Datasheet

22 Inductive Sensors
Precautions for Correct Use
Installation
Power Reset Time
The Proximity Sensor is ready to operate within 100 ms after power
is supplied. If power supplies are connected to the Proximity Sensor
and load respectively, be sure to supply power to the Proximity Sen-
sor before supplying power to the load.
Power OFF
The Proximity Sensor may output a pulse signal when it is turned
OFF. Therefore, it is recommended to turn OFF the load before
turning OFF the Proximity Sensor.
Power Supply Transformer
When using a DC power supply, make sure that the DC power sup-
ply has an insulated transformer. Do not use a DC power supply with
an auto-transformer.
Sensing Object
Metal Coating:
The sensing distances of the Proximity Sensor vary with the metal
coating on sensing objects.
Wiring
High-tension Lines
Wiring through Metal Conduit
If there is a power or high-tension line near the cable of the Proximity
Sensor, wire the cable through an independent metal conduit to pre-
vent against Proximity Sensor damage or malfunctioning.
Cable Tractive Force
Do not pull on cables with tractive forces exceeding the following.
Mounting
The Proximity Sensor must not be subjected to excessive shock with
a hammer when it is installed, otherwise the Proximity Sensor may
be damaged or lose its water-resistivity.
Environment
Water Resistivity
The Proximity Sensors are tested intensively on water resistance,
but in order to ensure maximum performance and life expectancy
avoid immersion in water and provide protection from rain or snow.
Operating Enviroment
Ensure the usage of the Proximity Sensor within its operating ambi-
ent temperature range and do not use the Proximity Sensor outdoors
so that its reliability and life expectancy can be maintained. Although
the Proximity Sensor is water resistive, a cover to protect the Proxi-
mity Sensor from water or water soluble machining oil is recommen-
ded so that its reliability and life expectancy can be maintained.
Do not use the Proximity Sensor in an environment with chemical
gas (e.g., strong alkaline or acid gasses including nitric, chromic, and
concentrated sulfuric acid gases).
Connecting Load to AC/DC 2-wire Sensor
Refer to the following before using AC or DC 2-wire Proximity Sen-
sors.
Surge Protection
Although the Proximity Sensor has a surge absorption circuit, if there
is any machine that has a large surge current (e.g., a motor or wel-
ding machine) near the Proximity Sensor, connect a surge absorber
to the machine.
Leakage Current
When the Proximity Sensor is OFF, the Proximity Sensor has lea-
kage current. Refer to page 9 Leakage Current Characteristics. In
this case, the load is imposed with a small voltage and the load may
not be reset. Before using the Proximity Sensor, make sure that this
voltage is less than the load reset voltage. The AC 2-wire Proximity
Sensor cannot be connected to any card-lift-off relay (e.g., the G2A)
because contact vibration of the relay will be caused by the leakage
current and the life of the relay will be shortened.
Loads with Large Inrush Currents (E2E-X@T@)
Connecting a load that has a large inrush current (e.g., a lamp or
motor) may result in a malfunction due to the inrush current causing
a load short-circuit.
Countermeasures Against Leakage Current
AC 2-wire Models
Connect a bleeder resistor as the bypass for the leakage current so
that the current flowing into the load will be less than the load reset
current.
As shown in the following diagram, connect the bleeder resistor so
that the current flowing into the Proximity Sensor will be 10 mA mini-
mum and the residual voltage imposed on the load will be less than
the load reset voltage.
Refer to the following to calculate the bleeder resistance and the allo-
wable power of the bleeder resistor.
R ≤ V
S/(10 – I) (kΩ)
P > V
S
2
/R (mW)
P: The allowable power of the bleeder resistor. (The actual power
capacity of the bleeder resistor must be at least a few times as
large as the allowable power of the bleeder resistor.)
I: Load current (mA)
The following resistors are recommended.
100 VAC (supply voltage): A resistor with a resistance of 10 kΩ maxi-
mum and an allowable power of 3 W minimum
200 VAC (supply voltage): A resistor with a resistance of 20 kΩ maxi-
mum and an allowable power of 10 W minimum
If these resistors generate excessive heat, use a resistor with a resi-
stance of 10 kΩ maximum and an allowable power of 5 W minimum
at 100 VAC and a resistor with a resistance of 20 kΩ maximum and
an allowable power of 10 W minimum at 200 VAC instead.
DC 2-wire Models
Connect a bleeder resistor as the bypass for the leakage current so
that the current flowing into the load will be less than the load reset
current.
Refer to the following to calculate the bleeder resistance and the allo-
wable power of the bleeder resistor.
R ≤ V
S/(iR – iOFF) (kΩ)
P > V
S
2
/R (mW)
P: The allowable power of the bleeder resistor. (The actual power
capacity of the bleeder resistor must be at least a few times as
large as the allowable power of the bleeder resistor.)
i
R: Leakage current of Sensors (mA)
i
OFF: Release current of load (mA)
The following resistors are recommended.
12 VDC (supply voltage): A resistor with a resistance of 15 kΩ maxi-
mum and an allowable power of 450 mW minimum
24 VDC (supply voltage): A resistor with a resistance of 30 kΩ maxi-
mum and an allowable power of 0.1 W minimum
Diameter Tractive force
4 dia. max. 30 N max.
4 dia. min. 50 N max.
Load
Bleeder resistor R
VAC power
supply V
S
Load
Bleeder resistor R