Design of a CMOS Calibrated Monolithic Illumination Meter for Monitoring Solar Radiation of Tomato Crops

In this paper, a complementary metal-oxide-semiconductor (CMOS) calibrated monolithic illumination meter for monitoring solar radiation of tomato crops is newly proposed. The output signal is a pulse stream, it could be easily sent over a wide range of transmission media, such as package switch network, radio, optical, infrared, ultrasonic, and so on. Another innovation is that the proposed calibration method can reduce the nonlinear error arising from sun sensors. By collocating with a monolithic sun sensor, which has a radiation range of 68.9-188.7 W/m², the corresponding output frequency ranges from 0.7 to 1.82 MHz. After calibration, a measured maximum frequency error is 1.63%. Measurement results have successfully verified all the functions and performance of the proposed calibrated monolithic illumination meter and confirmed it to be applied on monitoring solar radiation of tomato crops. The proposed CMOS calibrated monolithic illumination meter is suitable for measuring solar radiation devices, such as the devices for detecting solar radiation of crops.