What is the pressure range for an instrument air signal? Why?

• A. 3-15 psig. So you can tell if there is a leak
• B. 0-5 psig. To avoid leaks
• C. 20-60 psig. For quicker response
• D. 50-100 psig. To maintain strong actuation

Answer: (A)

Instrument air signals use a standardized low-pressure range to convey control information to pneumatic devices. The typical range is 3 to 15 psi gauge. This span provides enough force to move most pneumatic actuators against spring and friction, while staying small enough to keep regulators, valves, and piping simple, cost-effective, and safe.

Why not the other ranges? A 0–5 psi signal would have a very limited upper bound, making it hard to achieve full-range actuation with consistent resolution because small friction variations can dominate at low pressures. Higher ranges like 20–60 psi or 50–100 psi would demand stronger springs and larger hardware, increasing cost, risk, and complexity, and they aren’t necessary for standard pneumatic control signals.