speed sensor(continued)

[kaylob]

Hi Again;
I posted this question recently but I didn't have enough information on the application to provide enough detail.
We just purchased lab view 6.1 (Basic) and a 6035E card. We are trying to set up a speed sensor on a shaft and bring signal (pulses) back to LabView.
We would like to be able to get the period or preferably frequency from LabView.
If anyone knows of a good way to go about doing this I would really appreciate any help..

Regards,
Bernard

[mikeporter]

What does the signal coming from the end of the shaft look like? is it a single pluse per revolution, an encoder output? a pulse every degree of rotation?

The simple pluse outputs are the easest to do. You simply bring them in and count their pulse width (there's an example in LV). The reciprocal of the time required for a complete revolution gives you the speed in revs per sec. Multiply that value by 60 to get revs per minute.

Check the examples...

Mike...

[kaylob]

Mike,
We tried the measure frequency VI in the examples but we had no luck.
We ran the pulse through the Oscope (and the VI OSCOPE)and we've confirmed it's a square wave, single pulse per rev.
We wired the sensor into the gates and soucres as outlined in the manual for the the freq. measurement VI but again no luck.

Regards
Bernard

[mikeporter]

One thing to be careful of is that you have a very clean squarewave. In my experience the counter input is very sensitive to over- or under-shoot, ringing skewed edges and the like.

Go into measurement and automation and select test panel for the card you're trying to measure the clock with. Go to the Counter I/O tab.

For Counter Mode select "Simple Event Counting" and from the Event Source pop-up select the pin you have the clock connected to. Press the Start button.

You should see the Counter Value go up each time a pulse happens. If it doesn't there's either something wrong with the signal--or your card.

If this works there is something else wrong with either the example code or your setup. I have also found out the hard way th
at there is NO buffering on the digital inputs and is is very easy to fry counters...

Hope this helps...

Mike...

Let me know what you find.