The document discusses different types of proximity sensors including optical, inductive, reed switch, inductive magnetic, and capacitive sensors. It provides diagrams and descriptions of how each sensor type works, including notes on their sensing ranges, target materials detected, and factors that influence performance. The end of the document covers standard symbols used for sensors and connections to control systems.

1. Proximity sensors
Optical – Through-beam
Optical – Retro-reflective
Optical - Diffuse
Inductive
Reed switch
Inductive magnetic
Capacitive
Symbols
Connection
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 1 / 91

2. Optical sensors (Through-beam)
Type : Through-beam
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 2 / 91

3. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 3 / 91

4. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 4 / 91

5. Optical sensors (Through-beam)
Type : Through-beam
Targe
t
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 5 / 91

6. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 6 / 91

7. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 8 / 91

8. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 9 / 91

9. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 10 / 91

10. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 11 / 91

11. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 12 / 91

12. Optical sensors (Through-beam)
Type : Through-beam
Transmitter Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 13 / 91

13. Optical sensors (Through-beam)
Targe
t
Type : Through-beam
Transmitter Receiver
Long sensing distance: up to 30 metres with some devices
Will detect all but very transparent materials
Must be accurately aligned
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 14 / 91

14. Optical sensors (Retro-reflective)
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 15 / 91

15. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
R
Transmitter
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 16 / 91

16. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 17 / 91

17. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 18 / 91

18. Reflector
(prismatic)
Target
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 19 / 91

19. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 20 / 91

20. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 21 / 91

21. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 22 / 91

22. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 23 / 91

23. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 24 / 91

24. Reflector
(prismatic)
Optical sensors (Retro-reflective)
Type : Retro reflective
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 25 / 91

25. Reflector
Optical sensors (Retro-reflective)
T
R
Type : Retro reflective
Transmitter
/Receiver
Sensing distance : 1/2 to 1/3 of through-beam type (prismatic)
Not suitable for reflective or transparent targets
Target should be larger than the reflector
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 26 / 91

26. Optical sensors (Diffuse)
Type : Diffuse
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 27 / 91

27. Target
Optical sensors (Diffuse)
Type : Diffuse
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 28 / 91

28. Optical sensors (Diffuse)
Type : Diffuse
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 29 / 91

29. Optical sensors (Diffuse)
Type : Diffuse
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 30 / 91

30. Optical sensors (Diffuse)
Type : Diffuse
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 31 / 91

31. Optical sensors (Diffuse)
Type : Diffuse
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 32 / 91

32. Optical sensors (Diffuse)
Type : Diffuse
T
Transmitter R
/Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 33 / 91

33. Optical sensors (Diffuse)
Type : Diffuse
Transmitter
/Receiver
T
R
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
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 34 / 91

34. Inductive sensors
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 35 / 91

35. Inductive sensors
High frequency magnetic
field
(300 to 800 kHz)
Active surface
Resonant circuit coil
LED indicator
Connection cable
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 36 / 91

36. Inductive sensors
Sensor
Oscillation
Amplitude
Sensor
output
signal
ON
OFF
Targ
et
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 37 / 91

37. Inductive sensors
ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 38 / 91

38. Inductive sensors
ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 39 / 91

39. Inductive sensors
ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 40 / 91

40. Inductive sensors
ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 41 / 91

41. Inductive sensors
ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 42 / 91

42. Inductive sensors
ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 43 / 91

43. Inductive sensors
ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 44 / 91

44. Inductive sensors
ON
OFF
Target
Sensor
Oscillation
Amplitude
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 45 / 91

45. Inductive sensors
Will detect any conductive material
Quoted distances are for mild steel
Sensor performance can be affected by:
• Temperature
• Target material
• Target dimensions
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 46 / 91

46. Reed switch
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 47 / 91

47. Reed switch
Glass Tube filled
with nitrogen
Reed
contacts
LED
indicator
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 48 / 91

