High-capacity data acquisition system based on Cortex-M3 for aerospace applications

Present day launch vehicle telemetry systems require high resolution, precise data acquisition systems to accurately reveal the system performance in extreme environments. In order to achieve high resolution these data acquisition systems invariably use sigma delta ADCs. With the advent of IC technology it has been possible for chip manufacturers to integrate instrumentation amplifiers and Digital filtering functions along with sigma delta ADC cores on the same chip, thereby providing a lot of flexibility to system designers to design and develop miniaturized data acquisitions systems employing such chips. Off late miniaturization has become an important goal, for space launch vehicles to reduce the mass of avionics to enable them to ferry higher pay loads to orbits. This paper describes the design and development of a high channel capacity data acquisition unit which supersedes the currently used systems in terms of bandwidth, input ranges, mass per channel and temperature drift performance. This Data Acquisition system (DAS) can directly interface with RTD, thermocouple and pressure sensors. System has RS-485 interface to outside world for channel configuration programming and acquiring digitized data. The design is based upon Cortex-M3 ARM core based mixed signal microcontroller for signal conditioning and digitization, and 16-bit PIC microcontroller for control functions. Paper describes both the hardware and software design to meet the functional requirements. Finally the performance of the system is evaluated in terms of nonlinearity, accuracy and RSS error and compared with existing ones.