| Grid length | 5 mm |
| Nominal resistance | 350 Ω |
| Temperature-compensated | 10 to 300 °C |
Strain gauges
Strain gauges are electrical sensors used to measure mechanical deformation. They consist of a thin metal or plastic strip applied to a carrier film. When the strip is stretched or compressed, its length changes and so does its electrical resistance.
The change in resistance can be measured and is proportional to the change in length of the strip. The measurement is usually made using a bridge circuit that compares the resistance of the strain gauge with a reference resistance. The bridge is powered by a current source and the voltage difference at the two outputs of the bridge is measured.
The use of strain gauges is widespread in measurement technology and is used in many applications such as measuring stress and strain on mechanical components such as bridges, cranes, machinery, aircraft or in construction. Strain gages are also used in biomechanics, materials testing and many other areas of engineering.
There are several types of strain gages, varying in size, shape, material and sensitivity. Important factors when selecting strain gages are measurement ranges, sensitivity and temperature dependence. Depending on the application and measurement task, different strain gages may be required.
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The change in resistance can be measured and is proportional to the change in length of the strip. The measurement is usually made using a bridge circuit that compares the resistance of the strain gauge with a reference resistance. The bridge is powered by a current source and the voltage difference at the two outputs of the bridge is measured.
The use of strain gauges is widespread in measurement technology and is used in many applications such as measuring stress and strain on mechanical components such as bridges, cranes, machinery, aircraft or in construction. Strain gages are also used in biomechanics, materials testing and many other areas of engineering.
There are several types of strain gages, varying in size, shape, material and sensitivity. Important factors when selecting strain gages are measurement ranges, sensitivity and temperature dependence. Depending on the application and measurement task, different strain gages may be required.
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| Applications | Vehicles & Road Traffic |
| Grid length | 3 mm |
| Nominal resistance | 100 Ω |
| Base material | Polyimide |
| Grid length | 10 mm |
| Nominal resistance | 350 Ω |
| Base material | Polyimide |
| Grid length | 1.5 to 6 mm |
| Nominal resistance | 350 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 6 mm |
| Nominal resistance | 350 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 6 to 10 mm |
| Nominal resistance | 120 to 350 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 3 mm |
| Nominal resistance | 350 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 3 mm |
| Nominal resistance | 120 to 350 Ω |
| Temperature-compensated | -10 to 105 °C |
| Grid length | 1 to 4 mm |
| Nominal resistance | 120 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 20 to 40 mm |
| Nominal resistance | 13 to 44 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 5 mm |
| Nominal resistance | 350 Ω |
| K-factor | 2 |
| Grid length | 1 mm |
| Nominal resistance | 120 Ω |
| Grid material | CuNi alloy |
| Grid length | 3 to 6 mm |
| Nominal resistance | 120 to 350 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 0.6 to 6 mm |
| Nominal resistance | 120 to 700 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 0.6 to 10 mm |
| Nominal resistance | 120 to 350 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 1.5 to 10 mm |
| Nominal resistance | 120 to 350 Ω |
| Temperature-compensated | -10 to 120 °C |
| Grid length | 3 to 10 mm |
| Nominal resistance | 120 to 350 Ω |
| Temperature-compensated | -200 to 250 °C |
| Grid length | 30 to 120 mm |
| Nominal resistance | 120 Ω |
| Temperature-compensated | 0 to 50 °C |
| Grid length | 60 to 120 mm |
| Nominal resistance | 120 Ω |
| Temperature-compensated | 10 to 60 °C |
| Grid length | 0.2 to 1 mm |
| Nominal resistance | 120 Ω |
| Temperature-compensated | -30 to 120 °C |
To be able to detect the relatively small resistance changes of a strain gauge, bridge circuits are used for their measurement. This converts the relative resistance change into a voltage output. As a rule, half-bridge and full-bridge circuits are used, since temperature compensation can be achieved with these.
