It's actually impossible to be sure without more context what sense 'timed' is being used here — at first sight, it even seems to be used incorrectly.
'Timed' may refer to the fact that the pulses occur at / after a certain time, which if it is deliberately set = temporisé, but if it is fortuitous, or possibly preset, then it might be 'retardé'
HOWEVER, since we know what generates the pulses, it seems this is actually less likely.
It MIGHT mean that the moment in time at which they occur is 'controlled' by the movement of the conveyor-mounted switch — this isn't strcitly speakeing 'timed'
It MIGHT also mean that each pulse has a specific duration (which may be set independently of the conveyor movement itself. That could at a stretch be said to be a 'timed pulse' (= of time duration)
But my gut feeling is that in fact these ought to be 'timing pulses' — they determine how the automatic controller functions by 'telling' it where the conveyor has got to at any moment; in that sense, the control the timing of the programme. This could conceivably be your 'rythmer' — but notice it is not the pulses themsleves that are 'rythmées',but rather, are used to 'rythmer' something else.
Hopefully, the rest of your context will eventually make all this clear!

Les impulsions sont mesurées dans le temps