DESIGN OF A LOAD CELL WITH LARGE OVERLOAD CAPACITY

Abstract

To increase the signal-to-noise (S/N) ratio and sensitivity of a load cell, it is desirable to design a structure that generates large strain close to maximum allowable strain of the sensor material for a given rating load force. However, accommodating the margin of safety with respect to overloading, compromises the sensitivity. This paper presents the design, analysis, and prototype testing of a load cell which can provide large overload protection capacity without compromising the sensitivity of the sensor. This is achieved by a special design of sensor structure that becomes virtually rigid after its flexures reach their maximum deflection, thereby the sensor can be protected against a large over load. The sensor dimensions, which maximizes the sensor’s sensitivity, for given values of rating load and overload are obtained through mechanical strength analysis. A load cell prototype is fabricated and then tested to measure its linearity and overload characteristics. The experimental results show an accuracy of 0.2% of full scale and overload protection of the sensor flexures.