flow measurment using labview

[vnarang]

Hi

I am Vikas Narang I have rouble getting my flow meter hooked up with labview.I need some help badly.

Flow meter config are:

Range:0-18 gallons per min

K factor: 330 pulses per gallon

I am using NI 9201 to get voltage signals.

when I am seing the voltage signal in time domian I am seeing some kinda creepy signals in , positve and negative signal.I am sure its nt noise as when I disconnect flow mter from NI daq then I get signals like 4-10 mili volt.But I donot how to moeve further.Manual says flow meter genrated pulses number of pulses will tell abt flow in gallons.But I am confused abt how to measure pulses in Labview,I tried really hard to find.

Guys if any of you have any idea abt this it will be a great help

Thanks

[smercurio_fc]

What exactly are "creepy" signals? I'm not sure if I understood correctly, but do you believe it's not noise, or that it is? 4-10 mV with nothing connected is a bit high. Do you disconnect the flow meter at the end of the cables, or are you disconnecting the cables from the 9201? Are you using shielded cabling? Twisted pair? Have you read over this: http://zone.ni.com/devzone/cda/tut/p/id/3116

To measure the pulses you can use a counter. However, the 9201 doesn't have a counter, so you will need to do it in software. Basically, you collect the data, and count the pulses using the measurement functions that ship with LabVIEW. One that you can use is the Pulse Measurements.

[drjdpowell]

I think your flowmeter puts out digital pulses that you need to COUNT (not measure the voltage of).   You'll need a Digital unit to do that, not the Analog one that you are currently using.

-- James

[vnarang]

Hi

thanks for the reply.I have attached the manual of the flow meter.Pleasesee  the attached manual.Manual says flowmeter needs a DC supply of 5-30V.I am giving DC supply of 5 v to the flowmeter.when I am measuring the voltage output from the flow meter in time domain I am getting following signals.But the manual says i am supposed to get a square wave and I believe following mis not a square wave.I am getting the same signal in both cases I mean when there is flow thru the flow meter and when there is no flow thru the flow meter.

As per the manual flowmeter generates 330  pulses per gallon so as per my calculation frquency generated is 1100 pulses per sec.so I tuk sampling frequency of 5000hz and tried continuous samples and N samples both.But there is no change in the signal.I am not sure where i am going wrong.

Thanks

Vikas

[smercurio_fc]

That's just noise. It appears to me that you have a malfunctioning sensor, -or- a bad connection, -or- a miswired connection, -or- a bad DAQ card. Or more than one of the above. Have you verified the DAQ card works properly by injecting a DC signal into it directly? Have you looked at the sensor output on a scope? Have you double-checked your connections?

[vnarang]

Hi

I have three NI 9201 modules I checked with every Ni module and its the same result.I have four same flow meters I checked 3 of them and still the same result.

[vnarang]

I just had a word with manufactrers they told me,this flow meter gives out digital signals.So am I using wrong NI DAQ module to acurie the signals? Please tell me which module am I supposed to use to acquire the signal.

[Richard2950]

The data sheet is a bit vague, but it appears that the flowmeter has a magnet in its rotating blade and a Hall effect sensor that puts out a pulse every time the magnet passes. You should get a pulse train, the height of which is set by your power supply (5-30 V) and the frequency of which is set by the flow rate. Using a 5V power supply means your digital pulse train should be compatible with standard digital inputs such as those on the 9401 or 9403 modules. You then need to configure a counter/timer on your backplane to count these pulses and turn the frequency into a flow rate.

If you have an oscilloscope you should check the signal there so you know what you have and make sure it is compatible with the module you choose.

[AnalogKid2DigitalMan]

Do you have the (-) output of your 5V supply connected to the (-) or COM or GND input on your DAQ module? Not sure what the terminology is for that DAQ.

That is needed to complete the 'flow' of electrons.

-AK2DM

[vnarang]

I am using Ni 9401 to measure the count.I am using edge count to measure.I clicked on the test pannel and clicked on counter I/O option then selested respec counter and channel as i saw from device pinouts.

but I this thing is not counting counters.My counter values are zeroPlease help and let me  know where am wrong

regards

Vikas