Weighing sensors, as essential components in modern industrial and automation control systems, play an important role in converting the mass or gravity signals of objects into measurable electrical signals for output. From precision electronic scales to complex industrial automation production lines, the presence of weighing sensors is ubiquitous. However, its internal working principle is often overlooked. This article will delve into the working principle of weighing sensors and reveal how they convert weight information from the physical world into electrical signals in the digital world.

1、 Strain gauge principle: synergistic effect of elastic body and strain gauge

The working principle of the weighing sensor is based on the strain gauge principle, and its core components include an elastic body and strain gauges. Elastic body is a material that can undergo elastic deformation under external force, and strain gauges are fixed on the elastic body. When the measured object is placed on the weighing sensor, its gravity causes deformation of the elastic body, which in turn causes deformation of the strain gauge. This deformation will cause a change in the resistance value of the strain gauge, thus achieving the first step of converting gravity signals into electrical signals.

Specifically, strain gauges are usually made of metal resistance wires or thin films, which have the property of obstructing the flow of current. When a strain gauge is subjected to external force, its resistance value increases with the increase of deformation or decreases with the decrease of deformation. This change in resistance value can be amplified and measured through a Wheatstone bridge circuit.

2、 Wheatstone bridge: the key to amplifying electrical signals

The Wheatstone bridge is a circuit used to measure changes in resistance, consisting of four resistors (including two strain gauges and two fixed resistors). When the sensor is subjected to force causing a change in the resistance of the strain gauge, the bridge will lose balance and generate an electrical signal at the output end. The magnitude of this electrical signal is proportional to the force acting on the sensor, and can be optimized by adjusting the excitation voltage and resistance value of the bridge.

3、 Signal Processing and Output

The output signal of a weighing sensor is usually a millivolt level voltage signal, which needs to be amplified and filtered before it can be recognized and processed by subsequent circuits or systems. The amplification circuit can amplify weak voltage signals to a range suitable for subsequent circuit processing, while the filtering circuit can remove noise and interference from the signal, improving the stability and accuracy of the signal.

Finally, the processed electrical signal can be sent to an A/D converter for digital processing, or directly input to display devices such as PLC (Programmable Logic Controller) or secondary meters for indication. In this way, we can intuitively see the weight information of the object being measured.

4、 Applications and Challenges

Weighing sensors are widely used in various applications that require measuring the weight of objects, such as industrial automation production lines, logistics and warehousing, food processing, and other fields. However, it also faces some challenges in practical applications, such as environmental interference, temperature changes, long-term stability, etc. To address these issues, researchers are constantly exploring new materials and processes to improve the performance and reliability of weighing sensors.

summary

The working principle of a weighing sensor is based on the strain gauge principle and the Wheatstone bridge circuit, which converts the gravity signal of an object into a measurable electrical signal output through the synergistic effect of an elastic body and strain gauges. This process involves multiple steps such as resistance changes, electrical signal amplification, filtering, and digital processing. With the continuous advancement of technology and the expansion of application fields, weighing sensors will continue to play an important role in industrial automation and intelligent manufacturing. At the same time, we also look forward to the emergence of more innovative technologies and solutions in the future to address the challenges and difficulties of using weighing sensors in practical applications.

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