Measuring speed with incrementa​l single counter

Question

Hi,
I need to measure the rotational speed and acceleration of a wheel that has 3 hall sensors on it. I will use only 1 of them en it gives 24 pulses 0-5V for a 360° rotation. How can I measure the speed with only a pulse train. I dont have the Quadric encoder...
Now I'd like to measure the rotational speed using a counter of some sort, but the software I tried writing for it isnt working.
Thank you for your help

Answer 1

Hey Nitch,
Concerning the measurements errors:
As you get error when speeding up, it looks like the pulses coming from the hall sensors are to short to get measured by the counter.
Following the USB-6008 specifications, the pulse needs to have a minimum lenght of 100ns (both in high and low state).
As a counter is using edges to count the pulses (for USB-6008 only the falling edge) the edges need to comply with the TTL specifications which means that the rise and fall time of the pulse needs to be within the 50ns range. 
So please have a look at the pulse lenght at higher speeds (are they at least 100ns?) and make sure the pulse comply with the TTL specifications.
 If not you will have to add some additional electronics to reshape the pulses.
Looking at your program.
It's not nescesarry to have two loops.  It's very well possible to have two DAQ tasks within the same look.
Have a look at the Examples which come with LabVIEW --> Exampled Finder --> Hardware Input/Output --> DAQmx --> Synchronization --> Multi-Function.
There are some examples which so the combination of analog and digital input.
Anyhow you will have to remove the right while loop as the DAQ Express VI which apparently gives you the "spanning, stroom, gashendel" values will only start once you have done the counter measurements.  I assume that you would like to have the "spanning", "stroom", "gashendel" and"speed" synchronized measured.
Then you have the choice to log to file during acquisition or after the acquisition.
If you would like to log on the fly don't use the express VI's, but use the lower lever "File I/O" functions. These are faster (less processor time usage).
As you VI is written now, the left while loop will only output the lastest counter value measured to the next loop when you click the stop button for example.
You have to "Enable Indexing" of the m/s output tunnel.  Right click on the tunnel and you will be able to select "Enable Indexing".
This way the application will automatically create an array and each loop iteration the measured value will be added.  One the measurements have been done you can do analysis and save the data using the full array instead of point by point.
Again, also bring your "spanning, stroom and gashendel" inputs to the left loop.
In your right loop you also have a loop counter.
You can simply use the loop iteraction counter (the square box in the left bottom corner with the i).  This is also counting from 0 and incrementing by 1 each loop iteration.
Again, you can do this in the left loop and forget the second loop completely.
Hopes this will bring you a step further.
Don't hesitate to post the VI itself.  This is always easier to look at than an image.
This way we can also make some modications and post it back.
Best regards,
Joeri
National Instruments
Applications Engineering
http://www.ni.com/ask
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