The Research Of High Accuracy And Anti-cheating Electronic Scale

Electronic scale is a kind of quality measurement instrument with high accuracy,widely used in industrial production, business trade, transportation, mechanicalmanufacture, port measurement, health care, defense construction, scientific research,etc. It works fast and has a wide measurement range; it is also easy to operate and tobe conveniently controlled by computer. However, traditional electronic scale have somany drawbacks, such as low accuracy, incapability of undertaking tilting angleautomatic compensation, easy access to cheat and low interactivity and userfriendliness. Therefore, this thesis developed a kind of electronic scale with highaccuracy, tilting angle automatic compensation and anti-cheating.This thesis determines the design goals on the basis of the current situation ofelectronic scale. The signal acquisition module, anti-cheating module andhuman-computer interface module of high accuracy electronic scale are designed.Electronic scale software is based on the principles of modular design. Tilting angleautomatic compensation model, nonlinear correction method and temperaturecompensation method are proposed to compensate the error automatically which iscaused by tilting angle, non-linearity of sensor and temperature. The anti-cheating andhigh-accuracy electronic scale, which has the weighing range up to1000g, and thediscrimination is0.01g, is designed and finished. Finally, the test is implementedunder laboratory conditions. This research work focuses mainly on hardware designand software design, as well as tilting angle error compensation and non-linear errorcompensation. The main work and innovations are stated as follows:In the hardware design, microprocessor ADμC7060woks as the processing core,a24-bit precision Σ-Δ analog-digital converter AD7190is used for data acquisition;RFID and ADXL345are used to test and measure the tilting angle for automaticallycompensating the error caused by tilting angle. The hardware redundancy can preventhardware and software cheating. DS18B20works for temperature automaticcompensation.In software design, according to system requirements, the software is dividedinto sensors module, weighing signal acquisition module, anti-cheating module, faultdiagnosis module, human-computer interface module, and designed separately foreach module. In tilting angle automatic compensation mode, an automatic compensation modelis proposed, which is suitable for microcontroller to compensate the error caused bytilting angle effectively. In weighing information processing method, a piecewisenonlinear least squares method for weighing error correction is established, whicheffectively reduced the nonlinearity. The least squares surface fitting compensationmodel is built to reduce temperature influences.Field test results show that the maximum permissible error is less than0.05g, theweighing range is1000g and the discrimination is0.01g, which definitely meets therequirements of II level scale defined by “JJG555General Verification Regulation forNon-automatic Weighing Instrument”. The system maximum permissible error is lessthan0.2g when the inclination of tilting angle of weighing platform is less than15°,which works automatically. Meanwhile, it can effectively prevent seven kinds ofcommon cheating, and the system will give out the warning when cheating happens.