Namco Controls Proximity Sensor Glossary

Glossary

Proximity Sensor
Information

Axial Approach: The approach path of a target whose
center is the same as the centerline of the sensing field.

Capacitive Sensor: A solid state switch which senses
a changing dielectric mass. Usually adjustable and able to
sense most materials.

Complementary Output: A form “C” type output
(normally open and normally closed) which changes state
simultaneously when the sensor is actuated.

Proximity Sensors

Current Consumption (No Load Current): This

is the current consumption of a proximity sensor when the
output transistor is in the off state. It is indicated at the
maximum voltage rate.

Current Sinking (NPN): A negative switching output
in which the load current passes through the load first, then
“sinks” through the sensor.

Current Sourcing (PNP): A positive switching output
in which the current for the load is “sourced” through the
sensor.

Differential: The difference between the operating point
and the release point of a sensor.

LED: Namco proximity sensors feature a light emitting diode
to indicate with a red LED that the sensor output is conduct­ing. WFI proximity sensors have a red LED to show unit is
powered up and a green LED to indicate target is present.

Maximum Load Current: This is the maximum load at which
a proximity sensor may be operated continuously.

Minimum Load Current: The minimum current necessary to
assure proper output operation.

Operate Point: The point at which a target is sensed. (See
Fig. 1)

Release Point: The point at which the sensor returns to a
non-energized state as the target leaves the sensing field.
(See Fig. 1)

Repeatability: The relative variation in effective
operating distance measured repeatedly over an established
period of time during which environmental and electrical
conditions, (i.e., applied voltage, temperature, relative
humidity, mounting, etc.) are held constant.

Response Time: The time delay between when the target
appears at the operate point and the output is energized.

Dwell Time: The minimum time needed for a particular
target to be in the sensing field for the output to be energized
or de-energized.

Eddy Currents: Small circular currents induced on the
surface of a metallic target by an inductive sensor.

Hysteresis: The difference between the operating point
and the release point of a sensor. (See Fig. 1)

Inductive Sensor: A solid state switch which emits a
small directional radio frequency field. When a metallic target
enters the field, eddy current losses are created thereby
loading the oscillator. If this loading exceeds an internal
setpoint, the output of the sensor is energized.

Interference Protection: All Namco proximity
sensors feature an interference protection circuitry. This
feature assures that voltage peaks or release interference
caused by relays does not destroy the proximity sensor.

Leakage Current: The current which flows through the
load when the sensor is non-energized. Also called burden or
residual current.

release point
operate point

sensing range

proximity sensor

moving direction

Figure 1

standard

target

hysteresis

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Namco • 2013 West Meeting Street • Lancaster, SC 29720 • 1-803-286-8491 • FAX: [phone]

Reverse Polarity Protection: Usually a diode inserted in one
of the power leads of a D.C. Switch. This protects the internal
circuitry if connections are accidentally reversed.

Sensing Range: The distance from the sensing face to a
standard target at a specific temperature (usually 77°F).
Most industrial type sensors usually will hold this range +/­10% of rated sensing range. (See Fig. 1)

Range

Nominal
Range

Shielded Sensor: A sensor which has a very direc­tional sensing field. This allows the sensing face to be flush
mounted in metal.

Short Circuit Protection (SCP): Internal circuitry
which protects the sensor against accidental short circuits.
SCP is not intended to protect other control circuit compo­nents or interconnecting wiring.

Standard Target: A mild steel plate 1mm thick, with
sides equal to the diameter of the sensing face or 3 times
rated sensing range, whichever is greater. (See Fig. 1)

Switching Frequency: The maximum speed at
which a sensor will deliver discrete individual pulses as the
target(s) enter and leave the sensing field. This value is
always dependent on target size, distance from sensing face,
speed of target and switch type. The catalog values given are
obtained using a standard target.

Temperature Drift: The temperature drift indicates
the change of the switching point caused by ambient
temperature variations within the range of -13°F to +158°F.
The temperature of the measuring plate does not influence
the switching point. The switching point at -13°F to +158°F
may vary up to 10% compared to the point measured at
+68°F. (See Figure 2.)

+32˚ +68˚ +104˚ +140˚ +176˚

-4˚

Temperature (˚F)

Figure 2

Proximity Sensors

Unshielded Sensor: A sensor which has an extended
sensing range for its size. Must not be flush mounted in
metal unless a counterbore is cut such that the sensor is
not influenced by the surrounding metal.

Voltage Drop: The difference in voltage at the load

measured with and without the sensor in a circuit. Must be
taken into account when designing with any 2-wire device.

2013 West Meeting Street • Lancaster, SC 29720

1-803-286-8491 • FAX: [phone]

www.namcocontrols.com

For technical assistance, call 1-800-NAMTECH

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