	Photoelectric Sensors

Hints on Correct Use

Mounting

Type

External disturbance

Solution

Thrubeam

The receiver may detect a light beam reflected by the mounting surface.

	Position a light-shield so that the receiver will not detect a light beam travelling below the target.
	Raise the mounting position of the sensor head.

Reflective

A rough mounting surface may reflect the light beam, causing unstable detection.

Change the mounting height, or angle of the sensor head.

An object in the background may reflect the light beam, causing unstable detection.

	Provide a background object of low reflectance, such as a black wall, to prevent the sensor from detecting a reflected light beam.
	Provide as great a distance as possible between the target and background object.

The small-spot definite-reflective type or fixed-distance type, whose detection is not affected by background objects, is recommended in cases where the above solutions are not possible.

Alignment of optical axis (thrubeam type)

1.	Place the transmitter and the receiver face-to-face on a straight line.
2.	Rotate the receiver clockwise or counterclockwise to find the range where the indicator LED lights. Set the receiver at the mid-point of the range.
3.	Follow the same procedure for vertical alignment.

Mounting environment

Interference

When 2 or more sensors are installed side-by-side without sufficient distance between each other, the transmitted light from one sensor may be detected by the receiver of another, disturbing sensor operation.
This phenomenon is called interference.

Eliminating interference

1.	Use a sensor head with interference-prevention. (Only 2 interference-prevention type sensors can be mounted side-by-side.) PZ Series: Reflective and retro-reflective types

2.	Use a sensor head that can be switched to an alternate frequency. (Can be closely mounted.) PS2 Series: Thrubeam, reflective and retro-reflective types

3.	Allow sufficient distance between sensor heads to prevent interference. For further information, refer to the "Interference area" Characteristics chart for each model.
4.	For the thrubeam sensor, alternate the placement of the transmitters and receivers.

Problems may arise when thrubeam sensors are too close

*Set the transmitters and receivers such that a light beam emitted from a transmitter will not be received by the receiver of the adjacent sensor.

Ambient light and effect of external light

Diagram of how to accomodate strong ambient light sources

KEYENCE photoelectric sensors employ the pulse light emission method which ensures stable operation when external light is strong. However, a strong light beam emitted in the direction of the optical axis of the receiver will cause the sensor to malfunction. To correct this, change the angle of the sensor head, or provide a light-shield to prevent an external light beam from being emitted directly to the receiver.

Illumination

Illuminance(lux)	Conditions
100,000	Sunlight - clear sky
10,000	Sunlight - cloudy sky (32,000 lux)
1,000	Design office (1,000 to 1,500 lux)
100	Department stores (500 to 700 lux)
10	Candlelight at a distance of 30 cm 11.81" (15 lux)

Detecting shiny targets (retro-reflective type)

Retro-reflective sensor configuration for shiny targets

When using a retroreflective type sensor that is not equipped with the P.R.O. function, install the sensor head so that the distance from the target (L) is as long as possible and the optical axis is at a 30 to 45 degree-angle to the target.

Miscellaneous

When using a commercially available switching regulator, ground its chassis grounding and earth grounding terminals.
Isolate the sensor wiring from power lines and high voltage lines; otherwise, the sensor may malfunction due to noise interference.
Handle the photoelectric sensor carefully when mounting. Strong impact to the sensor head may damage the sensor's waterproof capability.

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