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Problem reading 4-20ma sensors

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Hi all.

Im having problems reading some 4-20 ma sensors with Xbee AIO Adapter.

I can read correct values of sensors with arduino using a 250 ohm resistor to convert 4-20ma to 1-5V and appling +12V to the sensor with and exteral power supply.
I can see how change the value when i apply heat to the sensor.

But when i connect the sensor to de AIO Adapter in 4-20ma mode, its reads always the same value (122). This value readed dont change the value when i apply heat to the sensor.

I follow all the instructions correctly from https://www.digi.com/wiki/developer/index.php/XBee_Analog_I/O_Adapter and i set terminal 1 and 2 for 4-20ma mode, d0 and d1 to 2 for analog input and P3=5 to output the 12V to the sensor. I also put on the dip switch 2 as manual says.

Any suggestions?

Thanks in advance.
asked Apr 25, 2014 in RF Solutions and XBee by sherkhan New to the Community (0 points)
recategorized Apr 10, 2018 by LeonidM
This is the diagram.

Your text to link here...

In this first image the multimeter shows me a 10 mA current, so the sensors works fine with the supply voltage of AIO Sensor.

But if i disconnect point A and connect it to pin1 on AIO Sensors as shows in picture 2, the multimeter shows me a 2 mA value.

So the sensors doesnt works when i close the circuit into AIO pin.

Your text to link here...
More Info.

The AIO Adapter config is


I can read the sensor value througth AI pin1 when connect a 250ohm resistor to ground as shows in picture3.

Did you solve your problem? Because I have the same when I use RS-485 Analog I/O Digital I/O works properly coupled to resistors, however when sensors 4-20mA are coupled didn’t work.

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1 Answer

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Hey I know its oldest question of the forum but is your project is in working fine ? If yes can you help me out with schematic as i am also trying same with the help of 4-20mA current loop receiver as mentioned below:

answered Apr 10, 2018 by snacleb23 New to the Community (4 points)