Research On Embedded Resistance Source With High Precision

As a sort of devices measuring various physical quantities, instruments are widely applied in industrial production. In order to ensure measuring accuracy and reliability, instruments must be calibrated before usage, which is demanded by national standards. DC resistance source, one of the most used calibration devices, could be applied to calibration of many instruments such as multimeters. However, precision of the resistance source in homemade process calibrators hardly meets the requirements currently, which makes it of great significance to study on resistance source.This thesis will design an embedded resistance source which has wide output range and high precision. As the basis of further design, fundamentals of resistance source will be studied, the overall design will be given, and errors will be analyzed. Both hardware and software designs will be given following theories. Experimental platform of proposed resistance source will be established to verify theories and show the precision. Detailed research contents are listed below:Firstly, overall design of proposed embedded high precision resistance source will be given in following steps. Fundamentals of both voltage-excited resistance source and current-excited resistance source will be studied and topology designs will be provided. Next, suitable conditions of both types will be analyzed, based on which arrangements of output range will be determined. Different circuit structures and reference resistors will be applied in different minor ranges in order to widen total output range of the device. Designed circuits will be simulated to verify their feasibilities.Secondly, error models for each segments in designed resistor sources will be established to calculate total absolute output errors of resistance source circuits. For each error sources, error compensations including hardware compensations and software compensations will be applied to increase precision. Then according to the technical index and error analysis, the type of key components will be determined.Thirdly, hardware and software designs will be given. Hardware design will include current measure module, voltage measure module, digital to analog module, embedded processor module and power module. Software design will include host software programming and embedded processor logic design. The host software aims to achieve human-computer interaction via communication with the processor. Embedded processor logic design, constituted of embedded software processor programming and peripheral logic circuit design, is the core of system control.Finally, experimental platform of proposed resistance source will be established to verify theories. Among the platform, multimeter is adopted as main measurement instrument while automatic test software is programmed to achieve auto-testing in the established resistance source. After experiments, output errors in each minor range will be given, and we will campare the test results before and after error compensations, caiculate the precision of resistance source and analyze the experimental results.