I am currently on the search for an inline conductivity sensor for a cooling circuit project (inline so that I can constantly monitor the conductivity of my medium in the circuit).
The whole circuit is to be controlled by an arduino uno R3 board.
One conductivity sensor which I am favoring has several communication possibilites: RS485 Modbus and analog 4-20mA. The sensor is connected to a transmitter which is what would be connected to the arduino board. I have attached the data sheet of the transmitter.
20276200T10Z000K000.pdf (1.0 MB)
The RS485 Modbus I have read that there are shields that can be attached to the uno board and an exisiting library, which means that the implementation should be fairly do-able.
For analog 4-20mA I have searched in the forum and found that connecting a 250 or 500 ohm resistor between sensor and arduino analog pin will convert the input current into 0-5V. This can then be easily read by the arduino. Is the implementation really this simple? On another website in Google search I read that a special converter would be needed which has a suitable resistor integrated.