Working principle of weighing sensor and its detection circuit

In principle, a weighing sensor is a pressure sensor, but it is just in a different shape. However, there are usually many ways to sense it, but the most common ones, such as those used in floor scales, are generally eddy current type.

That is to say, it has an eddy current trigger winding, and then a sensor to sense the eddy current intensity. Since the weighing sensor is a metal package as a whole, the eddy current inside it will be deformed after being compressed, and the eddy current will change. After amplification, the data can be read. Then, the material used to encapsulate this thing is usually a rigid material. In short, it is a general metal, such as steel, but it will definitely not be very soft. Because even if it is steel, even if it is deformed by a few microns under pressure, the change in eddy current is enough to sense how much it has changed. And if it is a soft metal, it may be easy to have problems when weighing heavy things. At least the pressure sensor that senses by eddy current is not made of soft metal.

The function of the weighing sensor detection circuit is to convert the resistance change of the resistance strain gauge into a voltage output. Because the Wheatstone bridge has many advantages, such as suppressing the influence of temperature changes, suppressing lateral force interference, and solving the compensation problem of weighing sensors more conveniently, the Wheatstone bridge has been widely used in weighing sensors. Because the full-bridge equal-arm bridge has the highest sensitivity, the parameters of each arm are consistent, and the influence of various interferences can easily offset each other, so weighing sensors all use the full-bridge equal-arm bridge. (end)