Design Of Intelligent Strain Gauge Load Cell

Weighing apparatus is the appliance to measuring the quality of objects, which isused in the widest applied range and has the biggest quantity of variety. The corecomponent of weighing apparatus is the load cell, whose function has the decisiveeffect on the whole index of the weighing apparatus. Intelligent load cell solves theproblem of great influence on simulating load cell by environment and the insufficientprecision. It can compensate the factor of precision restriction, including nonlinearity,temperature and creep compensation, and output the result by standard Bus interfacein the form of number.With the development of economy, the output value of China’s weighinginstruments and load cell industries has increased year by year, but in terms of thetechnical distribution, these industries has mainly centered on products with relativelybackward technology and low profits. Consequently, a new practical, intelligent straingauge load cell is of great significance in both the accumulation of technology andmarket competition.This thesis starts with particularly analyzing the weighing principle of the coresensor element resistance strain gauge of intelligent strain gauge load cell, and pointsout the influence and common solution given by the noise of electronic systemtowards the precision improvement of intelligent strain gauge load cell. Then takingthe model machine designed in this thesis as an example, demonstrate the hardwareand software design of intelligent strain gauge load cell. In hardware design, itparticularly demonstrates high-precision weighing data acquisition circuit consistingof strain guage circuit, low noise amplifier circuit, high-precision A/D convertercircuit and intelligent strain gauge load cell’s indispensable module design of MCUmanagement and arithmetic unit, communication interface. Based on the RTOSframework RL-RTX provided by MDK, all software modules are completed, includingthe data acquisition and preprocessing of weight and temperature, the design andrealization of communication protocol, and so on.After what have done before, this article analyses the causes of nonlinear errorand method of calculation in intelligent strain gauge load cell, and it shows themethod of compensation towards nonlinear error by Least Squares fitting. At the sametime, it demonstrates creep error and the influence of temperature in intelligent strain gauge load cell, and represents the way to compensate it.The intelligent strain gauge load cell designed in this article adopts RS-485connector, and has the function of nonlinearity and creep deformation, slowly driftingcompensation with wholly high precision. According to the verification regulationprovided by JJG669-2003load cell verification regulation, I conduct every index test,and the verification number of division reaches60000, which satisfy B level of loadcell index.