A strain gauge pressure sensor measures pressure by transforming applied mechanical force into an electrical signal. It works based on the principle that applying pressure to a material makes it to change shape. This leads to change in its electrical resistance. This change in resistance is to measured and correlated to the applied pressure.
Strain gauge pressure sensors come in various types. They find extensive use in industries like automotive, aerospace, manufacturing, medical, and research.
WORKING PRINCIPLE:
A strain gauge pressure sensor operates based on strain, resistance, and Wheatstone bridge circuit principles. The breakdown of its working mechanism is as follows:
Sensing Element:
The core component of a strain gauge pressure sensor is the sensing element.
It’s materials like metal foil, semiconductor-based strain gauges, or bonded metallic wire gauges. This sensing element is engineered to undergo deformation (strain) when subjected to pressure.
Strain and Resistance:
Hooke’s Law: Hooke’s Law states that applying external force, such as pressure, to a material results in its deformation or strain.
Change in Electrical Resistance: The strain experienced by the sensing element alters its electrical resistance. This change is directly proportional to the amount of strain applied. This follows the stress-strain relationship.
Wheatstone bridge Configuration:
Multiple strain gauges in a Wheatstone bridge circuit. The circuit consists of four resistive arms, typically forming a diamond-shaped configuration.
The strain gauges are strategically placed in the arms of the bridge circuit.
The bridge is balanced when no external force is applied, resulting in a zero output voltage.
Application of Pressure:
The sensing element undergoes deformation when pressure is exerted upon it. This causes a change in the resistance of the strain gauge.
This change in resistance disturbs the balance of the Wheatstone bridge circuit. Thus, it leads to an imbalance in the voltage across the bridge.
Output Signal:
An imbalance in the Wheatstone bridge circuit leads to an output voltage. The voltage correlates directly with the applied pressure.
This voltage output can be measured and calibrated to determine the precise pressure exerted on the sensing element.
Advantages of this Working Principle:
Accuracy: It offers precise pressure readings when calibrated appropriately.
Sensitivity: Detects small changes in pressure due to its high sensitivity to strain.
Versatility: Suitable for various pressure measurement applications across industries.
TYPES OF STRAIN GAUGE PRESSURE SENSOR AND ITS APPLICATIONS:
Linear Strain Gauge:
Linear strain gauges are designed with a single strain-sensitive element. This element is placed along the anticipated direction of strain within a material. They are commonly used to measure strain along a single axis or in a uniaxial manner.
Application: In structural engineering, these gauges are used to measure strain in beams or columns under load. They aid in assessing the material’s stress and deformation characteristics along a specific direction.
Rosette Strain Gauge:
Rosette strain gauges consist of multiple strain gauges arranged at specific angles to each other. Typically, these angles are at 0°, 45°, and 90° orientations. This arrangement allows for strain measurement in multiple directions. It provides comprehensive data on strain behavior in various axes.
Application: Strain gauges are extensively used in stress analysis and material testing. They provide detailed information about the principal stresses and strains within a material or structure. These gauges assist in identifying strain in both primary and secondary directions.
Diaphragm Strain Gauge:
Diaphragm strain gauges are placed on flexible diaphragms that gets deform under pressure. When the diaphragm experiences a change in pressure, it causes strain in the attached strain gauge. This results in changing its resistance. These gauges are commonly employed in pressure sensors and transducers.
Application: These are found in pressure measurement devices like pressure transducers. This transducers are used in automotive applications, industrial processes, and various pressure-sensitive systems. They accurately measure pressure-induced strain on the diaphragm to determine the applied pressure.
Shear Strain Gauge:
Shear strain gauges are specifically designed to measure shear strain. This strain occurs when two forces act parallel to each other but in opposite directions. These gauges are placed perpendicular to the direction of shear stress to accurately measure shear strain.
Application: They are used in applications where measuring shear strain is critical. For example, they are used in examining structural stability, testing materials, and assessing material response to shear stress.
Double Parallel Strain Gauge:
Double parallel strain gauges consist of two strain gauges positioned parallel to each other. This arrangement helps compensate for temperature changes and environmental effects. Thus, it provides more accurate measurements by minimizing errors caused by external factors.
Application: They are great for precise strain measurements, minimizing temperature impacts and outside interferences. They are commonly used in high-precision instrumentation and structural monitoring.
CONCLUSION:
Strain gauge pressure sensors represent a pivotal technological advancement. They bridge the gap between mechanical force and electrical signals for precise pressure measurements.
Their significance lies in their remarkable precision, offering high accuracy when appropriately calibrated. They show adaptability in various fields like automotive, aerospace, medical devices, and research labs.
Looking forward, the future of strain gauge pressure sensors appears promising. Ongoing sensor tech advancements promise more precise, durable, and affordable sensors. These innovations will strengthen their role in vital operations. They will ensure structural integrity and improve complex industrial processes.
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