Technical terms and keywords

What exactly is a 'nominal sensing range'? What does 'correction factor' mean? You will find an overview of technical terms related to sensor technology together with concise and clear explanations. Save yourself a laborious search and simply read it up here. You will find more detailed information in our specialist knowledge area – benefit from our know-how!

10 … 30 V
Voltage range The sensor may be operated at any voltage between 10 V and 30 V. At 10 V or less the sensor either works incorrectly or not at all. At more than 30 V it may sustain damage or even be destroyed.
1500 Hz
Hz stands for 'Hertz'. This unit of measurement indicates the number of binary switch-on / switch-off processes per second. Here: at most 1500 switch-on / switch-off processes per second. However, the sensor could just as well only be switched on once for 5 seconds in the course of a year – i.e. switch very seldom.
15 mA
Current consumption
3-wire technology
Two separate connection conductors for supplying the sensor with energy. Plus a signal output conductor. '3-wire technology' indicates a particular way of supplying the sensor with energy. It may or may not correspond with the number of wires present. There are 3-wire devices with 4 or even 8 connecting wires. But such devices are not referred to as 4-wire or 8-wire devices. Only the 2-wire device has only 2 connecting conductors. In this case, the energy is supplied via the same conductor that is used for the switching signal (energy supply: leakage current).
Abbreviation for aluminium.
Determination of the switching function of the signal output. E.g. NO (normally open) or NC (normally closed).
Operating voltage
Order of magnitude of the supply voltage for the sensor in terms of voltage type and range.
Background suppression
Distance range within which diffuse reflection sensors and optical distance sensors do not detect objects in the beam path (behind the object to be registered).
The sensing face of the sensor may engage flush with the metal installation environment, but it may also go beyond it.
Clamping range d [mm]
Settable diameter values for fixing straps for cylinder sensors
Travel speed
Maximum value for the speed with which a cylinder piston may traverse such that the cylinder sensor still switches.
Abbreviation for copper.
The combination mark of the UL company that includes the USA and Canada and is recognized by both countries. Devices displaying this mark satisfy the requirements of both countries.
DC: Direct Current – aka direct-current voltage
see PNP and DC
Electrical connection
The way the sensor is electrically connected. The primary techniques are: cable connection, clamping space connection, plug connection.
Electrical design
A general term that covers voltage type, polarity and switching function of a sensor's electronics and signal output.
Abbreviation for Electro-Magnetic Compatibility. Electromagnetic compatibility refers to a state – usually the desired state – in which technical devices do not interfere with each other on account of unwanted electrical or electromagnetic effects.
Current output [mA] – maximum load
Maximum load resistance for a sensor with 4-20 mA current output
Current output [mA] – minimum load
Minimum load resistance for a sensor with 0-10 V voltage output
EN 60947-5-2
European Standard for low-voltage switchgear and control gear, Part 5-2: Control circuit devices and switching elements - Proximity switches.
Vibration resistance
Capacity to withstand vibrations (measured as a multiple of the gravitational acceleration g)
Immunity to extraneous light [klx]
Maximum light intensity coming from an external source of light (e.g. sunlight) that a photoelectric sensor can receive without this causing interference
Housing materials
All the materials that are used for the housing of a sensor. Generally a combination of metals and plastics.
Assured sensing range Sa
The assured sensing range (Sa), also known as the operating sensing range, takes the effects of supply voltage, temperature and sample scatter on the sensor's sensing range into account. Between 0% and 81% of the nominal sensing range, reliable switching with standard target is guaranteed under all permissible operating conditions. Sa <= 0.81 of the nominal sensing range Sn.
Shock resistance
Capacity to withstand mechanical impacts (measured as a multiple of the gravitational acceleration g)
Alternative designations are initiator, inductive proximity switch, proximity sensor, position sensor. An inductive sensor is a sensor that reliably detects metallic objects without touching them and reports this by means of an electrical switching signal.
IO-Link device ID
Identification number for IO-Link devices
IO-Link revision
Version number for IO-Link, currently 1.1
Complete protection against contact with electrically conducting parts. Protection against ingress of dust, protection against water jets.
Complete protection against contact with electrically conducting parts. Protection against ingress of dust, protection on immersion in water under defined conditions: 1 m depth of water and 30 minutes duration.
Complete protection against contact with electrically conducting parts. Protection against ingress of dust, protection on immersion in water under defined conditions: 1 m depth of water and 7 days duration.
