Traditional altitude switch designs for harsh environments are mechanical in nature and operate by means of an inflatable bladder or bellows that mechanically depresses a pushbutton switch. The altitude trip point is set by mechanically adjusting the distance of the switch to the bellows. The mechanical action of the switch results in a loss of accuracy on the order of several thousand feet, forcing engineers to design interfacing systems with an extremely high error tolerance. Furthermore, these types of systems are typically large and unreliable, difficult to manufacture, and prone to failure under certain operating conditions.
The Microcontroller Altimeter (uCA), developed by engineers at NASA's Goddard Space Flight Center, overcomes these limitations by combining the robust and cost-effective nature of modern printed circuit board (PCB) and solid-state technology to deliver a system that is one-third the size of current systems while still maintaining the same switch channel density, and also providing auxiliary user outputs.
The uCA combines a high-accuracy integrated silicon pressure sensor with MOSFET technology to provide traditional normally open and normally closed switches capable of high-power switching for a wide variety of applications. The output of the sensor and switches is provided to the user for realtime altitude determination as well as discrete altitude trip point knowledge. Updates to the altitude trip points are facilitated through USB programming, which allows for in-field adjustment, and provides added flexibility late during integration and testing.