Short duration pulses not detected in a Digital Input on CompactDAQ with 9401

[gdlbb]

Hi everyone,

I have the following signal at the entry of my module 9401.

Zoomed it is like that :

So the lengh of the pusle is very short (1,5 ms)

I am able to count it using a counter and simple edge counting for instance.

But I don't want to use a counterbecause I don't need it and I need to save counters for other applications.

So, my point is : I'm not able to work with this signal using a digital input. I mean if you invert this signal and link it to a indicator like a LED, the LED never blink.

I did a test to know if it was my .vi the culprit.

I tried my .vi with a function generator, generating pulse like that but much longer (a 5V PWM with a duty cycle of 50%, instead of 0,003 % like here) and it works.

Do you know if it is because the duration of the pulse is too short it doesn't work ?

so do I need to make it longer with a monostable multivibrator (if i can avoid this I will be glad)

I'm using the .VI enclosed.

It's strange because I can count this signal but I cannot use it in a digital input !

Thank you very much , I can provide more informations if needed.

Guillaume.

P.S : My .vi aims to represent a camshaft turning. As input I have the camshaft speed (frequency) and the signal from the top dead center  (the one you have seen above).

I am measuring the time since I did not see the TDC (in sec) and the I multiply it by the speed, (in °/sec).

So I end up with the number of degrees travelled since the last TDC, So I know exactly, in real time, the actual position of the camshaft. Thank you again, gdlbb.