Complete protection against contact with electrically conducting parts. Protection against ingress of dust, protection against water during high-pressure / steam jet cleaning; specifically for road vehicles. Also a marking for use in the foodstuffs and pharmaceutical industries.
If the material of the damping object for the sensor differs from that of the standard target, sensing ranges arise that differ from the sensor's real sensing range Sr. They can be calculated with the aid of correction factors that are given in the technical data. Example: Nominal sensing range 20 mm, real sensing range 19.6 mm, correction factor (metal) for aluminium 0.4: This means that the current real sensing range to this material is 19.6 mm x 0.4 = 7.8 mm.
Short-circuit protection
Protection function for the sensor's signal output. If the load current significantly exceeds the rated current load capacity, the signal output automatically throttles the flow of current to a value that it can cope with.
Short-circuit protection cycled
If the load current significantly exceeds the rated current load capacity, the signal output is switched off. It switches back on again after a short time. If the current is still too high, the device switches off again. This process is repeated as long as the measured current value remains harmful for the signal output.
Plastic. Abbreviation for Liquid Crystal Polymer. A class of aromatic polymers displaying liquid crystal properties. Excellent dimensional stability and rigidity at very high temperatures. Very good strength characteristics. Low thermal expansion. Flame-retarding characteristics. Used in pump construction, electrical and electronics industries, protective clothing, space technology, sports equipment.
LED display
LED: Light-emitting diode. Source of light. Yellow LED: The signal output of the sensor has switched. Green LED: The sensor is electrically connected and under tension.
Type of light
Colour and wavelength of the light involved. nm – nanometre.
Metric thread. 12 mm diameter. 1 mm thread pitch.
Metric thread. 18 mm diameter. 1 mm thread pitch.
Metric thread. 30 mm diameter. 1.5 mm thread pitch.
Metric thread. 8 mm diameter. 1 mm thread pitch.
M8 – connector – gold-plated
Connector for the electrical connection to the sensor with 8 mm thread diameter. The pins have a brass core and they are gold-plated for better chemical resistance. With M8 connector; attention must be paid to the number of poles in the plug. A 3-pole M8 cable socket cannot be connected to a 4-pole plug and vice-versa.
Measuring range [m]
Range of distances that a photoelectric sensor can register and evaluate.
Measuring frequency [Hz]
Frequency with which optical distance sensors take measurements (PMD devices)
Abbreviation for brass. Brass is an alloy made of copper and zinc. It usually contains around 35% zinc. Brass has a density of approximately 8.5 g/cm3 and it melts at around 900 °C. Like copper, it can be readily shaped hot or cold, and it is more tensible than copper. Brass readily conducts heat and electricity. Brass can be cold forged well, and then 'relaxed' by means of subsequent heat treatment. Drills and saws should be relief ground and a relatively large point angle should be chosen. Like copper, brass is well suited to brazing and adhesive bonding. Brass is "Messing" in German.
Abbreviation for 'Mean Time To Failure'. A term from the area of safety technology. The MTTF indicates the reliability of the components used in a control system. It is one of several parameters that contribute to determining the performance level (PL). In DIN EN ISO 13849-1, the MTTFd is defined as the 'Mean Time To Dangerous Failure'.
The nominal sensing range describes the maximum distance a standard target may be removed from the sensor such that the sensor can still switch. It does not take production tolerances, temperatures or voltage fluctuations into account and therefore represents a theoretical value. It is also known as the 'rated sensing range'. A standard target is made of the material ST37 (mild steel), it is square and has a side length of 3 times Sn or the diameter of the sensing face, whichever is the greater. It is flat and even and one millimetre thick.
The sensing face of the sensor may on no account lie flush with the metal installation environment.
Polarity of the signal output – switching direction. The switching direction points towards plus. The minus or zero potential of the supply voltage is switched by the signal output. A characteristic of the NPN technology is that the load is permanently associated with plus. The opposite case is termed PNP switching.
points towards minus. The plus potential of the supply voltage is switched by the signal output. A characteristic of the PNP technology is that the load is permanently associated with minus. The opposite case is termed NPN switching.
