Nonlinear Error Compensation Of Resistance Transducer

The output signals of sensors are not usually standard and liable to be disturbed by electromagnetic signals, so they can not be transmitted for long distances, and need separately-designed subsequent service circuits, which increase the cost and decrease the commonality of these sensors. However, if sensor can be improved and changed into transducer which outputs standard signal, this problem will be solved. Transducer is a core component in measuring systems, and its accuracy play a decisive role in the performance of measuring systems. Nowadays, how to enhance the nonlinearity of transducer has already become an important task both at home and abroad. The main task of this project is to design transducer and their compensation circuits, and realizes compensation for the nonlinear errors of resistance transducers.This design is aiming to improve piezoresistive pressure sensor CYG101, a product of Shaanxi Qinming Electronic Group. CYG101's null shift is less than 0.1mV/4H, but its nonlinear error is relatively high compared to its repeatability error and hysteresis error, which make the overall precision of this sensor not very high. Consequently, the key problem to improve the precision of this sensor is whether the nonlinear error can be fixed.In this thesis, we firstly analyze the nonlinear error sources of the piezoresistive sensor and their corresponding compensation principle, and then bring forward compensation circuit models and parameter choosing method for two different kinds of nonlinear characteristic. Then, a nonlinear error compensation circuit for piezoresistive transducer is designed and developed on the basis of comparison and analysis between the AD693 from Analog Devices Corporation and the XTR115 from BURR-BROWN Corporation. This circuit can not only change sensor weak signal into(4～20)mA standard signal, but also compensate nonlinear error.The test results of nonlinear error experiments show that the function and performance of the new design circuit have met the challenge. The old piezoresistive pressure sensor with thousandth precision has been improved and become a high-precision pressure transducer with one ten thousandth precision. The compensation circuit of nonlinear error proposed in this thesis can be adopted for any kind of resistance sensors, so it has strong commonality and can be produced in large scale.