How do I adapt this example to count ticks/unit time?

Question

I found the attached example in Labview 2012, for counting ticks of an encoder wheel.  I can easily count ticks with this vi and my encoder wheel hardware.
I would like to be able to count ticks in a fixed time interval, and return a value of ticks/ms etc.  I would like to do this over and over again in WHILE loop structure.
How do I modify this example to count only for a fixed time interval, e.g. 50ms, output the number of counts, and then start over from zero again?
Alternatively, I could fix the number of ticks, and measure the time that it takes to count, e.g. count to 100 ticks, and tell me the time it took to get to 100 ticks.  Either way is acceptable for my application.  Both give me "ticks/time"
Can someone suggest an architecture to do this?  I'm a bit stuck on how to start.  I was looking at the timed loop structure, but, I can't figure out how the counter would reset to zero...it seems like it would add counts with successive iterations.
I am using cDAQ9174 and NI9401 module.
Thanks,
Dave
Attachments:
Count Digital Events_example.vi ‏23 KB

Answer 1

Hi Kevin,
I got the vi working, but, there is one weird aspect of it.  I am seeing these phantom signals.  Here are three samples of data collected varying the averaging period from 50ms to 1000 ms.  The rate the encoder is moving is about 1 revolution/second, not super fast by any means.  Notice that the phantom signals can be very large or very small
Phantom1 is 1000 ms period.
Phantom 2 is 100 ms period (it's hard to see on the picture, the actual frequency measurement is about 120Hz, as seen in the Excel file data)  The spike to 450,000HZ makes the rest of the data look like ZERO, but, it is actually similar to the others, since all three were collected at the same motor speed.
Phantom 3 is at 50 ms period.
The frequency is about 120 Hz.  This encoder has 120 ticks/revolution, so 120Hz, is one rev/second.
Is there a filter that can be added to eliminate these signals.  They are positively definitely and for certain, NOT real.  My system is a simple belt driven encoder from a DC motor at fixed speed for all three collections here...the spikes up and down are impossible.
I also attached my vi, in case you want to see if I ruined anything adding the WRITE TO SPREADSHEET function.  I will post in the next one..apparently there is  a limit of 3 attachments.
Thanks,
Dave
Attachments:
phantom1_1000ms period.jpg ‏45 KB
phantom 2_100ms.jpg ‏78 KB
phantom3_50ms period.jpg ‏75 KB