TEST CHAMBER ASSEMBLY THEORY OF OPERATION

TM 10-1670-305-23&P 0005 00-4 TEST CHAMBER ASSEMBLY 0005 00 THEORY OF OPERATION - CONT THEORY OF OPERATION (MODEL 453) The AR2 is installed inside the transparent altitude chamber during testing. The JUMP/OFF switch and piston rod of the AR2 engage fittings inside the chamber which enable the switch to be operated and the AR2 to be recocked after actuation without opening the chamber lid or returning the unit to ground level. The ON and OFF position of the JUMP/OFF switch are electrically monitored by magnetic sensors in the bottom wall of the chamber. An infrared LED emitter/detector switch mounted inside the air cylinder senses movement of the piston rod assembly at the instant the AR2 actuates. Signals from these sensors are transmitted to the control assembly through an electrical connector in the left side wall of the control assembly near the front. The combination vacuum pump/air compressor enables the operator to raise and lower the air pressure inside the sealed altitude chamber and thereby simulate the entire functional altitude range of the AR2. The compressor also provides regulated pressure to the air cylinder to cock the mechanism of the AR2. The necessary pneumatic plumbing connections between the pump/compressor unit, control assembly, and altitude chamber are located along the bottom left side wall of the control assembly. Power for the pump/compressor is supplied through a separate electrical connector, also located in the left side wall of the control housing. Routing and connections for all external electrical wiring and pneumatic plumbing are shown in schematics. The control assembly is a self-contained, independently calibrated, completely interchangeable modular unit. It contains a precision calibrated pressure sensor, a printed circuit board incorporating signal conditioning and complete system operating logic, digital displays which feature a preprogrammed microprocessor for making pressure-to-altitude conversion, pneumatic valve and regulators to control altitude, regulated power supplies to run associated electronic circuits and devices, and operational controls and indicator lights to perform and monitor the various test functions. A quick disconnect port is located in the front wall of the control assembly to permit attachment of a precision pressure standard during periodic altimeter calibration. A separate auxiliary chamber used for calibrating wrist altimeters may also be connected through this port. WP 0007 00 shows the configuration of the control panel. The altitude and fall rate displays are placed at the upper left with their respective setting controls at the right. The chamber can simulate altitudes greater than 35,000 feet MSL. The fall rate may be set to any value between approximately 10 and 240 feet per second, except that rates between 65 and 85 feet per second cannot be selected because actuation at these rates will cause increased wear to internal components of the AR2. The altitude display reads to the nearest foot, and the fall rate display reads to the nearest 0.1 foot per second with positive values indicating a descent and negative values indicating a climb. Although the displays are updated approximately two times per second, the internal circuitry of the altimeter is designed to instantaneously capture and hold the pressure sensor signal as soon as piston rod movement is detected by the infrared switch. The altitude corresponding to this pressure is then locked in and displayed as the actuation altitude at the next update interval. Six (6) push button controls and seven (7) indicator lights are located on the control panel. In addition to their primary functions, several of the controls are provided with interlocking logic circuitry to preclude operations which are out of sequence or which might damage the AR2. The description and function of the controls and lights are summarized in WP 0007 00.