Omron E3H2 DATASHEET

Miniature photoelectric sensors in cylindrical M8 and M12 housing

E3H2

• M8 or M12 sized cylindrical housings

when mounting space is crucial

• Retro-reflective models with two

teaching modes for standard and

semi-transparent objects

• pre-wired and connector models

Ordering Information

M12 cylindrical housing

Sensor type Sensing

distance

Through-beam 4 m

(adjustable)

Retro-reflective
with M.S.R.

Diffuse-reflec­tive

*1.

Models without teach-button are available. Contact your OMRON representative.

*2.

Without reflector; order reflector separately

2m
(teachable

300 mm
(teachable)

100 mm
(fixed)

Operation mode Connection method Order code

light on / dark on
selectable

*1

)

––2m–

–  ––

––2m–

–  ––

––2m–

–  ––

––2m–

–  ––

M8 cylindrical housing

Sensor type Sensing

distance

Operation mode Connection method Order code

NPN output PNP output

E3H2-T4C4M 2M E3H2-T4B4M 2M

E3H2-T4C4M-M1 E3H2-T4B4M-M1

E3H2-R2C4M 2M

E3H2-R2C4M-M1

E3H2-DS30C4M 2M E3H2-DS30B4M 2M

E3H2-DS30C4M-M1 E3H2-DS30B4M-M1

E3H2-DS10C4M 2M E3H2-DS10B4M 2M

E3H2-DS10C4M-M1 E3H2-DS10B4M-M1

NPN output PNP output

*2

E3H2-R2B4M 2M

*2

E3H2-R2B4M-M1

*2

*2

Through-beam 2 m dark on

light on

––2m–

 –––

––2m–

 –––

E3H2-T2C2S 2M E3H2-T2B2S 2M

E3H2-T2C2S-M5 E3H2-T2B2S-M5

E3H2-T2C1S 2M E3H2-T2B1S 2M

E3H2-T2C1S-M5 E3H2-T2B1S-M5

1E3H2

Accessories

Reflectors

Shape Type Material Features Size in mm Applicable Sensor Order code

General purpose
reflectors

Small size Surface screw

-ABS base

- Acrylic
surface

Surface screw
mounting
(diagonal holes)

mounting

60x40x7.5 - Retro-reflective photo-

electric sensors – non
polarizing

- Retro-reflective photo-

23x13.7x4.9 E39-R4

electric sensors – po­larizing (MSR)

E39-R1S

Simple mounting Round shape

with centered
mounting hole
for simple screw
mounting

General purpose
tape reflectors

- Acrylic Self adhesive

Pre cut

Diameter: 84
Depth: 7.4

40x35x0.6 E39-RS2

Sensor I/O connectors

Size Shape Type Features Material Order code

Nut Cable

M8 General pur-

pose
(screw)

M12 General pur-

pose
(screw)

Note: For the complete list of sensor I/O connectors refer to E26E Accessories datasheet.

3 pin (LED
optionally)

3 wire (LED
optionally)

4 wire PVC 2 m

Brass (CuZn) PVC 2 m

PUR 2 m

Brass (CuZn) PVC 2 m

PUR 2 m

PUR 2 m

XS3F-M08PVC3S2M
XS3F-M08PUR3S2M

XS2F-M12PVC3S2M
XS2F-M12PUR3S2M

XS2F-M12PVC4S2M
XS2F-M12PUR4S2M

E39-R7

XS3F-M08PVC3A2M
XS3F-M08PUR3A2M

XS2F-M12PVC3A2M
XS2F-M12PUR3A2M

XS2F-M12PVC4A2M
XS2F-M12PUR4A2M

2 Miniature Photoelectric Sensors

Specifications

Item Through-beam Retro-reflective with

M.S.R.

E3H2-T4 E3H2-T2 E3H2-R E3H2-DS30 E3H2-DS10

Sensing distance 4 m (adjustable) 2 m 2 m (teachable)

(when using E39­R1S)

Differential travel 20% max of sensing

distance

Light source
(wave length)

Power supply
voltage

Current consumption 45 mA max

Control output Load current: 100 mA max. (residual voltage 2 V max.);

Protective circuits Power supply reverse polarity protection, output short circuit protection

Response time Operation or reset:

Sensitivity
adjustment

Ambient illumination Incandescent lamp: 1500 lx max.; Sunlight: 5000 lx max.

