IEC 60382: Process Control Pneumatic Signals — Standard Pressure Ranges for Pneumatic Valve Positioners

Why Pneumatic Control Signals Are 3-15 psi, Not 0-15 psi — The Same “Live Zero” Philosophy as 4-20mA

IEC 60382:1991 specifies process control pneumatic signal standard ranges — 3-15 psi (20-100 kPa). 3 psi (not 0) as the zero-scale point mirrors the 4-20mA “live zero” philosophy: if pressure is 0, it means broken air line or compressor failure — open-circuit detection. 3 psi as the “true zero” guarantees minimum pressure to maintain pneumatic system operation at all times.

TNLab — 3-15psi and 4-20mA share the same engineering wisdom: let “zero signal” not equal “zero physical quantity.”