Development Of Sensor Comparison Mode’s Calibration Equipment For Electronic Price Scales

The electronic price scale belongs to legal measuring instrument in mostof the world. In accordance with the problem that the calibration item is tedious andthe calibration work is inefficient, a method by using the high-precision weighingsensor as the standard instead of weights was proposed. Based on the method, asensor comparison mode’s calibration equipment for electronic price scales wasdesigned. Main research contents are as follow:(1)The paper puts forward the technical index of the equipment, analyzes themethod of the traceability of the quantity values and the error distribution of theequipment. Then, the whole research scheme and principle of the equipment weredetermined. And it aiso analyzes the design of the main structure and the selection ofthe main components.(2)The design of the mechanical structure of the equipment includes three parts:the gravity producing equipment, the Z axis height adjusting equipment and thealuminum frame. When the processing is finished, the mechanical structure of theequipment was assembled and debugged. Then, the mechanical structure of theequipment is leveled. Meanwhile, the geometrical errors of the key mechanical partswere measuried.(3)The microchip ATmega8was the MPU. The paper completes the design ofthe hardware. It consists of the analog conversion module, the MPU module, theliquid crystal display module and the serial communication module and etc. Thesoftware development was built on the platform of LabVIEW. And the platformregards the PD algorithm was the losed-loop control algorithm to built the softwareof the man-machine interface.(4)The calibration experiment of the equipment was carried out. Experimentalresults show that the linearity of the load cell is±0.0023%and the resolution of theequipment is1g. The typically calibration points were carried out the uncertaintyevaluation. It shows that the uncertainty of the calibration point2.000kg was1.5g, the uncertainty of the calibration point20.000kg was3.2g and the uncertainty of thecalibration point30.000kg was4.7g. It fits the requirement of the designed technicalindex. In addition, a comparison/confirmation experiment was designed for furthervalidation.To sum up, the development of the sensor comparison mode’s calibrationequipment for electronic price scale will make a meaningful explorison on theweight’s substitution method of the small range scales.