Ambient temperature Operating:

Degree of protection EN 60529: IP67

Indicators Emitter: Power supply indicator: yellow

Weight

pre-wired
connector

Material

case
lens

Infrared LED (880 nm) Red LED (660 nm) Infrared LED (880 nm)

10 to 30 VDC, 10% ripple

E3H2-_C_: NPN
E3H2-_B_: PNP

Light-on/dark-on
selectable by wire

2.5 ms max

Potentiometer
adjuster

-25 to +55°C

Receiver: Operation indicator: yellow

approx 110 g
approx 40 g

nickel-plated brass
plastic

10% max of sensing distance

E3H2-T2_2_: dark
on
E3H2-T2_1_: light
on

Operation or reset:
1 ms max.

–Teach-in –

Operating:

-25 to +50°C

approx 90 g
approx 30 g

stainless steel
plastic

Light-on/dark-on selectable by wire

Operation or reset: 1.1 ms max

Operating: -25 to +55°C

Output indicator: yellow

approx 55 g
approx 20 g

nickel-plated brass
plastic

Diffuse-reflective

300 mm
(teachable)

100 mm (fixed)

3E3H2

Operation

Sensitivity adjustment

E3H2-T4

The emitter of the E3H2-T4 allows an adjustment of the emitted
amount of light by turning the potentiometer. Turn the potentiom­eter clockwise for increasing the amount of emitted light and
counter-clockwise for decreasing the amount of emitted light.

E3H2-R2

a) standard mode

To teach the retro-reflective model E3H2-R, place the sensor
with the lens facing the reflector. Press the teach button for 2­5 seconds. For remote teach connect the white wire (Pin 2) for
2-5 seconds to common (-).
The threshold is now set to 50% of the received light level.

b) high sensitivity mode (e.g. for semi-transparent models)

To teach the retro-reflective model E3H2-R in high sensitivity
mode, place the sensor with the lens facing the reflector.
Press the teach button for >8 seconds. For remote teach con­nect the white wire (Pin 2) for >8 seconds to common (-).

The threshold is now set just below the received light level.
If the teaching was successful the LED should no longer be flash­ing and a state change occurs when the light is interrupted.

E3H2-DS30

a) standard mode

To teach the diffuse-reflective model E3H2-DS30, place the

object in front of the sensor at the required sensing distance.

Press the teach button for 2-5 seconds. For remote teach

connect the white wire (Pin 2) for 2-5 seconds to common (-).

The threshold is now set to 50% of the received light level.

When the object is removed, a state change at the sensor

should occur. If this is not the case the high sensitivity mode

may be required.
b) high sensitivity mode

To teach the diffuse-reflective model E3H2-DS30 in high sen-

sitivity mode, place the object in front of the sensor at the

required sensing distance. Press the teach button for

>8 seconds. For remote teach connect the white wire (Pin 2)

for >8 seconds to common (-).

The threshold is now set just below the received light level.

When the object is removed, a state change at the sensor

should occur and the LED should no longer be flashing.

Operation mode selection

The light-on / dark-on operation mode can be selected by wire
(except for E3H2-T2). The white wire (Pin 2) can be connected to
plus (+), common (-) or left open (not connected) for the default
setting.

a) E3H2-T4 Receiver

Default setting (wire left open):DARK-ON
Connected to plus (+): LIGHT-ON
Connected to common (-): DARK-ON

b) E3H2-R2

Default setting (wire left open):DARK-ON
Connected to plus (+): LIGHT-ON
Connected to common (-): TEACH

c) E3H2-DS30

Default setting (wire left open):LIGHT-ON
Connected to plus (+): DARK-ON
Connected to common (-): TEACH

d) E3H2-DS10

Default setting (wire left open):LIGHT-ON
Connected to plus (+): DARK-ON
Connected to common (-): LIGHT-ON

For E3H2-T2 the operation mode is fixed and models with light­on and dark-on operation are available.

*1 In case the remote teach operation is required when the white wire is con-

nected to plus (+), add a 2.2 kΩ resistor between the white wire and (+)
to avoid a short circuit.

*1

*1

For E3H2-T2 and E3H2-DS10 the sensitivity setting is fixed.

