A Compact Software Programmable Data Acquisition System

The design and development of a software programmable data acquisition system is described here. The design based on sigma-delta ADCs and versatile microcontrollers enables the integration of signal conditioning and digitisation functions, high performance with respect to parameters such as accuracy and resolution and full software programmability of key channel specifications such as amplifier gain, signal bandwidth, sample rate and sensor excitation signal amplitude. This renders the system highly versatile with regard to interfacing to various sensors, ability to be configured in field for specific applications and compact, miniaturised and low-cost implementation which are very important for demanding applications like industrial and aerospace. The output interface for the system is serial RS-485 compliant and can be connected to equipments such as PCs and data analysers with standard, off-the-shelf interface cards. The same interface is used to configure the system in lab and field by downloading the channel parameters as specified above in the form of control data words from a PC and routing them to the appropriate ADC. The hardware design aspects such as the devices used and the output interface are described in brief. The on-board software running in microcontroller in both the normal data acquisition and ground programming modes along with the system programming methods are discussed in detail. The feasibility of further improving the channel density by using the ADCs in multiplexed mode and the overall data rate and throughput by use of advanced devices is also touched upon as avenues for future work.