The gauge factor
The relationship between the relative resistance of the material and the strain of the material is described by a proportionality factor called the gauge factor. It indicates the factor by which the relative change in resistance exceeds the relative change in length. The gauge factor is also called strain sensitivity or electrical strain factor. The gauge factor can only be calculated approximately. The gauge factor is determined experimentally by the manufacturer and is included as information on the supplied strain gauge. The gauge factor is determined at room temperature, unless otherwise specified, at 23°C. The gauge factor is therefore also temperature-dependent. This dependency is linear and is also included with the strain gauge at delivery in the form of a diagram.
The sensitivity of a strain gauge transducer refers to its input voltage and is specified in mV/V.
Basic structure of a strain gauge
Basically, strain gauges consist of a measuring grid made of arranged in a meandering pattern. This resistance material is protected against mechanical damage by a protective layer.
Strain gauge types
Wire strain gauges
Wire Strain Gauges are used today exceptionally for special applications.
Foil strain gauges
Today, foil strain gauges are used almost exclusively. Foil strain gages consist of an insulating carrier material and the measuring grid. The measuring grid consists of a resistance foil, which is applied to the carrier foil.
To achieve a correspondingly high resistance, the conductor frames are designed in a meandering shape. This conductor arrangement is called a grid. Depending on the measurement requirements, there are different grid sizes and grid arrangements. The meandering conductor arrangement also determines the magnitude of the cross-sensitivity. The cross-sensitivity is the error caused by the deformation of the conductor transverse to the measurement direction, since this deformation of the conductor also leads to a change in resistance.
Semiconductor strain gauges
Semiconductor strain gauges (SC strain gauges) do not operate on the principle of length and cross-section change of wire and foil strain gauges, but on the principle of piezoresistance change in semiconductors. The linearity is lower than with wire and foil strain gauges. Another disadvantage is the material brittleness. The temperature dependence is very high. Semiconductor strain gauges have a relatively small size
The gauge factor
The relationship between the relative resistance of the material and the strain of the material is described by a proportionality factor called the gauge factor. It indicates the factor by which the relative change in resistance exceeds the relative change in length. The gauge factor is also called strain sensitivity or electrical strain factor. The gauge factor can only be calculated approximately. The gauge factor is determined experimentally by the manufacturer and is included as information on the supplied strain gauge. The gauge factor is determined at room temperature, unless otherwise specified, at 23°C. The gauge factor is therefore also temperature-dependent. This dependency is linear and is also included with the strain gauge at delivery in the form of a diagram.
The sensitivity of a strain gauge transducer refers to its input voltage and is specified in mV/V.
Basic structure of a strain gauge
Basically, strain gauges consist of a measuring grid made of arranged in a meandering pattern. This resistance material is protected against mechanical damage by a protective layer.
Strain gauge types
Wire strain gauges
Wire Strain Gauges are used today exceptionally for special applications.
Foil strain gauges
Today, foil strain gauges are used almost exclusively. Foil strain gages consist of an insulating carrier material and the measuring grid. The measuring grid consists of a resistance foil, which is applied to the carrier foil.
To achieve a correspondingly high resistance, the conductor frames are designed in a meandering shape. This conductor arrangement is called a grid. Depending on the measurement requirements, there are different grid sizes and grid arrangements. The meandering conductor arrangement also determines the magnitude of the cross-sensitivity. The cross-sensitivity is the error caused by the deformation of the conductor transverse to the measurement direction, since this deformation of the conductor also leads to a change in resistance.
Semiconductor strain gauges
Semiconductor strain gauges (SC strain gauges) do not operate on the principle of length and cross-section change of wire and foil strain gauges, but on the principle of piezoresistance change in semiconductors. The linearity is lower than with wire and foil strain gauges. Another disadvantage is the material brittleness. The temperature dependence is very high. Semiconductor strain gauges have a relatively small size
What is a strain gauge and what is it used for?
A strain gauge is an electrical resistance sensor that is used to measure the elongation or deformation of a material. It consists of a thin metal strip or a thin film that is applied to a flexible carrier layer.
When the strain gauge is attached to a material and the material is subjected to stress or strain, the resistance of the strain gauge changes in proportion to the deformation of the material. This makes it possible to measure the elongation or deformation of the material.
Strain gauges are used in various applications, such as material testing, structural monitoring of buildings or bridges, machine monitoring or in medical technology. They are also frequently used in the automotive industry to monitor and optimize the load on components such as brakes, engines or chassis.
