Read a 4-20 ma sensor

Hi everybody,

I need to read the measured value from a flowmeter. It returns a signal in 4-20 ma. I've read on others posts that I can use a 250 ohms resistor to convert this current into a 1 to 5 volt so that I can read it on an analog pin.

But I don't know exactly how to do it. How to connect the resistor, the sensor and the arduino. In attachment you'll find the connection sketch of my sensor from its documentation.

The flowmeter is a PF3A7 from SMC and works under 24 VDC but i don't have any problem to power it.

I hope to be clear enough in my explanation.

Thanks by advance for your help.

Yes 250 ohm load will be 5.0V at 20 mA.

You need : separate 24V DC supply to the sensor, AND common ground sensor-arduino

Do a search on this forum, as you may expect it's a quite commonly asked question and there are lots of discussions on how to read them best. You'll also find it's generally better to use a 47 Ohm resistor (for a 0-1V signal) and enable the internal reference for better stability.

Thanks for your answers.

Yes I know that using the 47 ohms resistor I can have much higher resolution but as I told you my concern is about how to plug each wire of THIS sensor.

Do I have to connect the resistor (250 or 47 ohms) in serie right behind the white wire (analog output) of the sensor and to the AO Input of the Arduino ?

So: Sensor Analog Output --> serie connected resistor --> serie connected wire to the Arduino Analog Input

Am I correct ?

Thanls by advance.

White wire connects to your analog pin.

Otherwise wire as per the schematic you posted in #0. The load resistor is normally physically placed right at your Arduino.

Ok.

Could you verify the sketch in attachment please ?

sensor-connection.pdf (201 KB)

As said, use the circuit as you posted in #0. Connect the Arduino analog in to the white wire.

Ok but what about the resistor ?

That's your load.

Ah ok.

So it is in serie in between the sensor output and the arduino input.

thanks a lot for your help.

have a good day.

No, not there.
Just follow the schematic you posted yourself!
Between white wire and GND. White wire to the input.