Based on the logarithmic relationship between photovoltaic voltage and incident light intensity of a photo-detector, a simple and low-cost method is proposed to linearize the measurement of nonlinear variables related to light intensity. Theoretical analysis shows that this linear measurement method is feasible in a large measurement range if we choose a proper load resistance for the photodiode. Based on the Lambert-Beer law and the photovoltaic voltage-based measurement method, the linear measurements of liquid level and liquor concentration have been achieved experimentally by directly detecting the output voltage of a solar cell, and their nonlinearities are both less than 2.0%.

Date Published: 13 October 2008
PDF: 6 pages
Proc. SPIE 7128, Seventh International Symposium on Instrumentation and Control Technology: Measurement Theory and Systems and Aeronautical Equipment, 71281S (13 October 2008); doi: 10.1117/12.806739

Published in SPIE Proceedings Vol. 7128:
Seventh International Symposium on Instrumentation and Control Technology: Measurement Theory and Systems and Aeronautical Equipment
Jiancheng Fang; Zhongyu Wang, Editor(s)