Operating principle of a photoelectric sensor

Distance sensor with back- Time-of-flight (ToF) principle:

ground suppression The time of flight to the object is measured. This is proportional to the range. The
range is largely independent of the energy of the reflected light. Reflections on
the object do not lead to a falsification of the measured value.
2 Function The majority of sensors in this class provide “absolute measurements” (measur-
ing distance is output via IO-Link, for example).
Operating principle of a photoelectric sensor It is recommended that the light beam is terminated within the range of the effec-
tive background suppression and does not radiate “infinitely” far.
Through-beam sensor The transmitter (1) and the receiver (2)
1 2
are in separate housings.
The objects are detected by interrup-
tion of the light beam. 3 Technical data
Response time < 1/f (typically 1/2 f) unless indicated otherwise (f = switching frequency)
Distance sensors:
In situations with a brightness ratio (object to background) of 1:1, the response
time is approx. 2 / measuring frequency.
Output function Light-on mode: The receiver "sees" light and the output is switched.
Retro-reflective sensor The transmitter and receiver are inte- Through-beam and reflective = NC
grated in one housing (3). The light 3 4
Diffuse = NO
beam is reflected by a reflector (4).
Dark-on mode: The receiver "sees" dark and the output is switched.
The objects are detected by interrup-
Through-beam and reflective = NO
tion of the light beam.
Diffuse = NC
Programmable: Choice between light-on mode or dark-on mode.
Positive switching: Positive output signal (to L-).
Negative switching: Negative output signal (to L+).
Diffuse reflection sensor The transmitter and receiver are inte-
grated in one housing (3). The light
3 5
Rated insulation voltage AC units depending on UB: 140 V AC / 250 V AC
beam is reflected by an object (5). DC units with protection class II: 250 V AC
The objects are detected by reflection DC units with protection class III: 60 V DC
of the light beam based on the energet-
Rated frequency of the sup- 50 Hz / 60 Hz or direct voltage
ic, the triangulation or the time-of-flight
ply network
principle.
Energetic principle: Rated short-circuit current For short-circuit-proof units: 100 A
The range depends on the energy of Rated impulse withstand AC units depending on UB: 140 V AC = 2.5 kV or 250 V AC = 4 kV (≙ overvolt-
the reflected light. Depending on the voltage age category III)
object surface the light is reflected DC units with protection class II: 4 kV (≙ overvoltage category III)
1: Transmitter
more or less well: DC units with protection class III: 60 V DC: 1 kV (≙ overvoltage category II)
• good reflection: smooth / light 2: Receiver
object. 3: Transmitter and receiver Power-on delay time The time the sensor needs to be ready for operation after application of the oper-
• poor reflection: rough / dark object. ating voltage (typically < 300 ms).
4: Reflector
5: Object Operating voltage Voltage range in which the sensor operates reliably.
Use stabilised and smoothed direct current.
Diffuse reflection sensor Triangulation:
Take into account the residual ripple.
with background suppres- Evaluates the position where reflected light falls as the distance to an object
sion changes. The range is largely independent of the energy of the reflected light.
EMC Photoelectric sensors meet the requirements of EN 60947-5-2 so that Transport and Unless indicated otherwise in the data sheet, the following applies:
• there are no noise levels that affect other equipment in their intended operation. storage conditions Transport and storage temperature:
• they are sufficiently insensitive to electromagnetic interference to be expected Min. = - 40 °C.
during intended operation. Max. = max. ambient temperature according to the data sheet.
The relative air humidity (RH) must not exceed 50 % at +70 °C. At lower tempera-
Detection zone change Used for sensors with background suppression. Ability to recognise objects with dif- tures, a higher air humidity is permissible.
ferent reflections at the same distance. Shelf life: 5 years.
Excess gain Ratio between the received amount of light and the light amount required for switch- Transport and storage height: no restrictions.
ing. Range The mechanically usable distance between photoelectric sensor and object referred
Utilisation category AC units: AC-140 (control of small electromagnetic loads with holding currents < 200 to white paper 200mm x 200mm, 90% remission.
mA) Degree of soiling The products are designed for degree of soiling 3.
DC units: DC-13 (control of solenoids)
Preferred direction Note:
Accuracy graph Minimum distance between object and background depending on the range. The objects to be detected should move
Background suppression Optical process of the diffuse reflection sensor / distance sensor to distinguish the transversely to the lens of the sensor.
object from a reflective surface behind. In case of other directions of movement
it should be tested before whether a safe
Hysteresis Difference between switch-on and switch-off point <20% of the set range. switching function is guaranteed.

