What is Strain Gauge
A Strain gauge is a sensor whose resistance varies with applied force; It converts force, pressure, tension, weight, etc., into a change in electrical resistance which can then be measured. When external forces are applied to a stationary object, stress and strain are the result. Stress is defined as the object's internal resisting forces, and strain is defined as the displacement and deformation that occur.The strain gauge is one of the most important sensor of the electrical measurement technique applied to the measurement of mechanical quantities. Thus, strain gauges can be used to pick up expansion as well as contraction.
Advantages of Strain Gauge
High Sensitivity: Strain gauges have excellent sensitivity, allowing for accurate measurement of even minute deformations. This feature is crucial in civil engineering, as it helps detect structural movements or stress concentrations that may affect the integrity of a building or infrastructure.
Versatility: Strain gauges can be used on various materials such as concrete, steel, or composites, making them versatile for different civil engineering applications. They can be attached to surfaces or embedded within structures, enabling engineers to monitor strain at specific locations of interest.
Cost-Effective: Strain gauges offer a cost-effective solution for strain measurement compared to other techniques such as extensometers. They are relatively inexpensive and reusable, allowing for multiple measurements at different locations within a structure.
Real-Time Monitoring: Strain gauges provide real-time data, allowing engineers to monitor structural behavior continuously. This feature is particularly useful during load testing, construction, or seismic events, as it enables prompt identification of any excessive strains or deformations.
Why Choose Us
Our Factory
Xian Baochen Information Technology Co., Ltd. is located in high-tech Zone, Xi 'an, Shaanxi Province, China, is a focus on sensors, transmitters, inverters, power semiconductor devices and supporting instruments R & D, manufacturing, sales and service enterprises.
Wide Range of Applications
Through the EU CE, RoHs testing, products are widely used in petrochemical, water conservancy and hydrology, machinery and equipment, automobile manufacturing, industrial process control, weighing measurement, people's livelihood applications and other fields.
Strict Quality Control System
Able to efficiently produce large quantities of products, advanced production processes and stable supply chains, the implementation of strict quality control system. Constantly introduce new technologies and new materials to improve product performance and production efficiency.
Our Service
Able to quickly respond to customer needs, to provide personalized customization, timely delivery, professional technical support and perfect after-sales service.
Applications of Strain Gauges
Load cells and transducers
Load cells are used in many industries and applications to measure force and weight with precision and reliability. They are a critical part of weighing systems, such as industrial scales and balances, food processing, and logistics.
In construction, load cells monitor the weight and stability of structures, safety, and compliance with reliability. In research and development, load cells are used in experiments that require precise force measurements, such as material testing and biomechanics. Strain gauges in load cells make them a must-have tool in these fields.
Structural monitoring
Strain gauges are used in civil engineering to monitor the health of structures like bridges, buildings, and dams. By measuring the strain and stress in these structures, engineers can detect failures early and take preventive measures. This ensures the life and safety of critical infrastructure.
Aerospace
In aerospace, strain gauges test and monitor aircraft components under various stress conditions. This ensures parts can withstand operational stress, and improve safety and performance. Used in testing wings, fuselage, and other critical components during development and maintenance.
Automotive
In automotive, strain gauges measure stress and strain on various vehicle components, from chassis to suspension systems. This helps design safer and more efficient vehicles. Used in crash testing, durability testing, and real-time monitoring of vehicle dynamics.
Industrial machinery
Industrial machinery uses strain gauges for condition monitoring. They measure strain in critical components so maintenance can be scheduled proactively, reduce downtime, and prevent failures. This improves operational efficiency and reduces the risk of unexpected breakdowns.
Medical devices
In medical devices, strain gauges are used in prosthetics and other adaptive equipment to measure and adjust in real-time, to better patient outcomes. Prosthetics work correctly and provide the right support and flexibility.
A strain gauge is a sensor whose measured electrical resistance varies with changes in strain. Strain is the deformation or displacement of material that results from an applied stress. Stress is the force applied to a material, divided by the material's cross-sectional area. are designed to focus stress through beam elements where strain gauges are located. Strain gauges convert the applied force, pressure, torque, ect., into an electrical signal which can be measured. Force causes strain, which is then measured with the strain gauge by way of a change in electrical resistance. Then the voltage measurement is gathered using .
