how does it work THE LOAD CELL? Hooke's law - strain gauge

Summary

This video explains the workings of load cells, the essential components used in weighing systems. It details four types of load cells: pneumatic, hydraulic, strain gauge, and capacitive, each operating on different principles like air pressure, liquid pressure, electrical resistance, and charge storage. The video also discusses various industrial applications, such as salt production and metal stamping, where load cells are used to measure weight and force accurately. Additionally, it emphasizes the importance of selecting the right load cell based on sensitivity and accuracy to ensure optimal performance in production processes.

Takeaways

• 😀 Load cells are used in weighing scales to measure the weight of objects, and they operate by detecting the deformation caused by applied force.
• 😀 A load cell measures the force applied to an object, not the object's mass in kilograms, and works based on Hooke's Law, which relates deformation to the applied force.
• 😀 There are four types of load cells: pneumatic, hydraulic, strain gauge, and capacitive, each working on different principles and technologies.
• 😀 Pneumatic load cells use air pressure to measure weight. The deformation of an elastic diaphragm due to the applied load causes a change in air pressure, which is measured and converted into weight.
• 😀 Hydraulic load cells use pressurized liquid instead of air. The liquid inside a diaphragm and piston system deforms under pressure when an object is placed on it, and the pressure change is measured to calculate the weight.
• 😀 Strain gauge load cells, the most commonly used in industrial settings, measure changes in electrical resistance caused by deformation in the structure. These changes are proportional to the weight being applied.
• 😀 Strain gauge load cells are made of four extensometers arranged in a Wheatstone Bridge configuration, offering accurate measurements within a wide resistance range.
• 😀 Capacitive load cells work by measuring changes in the electrical charge stored between two parallel plates as the distance between them decreases due to the applied load.
• 😀 Load cells are used in various industrial applications, such as salt production, where they measure the weight of salt on a conveyor belt to control the process.
• 😀 Load cells are also used in metal stamping processes, where they detect the strength applied during molding to ensure accurate and safe production.
• 😀 Sensitivity and accuracy are key factors in selecting the most appropriate load cell for a process, with capacitive cells being the most sensitive and accurate, followed by strain gauge cells.

Q & A

What is a load cell?

A load cell is an electric component, specifically a transducer, that measures the deformation of a rigid body when a force is applied to it. It does not measure the object's mass but the force exerted on it.

How does a load cell work?

Load cells work based on Hooke's Law, which states that the deformation of an elastic body is directly proportional to the force applied to it. This deformation is measured by the load cell and converted into a weight reading.

What are the four main types of load cells?

The four main types of load cells are pneumatic cells, hydraulic cells, strain gauge extensometer cells, and capacitive cells.

How do pneumatic load cells operate?

Pneumatic load cells use air pressure to measure weight. An elastic diaphragm deforms when weight is placed on it, compressing the air inside. A pressure gauge detects the change in air pressure and converts it into a weight measurement.

What is the principle behind hydraulic load cells?

Hydraulic load cells use a fluid, typically water or oil, to measure weight. When an object is placed on the cell, a piston compresses the liquid, deforming the diaphragm, and a pressure sensor detects the pressure change to calculate the weight.

What makes strain gauge load cells popular in industrial applications?

Strain gauge load cells are popular because they provide precise measurements by changing electrical resistance when deformed. Their accuracy and ability to handle a wide range of weights make them widely used in industrial settings.

What is a Wheatstone Bridge configuration in strain gauge load cells?

A Wheatstone Bridge is a circuit configuration consisting of four strain gauges arranged in a rhombus shape. This setup allows for very accurate measurements of weight by measuring the changes in electrical resistance caused by deformation.

How do capacitive load cells function?

Capacitive load cells measure the change in the distance between two flat parallel plates when a load is applied. This causes a change in the electrical charge stored between the plates, which is then measured and converted into a weight reading.

Can you provide an example of an industrial application of load cells?

One example is in salt production, where a load cell measures the weight of salt on a conveyor belt. When the correct weight is reached, the system stops, and the salt is directed into a sack.

What factors should be considered when choosing a load cell for a process?

When choosing a load cell, the most important factors to consider are its sensitivity and accuracy. Capacitive cells are the most sensitive, followed by strain gauge cells, while air and hydraulic cells are less accurate.