Why 4 to 20 ma signals?

4 to 20 mA signals are commonly used in industrial applications for process control and instrumentation because they offer several advantages. This current range provides a clear distinction between zero and the lowest measurable signal (4 mA indicates the minimum value, while 0 mA is reserved for fault conditions). Additionally, current signals are less susceptible to noise and voltage drops over long distances compared to voltage signals, ensuring reliable data transmission. This standard also allows for easy integration of multiple sensors and devices in a control loop.