Accuracy: The agreement between the actual value and the measured value • Resolution: The change in measured variable to which the sensor will respond • Repeatability: Variation of sensor measurements when the same quantity is measured several times • Range: Upper and lower limits of the variable that can be measured • Sensitivity and Linearity Proximity Sensors • Widely used in general industrial automation – Conveyor lines (counting,jam detection, etc) – Machine tools (safety interlock, sequencing) • Usually digital (on/off) sensors detecting the presence or absence. | Industrial Sensors Proximity - Mechanical - Optical - Inductive Capacitive Position Velocity - Potentiometer Hugh Durrant-Whyte - LVDT - Encoders - Tachogenerator Force Pressure Vibration acceleration 1540 Introduction To Mechatronics Slide 2 Definitions Accuracy The agreement between the actual value and the measured value Resolution The change in measured variable to which the sensor will respond Repeatability Variation of sensor measurements when the same quantity is measured several times Range Upper and lower limits of the variable that can be measured Sensitivity and Linearity Hugh Durrant-Whyte 1540 Introduction To Mechatronics Slide 3 Proximity Sensors Widely used in general industrial automation - Conveyor lines countingjam detection etc - Machine tools safety interlock sequencing Usually digital on off sensors detecting the presence or absence of an object Consist of - Sensor head optical inductive capacitive - Detector circuit - Amplifier - Output circuit TTL solid state relay Hugh Durrant-Whyte 1540 Introduction To Mechatronics Slide 4 Mechanical Proximity Switches Example Mechanical Proximity Switches Essentially a mechanical switch On off operation only Two general modes - Normally Open NO - Normally Closed NC Come in a wide variety of mechanical forms For a wide range of uses Normally Closed Common Normally Open Hugh Durrant-Whyte 1540 Introduction To Mechatronics Slide 5 Hugh Durrant-Whyte 10 Introduction To Mechatronics Slide 6 1 When to Use Mechanical Proximity Switches Applications and Use of Mechanical Proximity Switches Where physical contact is possible Where definitive position is required In operation-critical or safety-critical situations Where environment conditions preclude the use of optical or inductive sensors Easy to integrate into machinery of all types Requires contact thus wear Range of voltages DC 0-1000V AC etc. Very robust explosion proof if required Usually used as - Limit switch - Presence absence indicator - Door closed open