Now that the process of strain measurements has been established, the next step when using strain gauges is getting useful data.The strain gauge must be connected to an electrical circuit that is capable of accurately responding to the minute changes in resistance associated with strain. Multiple strain gauges can be used in a divided bridge circuit to measure small changes in electrical resistance. This is called a Wheatstone bridge. In a Wheatstone bridge configuration, an excitation voltage is applied across the circuit, and the output voltage is measured across two points in the middle of the bridge. When there is no load acting on the load cell, the Wheatstone bridge is balanced and there is zero output voltage. Any small change in the material under the strain gauge results in a change in the resistance of the strain gauge as it deforms with the material. This causes the bridge to be thrown out of balance, resulting in a change in the output voltage. The resistance change is minute, which means that signal amplification is often needed to properly determine changes. The amplification process strengthens the strain signal changes; however, it also leads to more unwanted noise also being detected in the signal. Signal conditioning filters out the excess noise, ensuring accurate and understandable data.
Different Types of Strain Gauge Geometries
Linear Strain Gauge
A linear strain gauge is used to record strain in the direction in which its measuring grid is aligned. It is typically mounted in the direction of the main force, for which the direction of the force must be known. This geometry of strain gauge is preferred when measurements are to be performed in one direction only. For instance, in applications such as aircraft component testing, medical device and equipment manufacturing, linear strain gauges can be positioned to measure bending, axial and torsion strain. The linear strain gauge pattern can also be used in S-Beam, binocular, reverse bending and dual beam load cell and pressure transducer designs.
A double-linear strain gauge is an enhanced version of a linear strain gauge with two linear measuring grids arranged parallel to each other. This type of configuration is mainly designed for applications where double-sided strain measurements are required, for instance, to record the bending load of a bending beam. During such measurements, four active strain gauges are used in the Wheatstone bridge circuit.
Shear Strain Gauge
A shear strain gauge consists of two measuring grids arranged at an angle of 45° to the strain gauge axis and 90° to each other. It is mainly used to measure torque in a rotating object that includes measurements on torsion bars and determining shear stresses as they occur in shear beams in the area of neutral fibres. They are used in the construction of torque transducers or shear force transducers.
Rosette Strain Gauge
Rosettes with 2 and 3 measuring grids are widely used in various applications. A T-rosette strain gauge has two measuring grids arranged on a carrier perpendicular to each other, whereas the 3-grid geometry has 3 measuring grids spaced at different angles. These multiple strain gauge configurations are suitable for applications where biaxial stress state is to be determined with unknown principle directions based on magnitude and direction. Using a rosette strain gauge allows for different directional strain measurements which provides a more accurate evaluation of the surface strain to be measured. It is mainly preferred for strain measurement in tensile or compression bars.
Chain Strain Gauge
A strain gauge chain consists of a series of 10-15 very small evenly spaced grids sharing the same carrier. This type of configuration is ideal for measuring strain gradient i.e., the stress curve over a specific section or the shift in the peak value due to the impact of load being introduced at a moving point. The design of chain strain gauges includes measuring grid in parallel or perpendicular direction to the longitudinal chain axis.
Full-bridge Strain Gauge
A full-bridge strain gauge is composed of four measurement grids that are switched to a Wheatstone full bridge. Each measuring grid is offset to the next grid at an angle of 90°. Its common applications include measurements on torsion bars, tension or compression bars and shear stresses occurring in shear beams around the neutral fibre. The full-bridge strain gauges are also designed to manufacture precision force transducers which employ bending beam working principle.
Factors to Consider While Selecting a Strain Gauge
Strain Gauge Construction
There are a variety of strain gauge geometries available in terms of grid positioning, shape, number, and orientation. These design configurations are meant for measuring strain developed due to stress exerted in different directions. These designs include linear, double linear, T-rosette, shear, full-bridge, and many other variants of strain gauges applicable for a full range of gauge installation and strain measurement requirements.