When the strain gauge is attached to a material and the material is subjected to stress or strain, the resistance of the strain gauge changes in proportion to the deformation of the material. This makes it possible to measure the elongation or deformation of the material.
Strain gauges are used in various applications, such as material testing, structural monitoring of buildings or bridges, machine monitoring or in medical technology. They are also frequently used in the automotive industry to monitor and optimize the load on components such as brakes, engines or chassis.
How does a strain gauge work and what physical principles are it based on?
A strain gauge is an electrical sensor that is used to measure the elongation or deformation of an object. It consists of a thin, flexible metal strip attached to a carrier foil.
The physical principles on which a strain gauge is based are the piezoresistive effect and the geometric effect.
The piezoresistive effect states that the electrical resistance of a material depends on its mechanical elongation. When a strain gauge is stretched, its length and cross-section change, which leads to a change in electrical resistance. This change in resistance can be measured and used to determine the elongation.
The geometric effect refers to the change in the cross-section of the strain gauge when stretched. If the cross-section of the strip becomes smaller, its electrical resistance increases. By combining the geometric effect with the piezoresistive effect, the sensitivity and accuracy of the strain gauge is improved.
To measure the change in resistance, the strain gauge is integrated into a Wheatstone bridge circuit. The bridge circuit consists of four resistors, one of which is the strain gauge. When the strain gauge is stretched, its resistance changes and so does the ratio of the resistances in the bridge. This change can be measured with the aid of an electronic circuit and used to determine the elongation.
Strain gauges are often used in measurement technology to measure the strain of structures such as bridges, buildings, airplanes, vehicles and machines. They are very precise and can detect small strains in the micrometer range.
The physical principles on which a strain gauge is based are the piezoresistive effect and the geometric effect.
The piezoresistive effect states that the electrical resistance of a material depends on its mechanical elongation. When a strain gauge is stretched, its length and cross-section change, which leads to a change in electrical resistance. This change in resistance can be measured and used to determine the elongation.
The geometric effect refers to the change in the cross-section of the strain gauge when stretched. If the cross-section of the strip becomes smaller, its electrical resistance increases. By combining the geometric effect with the piezoresistive effect, the sensitivity and accuracy of the strain gauge is improved.
To measure the change in resistance, the strain gauge is integrated into a Wheatstone bridge circuit. The bridge circuit consists of four resistors, one of which is the strain gauge. When the strain gauge is stretched, its resistance changes and so does the ratio of the resistances in the bridge. This change can be measured with the aid of an electronic circuit and used to determine the elongation.
Strain gauges are often used in measurement technology to measure the strain of structures such as bridges, buildings, airplanes, vehicles and machines. They are very precise and can detect small strains in the micrometer range.
What types of strain gauges are there and what are the differences between them?
There are different types of strain gauges, including
1. Metallic strain gages: These usually consist of a thin metal foil, such as aluminum or constantan. They are robust and can withstand high elongation. They are often used in applications where high accuracy and durability are required.
2. Semiconductor strain gages: These consist of semiconducting materials such as silicon. They have a higher sensitivity than metallic strain gauges and offer better long-term stability. They are often used in applications where high precision and low drift are required.
3. Carbon nanotube strain gages: These consist of carbon nanotubes applied to a flexible substrate. They are characterized by their high sensitivity and their ability to measure very small strains. They are often used in applications where high resolution and miniaturization are important.
The differences between the various types of strain gages lie mainly in their sensitivity, their robustness, their long-term stability and their cost. Metallic strain gauges are generally cheaper and more robust, while semiconductive strain gauges offer higher sensitivity and better long-term stability. Carbon nanotube strain gages are very sensitive and provide high resolution, but are often more expensive and less robust. The selection of the appropriate type of strain gauge depends on the requirements of the specific application.
1. Metallic strain gages: These usually consist of a thin metal foil, such as aluminum or constantan. They are robust and can withstand high elongation. They are often used in applications where high accuracy and durability are required.
2. Semiconductor strain gages: These consist of semiconducting materials such as silicon. They have a higher sensitivity than metallic strain gauges and offer better long-term stability. They are often used in applications where high precision and low drift are required.
