When we go to the vegetable market to buy vegetables, we can see the electronic scale in each stall. Choose the vegetables you want to buy and put them on the electronic scale. You can see the clear and accurate weight and price in an instant to complete the transaction. In this seemingly simple process, do you know what has changed inside the electronic scale?
Before studying how the electronic scale weighs, first look at how the spring scale works. The spring scale weighs the weight of articles through the deformation of the spring. The heavier the things in the scale, the longer the spring will be pulled. Through the deformation degree of the spring, we can know the weight of the goods. There is also a very small spring - strain gauge in the electronic scale. The electronic scale weighs the weight of goods through it.
Strain gauge is a kind of conductor or semiconductor that can let current pass through. When something is pressed on the strain gauge, the strain gauge will deform like a spring. It doesn't grow, it flattens. The flattened strain gauge will affect the passage of current (the resistance of the strain gauge becomes larger). By measuring the change of current flowing on the strain gauge, the electronic scale can know the weight of what is weighed.
However, even if a heavy object is pressed on the strain gauge, its deformation is very small. In order to detect this subtle change, the electronic scale needs a filter circuit that can amplify the electrical signal. In addition, it also needs to filter out the noise of electrical signal in order to improve the measurement accuracy. In addition to the strain gauge and amplification filter circuit, the electronic scale also has a brain - the central processing unit. Taking the electronic scale in the vegetable market as an example, the CPU is responsible for receiving the vegetable price setting. Multiply the unit price of the dish by the weight of the dish to obtain the total price of the dish, and output this information to the electronic display screen.