4 Miniature Photoelectric Sensors

Engineering data (typical)

Parallel operating range

Through-beam models Retroreflective models

E3H2-T4 E3H2-T2 E3H2-R2

200

100

Distance Y (mm)

0

-100

-200
012345

Distance X (m)

250

200

150

Distance Y (mm)

100

50

0

-50

-100

-150

-200

-250

0.00 0.50 1.00 1.50 2.00 2.50

Operating range

Diffuse reflective models

E3H2-DS30 E3H2-DS10

20

10

Distance Y (mm)

White paper 90%

20

Distance (mm)

10

Distance X (m)

White paper 90%

40

20

Distance Y (mm)

0

-20

-40
012

Distance X (m)

0

-10

Gray paper 18%

-20
0102030

Distance X (cm)

0

-10

-20
0246810

Gray paper 18%

Distance X (cm)

Excess gain vs. distance

Through-beam models Retroreflective Models

E3H2-T4 E3H2-T2

1000

Gain

100

10

1

0

012345

Distance (m)

100

Excess Gain

10

1

0

0,00 0,50 1,00 1,50 2,00 2,50

Distance (m)

E3H2-R2

1000

Excess Gain

100

10

1

0

012

Distance (m)

5E3H2

Diffuse reflective Models

100

10

1

3020100

0

Distance X (cm)

Gain

White paper 90%

Gray paper 18%

1000

12

0

1

10

100

0

246810

Excess Gain

Distance (cm)

White paper 90%

Gray paper 18%

E3H2-DS30 E3H2-DS10

6 Miniature Photoelectric Sensors

Output Circuit Diagram

PNP Output

Model Operation

mode

E3H2-T4B@

Light ON For through-

E3H2-R2B@
E3H2-D@B@

Dark ON For through-

Timing charts Mode

selector switch

beam and retro-

Light Incident

Light Interrupted

Operation indicator
(yellow)

Output transistor

Load
(e.g. relay)

Operate

ON

OFF

ON

OFF

Reset

reflective: con­nect the white
wire (Pin 2) to the
brown wire
(Pin 1).
For diffuse-re­flective: open (do
not connect) the
white wire
(Pin 2).

beam and retro-

Light Incident

Light Interrupted

Operation indicator
(yellow)

Output transistor

Load
(e.g. relay)

Operate

ON

OFF

ON

OFF

Reset

reflective: open
(do not connect)
the white wire
(Pin 2).
For diffuse-re­flective: connect
the white wire
(Pin 2) to the
brown wire (Pin

1).

Through-beam emitter

Power
indicator
(yellow)

Photo­electric
Sensor
Main
Circuit

1

3

Brown

Blue

Output circuit

Through-beam receiver, retro-reflective,
diffuse-reflective

Operation
indicator
(Yellow)

Photo­electric
Sensor
Main
Circuit

Mode Selection /
Te ac h

Connector Pin Arrangement

1

2

4

3

Connector Pin Arrangement

1

2

10 to 30 VDC

4

3

Z

(Control

output)

10 to 30 VDC

Brown

1

D

Black

4

100 mA
max.

3

Blue

2

White

Load

(Relay)

0 V

E3H2-T2B@ Light ON n.a. fixed for

Light Incident

Light Interrupted

Operation indicator
(yellow)

Output transistor

Load
(e.g. relay)

Operate

E3H2-T2B1@

ON

OFF

ON

OFF

Reset

Dark ON n.a. fixed for

Light Incident

Light Interrupted

Operation indicator
(yellow)

Output transistor

Load
(e.g. relay)

Operate

ON

OFF

ON

OFF

Reset

Through-beam emitter

Power
indicator
(yellow)

Photo­electric
Sensor
Main
Circuit

E3H2-T2B2@

Brown

1

Blue

3

Through-beam receiver

Operation
indicator
(Yellow)

Connector Pin Arrangement

Connector Pin Arrangement

10 to 30 VDC

Photo­electric
Sensor
Main
Circuit

10 to 30 VDC

Brown

1

D

Z

Black

4

(Control

output)

4

1

3

4

1

3

100 mA
max.

