Hydraulic load cells

Hydraulic load cells are instruments used to measure the force or torque in hydraulic systems. They consist of a cylinder filled with a hydraulic fluid and a piston that moves inside the cylinder. When a force is applied to the piston, the fluid in the cylinder is compressed, which leads to an increase in pressure. This pressure can then be measured to determine the force exerted on the piston.

Hydraulic load cells are used in various applications where accurate measurement of force or torque is required. They are often used in industry to monitor machines and systems to ensure that they operate within the prescribed limits. They are also used in materials testing to measure the strength of materials by measuring the force exerted on them. They are also used in research and development to analyze and optimize the performance of motors, pumps and other hydraulic systems.

Hydraulic load cells are devices that are used to measure the force acting on a load. They are based on the principle of hydraulics.

The basic principle of hydraulic load cells is based on the application of Pascal's law, which states that pressure changes in an incompressible fluid (such as hydraulic oil) are transmitted evenly in a closed system.

A typical hydraulic load cell consists of a cylindrical housing filled with hydraulic oil. There are connections at both ends of the housing through which the hydraulic oil is connected to the load to be measured via pipes. There is a piston in the center of the housing that can move freely.

When a force acts on the load to be measured, this force is transferred to the hydraulic oil. The hydraulic oil transfers the pressure evenly to the piston inside the load cell. The piston moves due to the pressure exerted on it and presses the hydraulic oil into a pressure measuring chamber.

The pressure measuring chamber contains a diaphragm or a strain gauge that measures the deformation of the piston. This deformation is proportional to the force exerted on the load. The force can be determined by measuring the deformation.

The measured force can either be read directly from a scale on the load cell or recorded by connecting the load cell to a measuring device such as a pressure gauge or a computer.

Hydraulic load cells are used in various applications, such as industrial production, component testing or materials research. They are characterized by their high accuracy, their robustness and their ability to measure large forces.

Hydraulic load cells offer several advantages compared to other measuring methods:

1. High accuracy: Hydraulic load cells provide precise measurement results with an accuracy of up to 0.1 % of the full scale. As a result, they can detect the smallest changes in force and are ideal for applications that require high measuring accuracy.

2. Large measuring range: Hydraulic load cells can be used in a wide measuring range, from a few Newtons up to several 1000 kN. This means they are versatile and can be used for both small and large forces.

3. High overload safety: Hydraulic load cells are robust and can withstand high overloads without compromising measuring accuracy. This makes them ideal for applications where sudden load peaks can occur.

4. Low dead weight: Hydraulic load cells have a low dead weight, which means that they do not influence or deform the structure to be measured. This is particularly important for dynamic measurements where rapid changes in force need to be recorded.

5. Long service life: Hydraulic load cells are durable and low-maintenance thanks to their robust design and the use of high-quality materials. They can provide reliable measurements over a long period of time.

6. Easy installation and handling: Hydraulic load cells are generally easy to install and operate. They can be easily integrated into existing systems and do not require any complex adjustments or calibrations.

Overall, hydraulic load cells offer a precise, versatile and reliable method of measuring forces in various applications, such as materials testing, mechanical engineering, the automotive industry and many other areas.

There are various types of load cells, which differ depending on the application and measuring principle. Here are some of the most common types of load cells:

1. Strain gauge load cells: This type of load cell is based on the strain gauge principle. They are applied to the surface of the can and expand or contract when a force is applied to them. The change in resistance of the strain gauges is then measured and converted into a force. This type of load cell is simple and inexpensive, but it can be susceptible to the effects of temperature and humidity.

2. Wired load cells: These load cells are equipped with a cable that is connected to a measuring device or a data logger unit. They are ideal for applications where the measurement is to take place at a specific location, as the cable enables the measurement data to be transmitted. However, this type of load cell can restrict freedom of movement and is not suitable for applications where the force measurement must be carried out in motion.

3. Wireless load cells: These load cells use wireless technology to transmit the measurement data to a receiving device. They offer greater flexibility and mobility as they do not require a cable connection. They are ideal for applications in which force measurement is to take place in motion. However, wireless load cells are generally more expensive than wired load cells and may require a battery or rechargeable battery for operation.

4. Hydraulic and pneumatic load cells: This type of load cell uses hydraulic or pneumatic systems to measure the force. They are ideal for applications where high forces need to be measured or when force measurement is required in harsh environments. However, this type of load cell is generally more expensive and requires special installation and maintenance.

