Abstract:
There are a vast number of field–portable data loggers currently on the market. They
differ greatly in terms of capability and complexity, in many cases being application or
function specific. A survey was undertaken to identify market trends and future
developments, system hardware specifications and the technologies employed. After
comparing system specifications, it was apparent that there was a strong correlation
between system performance and power consumption - high performance systems tend
to be power hungry, and are typically larger and heavier than their lower performance
counterparts.
The aim of this project was to design the core of an advanced, flexible, low-power
portable data acquisition system, a ‘personal’ data logger (PDL), suitable for medical or
athletic performance monitoring. The pocket-sized target system should be capable of
high performance - sampling daily or up to 20,000 samples per second – with low
power operation, and should be able to measure both analogue and digital signals. The
data must be stored in a high-capacity non-volatile memory card, with USB and RS-232
ports provided for data upload and system configuration.
With the design specification defined, low power design techniques and the various
battery and power supply options were investigated. A survey of system components
was carried out and suitable low-power parts identified and selected for the design.
After checking the project schematics, the circuit board was designed, manufactured
and carefully assembled, ready for function and performance testing.
The test results indicated that the project met the design specification, demonstrating
its potential for use in a small portable personal data logger. Further work would be required to refine the power supply and power management systems, add an interface
board housing a real-time clock, analogue signal conditioning, and input and output
connectors, and to develop embedded system software.