3

Blue

Load

(Relay)

0 V

7E3H2

NPN Output

Light Incident

Light Interrupted

ON

OFF

ON

OFF

Operate

Reset

Operation indicator
(yellow)

Output transistor

Load
(e.g. relay)

Model Operation

mode

E3H2-T4C@

Light ON For through-

E3H2-R2C@
E3H2-D@C@

Dark ON For through-

Timing charts Mode

selector switch

Light Incident

Light Interrupted

Operation indicator
(yellow)

Output transistor

Load
(e.g. relay)

Operate

ON

OFF

ON

OFF

Reset

beam and retro­reflective:
connect the
white wire (Pin 2)
to the brown wire
(Pin 1).
For diffuse-re­flective:
open (do not con­nect) the white
wire (Pin 2).

beam and retro­reflective:
open (do not con­nect) the white
wire (Pin 2).
For diffuse-re­flective:
connect the
white wire (Pin 2)
to the brown wire
(Pin 1)

Through-beam emitter

Power
indicator
(yellow)

Photo­electric
Sensor
Main
Circuit

Output circuit

Through-beam receiver, retro-reflective,
diffuse-reflective

Operation
indicator
(Yellow)

Photo­electric
Sensor
Main
Circuit

Mode Selection /
Te ac h

Connector Pin Arrangement

1

2

3

Brown

1

10 to 30 VDC

Blue

3

Connector Pin Arrangement

4

(Control

output)

D

Z

2

Brown

1

4

Black

Blue

3

2

White

1

4

3

100 mA
max.

10 to 30 VDC

Load

(Relay)

0 V

E3H2-T2C@ Light ON n.a. - fixed for

Light Incident

Light Interrupted

Operation indicator
(yellow)

Output transistor

Load
(e.g. relay)

Operate

ON

OFF

ON

OFF

Reset

E3H2-T2C1@

Dark ON n.a. - fixed for

Light Incident

Light Interrupted

Operation indicator
(yellow)

Output transistor

Load
(e.g. relay)

Operate

Through-beam emitter

ON

OFF

ON

OFF

Reset

Power
indicator
(yellow)

Photo­electric
Sensor
Main
Circuit

E3H2-T2C2@

Brown

1

Blue

3

Through-beam receiver

Operation
indicator
(Yellow)

Photo­electric
Sensor
Main
Circuit

Connector Pin Arrangement

Connector Pin Arrangement

10 to 30 VDC

Brown

1

(Control

output)

4

Black

D

Z

Blue

3

4

1

3

4

1

3

100 mA
max.

10 to 30 VDC

Load

(Relay)

0 V

8 Miniature Photoelectric Sensors

Dimensions

4

Ø3.75

122.34.44.4

65.5

212.3

54.5

Power inidcator (yellow)

Potentiometer
adjuster

Power inidcator (yellow)

Potentiometer
adjuster

1 38.3 8.7 6

(54)

M8x0.75

M8x1

n° 4 x Ø2

9.5

M8x0.75

49

1 42.7

Ø6.5

Ø3.1

Emitter:
power indicator (yellow)
Receiver:
operation indicator (yellow)

Emitter:
power indicator (yellow)

Receiver:
operation indicator (yellow)

4

Ø3.75

122.34.44.4

65.5

212.3

54.5

Operation inidcator (yellow)

Teach button
(E3H2-DS30 only)

Operation inidcator (yellow) Teach button (E3H2-DS30 only)

Note: All units are in millimeters unless otherwise stated.

Pre-wired models Connector models

E3H2-T4
Emitter

E3H2-T4
Receiver

E3H2-T2
Emitter/
Receiver

E3H2-R2

E3H2-D

Operation indicator (yellow) Operation indicator (yellow)

55.3

55

2.5 34 17.7

M12x1

Operation indicator (yellow) Teach button Operation indicator (yellow) Teach button

0.8

2.8

66.3

4

2.5 34 22 6.5 1

M12x1

66

M12x1

9E3H2

Safety precautions

! Warning

This product is not designed or rated for directly or
indirectly ensuring safety of persons. Do not use it for
such a purpose.

! Caution

Do not use the product with voltage in excess of the
rated voltage. Excess voltage may result in malfunc­tion or fire.

Never use the product with an AC power supply.
Otherwise, explosion may result.

When cleaning the product, do not apply a high-pres­sure spray of water to one part of the product. Other­wise, parts may become damaged and the degree of
protection may be degraded.

High-temperature environments may result in burn
injury.

Precautions for Safe Use

The following precautions must be observed to ensure safe
operation of the Sensor.

