Load cells

Load cells are electronic sensors that are used in weighing systems to measure the weight or mass of an object. They are made of a metal alloy that is produced in a specific shape and thickness to enable precise and accurate measurement.

The functionality of a load cell is based on the principle of strain measurement. When a mass is placed on the load cell, it causes a deformation or expansion of the metal. This deformation changes the electrical resistance of the metal alloy, as the electrical resistance of metals depends on their length and thickness.

The load cell usually contains four strain gauges, which are attached to the live points of the metal. These strain gauges are electrical resistors that change with the deformation. The electrical resistance can be measured by applying a constant electrical voltage to the load cell. The greater the deformation of the load cell, the greater the change in electrical resistance.

The change in electrical resistance is converted into a proportional electrical voltage, which is then converted into a digital display or output signal by an A/D converter. The digital display shows the weight or mass of the object placed on the load cell.

Load cells are used in various applications such as scales for industrial or commercial use, in medical devices, in vehicles for weight measurement and in many other applications where accurate weight measurements are required.

There are different types of load cells that are used depending on the application. Here are some of the most common types of load cells:

1. Compression load cells: These load cells are used to measure compressive forces and are generally widely used in industry. They are used, for example, in materials testing, in the construction industry or in the packaging industry.

2. Tension load cells: These load cells are used to measure tensile forces and are used in various industrial sectors such as mechanical engineering, the marine industry and the automotive industry.

3. Thrust load cells: These load cells are used to measure thrust forces, for example in the aviation industry, in construction or in robotics.

4. Bending moment load cells: These load cells are used to measure bending moments and are often used in the construction industry, in bridge building or in wind energy.

5. Torque load cells: These load cells are used to measure torques and are used in the automotive industry, in the construction of engines or in the aviation industry.

6. Compact load cells: These load cells are small and compact and are often used in medical technology, in laboratories or in the food industry.

7. Hygienic load cells: These load cells are specially designed for use in hygienic environments and are used in the food, pharmaceutical and cosmetics industries.

This list is not exhaustive, as there are other types of load cells that have been developed depending on the specific application.

Various attributes and parameters are important when selecting a load cell. Here are some of them:

1. Load capacity: The load capacity of the load cell indicates the maximum weight it can measure. It is important to select a load cell with sufficient load capacity for the planned applications.

2. Accuracy: The accuracy of a load cell indicates how precisely it can measure the weight. The lower the measurement deviation, the more accurate the load cell is. Accuracy is particularly important for applications that require high precision, such as in industry or in the laboratory.

3. Linearity: The linearity of the load cell describes how well it can display the weight linearly over the entire measuring range. Good linearity is important in order to achieve accurate measurement results.

4. Temperature compensation: Load cells can be affected by temperature fluctuations. Good temperature compensation ensures that the measurements remain accurate regardless of the ambient temperature.

5. Protection type: Depending on the application environment, it may be important to choose a load cell with a certain protection class to protect it from moisture, dust or other external influences.

6. Mounting type: Load cells are available in various mounting types, such as tension or compression versions. The selection of the right type of mounting depends on the specific requirements of the application.

7. Robustness: Depending on the area of application, it is important to select a robust and durable load cell that can withstand the requirements. This can be the case in harsh industrial environments or in vehicle scales, for example.

8. Connection type: The connection type of the load cell can also be important. Depending on the application, it may be necessary to select a load cell with specific connections or communication interfaces to enable seamless integration into the overall system.

This list is not exhaustive and there may be other specific requirements depending on the application. It is important to carefully analyze the individual requirements and select the right load cell accordingly.

Load cells are usually calibrated by comparison with a known mass. Various methods are used, depending on the type of load cell and the required accuracy.

A frequently used method is static calibration, in which the load cell is loaded with a series of known masses. The output signals of the load cell are measured and compared with the expected values. Based on these comparative measurements, a calibration curve can be created which shows the relationship between the output voltage of the load cell and the actual mass.

Another method is dynamic calibration, in which the load cell is loaded with a sinusoidal load or pulses. The output signals of the load cell are recorded and analyzed in order to perform the calibration.

There are various standards for the calibration of load cells, depending on the area of application and the required accuracy. An internationally recognized standard is ISO 376, which specifies the requirements for the calibration of load cells. Among other things, this standard specifies the minimum accuracy requirements, the test methods and the measurement uncertainty.

There are also industry-specific standards, such as OIML R60 for load cells in retail or ASTM E74 for load cells in materials testing. These standards define specific requirements and test procedures for certain applications.

Calibration of load cells should be carried out regularly to ensure the accuracy and reliability of measurements. The frequency of calibration depends on various factors, such as the frequency of use, the ambient conditions and the specific requirements of the application.

The use of load cells is widespread in various industries and applications and can be beneficial in many areas. Here are some industries and applications that benefit most from the use of load cells:

1. Industrial manufacturing: Load cells are often used in industrial production to measure the weight of products, materials or containers. This can be useful in various areas such as the food industry, the chemical industry, metal processing and other manufacturing processes.