Short-circuit protection Units with pulsed short-circuit protection can react sensitively to incandescent
lamps, electronic relays and other low-resistance loads.
Measuring frequency Used for distance sensors. Number of measurements per second (Hz).
In situations with a brightness ratio (object to background) of 1:1, the switching fre- Wave lengths according to the data sheet
quency is approx. measuring frequency / 3.
Repeatability < 10% of the set range unless indicated otherwise.
Minimum load current Smallest operating current to maintain the conductivity of the switching element.
Polarisation filter A very fine filter which only allows light waves on a specific plane to pass (for exam-
ple: horizontal light waves). 4 Electrical connection
Product standard IEC 60947-5-2
Connection systems
Range The maximum usable distance between transmitter and receiver (through beam) or
sensor and reflector (reflective). 2-wire technology 3-wire technology 4-wire technology
(negative or positive switching) (negative or positive switching) (positive switching, normally closed
Leakage current Current for the internal supply of 2-wire units; also flows through the load when the and normally open)
output is blocked. +UB / L1 +UB
+UB
Switching frequency Maximum number of signal changes at the switching output per second (in Hz).
Protection rating Describes the protection of electric equipment by means of housings, covers, enclo-
sures and is indicated by the IP code.
0V / N 0V
Voltage drop Voltage across the output switching element in the conductive state. 0V
≤ 2.5 V unless indicated otherwise.
Reflective objects With reflective objects it may make sense to align the unit at an angle of approx. 5° -
10° to the object. 1: Use a miniature fuse according to the technical data sheet, if specified.
Recommendation: Check the safe functioning of the unit after a short circuit.
Radiation power Classification of the radiation power:
• laser classes according to EN60825-1:2014-05 2: Negative switching: 4: Sensor 1
• LED units according to DIN EN62471:2009, risk group 0 3: Positive switching: 5: Sensor n
Current consumption No-load current for internal supply of 3 or 4-wire DC units.
Parallel connection (OR) 5 Installation
Parallel connection 3-wire units Parallel connection 2-wire units 5.1 Minimum clearance for installing sensors of the same type
The current consumption of all non-switched units Not possible.
adds up. The units can be used in combination with Malfunction of the units possible.
mechanical switches.
Units of the same kind can influence each other when they are mounted side by
+UB side.
► Observe the following installation notes.
Through beam sensors
0V 1 2 1: Transmitter
2: Receiver
Series connection (AND) is not recommended since the power-on delay times,
voltage drops and current consumption add up. UBmin (sensor) and UHIGH min
(load) must remain unchanged.
4.1 Pin configuration of connectors and cables
Standard configuration 3-wire DC: 2 1

Cable Terminal chamber US-100 connector

L+ BN 1/3 Pin 1 / BN
Retro-reflective sensors
L- BU 2/4 Pin 3 / BU
1: Reflector
Output BK X Pin 2 / WH
2: Transmitter and receiver
Pin 4 / BK
3: Object
1 2 3 2 1
Colours
BK: Black BN: Brown
BU: Blue WH: White

4.2 Pin configuration of the US-100 connectors

Diffuse sensors
View on the connector on the unit:
Pin 4: BK Pin 3: BU 1: Transmitter and receiver
2: Object
Pin 1: BN Pin 2: WH

1 2
Cable and connector configuration as well as unit data of special variants Data
sheet.

Photoelectric sensors with red or infrared light emit a cone-shaped light beam.

Depending on the application there are other possible solutions.

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