The document discusses different types of sensors based on their output and principles of operation. There are discrete (digital) sensors that provide a single logical output and proportional (analog) sensors that provide an output such as voltage or current. Optical, inductive, reed, magnetic, and capacitive sensors are described in terms of their operating principles, outputs, advantages, and limitations. Symbols are provided for common sensor types.

1. SENSORS

2. 2 Classification of Sensor based on Output Discrete (sometimes called digital , logic , or bang-bang ) - sensors provide a single logical output (a zero or one) Proportional (sometimes called analog ) - provide an analog output. The output may be a voltage, current, resistance, or even a digital word containing a discrete value.

3. For discrete sensors, there are two types of outputs the NPN or sinking output, the PNP or sourcing output

4. + 18 to 30 Volts DC. 0 V Output 24v DC 0v PNP Type Output is Positive Positive switching

5. + 18 to 30 Volts DC. 0 V Output 24v DC 0v NPN Type Output switches through to 0v Negative switching

6. Proximity Sensors Optical Inductive Reed Switch Inductive Magnetic Capacitive Symbols Connection

7. Optical Sensors Type : Through-beam

8. Electronic Sensors : Capacitive Proximity Sensor G 1. Oscillator 2. Demodulator 3. Triggering Stage 4. Switching status LED indicator 5. Output Stage with protective Circuit 6. External Voltage 7. Internal Stabilized Voltage 8. Active Switching Zone (Condenser) 9. Switching Output 1 2 3 4 5 9 7 6 8

9. Target Optical Sensors Type : Through-beam Transmitter Receiver

10. Optical Sensors Type : Through-beam Transmitter Receiver

11. Optical Sensors Type : Retro reflective

12. Optical Sensors Type : Retro reflective Reflector (prismatic) Transmitter / Receiver T R

13. Transmitter / Receiver Reflector (prismatic) T R Optical Sensors Type : Retro reflective

14. Transmitter / Receiver Reflector (prismatic) T R Optical Sensors Type : Retro reflective

15. Optical Sensors Type : Diffuse

16. Optical Sensors Type : Diffuse Target Transmitter / Receiver T R

17. Transmitter / Receiver Optical Sensors Type : Diffuse T R

18. Transmitter / Receiver Optical Sensors Type : Diffuse Sensing distance : much less than reflex type, actual distance depends on colour and reflective nature of the surface Larger targets result in longer sensing distances Not suitable for dirty environments T R

19. Inductive Sensor

20. Electronic Sensors : Inductive Proximity Sensor G 1. Oscillator 2. Demodulator 3. Triggering Stage 4. Switching status LED indicator 5. Output Stage with protective Circuit 6. External Voltage 7. Internal Stabilized Voltage 8. Active Switching Zone (Coil) 9. Switching Output 1 2 3 4 5 9 7 6 8

21. Connection cable LED indicator Resonant circuit coil Active surface High Frequency magnetic field (300 to 800 kHz) Inductive Sensor

22. Sensor Oscillation Amplitude Sensor output signal ON OFF Target Inductive Sensor

23. Oscillation Amplitude Sensor output signal ON OFF Sensor Target Inductive Sensor

24. Oscillation Amplitude Sensor output signal ON OFF Sensor Will detect any conductive material Quoted distances are for mild steel Sensor performance can be affected by:- Temperature, Target material, and Target dimensions. Target Inductive Sensor

25. Reed Switch

26. Glass Tube filled with nitrogen Reed contacts LED indicator

27. Reed Switch 24v

28. Interference from other magnetic fields must be avoided. If positioned in mid stroke, switching point will vary depending on direction of appoach. Maximum current must be limited to avoid burning of the reed contacts. Reed Switch

29. Inductive Magnetic Sensor

30. Connection cable LED Indicator Resonant circuit coil High Frequency magnetic field Inductive Magnetic Sensor

31. Inductive Magnetic Sensor

32. Inductive principle of operation - but only reacts to magnetic fields Interference from other magnetic fields must be avoided. Solid state device - higher switching frequency - 1kHz Inductive Magnetic Sensor

33. Capacitive Sensor

34. Electronic Sensors : Capacitive Proximity Sensor G 1. Oscillator 2. Demodulator 3. Triggering Stage 4. Switching status LED indicator 5. Output Stage with protective Circuit 6. External Voltage 7. Internal Stabilized Voltage 8. Active Switching Zone (Condenser) 9. Switching Output 1 2 3 4 5 9 7 6 8

35. Connection cable Adjusting screw LED indicator Active surface Active electrode Earth electrode Electrostatic field Sensor is looking for a change in capacitance in the active field Capacitive Sensor

36. Capacitive Sensor

37. Capacitive Sensor Detects any material denser than air. (as long as there is enough of it) Can be adjusted for sensitivity Can be affected by dusty environments

38. Capacitive Sensor As the level rises the fluid affects the sensor field.

39. Sensor Symbols

40. + 18 to 30 Volts DC. 0 V Output Inductive Capacitive Optical Magnetic Ultrasonic Normally open Normally closed

42. Oscillation Amplitude Sensor output signal ON OFF Sensor Will detect any conductive material Quoted distances are for mild steel Sensor performance can be affected by:- Temperature, Target material, and Target dimensions. Target Inductive Sensor

43. Capacitive Sensor Detects any material denser than air. (as long as there is enough of it) Can be adjusted for sensitivity Can be affected by dusty environments

44. Target Optical Sensors Type : Through-beam Long sensing distance : up to 30 metres with some devices Will detect all but very transparent materials Must be accurately aligned Transmitter Receiver

45. Transmitter / Receiver Optical Sensors Type : Reflex Reflector (prismatic) Sensing distance : 1 / 2 to 1 / 3 of through-beam type. Not suitable for reflective or transparent targets Target should be larger than the reflector T R

46. Transmitter / Receiver Optical Sensors Type : Diffuse Sensing distance : much less than reflex type, actual distance depends on colour and reflective nature of the surface Larger targets result in longer sensing distances Not suitable for dirty environments T R

47. Interference from other magnetic fields must be avoided. If positioned in mid stroke, switching point will vary depending on direction of appoach. Maximum current must be limited to avoid burning of the reed contacts. Reed Switch

48. Inductive principle of operation - but only reacts to magnetic fields Interference from other magnetic fields must be avoided. Solid state device - higher switching frequency - 1kHz Inductive Magnetic Sensor