Wiring of externaly powered PH Meter & Arduino (4-20ma)


A few questions regarding my Hanna PH Meter (PDF Manual - HI8711E - Product page - HI8711E)

  • The unit is powered from the wall 120v
  • There's a recorder Output 0-20 mA or 4-20 mA (isolated). At Ph 8 it output 11.30vdc.
  • 5vdc supply is also available from the unit.

The arduino uno is powered straight from a computer psu, which also power a raspberry pi, both of them are connected to each other through usb (serials). They also require to share ground since they're working together on certain part of the project.

So, how should i wire the sensor to the arduino, since they're unable to share common ?

Should a 250ohm across the 4-20ma output be appropriate?

Thanks !

The sensor forces a current through the load by changing the output voltage. At 20 mA you cannot have more than 5v so 250 ohm would work.

Connect to the Arduino between the analogue input and ground, noting the correct polarity.