3. Carbon nanotube strain gages: These consist of carbon nanotubes applied to a flexible substrate. They are characterized by their high sensitivity and their ability to measure very small strains. They are often used in applications where high resolution and miniaturization are important.
The differences between the various types of strain gages lie mainly in their sensitivity, their robustness, their long-term stability and their cost. Metallic strain gauges are generally cheaper and more robust, while semiconductive strain gauges offer higher sensitivity and better long-term stability. Carbon nanotube strain gages are very sensitive and provide high resolution, but are often more expensive and less robust. The selection of the appropriate type of strain gauge depends on the requirements of the specific application.
Where are strain gages typically used and what advantages do they offer in these applications?
Strain gages are typically used in many areas of engineering and materials testing. Here are some common applications:
1. Structural monitoring: Strain gauges are used to monitor the structural integrity of structures such as bridges, buildings and pipelines. They help to detect possible damage or deformation at an early stage and carry out repairs before more serious problems occur.
2. Load measurement: Strain gauges are used to measure the load on components such as steel beams, welded joints and pipelines. This enables engineers to determine the load-bearing capacity of these components and ensure safety.
3. Automotive applications: Strain gages are used in the automotive industry for various applications, including measuring the load on vehicle parts such as bodywork, frames and suspension systems. This helps manufacturers to improve the strength and durability of their vehicles.
4. Mechanical engineering: Strain gauges are used in machines and systems to measure the load on components such as shafts, bearings and gears. This enables engineers to monitor the performance of the machines and identify potential problems at an early stage.
The advantages of using strain gages in these applications are:
- High accuracy: Strain gages can provide very precise measurements, which is crucial for applications where accurate data is required.
- Simple installation: Strain gages can simply be attached to the surface of the component to be measured, which makes them relatively easy to install.
- Low costs: Strain gauges are relatively inexpensive compared to other measuring devices, which makes them an economical solution for many applications.
- Versatility: Strain gauges can be attached to various materials and surfaces and can therefore be used in a wide range of applications.
- Real-time monitoring: Strain gauges enable real-time monitoring of component stress, allowing engineers to react quickly to changes and prevent potential damage.
1. Structural monitoring: Strain gauges are used to monitor the structural integrity of structures such as bridges, buildings and pipelines. They help to detect possible damage or deformation at an early stage and carry out repairs before more serious problems occur.
2. Load measurement: Strain gauges are used to measure the load on components such as steel beams, welded joints and pipelines. This enables engineers to determine the load-bearing capacity of these components and ensure safety.
3. Automotive applications: Strain gages are used in the automotive industry for various applications, including measuring the load on vehicle parts such as bodywork, frames and suspension systems. This helps manufacturers to improve the strength and durability of their vehicles.
4. Mechanical engineering: Strain gauges are used in machines and systems to measure the load on components such as shafts, bearings and gears. This enables engineers to monitor the performance of the machines and identify potential problems at an early stage.
The advantages of using strain gages in these applications are:
- High accuracy: Strain gages can provide very precise measurements, which is crucial for applications where accurate data is required.
- Simple installation: Strain gages can simply be attached to the surface of the component to be measured, which makes them relatively easy to install.
- Low costs: Strain gauges are relatively inexpensive compared to other measuring devices, which makes them an economical solution for many applications.
- Versatility: Strain gauges can be attached to various materials and surfaces and can therefore be used in a wide range of applications.
- Real-time monitoring: Strain gauges enable real-time monitoring of component stress, allowing engineers to react quickly to changes and prevent potential damage.
What challenges can arise when using strain gages and how can they be overcome?
Various challenges can arise when using strain gages:
1. Temperature dependence: Strain gauges are sensitive to temperature fluctuations. A change in the ambient temperature can lead to measurement errors. This can be achieved by using temperature-compensated strain gauges or by compensating for temperature changes using suitable software algorithms.
2. Alignment: The correct alignment of the strain gauges is crucial for accurate measurements. Incorrect alignment can lead to measurement errors. To overcome this problem, the strain gauges should be attached carefully and precisely. The use of templates or devices for precise placement can help.
