A microcontroller-based data acquisition system for solar radiation and environmental monitoring

The hardware design and operation of a battery-powered microcontroller-based data acquisition system (DAS) for unattended remote measurements are presented. The system was designed around the ST62E20 8-bit microcontroller and applied for solar radiation monitoring. The measurement system uses the SolData silicon-cell pyranometer as the solar radiation sensor. The data from the sensor is collected by means of on-chip A/D converter and stored in a serial EEPROM until uploaded to a portable computer. Keeping the DAS in a low-power mode, which is only interrupted when measurements are to be taken or when a computer is connected to retrieve the stored data, minimizes power consumption. An on-chip timer provides an interrupt to awaken the system from its low-power wait mode at 10-min intervals to sample and store the data. At the end of each data collection period, the acquired data will be transmitted to the computer through the RS232 serial port for subsequent analysis. Only unprocessed data is stored in EEPROM. Quality control and data analysis is done off-line in the laboratory to minimize system cost, complexity and system downtime. Field tests and comparisons of this measurement system against the standard Eppley precision spectral pyranometer (PSP) have shown a slightly nonlinear correlation and that the accuracy of this measurement system as applied to solar radiation monitoring is fairly good, typically ±13 W/m²