A Novel Optical Method to Measure Weight by Using Linear Extension Spring

We present a novel optical method suitable for measuring the weight of solid and liquid materials in small quantities. In this method, a longitudinal elongation of helical spring, resulting from an applied weight, increases the separation between a diverging light source and a photoresistor. As a result, resistance of the photoresistor increases with applied weight. An experimental observation shows that the method has good resolution, small nonlinearity, insignificant hysteresis, and good repeatability with a dynamic range of 100 g. This method has the potential for a use in precise and accurate measurement of mass and weight of biochemical reagents, precious metals, gemstones, etc., in small quantities.