What Is a Weight Sensor?
A weight sensor is a device used to measure the weight of an object.
Currently, load cells are predominantly used for this purpose. Before their advent, mechanical lever-type scales were common, but they required frequent calibration and maintenance for accuracy.
Load-cell scales, designed without moving or friction parts, are less prone to breakage and require only simple maintenance. They are known for their high measurement accuracy and minimal temperature effects during measurement and are now widely used in various applications.
Uses of Weight Sensors
Weight sensors are used across diverse fields. Their most direct application is in measuring the weight of objects, such as weighing patients in hospital beds or checking product weights in production lines.
These sensors also measure pressure, thereby enabling the measurement of load on objects. For instance, they can determine the torque of vehicle engines and the load on their wheels.
Principle of Weight Sensors
Load cells, the most common type of weight sensor, come in various forms: hydraulic, pneumatic, and strain gauge load cells, with strain gauge load cells being the most widespread.
1. Hydraulic Load Cells
Hydraulic load cells contain fluid and measure weight based on the pressure changes within the fluid as force is applied. They are suitable for hazardous areas as they don’t use electronic components and are often used for weighing tanks and hoppers.
2. Pneumatic Load Cells
Pneumatic load cells utilize air pressure for detection. They use multiple damping chambers to enhance measurement accuracy. Being air-filled, they pose a reduced risk of contamination if broken compared to hydraulic systems.
3. Strain Gauge Load Cells
Strain gauge load cells convert force into an electrical signal. They work by detecting changes in electrical resistance caused by deformation under force. The resistance change is proportional to the force applied, allowing for accurate weight measurement.
Types of Weight Sensors
Besides load cells, there are other types of weight sensors:
1. Piezoelectric Element Type
Piezoelectric elements, made from materials like quartz or ceramics, generate an electrical charge under applied force. The change in charge is measured to determine weight or strain.
2. Capacitance Type
These sensors measure changes in capacitance caused by deformation in response to pressure, translating it into weight data.
3. Film Lamination Type
Using sheet type switches, this type is used for weight detection or to detect contact with an object.
4. Sheet/Mat Type
Sheet or mat-type sensors detect the presence or absence of weight. Known as pressure-sensitive sheets or mat switches, they consist of two layers of material that deform under weight or load, with piezoelectric or capacitive elements and contacts on their surfaces.
These sensors are used in applications like automatic doorways and bumpers of unmanned vehicles to detect human contact.
Further Information on Weight Sensors
Weight Sensors and IoT
Weight sensors are increasingly used in IoT-related applications. For instance, they detect the presence or absence of objects on automated conveyor lines or stock in automated warehouses.
They also enable automated stock counting and shipment quantification by weight. This functionality is expected to facilitate remote management of warehouse systems and other logistics applications.