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Topic: OMEGA low flow meter wiring (Read 1 time) previous topic - next topic

medkhai

May 06, 2013, 03:04 am Last Edit: May 06, 2013, 03:06 am by medkhai Reason: 1
I plan to use this sensor for a project. I needed a low flow sensor able not to break with high pressure (for safety it should withstand up to 500PSI, although during normal use it should be below 150PSI).

http://www.omega.com/Manuals/manualpdf/M5171.pdf

I read in the datasheet above that the output is "Output NPN Sinking Open Collector @ 20 mA, Max"
and

"The output signal is a square wave signal, whose frequency varies linearly with flow rate. An external pull-up resistor (user-supplied) is required to insure that the open collector will sink less than 20 mA."

Can I wire this sensor as in the attached image, or am I missing something?

Thank you
Med

Erdin

Is that a 10k resistor ?
I think 10k or 4k7 is just fine. 10k is in the datasheet.

That datasheet is a lot confusing. The person who wrote that must hve been drunk.
Connect Arduino GND pin to sensor (-) / 0VDC / ground.
Connect Arduino 5V pin to sensor V+
Connect Arduino input pin (preferably a digital input pin) to sensor OUTPUT.

Connect the resistor from the OUTPUT to V+ (5V).

The output is a square wave, so you don't need an analog input. You can use the analog input as a digital input of course.

Did you understand this sentence : "Output NPN Sinking Open Collector @ 20 mA, Max" ?
NPN = NPN transistor inside
Sinking = if active the output is pulled to ground.
Open Collector = if not active the ouput is floating.
20 mA max = the maximum, so a nice value would be roughly 1mA.

medkhai

Thank you for your reply.
So I modified the connections as attached.

- The digital pin I think should be an interrupt PIN right? Like pin 3 on the arduino.

- Changed the resistor value to 4.7KOhm to limit current to 1mA
- and moved it as pullup between +5V and OUTPUT

Thank you for point out the mistakes to me :-)
Med


Erdin

Looking good.

But now the sketch.
You need a frequency counter or something like that.

bram50

Hello, do you know what the output voltage of this device is? Thank you.

retrolefty


Hello, do you know what the output voltage of this device is? Thank you.


Being open collector output, it's whatever voltage you wire it to. The easiest way to wire that to a arduino is to just wire it's output pin to a arduino digital input pin, then ground wire to arduino ground pin. Then just enable the internal pull-up resistor for the digital input pin you use.


bram50

great, thanks for the reply. I am using http://www.omega.com/Manuals/manualpdf/M4172.pdf flowmeter. I am using an external 12V power supply for the flowmeter. So i think i can connect arduino gnd to flowmeter gnd and pwr supply gnd, flowmeter signal to arduino digital pin with internal pullup R enabled, and flowmeter power to external power.

retrolefty


great, thanks for the reply. I am using http://www.omega.com/Manuals/manualpdf/M4172.pdf flowmeter. I am using an external 12V power supply for the flowmeter. So i think i can connect arduino gnd to flowmeter gnd and pwr supply gnd, flowmeter signal to arduino digital pin with internal pullup R enabled, and flowmeter power to external power.


That should work fine. You could do without the 12vdc supply as that document says the flowmeter will work with down to +5vdc to the supply terminal which is available on the arduino 5V pin.


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