It is important to note that there are many other specialized types of load cells designed for specific applications. Choosing the right type of load cell depends on the requirements of the application in question, such as the required accuracy, the environment and the type of force to be measured.

Hydraulic load cells are used in various applications to measure and monitor forces. Here are some examples of their areas of application:

1. Industrial manufacturing: Hydraulic load cells are often used in industrial production to measure forces during pressing, punching, welding, bending and other manufacturing processes.

2. Automotive industry: In the automotive industry, hydraulic load cells are used to measure forces when testing vehicle components such as brakes, steering, suspension and engines.

3. Construction and construction industry: In the construction industry, hydraulic load cells are used to measure forces when lifting heavy loads with cranes, when pushing or pulling components and when testing material strength.

4. Aerospace industry: In the aerospace industry, hydraulic load cells are used to measure forces when testing aircraft and spacecraft components, for example when load testing wings or monitoring engine force.

5. Food industry: Hydraulic load cells are used in the food industry to measure forces when mixing, kneading, cutting or packaging food.

6. Medical technology: In medical technology, hydraulic load cells are used to measure forces in medical processes such as prosthesis manufacture, rehabilitation or orthopaedic diagnostics.

These areas of application are not exhaustive and hydraulic load cells can also be used in other industries and applications where the measurement and monitoring of forces is required.

Hydraulic load cells are instruments used to measure the force exerted on a component or structure. They consist of a piston-cylinder unit in which the force is generated by the pressure of a hydraulic fluid on the piston. The force is then measured by the pressure generated in the hydraulic fluid.

The accuracy of hydraulic load cells depends on various factors, such as the quality of the materials used, the design of the system and the calibration of the measuring devices. As a rule, hydraulic load cells can achieve a high accuracy of around ±0.1% of the measured force.

However, various measurement errors can occur which can affect the accuracy. One possible fault is a leak in the hydraulic fluid, for example, which can lead to a loss of pressure and thus falsify the measurement. Inadequate sealing of the piston-cylinder unit can also lead to faults.

Other possible sources of error are friction in the moving parts, which can lead to inaccuracies in the measurement, and temperature fluctuations, which can change the pressure in the hydraulic fluid.

To ensure the accuracy of the measurements, it is important to calibrate the hydraulic load cell regularly and check for possible sources of error.

The following attributes should be taken into account when selecting a hydraulic load cell:

1. Measurement range: The load cell should have a sufficiently large measuring range to cover the forces to be measured.

2. Accuracy: The accuracy of the force measurement is an important factor. The more accurate the measurement, the more precise the results can be.

3. Sensitivity: The sensitivity of the load cell indicates how well it can measure small changes in force. High sensitivity is particularly important when it comes to measuring small forces.

4. Robustness: The load cell should be robust and resistant to withstand the conditions in the environment. For example, it should be protected against shocks, vibrations and high temperatures.

5. Calibration: It is important that the load cell is calibrated to ensure accurate measurement results. Regular calibration should be possible in order to maintain the accuracy of the measurements.

6. Mounting and connection options: The load cell should have suitable mounting and connection options so that it can be easily integrated into the existing system.

7. Compatibility: The load cell should be compatible with the measuring devices and software solutions used in order to facilitate the integration and evaluation of the measurement data.

8. Price-performance ratio: The price-performance ratio should be reasonable. It is important to choose a load cell that meets the requirements but does not exceed the budget.

Hydraulic load cells are usually calibrated on special calibration test benches. The can is loaded with known forces and the signals generated by the can are measured and compared with the actual forces.

There are various standards that can be used for the calibration of hydraulic load cells, depending on the area of application and requirements. Some of the common standards are:

1. ISO 376: This standard specifies the general requirements for the calibration of force gauges and describes the procedures for determining accuracy.

2. DIN 51221: This standard specifies the requirements for the calibration of hydraulic load cells and describes the procedures for determining the accuracy.

3. ASTM E74: This standard provides instructions for the calibration of force gauges and specifies the procedures for determining the measurement uncertainty.

4. NIST Handbook 44: This manual contains instructions for the calibration of force gauges and describes the procedures for determining accuracy in accordance with the regulations of the National Institute of Standards and Technology (NIST) in the USA.

When calibrating hydraulic load cells, it is important to use the correct standards in accordance with national regulations and the requirements of the respective application. It is recommended to use the services of an accredited calibration laboratory to ensure accurate and reliable calibration.