Dev Tools · 1h ago
Why 4-20mA sensors reserve 0mA for fault detection
The 4-20mA analog standard, dating from the 1950s, maps sensor measurements to current, with 4mA representing the bottom of the range and 20mA the top. Zero mA is reserved to indicate a broken wire or dead transmitter, providing built-in fault detection. The NAMUR NE43 convention defines normal measurement between 3.8 and 20.5 mA, with values below 3.6 or above 21.0 signaling failure.
Meridian48 take
A reminder that industrial IoT's physical layer still relies on a 70-year-old analog standard—developers ignore it at their peril.
industrial-iotsensor-standards