Johan Nagstrup

MEMS climate sensor for crops in greenhouses

We have developed and fabricated a multi-sensor chip for greenhouse applications and demonstrated the functionality under controlled conditions. The sensor consists of a humidity sensor, temperature sensor and three photodiodes sensitive to blue, red and white light, respectively. The humidity sensor responds linearly with humidity with a full scale change of 5.6 pF. The best performing design measures a relative change of 48%. The temperature sensor responds linearly with temperature with a temperature coefficient of resistance of 3.95 ? 10?3 K?1 and a sensitivity of 26.5 ? ?C?1. The three photodiodes have been characterized and show an almost ideal diode behavior with an ideality factor of 1.27 and a series resistance of 14.9 ?. The diodes are sensitive to blue, red and white light with the measured quantum efficiencies of 69%, 81% and 68%, respectively. The temperature and humidity sensors have further been tested on plants in a greenhouse, demonstrating that individual plant behavior can be monitored.