Flow Meter - programming.

[gregorian7]

Hi,

I am using NI - USB 6215. 

Currently working on flow meter. I supply voltage 24V and read impulse voltage 12V which is wrong according to datasheet. Vimpulse = Vsupply -1V (attached data sheet).

I run the test rig, so I got some flow through the meter, run program from examples ‘Counter – Read Encoder’. It works fine, I can count Position both direction. Only problem I am having is to I work out how many Pulses Per Rev my meter generates.   Also how to convert impulse count to flow (l/min)?

I do know K factor which is 500 Imp./l. but how do I know what flow is if program adds counted impulses to one figure. I don’t need  to measure amount of fluid gone through the meter only work out current flow.

Do I have to count impulses separately for each while loop iteration then ?

Many Thanks,

gregorian7

[ML927]

Hey Greg,

What flow meter do you use ? I guess it is the VS2.

The 500 you give us is equal to 500 impulse/l which is 20ml/impulse.

From that :

1. Either you want the total volume and you just add 20ml for each impulse measure
2. Either you really want a flow value in l/min. In that case you just measure the number of impulse at two different time, get the time difference between the two measures, and do the simple math to get your value.

As for the 12V vs 24V, what do you use to acquire the 12V ? My guess is that 12V might be the right value depending on what type of acquisition you do. If you use a multimeter in DC mode while mesuring your signal, it will return the average value of your signal which is approx. 11,5V.

[gregorian7]

Hi ML927,

Thanks for reply.

Sorry I forgot to add info. about model. It's V2.

How did you work it out

I'd like to measure flow value. Can I use example vi (attached) to count impulses (need to encoded signal and count impulses) or this VI counting position not impulses?

I am not very familiar with counters in Labview. If I use shift register and set iteration time 100ms and measure impulses each time and do the calculations as I add this modification to the example attached.

Yes, I have used DMM to measure voltage on each channel.

Thanks,

gregrorina7

[ML927 · Accepted solution]

Yes you should be able to use that example for your application. Juste be careful : I doubt the counters input will stand 24V !! As for the flow, you can try to average the counter value difference against time, like this.