Sensor Glossary of Technical Definitions and Terminology
Active Surface:
Portion of the sensor from which the electromagnetic field radiates.

Analog Output:
The output voltage is proportionately to the distance of the target to the sensor's active surface.

Complementary Outputs (N.O. & N.C.):
A proximity sensor that features both normally open and a normally closed output, which can be used simultaneously.

Correction Factors:
Multiplication factors taking into account variations in the target material composition. When calculating actual sensing distance, this figure should be multiplied by the normal sensing distance, Sn.

Current Sinking: See NPN

Current Sourcing: See PNP

Damping Material:
Material which causes a decrease in the strength of the electromagnetic or electrical field produced by the sensing coil.

Differential Travel: See Hysteresis.

Dynamic Output:
A sensor output that outputs a short pulse of a defined period when a target is detected.

Effective Operating Distance - 'Sr':
The operating distance of an individual proximity switch measured at stated temperature and voltage. It takes into account variations in manufacturing tolerances.

Ferrous Metal: Any metal containing iron.

Flush Mounting:
A shielded or embedded proximity sensor can be flush mounted in metal. It can be surrounded by metal up to the active sensing face.

The difference, in percentage (%),of the nominal sensing distance between the operate (switch on) and release point (switch off) when the target is moving away from the sensor's active face. Without sufficient hysteresis a proximity sensor will "chatter" (continuously switch on and off) when there is a significant vibration applied to the target or sensor.

Leakage Current:
Current which flows through the output when the output is in an "off" condition or de-energized.

Light Emitting Diode used to indicate sensor status.

A device that consumes power to perform a function.

Maximum Load Current:
The maximum current at which the proximity sensor can be continuously operated.

Minimum Inrush Current:
The maximum current level at which the proximity sensor can be operated for a short period of time.

Minimum Load Current:
The minimum amount of current required by the sensor to maintain reliable operation.

Namur Sensor:
A 2-wire, variable resistance sensor which requires a remote amplifier for operation. Typically used in intrinsically safe applications.

Nominal Sensing Distance:
The distance,Sn, at which an approaching target activates (changes state of) the proximity output. This is also called the rated operating distance.

Non-Ferrous Metal:
Any metal which does not contain iron.

Non-Flush Mounting:
Unshielded, or non-embeddable sensors must have a so called "free zone" around the sensor head, with no non-target metal present to operate satisfactorily.

Normally Closed:
Output opens when an object is detected in the active switching area.

Normally Open:
Output closes when an object is detected in the active switching area.

The sensor switches the load to the positive terminal. The load should be connected between the sensor output and positive terminal.

Operating Distance, Assured:
Between 0 and 81% of the rated operating distance for inductive proximity switches. It is specified as Sa.

Operating Distance, Rated:
The operating distance specified by the manufacturer and used as a reference value. Also known as nominal sensing distance, Sn.

Overload Protected:
The ability of a sensor to withstand load currents between continuous load rating and a short circuit condition without any damage.

The sensor switches the load to the negative terminal. The load should be connected between the sensor output and negative terminal.

Programmable Output, (N.O. or N.C.):
Output which can be changed from N.O. to N.C. or N.C. to N.O. by way of a switch or jumper wire. Also known as selectable output.

Rated Operating Distance - 'Sn':
Sometimes called nominal operating distance, it does not take into account manufacturing tolerances or variations in temperature or voltage.

The repeat accuracy of a sensor to detect an object at the same distance away from the active sensing face. It is expressed as a percentage of the sensing distance, or can be calculated as a specific measurement value.

Residual Voltage:
The voltage across the sensor output while energized and switching the maximum load. It is the voltage drop across the sensor.

Response Time: See Switching Frequency

Reverse Polarity Protection:
Proximity sensors which are protected against a reversal in voltage polarity.

The variance between peak-to-peak values in DC voltage. It is expressed as a percentage of rated voltage.

Sensing Face:
A surface of the proximity sensor parallel to the target, from which the operating distance is measured

Sometimes called Flush or Embedded.

Short Circuit Protection:
Sensor protected from damage when a shorted condition exists for an indefinite period of time without change.

Static Output:
A sensor output that stays energized as long as the target is present.

Supply Current:
The current consumed by the proximity switch when the output transistor is in the off condition.

Switching Frequency:
The maximum number of times per second the sensor can change state, (ON and OFF), usually expressed in Hertz (Hz)., as measured by DIN EN 50010.

Object which activates the sensor.

Temperature Drift:
Specification used to indicate the change in switching point caused by temperature variations within a specified ambient temperature range. Expressed as a percentage of the sensing distance.

Useable Operating Distance - 'Su':
The operating distance measured over a voltage range of 85% to 110% of its rated voltage. It allows for manufacturing tolerances.

Voltage Drop:
The maximum voltage drop across a conducting sensor.

Weld Field Immunity (WFI):
The ability of a sensor not to false trigger in the presence of strong electromagnetic fields.

Wire Break Protection:
The output is off if either power supply wire is broken.


Trogamid T – Polyamide, used in cylindrical, block and limit style sensors. Hard, rigid, good resistance to chemicals, resists caustic cleaners, approved for food contact.

Polybutelyne terephthalate, used in block sensors and front caps of cylindrical nickel plated brass units. Excellent mechanical strength and temperature resistance. Self-extinguishing and flame retardant. Weld splash proof.

Polyamid (Nylon), used in limit style sensors. Excellent mechanical strength, temperature resistant, accepted in food industry.

Acrylonitrile-Butadiene-Stypol. Used in ring sensors. Impact resistant. Rigid.

Polyurethane, used in cables and cable assemblies. Elastic, abrasion proof, impact resistant, unaffected by oil, grease and solvents.

Polyvinylchloride, used on cables and cable assemblies. Good mechanical strength, resistant to chemicals.

Used on weld immune cylindrical sensors. Highest resistance to high temperature and chemicals.

Brass, Nickel Plated, used on cylindrical sensors. Rugged, resists thread damage. Aluminum, used on block and ring sensors. Lightweight, excellent strength to weight ratio. Resistant to corrosion.

For more information contact Altech at:
908-806-9400 • 908-806-9490 (FAX) • • 35 Royal Road, Flemington, NJ 08822