A linear strain gauge is typically mounted in the direction of the main force, whereas the double-linear configuration is made of two linear strain gauges and is designed for double-sided mounting on a bending beam. A rosette configuration consists of two or more strain gauges aligned together at certain angles to measure strain developed from an unknown principle direction. It is preferred for strain measurement in tensile or compression bars. A shear strain gauge is used to measure torque in a rotating object or a shear beam and is designed with two grids at an angle of 45 degrees from the torsion shaft. Other configurations of strain gauges are designed based on further advanced geometries and configurations of rosette, linear and shear strain gauges to serve complex applications. Therefore, depending on the direction of strain and the structure of the measuring object, a strain gauge design should be selected.
Gauge Length
The gauge length of a strain gauge has a huge impact on strain measurement. It is the measure of the actual grid length in the sensitive direction. Strain gauges with small gauge lengths are generally employed for measuring stress peaks. Selecting a gauge with a shorter gauge length will be suitable for surfaces with small mounting space, where accuracy is not a critical aspect. It is ideal for measuring strains on a fillet, hole, or notch with a small diameter. On the other hand, a strain gauge with larger gauge lengths can be employed for strain measurement on inhomogeneous materials such as concrete. Generally, in these inhomogeneous structures, the measure of average strain within the measuring grid range is sought. With larger gauge lengths, it is possible to span several pieces of aggregate in order to measure the representative strain in the structure.
Electrical Resistance of Strain Gauge
The gauge resistance of a strain gauge is the measure of the electrical resistance of the gauge at room temperature under no external stress. The generally available gauge resistances are 60 Ω, 120 Ω, 350 Ω, and 1000 Ω. The strain gauges with electrical resistances 60 Ω, 120 Ω can be considered as low resistance strain gauges, the 350 Ω and 1000 Ω variants can be categorised as high resistance strain gauges.
The choice of resistance of a strain gauge is dependent on the overall size of the gauge grid, cost, and certain performance parameters. A higher resistance gauge is preferred when the requirement is to reduce the heat generation rate. This is due to the fact that the reduction in the current flow associated with the higher resistance reduces gauge self-heating. However, a strain gauge with low resistance is more likely to develop self-heating at a given excitation voltage for the Wheatstone bridge circuit as compared to the high resistance strain gauge. It also requires a higher power to operate, which is why it is advised to go for high resistance, preferably 350 Ω or 1000 Ω, if the Wheatstone bridge is battery operated. On the other hand, a low resistance strain gauge offers advantages including a lower influence of a change in the isolation resistance and a lower influence of electromagnetic interferences.
Temperature Compensation
Temperature changes can have huge impacts on the strain measurement of an object. This is mainly due to the fact that the material used for constructing the object expands as the temperature increases. For this reason, self-compensated strain gauges are employed for operations with inconsistent temperatures. These strain gauges are developed to compensate for the temperature behaviour of certain materials such as plastic, steel, aluminium or titanium by their own temperature behaviour. Therefore, it is important to select a strain gauge having a similar temperature response as the material.
Calibration: Accurate calibration is crucial to establish a calibration curve. This involves comparing the output of the strain gauge with known reference loads or strains. Regular recalibration is necessary to maintain accuracy over time.
Installation: Proper installation of strain gauges is essential for accurate measurements. Bonding or attaching the strain gauges to the structure at specified locations should be done carefully, following manufacturer guidelines. Controlling thermal effects and minimizing external influences is critical for precise readings.
Environmental Conditions
Accuracy can be influenced by environmental factors such as temperature, humidity, and vibrations. It is important to account for these conditions during data analysis and planning during the design of any system.
Strain Gauge Quality
The quality of strain gauges used affects accuracy. High-quality strain gauges manufactured with precision and tight tolerances provide more reliable and accurate measurements.
Data Acquisition and Analysis
The accuracy of measurements depends on the quality of the data acquisition system and the analysis techniques employed. Properly calibrated equipment, signal conditioning, and appropriate filtering contribute to accurate results.
FAQ
As one of the leading strain gauge manufacturers and suppliers in China, we warmly welcome you to wholesale cheap strain gauge in stock here from our factory. All customized products are with high quality and competitive price.
Full Bridge Strain Gauge, strain gauge