Operating Environment

Do not use the Sensor in an environment where explosive or
flammable gas is present.

Connecting Connectors

Be sure to hold the connector cover when inserting or removing
the connector. Be sure to tighten the connector lock by hand;
do not use pliers or other tools. If the tightening is insufficient, the
degree of protection will not be maintained and the Sensor may
become loose due to vibration. The appropriate tightening torque
is 0.4 to 0.5 N·m for M12 connectors and 0.3 Nm for M8 connec­tors.

Load

Do not use a load that exceeds the rated load.

Environements with Cleaners and Disinfectants

Do not use the Sensor in environments subject to cleaners and
disifectants. They may reduce the degree of protection.

Modifications

Do not attempt to disassemble, repair, or modify the Sensor.

Outdoor Use

Do not use the Sensor in locations subject to direct sunlight.

Cleaning

Do not use thinner, alcohol, or other organic solvents. Otherwise,
the optical properties and degree of protection may be degraded.

Surface Temperature

Burn injury may occur. The Sensor surface temperature rises de­pending on application conditions, such as the surrounding tem­perature and the power supply voltage. Use caution when
operating or washing the Sensor.

Precautions for Correct Use

Do not use the Sensor in any atmosphere or environment that
exceeds the ratings.

Do not install the Sensor in the following locations.

(1)Locations subject to direct sunlight
(2)Locations subject to condensation due to high humidity
(3)Locations subject to corrosive gas
(4)Locations where the Sensor may receive direct vibration or

shock

Connecting and Mounting

(1)The maximum power supply voltage is 30 VDC. Before turning

the power ON, make sure that the power supply voltage does
not exceed the maximum voltage.

(2)Laying Sensor wiring in the same conduit or duct as high-volt-

age wires or power lines may result in malfunction or damage
due to induction. As a general rule, wire the Sensor in a sepa­rate conduit or use shielded cable.

(3)Use an extension cable with a minimum thickness of 1 mm

and less than 100 m long.
(4)Do not pull on the cable with excessive force.
(5)Pounding the Photoelectric Sensor with a hammer or other

tool during mounting will impair water resistance.
(6)Mount the Sensor either using the bracket (sold separately) or

on a flat surface.
(7)Be sure to turn OFF the power supply before inserting or re-

moving the connector.

Cleaning

Never use thinner or other solvents. Otherwise, the Sensor sur­face may be dissolved.

Power Supply

If a commercial switching regulator is used, ground the FG (frame
ground) terminal.

Power Supply Reset Time

The Sensor will be able to detect objects 150 ms after the power
supply is tuned ON. Start using the Sensor 150 ms or more after
turning ON the power supply. If the load and the Sensor are con­nected to separate power supplies, be sure to turn ON the Sensor
first.

Turning OFF the Power Supply

Output pulses may be generated even when the power supply is
OFF. Therefore, it is recommended to first turn OFF the power
supply for the load or the load line.

Load Short-circuit Protection

This Sensor is equipped with load short-circuit protection, but be
sure to not short circuit the load. Be sure to not use an output cur­rent flow that exceeds the rated current.

Water Resistance

Do not use the Sensor in water, rainfall, or outdoors.

2

10 Miniature Photoelectric Sensors

11E3H2

WARRANTY

In the interest of product improvement, specifications are subject to change without notice.Cat. No. E64E-EN-01B

OMRON EUROPE B.V.

Wegalaan 67-69,
NL-2132 JD, Hoofddorp,
The Netherlands
Phone: [phone]
Fax: [phone]
www.industrial.omron.eu

OMRON’s exclusive warranty is that the products are free from de­fects in materials and workmanship for a period of one year (or other
period if specified) from date of sale by OMRON.

OMRON MAKES NO WARRANTY OR REPRESENTATION, EX­PRESS OR IMPLIED, REGARDING NON-INFRINGEMENT, MER­CHANTABILITY, OR FITNESS FOR PARTICULAR PURPOSE OF
THE PRODUCTS. ANY BUYER OR USER ACKNOWLEDGES THAT
THE BUYER OR USER ALONE HAS DETERMINED THAT THE
PRODUCTS WILL SUITABLY MEET THE REQUIREMENTS OF
THEIR INTENDED USE. OMRON DISCLAIMS ALL OTHER WAR­RANTIES, EXPRESS OR IMPLIED.

