High Speed Velocity Measurment Using Timer/Counter


Thread Starter

Bill Calderhead

I have an application to measure the speed of a projectile over a four inch span with speeds typically between 100 and 150 fps. This a non-contact application using two infrared retro-reflective sensors.

Currently, I have had to implement a custom circuit to transform the two pulses into a single pulse used to gate a timer on the timer/counter card. This is effective but I would like to get away from the custom circuit.

Is anyone aware of a mode of the AM9513A that can input two signals - one to start a timer, the second to stop the timer?


Darren Tichbourne

Hi Bill,

This brings back memories. I designed a circuit 12 yrs ago very similiar to the one you describe. It had to measure the velocity of a 1/2" steel ball bearing travelling at approx. 300 fps. It was part of a regulatory ballistics test that had to be done on plastic lawnmower decks. Used half a dozen cmos chips and 2 photo-transistors and IR diodes. Sensors were mounted about 6" apart if my memory serves me, inside a steel tube. I measured the time between triggering the sensors, start/stop then displayed the converted value in feet per minute on a LED display.

Interesting how applications surface at times, and how new solutions sometimes use the same principles & technology.

Darren E. Tichbourne

President, CET
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