Compared with traditional mechanical scales, electronic scales tend to have high precision, high speed, good stability and easy to use; their functions tend to be intelligent, and application performance tends to be comprehensive. At present, traditional desktop electronic scales used in commercial trade have large limitations, low precision, large size, inconvenient carrying, and restricted application sites. In order to solve these problems, this paper uses sensor technology, computer technology combined with data processing technology to design a new smart metering device with a portable electronic scale.
1, system hardware designUnder the premise of considering the practical cost performance and cost performance, the system has completed the design of the electronic scale, which is divided into parts according to the function: controller part, measurement part, data display part, keyboard part and circuit power part, the overall scheme block diagram As shown in Figure 1. The system weight detection part uses the load cell to detect the pressure signal, and obtains a weak voltage signal, and then processed by the processing circuit (such as the filter circuit and the differential amplifier circuit), and then sent to the A/D converter in the single chip microcomputer to convert the analog quantity. For digital output, the controller accepts the digital signal from the A/D converter output and, after calculation, converts the digital signal to the actual quality signal of the object and sends it to the display unit.
Figure 1 overall system plan
1.1, data acquisition moduleThe elastic part of the load cell in the electronic scale adopts a cantilever beam structure. The elastic body of the cantilever beam structure has high strength, high precision, good stability, wide range of range, and one end of the cantilever beam is fixed at one end, and one end is subjected to force. This structure is used for the measurement of pressure or tension.
1) SP20C-G501 ​​resistance strain sensor
The system adopts SP20C-G501 ​​resistance strain sensor. The load cell is mainly composed of elastic body and resistance strain gauge cable, and its maximum range is 1kg. The load cell is composed of a combined S-beam structure and a metal foil strain gauge. It has the characteristics of dustproof seal, wide measuring range, high precision, stable and reliable performance, convenient installation and use. The SP20C-G501 ​​resistance strain sensor adopts a bridge structure, which has self-compensation function, strong temperature drift suppression, and easy zero adjustment. Fig. 2 is a schematic diagram of the SP20C-G501 ​​pressure sensor. Four strain gauges of the bridge are attached to the elastic beam, and the change of the resistance of the elastic beam due to the change of gravity is measured. Working principle: When the elastic body of the cantilever beam is deformed by force, the strain gauge integrated with the elastic body is deformed accordingly, and the resistance value of the strain gauge changes linearly in the measurement range, and is converted into a corresponding voltage by the conversion circuit. The amount of change. In Figure 2, each bridge arm resistance change value ΔRi<<Ri, initial value R1=R2=R3=R4, and the bridge output resistance is infinite, the bridge output voltage Uo is
This equation shows that the output voltage Uo of the bridge is proportional to the algebraic sum of the strains experienced by the strain gauges of the four bridge arms.
Curing Screen Protector,Hydrogel Phone Cutting Machine,Protective Film Cutter Machine,Screen Protcter Custting Machine
Shenzhen TUOLI Electronic Technology Co., Ltd. , https://www.szhydrogelprotector.com