Sensors (Potentiometer and Strain Gauge)
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This document discusses sensors and actuators, providing classifications of common sensors. It focuses on displacement, position, and proximity sensors, describing four main types: potentiometer sensors, strain gauge sensors, capacitive sensors, and linear variable differential transformers (LVDTs). For each sensor type, it provides the underlying measurement principle, relevant mathematical expressions, and examples of applications. The document is intended as a reference for mechatronics and manufacturing automation.
Sensors (Potentiometer and Strain Gauge)
- 2. SENSOR VS ACTUATOR SensorNon Electrical IN (Quantity) Electrical OUT (Signal) ActuatorElectrical IN (Signal) Non Electrical OUT (Quantity) Source : P.P.L. Regtien (Auth.) - Sensors for Mechatronics(2012)
- 3. SENSORS CLASSIFICATION 1.Displacement, Position & Proximity 2.Velocity and Motion 3. Force 4.Fluid Pressure 5.Liquid Flow 6.Liquid Level 7.Temperature
- 4. Measures the length of the straight line between two defined points. Measures the change of position relative to a reference point. Measures the co-ordinates of a specified point of an object in a specified reference system. • Determines the sign (positive or negative) of the linear distance between an object point and a fixed reference point; also called a switch. • A contact-free displacement or distance sensor for short distances (down to zero) DISTANCE SENSOR DISPLACEMENT SENSOR POSITION SENSOR PROXIMITY SENSOR Source : P.P.L. Regtien (Auth.) - Sensors for Mechatronics(2012)
- 5. DISPLACEMENT SENSORS 1. Potentiometer Sensor 2. Strain Gauge Element 3. Capacitive element based Sensor 4. Linear Variable Differential Transformer (LVDT)
- 6. POSITION & PROXIMITY SENSORS 1. Eddy current proximity sensor 2. Inductive proximity switch 3. Optical Encoder 4. Pneumatic Sensor 5. Proximity Switch 6. Hall effect sensor
- 7. 1. POTENTIOMETER SENSOR Principle : Conversion of mechanical displacement into an electrical signal.
- 8. 1. POTENTIOMETER SENSOR Mathematical Expression : 𝑉𝑂 = 𝐼𝑅 𝐴 But 𝐼 = 𝑉𝑠 𝑅 𝐴+𝑅 𝐵 , Therefore 𝑉0 = 𝑉𝑠 𝑅 𝐴 𝑅 𝐴+𝑅 𝐵 As we know that 𝑅 = 𝜌𝐿 𝐴 , where ρ is electrical resistivity, L is length of resistor and A is area of cross section 𝑉𝑂 = 𝑉𝑠 𝐿 𝐴 𝐿 𝐴 + 𝐿 𝐵
- 9. 1. POTENTIOMETER SENSOR Applications: • Control systems with a feedback loop • Machine-tool controls, Elevators, Liquid-level assemblies, Forklift trucks, Automobile throttle controls • Control of injection moulding machines, Woodworking machinery, Printing, Spraying, Robotics. Source : NPTEL (Mechanical – Mechatronics and Manufacturing Automation)
- 10. 2. STRAIN GAUGE ELEMENT The strain in an element is a ratio of change in length in the direction of applied load to the original length of an element. i.e. The strain changes the resistance R of the element.
- 11. 2. STRAIN GAUGE ELEMENT Mathematical Expression : Δ𝑅 𝑅 𝛼 𝜀 ⇒ Δ𝑅 𝑅 = 𝐺 𝜀 where G is the constant of proportionality and is called as gauge factor. This change in resistance can be detected by a using a Wheatstone’s resistance bridge. In the balanced bridge we can have a relation, 𝑅2 𝑅1 = 𝑅 𝑥 𝑅3 where 𝑅 𝑥 is resistance of strain gauge element, 𝑅2 is balancing/adjustable resistor, 𝑅1 and 𝑅3 are known constant value resistors.
- 12. 2. STRAIN GAUGE ELEMENT Applications: • Experimental stress analysis and diagnosis on machines and failure analysis. • Multi-axial stress fatigue testing, residual stress and vibration measurement, torque measurement, bending and deflection measurement, compression and tension measurement and strain measurement. • As sensors for machine tools and safety in automotive. Source : NPTEL (Mechanical – Mechatronics and Manufacturing Automation)
- 13. REFERENCES 1. NPTEL – Mechanical – Mechatronics and Manufacturing Automation 2. P.P.L. Regtien (Auth.) - Sensors for Mechatronics(2012) 3. W. Bolton (Auth.) - Mechatronics Electronic control systems in mechanical and electric engineering