Arduino Mini and 4-20mA loop powered transmitters

Projects General Guidance
1

Hello

In industry we usually power 4-20mA transmitters via the 4-20mA loop @ 12-24V DC. This implies they are two wire devices which provide 4-20mA output @ 12 or 24VDC depending on the measured variable (e.g. pressure).

Is it possible to some how have the Arduino mini power these transmitters at 12 or 24V DC and accept the 4-20mA input (which I can conver to 0-5V using a resistor)?

One option would be to supply the voltage regulator to the mini @ 16V, then have the regulator step it down to nominal supply voltage for the mini and use the 16V to power the transmitter and take the current reading back to the mini analog input, but then the transmitter will always be on? Or does the analog input pins act as an open circuit when the chip is in sleep mode?

I would like the chip to wake up periodically, power the transmitter up for a minute, record the measured value (0-5V via resistors) then go back into deep sleep, cutting power from the transmitter completely.

2

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html .

If you google Arduino 4 - 20mA input
You will see quite a few solutions, including interface PCBs.

Tom... :slight_smile:

3

Thanks for the reply

I have googled extensively and all pages seem to mention feeding the transmitter with an external supply then converting the 4-20mA output from the transmitter into a 0-5V voltage.

That's simple enough, however the transmitter will remain on and drain the battery in no time.

The only way I can think of doing this is to feed the supply voltage through a transistor and having the arduino switch the supply on to the transmitter via the transistor and then reading, by converting, the 4-20mA signal into 0-5V