 2 and 3 haven’t triggered yet (I’m a little surprised but I’ve seen weirder stuff). I’d look at two ways to deal with it, one, you could add a timer that delays the start of the process a few milliseconds giving the other two sensors time to react or if you can stagger the sensors so that sensors 2 and 3 are in front of sensor 1. Then when sensor 1 triggers the process 2 and 3 are already tripped (assuming the box is that high).

When any sensor is triggered set a latch for that sensor. When all sensors are clear for X time use a one-shot (timer done?) to selectively move a unique value for each latch set to a single integer. Arrange these move rungs in scan order low-to-high. Don't forget to reset the latches for the next cycle.

How about this?