How can I find the frequency of a signal from a turbine flowmeter?

[moebeth]

My turbine flow meters output a voltage signal frequency. Is there are way that I can find the frequency in LabVIEW? Right now I have the flow meters wired to my card as analog inputs. Maybe I need to wire them in differently.

[Yves]

About the wiring: I would take the counter input of your device. this makes the programming much easier.
About the programming: you'll find the vi's in "daq acquisition" -> "counter".

[moebeth]

I've found the vi's I believe. I don't really understand how to use the counter input. I am using a PCI-6024E. My flow meters have two prongs with no polarity and do not require power. I would put one wire from the flow meter in the counter, correct? But where does the other go? Do I have to use a gate? Thanks for the help.

[Rick]

"moebeth" wrote in message
news:50650000000500000006DD0100-1079395200000@exchange.ni.com...
> I've found the vi's I believe. I don't really understand how to use
> the counter input. I am using a PCI-6024E. My flow meters have two
> prongs with no polarity and do not require power. I would put one
> wire from the flow meter in the counter, correct? But where does the
> other go? Do I have to use a gate? Thanks for the help.

Software guys may frown but you may wish to use an LM2907 or LM2917 F to V
(from the OTHER National) to convert your mag pickup signal from the
flowmeter to an analog voltage first...

[chericks1]

Dear moebeth,

To address your question, can you include more information about the flow meters? As far as I know, turbine flow meters can have outputs of analog voltage, analog current, frequency/pulse, or switch.

If the meters are outputting a voltage, then connect it as an analog voltage input and use the analog voltage virtual channel.

If the meters are outputting a frequency or pulse, connect it as a counter input. With the counter input, you would need to program in LabVIEW without using a virtual channel. Instead, you would use the counter VIs. There are shipping examples included with LabVIEW. Measure Frequency (DAQ-STC).vi can be used just by pressing Run if you wire the signal into the source of whichever counter you want to use and th
e ground into DGND.

Let me know if you have any further questions or if this does not resolve your issue.

Thanks again and have a great day!

Chad AE
Applications Engineer - National Instruments

[moebeth]

I think I figured it out. My flowmeters output a frequency. I can't find a counter input on my DAQ board, but I wired my flowmeters into the analog input. Then I used Extract Single Tone to get the frequency. The reading I get in Labview matches with the mechanical flowmeter I plumbed into my system.
Thanks for your help.

[Yves]

On DAQ6024E the counter input is called GPRCTR0_SOURCE on PIN #42 and #37.
Refer to your handbook p 4-30 and ff for the function description.