company news about Why is the signal transmission in industrial automation using 4mA to 20mA，not 0 to 20mA? Or 0 to 10V?

This is not chosen randomly; it is the best choice that engineers have summarized over decades.

First.

4mA is "live zero" - it can distinguish whether "the equipment is broken" or "the data is 0".

If you use 0mA to represent the minimum value (for example, temperature 0°C), then: a broken wire is also 0mA; actually measuring 0°C is also 0mA; there is no way to tell, is it the equipment broken, or is the data really 0!

So 4mA = the sensor is "working normally, with the value being the minimum". Less than 3.6mA = abnormal, broken wire, short circuit;

More than 20.5mA = possible overload or beyond the measurement range.

This is the "fault detection capability", which voltage signals (0-5V) cannot achieve.

Second.

Anti-interference for current transmission, works well over long distances.

o In industrial sites such as factories and buildings, the wiring can often be several hundred meters long; voltage signals (such as 0-5V) are prone to interference or voltage drop; while current signals do not decrease with the increase in line length; as long as the circuit is closed, the current remains constant.

Therefore, 4-20mA is much more reliable than voltage signals.

The third.

One Wire for Measurement + Power Supply

Many on-site sensors are powered by the "4~20mA" current, and no additional power cables are required; for example, pressure transmitters, temperature transmitters, etc., they directly draw power from the circuit and send data using ~20mA. This simplifies wiring, which is particularly important in hazardous or long-distance scenarios.

And the last.

Low current power consumption, suitable for intrinsically safe explosion-proof scenarios.

The total power consumption of 4-20mA is very low (maximum 24V × 20mA = 0.48W), making it suitable for use in explosion-proof scenarios such as petrochemical plants; voltage systems are prone to generating sparks, which increases the risk factor.

The 4-20mA circuit is the most classic analog signal standard in industrial fields. It is resistant to interference, saves power lines, enables fault detection, and is safe and stable.

The 4mA starting point ensures that whether the equipment is functioning properly can be identified, and it is the best choice based on decades of experience.