Can I connect third party sensors with 4-20mA sensor? You can apply more than the 5VDC, but you need to be careful not to exceed the 20mA current. The 4-20mA sensor has an internal impedance of 20 Ohms, so if you need to apply, for example 12VDC instead of the 5V, you should then install a resister of 580 Ohms (current will be 20mA). If you were to apply 48VDC, then the resistor should be 2.38K Ohms. You don?t need to install any resister if your third party sensor output is 4-20mA