Analog Sensing of Displacement Using Silicon Solar Cell

A silicon solar cell is used for an optical sensing of displacement in an analog form. The sensor consists of a set of lamp and cell with a lamp-control circuit, where a shutter interrupts the light beam. The principle of operation, linearity, temperature effect, frequency response, and associated circuit design are described. Experimental results on the characteristics of the cell and the sensing circuit are presented. A linearity of ±0.5 percent and a temperature coefficient of 90 ppm/°C are obtained on the simple set. An application to a pressure gauge is also given.