4-20mA Pressure Transmitter


Thread Starter

Prakash Phatak

I am using 4-20mA pressure transducer and control valve in my application. The transducer and control valve are located at 150mtr from the control unit. I would like to know how much distance I can go with this.


Christian Felde

I assume it's the pressure transmitter who also supply the 4-20mA current?

Is there a 250Ohms resistance over the input pins at the controller?

Look up how much resistance the pressure transmitter is able to deal with and still deliver the current it wants to. Normally you'll find this in it's documentation.

Then it's not really difficult. Just figure out how much resistance it will be/is in the cable and add the 250Ohms resistance at the controller if needed, and you'll see if your within the limit.

Vitor Finkel


Depending on your Power supply voltage ( and transmitter ability to handle it ) and wire gauge ( total wiring resistance ) theoretically there is no limit to the length of a current signal line. In practice, I've seen applications where one kilometer was good enough a limit. Obviously if your available output voltage is 12 Vdc and your wire gauge is #22, you will never go that far.
The distance is unlimited for a current loop. However, remember / apply ohms law. There will be a voltage drop V=IR. Consequently, the longer the wire run the higher the resistance/voltage loss. Your design implementation should size these conductors to minimize the voltage drop as close to zero as practical which will help maintain the 4-20 mA signal.