Instrumentation
I/P Converter Calculator
Current-to-pneumatic (and reverse) signal conversion with custom input/output ranges.
Ranges
mA → psi
psi → mA
Enter values and calculate.
About This Calculation
An I/P (current-to-pneumatic) converter bridges an electronic 4-20mA control signal to the 3-15psi (or 0.2-1.0 bar) pneumatic signal that drives a pneumatic control valve actuator or positioner — essential wherever electronic control systems need to operate legacy or intrinsically-safe pneumatic final control elements. The device works by using the input current to control a nozzle-flapper or similar pneumatic amplifier, converting a small electrical signal into a proportional, much higher-force pneumatic output capable of actually moving a valve stem against process pressure and spring force.
Frequently Asked Questions
Why is 3-15 psi the standard pneumatic signal range?
It’s a long-established industry convention (predating widespread 4-20mA electronics) chosen to give a usable working range above atmospheric pressure while staying within instrument air supply pressure limits — like 4-20mA’s live zero, the 3psi baseline (rather than 0psi) also helps distinguish a genuine zero-demand signal from a lost air supply.
Why would anyone still use a pneumatic final control element instead of an electric actuator?
Pneumatic actuators are inherently simple, fail-safe (spring return to a defined position on air loss), and intrinsically safe without special electrical certification — genuinely valuable properties in hazardous-area process plants, which is why I/P converters remain common even in otherwise fully electronic control systems.
Is the I/P conversion linear across the whole range?
A well-calibrated I/P converter is designed to be linear — 4mA corresponds to 3psi, 20mA to 15psi, with proportional values in between — but like any instrument it has its own accuracy and linearity specification that should be checked against the application’s control requirements, not assumed perfect.