2. Logistics and transportation: Load cells are used in logistics and transportation applications to measure the weight of freight or loads. This is important in order to comply with the weight limits of vehicles or containers and to avoid overloading.

3. Medical and pharmaceutical industry: In the medical and pharmaceutical industry, load cells are used to measure the weight of patients, medicines or other materials. This is important for dosing medication and monitoring patients.

4. Agriculture: In agriculture, load cells are used to measure the weight of harvests, animals or animal feed. This can help to monitor production volumes and control feed rations for animals.

5. Environmental monitoring: Load cells are also used in environmental monitoring applications to measure the weight of waste containers, recycling materials or waste water samples. This can help with the management of waste and recycling programs.

6. Laboratories and research facilities: Load cells are used in laboratories and research facilities to measure the weight of substances, samples or materials. This is important for accurate measurements and experiments.

This list is not exhaustive, as load cells can be used in many different industries and applications. The use of load cells depends on the specific requirements and needs of the respective industry or application.

Modern load cells offer several advantages compared to older models:

1. Accuracy: Modern load cells are able to measure weights with greater accuracy. They are able to deliver precise values, which is particularly important when it comes to weight measurements in industrial or commercial applications.

2. Reliability: Modern load cells are generally more robust and resistant to external influences such as vibrations, shocks or temperature fluctuations. They are designed to deliver reliable results under extreme conditions.

3. Compactness: Modern load cells are smaller and more compact than older models. This makes them easier to install and transport. They can be used in various applications, even in confined spaces.

4. Digitization: Modern load cells are often equipped with digital technology that enables weight data to be transmitted directly to a higher-level system. This facilitates integration into automated processes and enables simple data acquisition and analysis.

5. Adaptability: Modern load cells can be adapted to different requirements. They can be available in different sizes and capacities and are versatile in both industrial and commercial applications.

In summary, modern load cells offer improved accuracy, reliability, compactness, digitalization and adaptability compared to older models. These advantages make them the preferred choice in various weight measurement applications.

Environmental influences such as temperature or humidity can affect the accuracy of load cells. Here are some implications and possible solutions:

1. Temperature: A change in ambient temperature can lead to expansion or contraction of the materials in the load cell, resulting in measurement errors. To solve this problem, temperature-compensated load cells are used, which are equipped with sensors to measure and automatically compensate for temperature changes.

2. Humidity: Moisture can lead to corrosion of the load cell, which impairs accuracy. One way to solve this problem is to use load cells made of corrosion-resistant materials such as stainless steel. Another option is to place the load cell in a closed housing to protect it from moisture.

3. Vibrations: Vibrations in the environment can lead to measurement errors. To avoid this, load cells are often mounted in special holders that dampen vibrations and improve accuracy.

4. Electromagnetic interference: Electromagnetic fields can influence the accuracy of load cells. One solution is to place the load cell in a shielded housing to minimize electromagnetic interference.

5. Static charge: Static charge can lead to incorrect measurements. One way to solve this problem is to provide the load cell with an antistatic coating or to use it in an area with controlled humidity to reduce static charge.

It is important that load cells are regularly maintained and calibrated to ensure that they continue to provide accurate readings.

There are several trends and developments to be observed in the field of load cell technology:

1. Miniaturization: Load cells are becoming smaller and more compact, which leads to improved integration in various applications. This enables, for example, the development of portable scales or the integration of load cells into mobile devices.

2. Wireless communication: Load cells are increasingly being equipped with wireless communication technology to enable simple and fast data transmission. This enables, for example, the integration of load cells into IoT systems or the remote monitoring and control of weighing processes.

3. Digitization: Traditional analog load cells are increasingly being replaced by digital load cells, which offer greater accuracy and reliability. Digital load cells can also be equipped with advanced functions such as self-calibration or automatic error detection.

4. Improved accuracy and resolution: Thanks to the use of advanced materials and technologies, load cells are becoming increasingly accurate and offer a higher resolution. This makes it possible, for example, to measure the weight of very small or light objects with high precision.

5. Robustness and reliability: Load cells are becoming increasingly robust and resistant to external influences such as vibrations, shocks or environmental influences such as humidity or temperature fluctuations. This enables load cells to be used in demanding environments such as industrial applications.

6. Automation and integration: Load cells are increasingly being used in automated processes and integrated into existing systems. For example, they can be used in conjunction with robots or in production lines to carry out weight measurements and checks in real time.

7. Sustainability: There is also an increasing demand for more environmentally friendly load cell technologies. Manufacturers are therefore working on the development of energy-efficient load cells and the use of environmentally friendly materials.

These trends and developments are helping to ensure that load cells can be used in more and more areas of application and that the performance and flexibility of weighing technology is continually being improved.