1ms Time Loop / Event Trigger from Counter

[seascan]

Hi.  I'm pretty new to LabView so I'm am hoping this is an easy question:

I need to read the pulse signal from some reluctors (toothed wheels that pulse a signal with each passing tooth).  The amplitude of each pulse is above 2.2V so I was planning on using TTL counters.

I need to record the status of 5 counters with each increment of one of the counters  For the RPM and tooth count, I can do this with a 1ms timed loop.

Question:  Can windows successfully give a 1ms (accurate) timed loop?  I know this depends on how much I am doing inside the loop but, for now, I just need to read 5 counters and store the data with a timestamp.

Is it possible to make a counter throw an event?  If the counter is incrememented, can LabView be notified to then go off and handle a block of code?

Thanks for any help you can offer!

[majoris]

What hardware are you using?

[Ben]

I have driven multiple timed loops under Windows XP (LV 7.1) at 1KHz.

It requires carefully tailoring of the OS environment but it does work.

As an alternative a counter borad that supports bufering may aleviate that requirement.

Ben

[seascan]

I'm using the four timers on the 9188 chassis (read through a 9401 Digital card).

[majoris]

I assume you also have an analog input card for the chasis?

So, it's probably possible to get 1ms timing with software timed loops, however based on my quick check of the manual for your chasis

http://www.ni.com/pdf/manuals/372780c.pdf (see section 2-2 for example)

You can use an Analog Comparison Event or a PFI channel to trigger a sample (i.e. your generated pulse is the sample clock). This could allow you to use your pulse to trigger an analog sample. Now, this doesn't get you timing information (it just gets you the value of the analog input at the time the event occurs). To get a time, you can use the counters on the digital card in the same way. You have the counters be driven by a fast sample, on-board clock. Then you can use your pulse events again to sample that clock. So each pulse, you get one analog voltage sample and one time sample from the counter. The resolution on this counter will be great, depending on how fast your counters can be driven (sometimes NI counters can actually be driven faster than the fastest available clock on the card or chasis). 

Or you can just do the software loop.