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Basic Proximity Sensor Operations


The inductive proximity will sense all metals. The exact point
at which a target will be detected is influenced by the type of
metal, its size and surface area. The following charts show the
sensing fields for a standard target: 45mm sq., mild steel, 1mm

Standard Range

Shielded – Can be mounted flush with metal surface.

Extended Range

Non-shielded – Can not be mounted flush with metal surface

The two most common approach directions are axial (head-on) and
lateral (from the side). Detection occurs at the point where the
target first touches the envelope of the sensing curve. The curve
shown is for a standard target and must be corrected for other size

Correction Factors for Typical Target Materials Based on Standard Size

Target Material Corrective Factor
Steel 1020 1.00
430 Stainless 1.03
302 Stainless .85
Brass .50
Aluminum .47
Copper .40

Operation of Photo-Electric Sensors


This type of sensor detects the reflection of transmitted light
from the surface of an object. Shortest sensing range of all


This type of sensor utilizes a special reflector to return the
beam directed at it from the sensor. An object between the sensor
and reflector is senses when it interrupts the beam. Medium sensing


Separate emitter and receiver provide maximum detection range
and most positive type of sensing for opaque objects. When an
object interrupts the beam from emitter to receiver, the object is

Operation of 2-wire and 3-wire sensors

A/C 2 Wire NO

2-Wire Devices: 2-wire sensors are intended to be connected tin
series with the controlled load. Because these sensors derive the
power to energize their internal electronics through the load they
control, a minimum current is drawn through the load when the
sensor is in the open stat. This current is so small that it can be
ignored and will not turn on electro-mechanical devices such as
relays and solenoids. However, this current could be enough to
operate an electronic load. Cutler-Hammer’s 2-wire sensors have the
lowest leakage current in the industry and are suitable for many
electronic loads.

A/C 3 wire NO/NC or DC PNP

3-WIRE DEVICES: 3-wire sensors derive their power directly
across the line and therefore have no current leakage to the

Operation of Logic Modules
On Delay Adjustable delay between time object is sensed and time switch
function occurs.
Off Delay Adjustable delay between time object leaves sensing field &
time switch transfers back to non-sensing state.
On & Off Combination of Above.
Delayed Single Shot Adjusts length of time switch remains in “ON’ cycle after
object is sensed regardless of length of time object stays in
sensing field. “ON” cycle can also be delayed after object is first