Photoelectric Sensors Technical Guide

Noise

Countermeasures for noise depend on the path of noise entry, frequency components, and wave heights. Typical measures are as given in the

following table.

● Wiring

Cable

Unless otherwise indicated, the maximum length of cable extension is

100 m using wire that is 0.3 mm2 or greater.

Exceptions are indicated in Safety Precautions in individual product

information.

Cable Tensile Strength

When wiring the cable, do not subject the cable to a tension greater than

that indicated in the following table.

Note: Do not subject a shielded cable or coaxial cable to tension.

Repeated Bending

Normally, the Sensor cable should not be bent repeatedly.

(For bending-resistant cable, see Attachment to Moving Parts on

page C-4.)

Separation from High Voltage (Wiring Method)

Do not lay the cables for the Sensor together with high-voltage lines

or power lines. Placing them in the same conduit or duct may cause

damage or malfunction due to induction interference. As a general

rule, wire the Sensor in a separate system, use an independent metal

conduit, or use shielded cable.

Work Required for Unconnected Leads

Unused leads for self-diagnosis outputs or other special functions

should be cut and wrapped with insulating tape to prevent contact with

other terminals.

Type of noise

Noise intrusion path and countermeasure

Before countermeasure

After countermeasure

Common mode noise

(inverter noise)

Common noise

applied between the

mounting board and

the +V and 0-V

lines, respectively.

Noise enters from the noise source through the frame

(metal).

(1) Ground the inverter motor (to 100

Ω or less)

(2) Ground the noise source and the power supply (0-V

side) through a capacitor (film capacitor, 0.22 μF, 630

V).

(3) Insert an insulator (plastic, rubber, etc.) between the

Sensor and the mounting plate (metal).

Radiant noise

Ingress of high-fre-

quency electromag-

netic waves directly

into Sensor, from

power line, etc.

Noise propagates through the air from the noise source

and directly enters the Sensor.

• Insert a shield (copper) plate between the Sensor and

the noise source e.g., a switching power supply).

• Separate the noise source and the Sensor to a distance

where noise does not affect operation.

Power line noise

Ingress of electromag-

netic induction from

high-voltage wires

and switching noise

from the switching

power supply

Noise enters from the power line.

• Insert a capacitor (e.g., a film capacitor), noise filter (e.g.,

ferrite core or insulated transformer), or varistor in the

power line.

IM

Sensor

Noise

+V

0V

Inverter

motor

Mounting block

(metal)

IM

Sensor

Insert an insulator.

Inverter motor

+V

0V

Noise

Noise

Mounting block

(metal)

(3)

(2)

(1)

Noise

Sensor

Noise

source

+V

0V

Sensor

Shield plate (copper)

Noise

source

+V

0V

Sensor

Noise

Noise

+V

0V

Sensor

Insert a capacitor, etc.

Noise

+V

0V

Cable diameter

Tensile strength

Less than 4 mm

30 N max.

4 mm or greater

50 N max.

Power line

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C-3

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