Converting between altitude and pressure, maintaining stable chamber conditions, and logging test data per DO-160 and MIL-STD-810 requirements — here's the implementation.
ISA Model: Altitude to Pressure
The ISA (International Standard Atmosphere) model converts altitude to atmospheric pressure across the troposphere and lower stratosphere. The chart below maps the pressure curve against the DO-160 Category B test points used for commercial avionics qualification:
Vacuum Chamber Control and Test Logging
The chamber controller runs a PID-style control loop: it reads the current pressure, computes the error against the target altitude pressure, and drives the pump or vent valve accordingly. Once the reading stabilizes within +/-2 mbar over a 60-second window, the test data is logged in MIL-STD-810 Method 500.6 format. The flow below shows the full decision logic:
The Neometrix Pneumatic Vacuum Test Rig implements the ISA model and PID chamber control with real-time DAQ output.