3. Bonding: Bonding the strain gauges to the surface can be a challenge. Uneven or insufficient bonding can lead to measurement errors. Careful preparation of the surface and the use of suitable adhesives can help to overcome this problem.
4. Signal noise: Strain gages can be sensitive to electrical noise, which can lead to inaccurate measurements. Signal noise can be reduced by using amplifiers and filters.
5. Calibration: Strain gauges must be calibrated to ensure accurate measurement results. Incorrect calibration can lead to measurement errors. It is therefore important to regularly check and calibrate the strain gauges in order to detect and correct any deviations.
By considering and overcoming these challenges, accurate and reliable measurements can be achieved with strain gages.
1. Temperature dependence: Strain gauges are sensitive to temperature fluctuations. A change in the ambient temperature can lead to measurement errors. This can be achieved by using temperature-compensated strain gauges or by compensating for temperature changes using suitable software algorithms.
2. Alignment: The correct alignment of the strain gauges is crucial for accurate measurements. Incorrect alignment can lead to measurement errors. To overcome this problem, the strain gauges should be attached carefully and precisely. The use of templates or devices for precise placement can help.
3. Bonding: Bonding the strain gauges to the surface can be a challenge. Uneven or insufficient bonding can lead to measurement errors. Careful preparation of the surface and the use of suitable adhesives can help to overcome this problem.
4. Signal noise: Strain gages can be sensitive to electrical noise, which can lead to inaccurate measurements. Signal noise can be reduced by using amplifiers and filters.
5. Calibration: Strain gauges must be calibrated to ensure accurate measurement results. Incorrect calibration can lead to measurement errors. It is therefore important to regularly check and calibrate the strain gauges in order to detect and correct any deviations.
By considering and overcoming these challenges, accurate and reliable measurements can be achieved with strain gages.
How are strain gages calibrated and how accurate are the measurement results?
Strain gauges are typically calibrated by comparison with a known reference strain. For this purpose, the strain gauge is attached to a suitable test device and brought to a defined strain. The output signals of the strain gauge are then compared with the actual strains generated by the tester. In this way, the sensitivity of the strain gauge can be determined and corrected if necessary.
The accuracy of the measurement results depends on various factors, such as the quality of the strain gauge, the calibration method and the measuring environment. As a rule, modern strain gages can achieve an accuracy in the range of ±0.1 % to ±1 %. Even higher accuracies can be achieved for very precise applications.
It is important to note that the accuracy of the measurement results depends not only on the calibration, but also on other factors such as the stability of the measuring environment, the mounting of the strain gauge and the behavior of the material to be measured. It is therefore advisable to take all relevant factors into account when using strain gauges in order to achieve accurate and reliable measurement results.
The accuracy of the measurement results depends on various factors, such as the quality of the strain gauge, the calibration method and the measuring environment. As a rule, modern strain gages can achieve an accuracy in the range of ±0.1 % to ±1 %. Even higher accuracies can be achieved for very precise applications.
It is important to note that the accuracy of the measurement results depends not only on the calibration, but also on other factors such as the stability of the measuring environment, the mounting of the strain gauge and the behavior of the material to be measured. It is therefore advisable to take all relevant factors into account when using strain gauges in order to achieve accurate and reliable measurement results.
What new developments are there in the field of strain gages and how could they expand the range of applications?
There are various new developments in the field of strain gauges that could expand the range of applications:
1. More flexible and thinner materials: Researchers are working on producing strain gauges from more flexible and thinner materials. This would make it possible to use them in areas where previous measuring strips could not be used due to their stiffness or size.
2. Wireless transmission of measurement data: Another development is the wireless transmission of measurement data, which makes it possible to monitor the strain gauges remotely in real time. This could be used, for example, in the structural monitoring of buildings or in medical diagnostics.
3. Integrated sensors: Strain gauges with integrated sensors are also being developed that can provide additional information, such as temperature or pressure measurements. This integration enables a more precise and comprehensive measurement of strains and opens up new application possibilities in various areas.
