High Temporal Accuracy for Extensive Sensor Networks

The Defence Science and Technology Organisation (DSTO) has developed a versatile, low power, and networked sensor interface design suitable for use with a wide range of sensors. The sensor interfaces consist of: 1) core hardware and software that is the same for any sensor and 2) sensor specific hardware and software. The core software provides basic communications routines and manages a simple file operating system. These files constitute the software for interfacing and control of the hardware for specific sensors. The whole system is implemented on the low power Texas Instruments MSP430 series of microcontrollers and results in a consistent interface to a data logging or network control system, no matter what sensor is in use. A network approach has been adopted to reduce the wiring requirements for large numbers of sensors. However, networking introduces complexity, especially in regards to time synchronization of medium-to-high speed sensors, considered here as sensors requiring measurements rates in the range 100-5000-Hz range, such as strain gauges and accelerometers. In these applications, it can also be useful to only acquire data when there is interesting activity to avoid collecting large amounts of essentially zero valued data points and thus reduce the data storage requirements. This paper covers the software and hardware design considerations to achieve temporally correlated measurements from a widely distributed sensor network based on the DSTO sensor interface. The ultimate performance of the DSTO implementation is investigated and experimental results are compared with the predicted response.