LIMITATIONS OF LIABILITY

OMRON SHALL NOT BE RESPONSIBLE FOR SPECIAL, INDI­RECT, OR CONSEQUENTIAL DAMAGES, LOSS OF PROFITS OR
COMMERCIAL LOSS IN ANY WAY CONNECTED WITH THE
PRODUCTS, WHETHER SUCH CLAIM IS BASED ON CONTRACT,
WARRANTY, NEGLIGENCE, OR STRICT LIABILITY.

In no event shall responsibility of OMRON for any act exceed the in­dividual price of the product on which liability is asserted.

IN NO EVENT SHALL OMRON BE RESPONSIBLE FOR WARRAN­TY, REPAIR, OR OTHER CLAIMS REGARDING THE PRODUCTS
UNLESS OMRON’S ANALYSIS CONFIRMS THAT THE PROD­UCTS WERE PROPERLY HANDLED, STORED, INSTALLED, AND
MAINTAINED AND NOT SUBJECT TO CONTAMINATION, ABUSE,
MISUSE, OR INAPPROPRIATE MODIFICATION OR REPAIR.

SUITABILITY FOR USE

THE PRODUCTS CONTAINED IN THIS DOCUMENT ARE NOT
SAFETY RATED. THEY ARE NOT DESIGNED OR RATED FOR EN­SURING SAFETY OF PERSONS, AND SHOULD NOT BE RELIED
UPON AS A SAFETY COMPONENT OR PROTECTIVE DEVICE
FOR SUCH PURPOSES. Please refer to separate catalogs for OM­RON's safety rated products.

OMRON shall not be responsible for conformity with any standards,
codes, or regulations that apply to the combination of products in the

customer’s application or use of the product.

At the customer’s request, OMRON will provide applicable third party
certification documents identifying ratings and limitations of use that
apply to the products. This information by itself is not sufficient for a
complete determination of the suitability of the products in combina­tion with the end product, machine, system, or other application or
use.

The following are some examples of applications for which particular
attention must be given. This is not intended to be an exhaustive list
of all possible uses of the products, nor is it intended to imply that the
uses listed may be suitable for the products:

• Outdoor use, uses involving potential chemical contamination or

electrical interference, or conditions or uses not described in this
document.

• Nuclear energy control systems, combustion systems, railroad sys-

tems, aviation systems, medical equipment, amusement machines,
vehicles, safety equipment, and installations subject to separate in­dustry or government regulations.

• Systems, machines, and equipment that could present a risk to life

or property.

Please know and observe all prohibitions of use applicable to the
products.

NEVER USE THE PRODUCTS FOR AN APPLICATION INVOLVING
SERIOUS RISK TO LIFE OR PROPERTY WITHOUT ENSURING
THAT THE SYSTEM AS A WHOLE HAS BEEN DESIGNED TO
ADDRESS THE RISKS, AND THAT THE OMRON PRODUCT IS
PROPERLY RATED AND INSTALLED FOR THE INTENDED USE
WITHIN THE OVERALL EQUIPMENT OR SYSTEM.

PERFORMANCE DATA

Performance data given in this document is provided as a guide for
the user in determining suitability and does not constitute a warranty.
It may represent the result of OMRON’s test conditions, and the users
must correlate it to actual application requirements. Actual perfor­mance is subject to the OMRON Warranty and Limitations of Liability.

CHANGE IN SPECIFICATIONS

Product specifications and accessories may be changed at any time
based on improvements and other reasons.

It is our practice to change model numbers when published ratings or
features are changed, or when significant construction changes are
made. However, some specifications of the product may be changed
without any notice. When in doubt, special model numbers may be as­signed to fix or establish key specifications for your application on
your request. Please consult with your OMRON representative at any
time to confirm actual specifications of purchased products.

DIMENSIONS AND WEIGHTS

Dimensions and weights are nominal and are not to be used for man­ufacturing purposes, even when tolerances are shown.

ERRORS AND OMISSIONS

The information in this document has been carefully checked and is
believed to be accurate; however, no responsibility is assumed for
clerical, typographical, or proofreading errors, or omissions.

PROGRAMMABLE PRODUCTS

OMRON shall not be responsible for the user’s programming of a pro­grammable product, or any consequence thereof.

12 Miniature Photoelectric Sensors