Why Use 4–20 mA Signal? | Comparison: 4–20 mA vs 0–10 V Signal

Why Use 4–20 mA Signal? | Comparison: 4–20 mA vs 0–10 V Signal

The 4–20 mA analog signal is widely used in industrial instrumentation due to its high reliability and accuracy in transmitting process values such as pressure, temperature, flow, and level. 

1. Live Zero Detection

Using 4 mA as the starting point (instead of 0 mA) helps differentiate:

• 4 mA = 0% process value
• 0 mA = cable break / device fault

2. Prevents Signal Loss Over Long Distances

Current loops do not drop with cable length like voltage signals. Even with long cable runs, the current remains stable.

3. High Noise Immunity

4–20 mA loops are less affected by electrical noise, making them reliable in industrial environments with motors, VFDs, and heavy equipment.

4. Power + Signal on Same Two Wires

Loop-powered transmitters use the same pair of wires for power supply and signal, reducing wiring complexity and cost.

5. Supports HART Communication

The 4–20 mA signal can carry digital HART data on top of the analog signal for configuration and diagnostics.

6. Simple, Accurate & Industry Standard

The design is simple, stable, and suitable for long distances with high accuracy.

Comparison: 4–20 mA vs 0–10 V Signal

Feature	4–20 mA Signal	0–10 V Signal
Signal Type	Current Loop	Voltage Signal
Live Zero Detection	Supported (4 mA ≠ fault, 0 mA = fault)	Not supported (0 V and fault look similar)
Signal Drop Over Distance	No drop — current stays constant	Voltage drops significantly with cable length
Noise Immunity	Very high noise immunity	More sensitive to electrical noise
Typical Distance	Up to several kilometers	Short distances only
Power + Signal on Same Wires	Yes (2-wire loop)	No
Wiring Complexity	Simple	Requires separate power and signal wires
Accuracy	High accuracy over long distances	Accuracy decreases with wire length
Common Applications	Industrial sensors, transmitters, PLC/DCS	Short-distance controls, lab equipment
HART Support	Yes (HART communication supported)	No