48. Reed switch
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 49 / 91

49. Reed switch
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 50 / 91

50. Reed switch
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 51 / 91

51. Reed switch
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 52 / 91

52. Reed switch
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 53 / 91

53. Reed switch
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 54 / 91

54. Reed switch
24v
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 55 / 91

55. Reed switch
24v
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 56 / 91

56. Reed switch
Interference from other magnetic fields must be avoided.
If positioned in mid stroke, switching point will vary depending on direction of approach.
Maximum current must be limited to avoid burning of the reed contacts.
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 57 / 91

57. Inductive magnetic sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 58 / 91

58. Inductive magnetic sensor
Connection
cable
LED
Indicator
Resonant circuit
coil
High
frequency
magnetic
field
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 59 / 91

59. Inductive magnetic sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 60 / 91

60. Inductive magnetic sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 61 / 91

61. Inductive magnetic sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 62 / 91

62. Inductive magnetic sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 63 / 91

63. Inductive magnetic sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 64 / 91

64. Inductive magnetic sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 65 / 91

65. Inductive magnetic sensor
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
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 66 / 91

66. Capacitive sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 67 / 91

67. Capacitive sensor
Sensor is looking for a
Electrostatic field change in capacitance in the
active field
Active surface
Active electrode
Earth electrode
LED indicator
Adjusting screw
Connection cable
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 68 / 91

68. Target Capacitive sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 69 / 91

69. Capacitive sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 70 / 91

70. Capacitive sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 71 / 91

71. Capacitive sensor
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 72 / 91

72. 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
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 73 / 91

73. Capacitive sensor
Sensor is adjusted so that
it does not ‘see’ the wall of
the vessel.
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 74 / 91

74. Capacitive sensor
As the level rises the fluid
affects the sensor field.
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 75 / 91

75. Capacitive sensor
Until the sensor switches.
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 76 / 91

76. Sensor symbols
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 77 / 91

77. + 18 to 30 Volts
DC.
0 V
Output
Inductive
Capacitive
Optical
Magnetic
Ultrasonic
Normally
open
Normally
closed
Sensor symbols
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 78 / 91

78. + 18 to 30 Volts
DC.
0 V
Sensor symbols
Capacitive Sensor with
Normally open function
Output
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 79 / 91

79. Sensor connection
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 80 / 91

80. + 18 to 30 Volts DC
0 V
Output
Sensor connection
24v
DC
0v
PNP Type
• Output is Positive
• Positive switching
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 81 / 91

81. Sensor connection
NPN Type
• Output switches
through to 0v
• Negative switching
+ 18 to 30 Volts DC
0 V
Output
24v
DC
0v
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 82 / 91

82. Sensor connection
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 83 / 91

83. + 18 to 30 Volts
DC.
0 V
Output
Inductive
Capacitive
Optical
Magnetic
Ultrasonic
Normally
open
Normally
closed
Sensor connection
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 84 / 91

84. Inductive sensor
Will detect any conductive material
Quoted distances are for mild steel
Sensor performance can be affected by:-
• Temperature
• Target material
• Target dimensions.
Oscillation
Amplitude
ON
OF
F
Targe
t
Sensor
Sensor
output
signal
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 85 / 91

85. 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
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 86 / 91

86. 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
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 87 / 91

87. Optical sensors
Type: Retro-reflective
Sensing distance : 1/2 to 1/3 of through-beam
Not suitable for reflective or transparent
targets
Target should be larger
than the reflector
T
R
Transmitter / Receiver Reflector
(prismatic)
type.
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 88 / 91

88. 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
Transmitter /
Receiver
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 89 / 91

89. Reed switch
Interference from other
magnetic fields must be
avoided.
If positioned in mid stroke,
switching point will vary
depending on direction of
approach.
Maximum current must be
limited to avoid burning of the
reed contacts.
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 90 / 91

90. Inductive magnetic sensor
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
17.10.03 © Festo Didactic – Training and Consulting Sensors No. 91 / 91