Change sensor's common to low!!!

[auto_mitch]

Hi.
i have a problem with a pressure sensor. The sensor output is 4-20mA.
The common of the output is at high (+24V). I want to change the common to low (0V, GND) to plug the sensor to plc.
Could u help me???

 

[IanP]

Normally you should run pressure transducer of +V (in your case 24Vdc) and inside your PLC you will find 250 ohm termination resistor which is used for 1(4mA)-5(20mA)V range and that is typical configuration.
If you want to run it of 0V check if your plc has differential inputs. If it has check in specification what is max common voltage for these inputs and if it is above 24Vdc connect negative pol of pressure Tx to 0V, positive pol to 250 ohm(or other, depending on gain, range etc..) resistor and the other end of resistor to 24Vdc and measure voltage across this resistor.
'If you want to decrease levels you can connect another resistor betwenn 250 ohm and 24Vdc but make sure that your pressure Tx operates within its operating voltage range (usually min voltage will be somewhere around 10Vdc)
It is not good practice but can be done... 8)