4. Miniaturization: Advances in microelectronics are making it possible to design strain gages that are ever smaller and more compact. This means they can be used in areas where previous measuring devices were too large or too bulky, such as in biomedicine or wearables.
5. Extended areas of application: As a result of the developments mentioned above, strain gages could be used in many new areas of application. These include, for example, monitoring sports equipment, controlling the movements of robots, measuring loads in aerospace and patient monitoring in medicine.
These new developments open up a wide range of applications for strain gauges and enable more precise, efficient and flexible strain measurement in various areas.
1. More flexible and thinner materials: Researchers are working on producing strain gauges from more flexible and thinner materials. This would make it possible to use them in areas where previous measuring strips could not be used due to their stiffness or size.
2. Wireless transmission of measurement data: Another development is the wireless transmission of measurement data, which makes it possible to monitor the strain gauges remotely in real time. This could be used, for example, in the structural monitoring of buildings or in medical diagnostics.
3. Integrated sensors: Strain gauges with integrated sensors are also being developed that can provide additional information, such as temperature or pressure measurements. This integration enables a more precise and comprehensive measurement of strains and opens up new application possibilities in various areas.
4. Miniaturization: Advances in microelectronics are making it possible to design strain gages that are ever smaller and more compact. This means they can be used in areas where previous measuring devices were too large or too bulky, such as in biomedicine or wearables.
5. Extended areas of application: As a result of the developments mentioned above, strain gages could be used in many new areas of application. These include, for example, monitoring sports equipment, controlling the movements of robots, measuring loads in aerospace and patient monitoring in medicine.
These new developments open up a wide range of applications for strain gauges and enable more precise, efficient and flexible strain measurement in various areas.
What alternatives are there to strain gauges and in which situations might they be more suitable?
There are several alternatives to strain gauges that may be more suitable depending on the application. Some of these alternatives are:
1. Optical strain measurement: Optical methods such as digital image correlation (DIC) are used to measure deformations. This method enables non-contact measurement and offers greater accuracy than strain gauges. Optical strain measurement is particularly suitable for complex geometries or materials where the application of strain gauges is difficult.
2. Ultrasonic measurement: Ultrasound is used to measure deformations by measuring the travel time of sound waves through the material. This method is non-contact and is well suited for dynamic measurements. Ultrasonic measurement can be used at high temperatures or in environments with vibrations where strain gages cannot be used.
3. Magnetic strain measurement: Magnetic sensors are used to measure deformations. This method is well suited for materials with magnetic attributes and enables non-contact measurement. Magnetic strain measurement can also be used at high temperatures or in environments with vibrations.
4. Capacitive strain measurement: This method uses capacitive sensors to measure deformations. This method enables non-contact measurement and offers high accuracy. Capacitive strain measurement is particularly suitable for small deformations or for materials where the application of strain gauges is difficult.
The choice of the best alternative to strain gauges depends on various factors, such as the type of material, the complexity of the geometry, the environmental conditions and the desired accuracy. It is important to consider the specific requirements of the application in order to select the most suitable alternative.
1. Optical strain measurement: Optical methods such as digital image correlation (DIC) are used to measure deformations. This method enables non-contact measurement and offers greater accuracy than strain gauges. Optical strain measurement is particularly suitable for complex geometries or materials where the application of strain gauges is difficult.
2. Ultrasonic measurement: Ultrasound is used to measure deformations by measuring the travel time of sound waves through the material. This method is non-contact and is well suited for dynamic measurements. Ultrasonic measurement can be used at high temperatures or in environments with vibrations where strain gages cannot be used.
3. Magnetic strain measurement: Magnetic sensors are used to measure deformations. This method is well suited for materials with magnetic attributes and enables non-contact measurement. Magnetic strain measurement can also be used at high temperatures or in environments with vibrations.
4. Capacitive strain measurement: This method uses capacitive sensors to measure deformations. This method enables non-contact measurement and offers high accuracy. Capacitive strain measurement is particularly suitable for small deformations or for materials where the application of strain gauges is difficult.
The choice of the best alternative to strain gauges depends on various factors, such as the type of material, the complexity of the geometry, the environmental conditions and the desired accuracy. It is important to consider the specific requirements of the application in order to select the most suitable alternative.