Current flow rate - Pulses as input

[MortenE]

Hello Labview help'ers

I am currently trying to calculate an flow rate from a water flow meter which gives 1 plus / per metric liter. (Using NI 6008 , two pulses per minute)

My idea is to calculated the time between to pulse , using a shift register and timestamps.

I found another example but not in Lab view.

I have spend the last 3 hours seaching in this forum and can see other has had the same problem but no generic solution.

Flow Gague 

http://www.practicalarduino.com/projects/water-flow-gauge

Code for Micro controller with Flow Gague

http://github.com/practicalarduino/WaterFlowGauge/blob/master/WaterFlowGauge.pde

http://forums.ni.com/ni/board/message?board.id=170&message.id=212735&query.id=5446257

http://forums.ni.com/ni/board/message?board.id=170&message.id=191867#M191867 

[Greg_J]

Hi MortenE,

It sounds like your approach of measuring the period and directly converting it to flowrate is your best bet.  Since the counter on the NI USB 6008 does not have a gate, it cannot perform period/frequency measurements directly from the hardware.  Here are a few resources that explain how to use edge counting to perform your period/frequency measurements with LabVIEW and NI-DAQmx:

Example: Can I Use the USB-6008/6009 for Period Measurement Using Events?

Community Example: Software-Timed Frequency Measurement Using Edge Counter

Note that some of the examples provided in these links may not be ideal for low frequency measurements.  If you find yourself needing better accuracy for a low frequency measurement, perhaps it would be best to simply monitor an analog or digital line directly for a level change to calculate the elapsed time between subsequent pulses.

I hope this helps!