Why is 4 to 20mA standard?
Why is 4 to 20mA standard?
Because it is simple, reliable, and strong, the 4 to 20 mA current loop is a common standard in industrial automation and instrumentation. This is why it became the standard of choice:
Zero Signal Detection (Live Zero at 4 mA)
If you use 4 mA as the baseline or “live zero” instead of 0 mA, the system can tell the difference between a legal zero measurement and a defect, like a damaged wire or device failure. Usually, a reading of 0 mA means something is wrong, which makes it easier to find the problem.
Less Signal Loss Over Distance
Current doesn’t decline across extended cable lengths like voltage signals do, even if the wires have resistance. This means that the 4-20 mA loop is great for sending signals over hundreds of meters without needing to use signal amplifiers.
Simple and Cost-Effective
A 4-20 mA loop is a two-wire circuit that sends the signal and powers the field device via the same pair of wires. This cuts down on the amount of wiring, the difficulty of installation, and the expense compared to having separate power and signal lines.
Noise Immunity
Current loops are naturally resistant to electrical noise and interference, which is very important in noisy industrial settings where motors, drives, and switching devices can mess up voltage signals.
Compatibility and Standardization
All PLCs, DCSs, transmitters, and controllers support the 4-20 mA standard. This makes sure that devices from different manufacturers can work together.
In short, 4-20 mA is the standard because it is reliable, can find faults, is accurate over long distances, and is cost-effective. These are all important factors in process control and automation.