Measuring pulses through a current module?

[Kirkface]

Hello,

I am new to LabView. I have a flow meter(PNP Hall effect) that is pulsing between 0 and 18 Amps (essentially a 0-24V square wave) and going into a cDAQ current module(NI 9203). How can I use labVIEW to measure the frequency of the pulse?

Thankyou,

Kirkland

[falkpl]

What is the frequency and duty of the signal in question?
What is the required accuracy of the frequency you need?

Typically high accuracy is done with a counter, but you can continiously sample the signal and use the signal processing vis to get out the frequency this requires you to sample the signal at a higher rate than the square rate period (Min of 2 x but preferable 10x or more).

[Wayne.C]

Kirkland,

What make/model of flowmeter are you using?  Most of these are designed to output a pulse train that is input to a counter.

[Peñata]

Hi Kirkface,

I would also recommend to take a look at the shipping examples for doing frequency measurements. The example can be found in the NI Example Finder. The NI Example Finder can be launched by going to Help»Find Examples.... Then browse to Hardware Input and Output»DAQmx»Counter Measurements»Digital Frequency.

Aaron P

National Instruments

Applications Engineer

http://www.ni.com/support

[falkpl]

The NI 9203 does not have a counter on it so before you try using a counter you mush validate that you have a counter on your system.  If you are using a newer usb chassis for your backplane of the NI 9203 you can use on of the builtin counters and use one of your pfi lines to do this.  MAKE SURE YOU CONDITION THE VOLTAGE TO TTL levels because you mentioned that you have a 24V signal, and you want to input ~5V max on most counters.  I assumed that you have no counters avaliable that is why I suggested the ineligant method of continious sampleing (at >2x your max frequency) and processing the signal for frequency using the signal processing palette.

[Kirkface]

Thanks all for your advise. I am using a cDAQ with current module. The signal duty is 50% and frequency around 30Hz. I have tried using the "Timing and transition measurements" however the frequency seems to bounce around. It seems to pickup other frequencies. I will try use a filter to help eliminate the higher frequencies.My cDAQ does not have a counter. Any other tools from the palette anyone can suggest?

Cheers,

Kirkland