What exactly is the difference between the 4-20 mA output signal in 2- and 3-wire technology? This question is answered best from the viewpoint of the user: An output signal in 2-wire technology means:
- less wiring required
- better EMC protection, since interferences can be filtered more easily
- better protection against wiring errors
The only advantage of 3-wire technology is that higher ohmic loads are possible, i.e., the current loop can also be operated on a measuring instrument of relatively high input impedance. Conclusion: With the exception of a high ohmic load requirement, 4-20 mA in 2-wire technology offers the user clear advantages- also over other signals, such as 0-10 V.