Pressure resistance [bar]
Pressure value that the sensor can withstand without damage over an indefinite period
Process data analogue
Output signal in the form of 4-20 mA current or 0-10 V voltage
Process data binary
Output signal logical 0 or 1
Specific device parameters for IO-Link sensors
PWM (pulse width modulation)
Pulse width modulation (PWM for short) is a standard procedure for modulating a signal that changes between two values (e.g. one and zero). The modulation changes pulse length and the frequency of the signal. In practice, LEDs can be dimmed in this way, as the rapid switching on and off is perceived by the human eye only as a change in luminosity. PWM signals are generated with suitable I/O boards and are common in mobile PLCs.
90% to 110% of the nominal sensing range
Response sensitivity
Value of the magnetic field strength in mT at which a magnetic sensor switches
Salt spray test
Standardized corrosion resistance test for sensors
The sensing range is the physical displacement at which a metallic measurement plate approaching the sensing face triggers a signal change at the output. The signal output remains switched within the sensing range.
The switching frequency refers to the maximum number of binary switch-on and switch-off signal output operations per second. Ideally, the switch-off time is twice the length of the switch-on time.
Switching status
Visual display (LED) of the switching status of the binary signal output. For inductive proximity sensors, the switching status is indicated by means of a yellow LED on the device.
Normally open
A switching function of a binary signal output. If a sensory event occurs in the active range, the switching signal changes from 'Off', 'Low' or '0 volts' to 'On', 'High' or to the operating voltage (e.g. 24 VDC).
The protection rating is an indication of the suitability of electrical equipment for a range of environmental conditions, as well as the degree of protection for people using it with regard to potential hazards. Protection ratings are determined according to DIN 40 050. Protection ratings are indicated by means of internationally valid abbreviations (IP = International Protection (marking)). The abbreviation IP is followed by two digits as well as two additional letters if required. The first digit indicates the degree of protection against the ingress of solid bodies. The second digit indicates the degree of protection against the ingress of water at room temperature.
Protection class
The protection classes are designed for the categorization and marking of electrical equipment. They provide information regarding the safety measures in place to prevent electric shock. There are four protection classes: 0, I, II, III. Equipment is marked with the aid of symbols.
Protection class III equipment operates with so-called SELV, which stands for 'Safety Extra Low Voltage'. This means that no special protection is required. Protection class II devices have enhanced or even duplicated insulation to the housing. Protection class I is the protective earth (yellow-green connection wire).
SDCI Standard
Single-drop digital communication interface for small sensors and actuators in accordance with IEC 61131-9
Adjustment range [mm]
For a capacitive sensor, the adjustment range is the range within which it can be set using a potentiometer or teach keys. Depending on the medium / target, the adjustment range can vary in terms of values / displacements.
Shock resistance
Capacity to withstand mechanical impacts (measured as a multiple of the gravitational acceleration g)
SIO mode
Standard input-output mode for IO-Link devices
Voltage drop
The voltage drop or IR drop is a potential difference existing between two points of a resistor through which current flows – in this case the signal output of the sensor between the connection pins 1 and 4. When the sensor signal output is in the through-connected state, only the voltage value reduced by the given amount is available to the connected load (relay, PLC input).
Construction steel according to DIN 17100. Unalloyed and untreated (usually hot rolled or normalized). Construction steels are identified by 'St' and the minimum tensile strength. Common constructions steels are, for instance: St33, St34, St37, St42, St50, St60. The carbon content increases with increasing tensile strength. For a 'St34' steel, this is 0.17%, and for a 'St50' steel around 0.2%.
Power-on delay time
The time that elapses before the sensor is ready for operation.
Long-term shock resistance
Capacity to withstand regularly occurring mechanical impacts (measured as a multiple of the gravitational acceleration g)
The type of electrical connection.
Current consumption
Current required to supply the device itself with energy. The value specified in the data sheet for 3-wire devices applies to through-connected devices without load.
Current carrying capacity
The maximum load current for the signal output of the sensor. If this amount is exceeded, the sensor's protective functions such as overload protection and short-circuit protection are triggered. Without such protective functions, the sensor would be destroyed by excessive loads.
supply class 2
Part of the UL approval.
Switch point drift [% of Sr]
Temperature-related deviation of the switch point
Temperature range
The temperature range indicates the temperatures at which the proximity sensor can be used. Full functionality can only be guaranteed if the sensor is operated within the specified temperature limits.
Transfer type
Specification of the interface with transfer rate for IO-Link devices
The sensor may be operated while exceeding the specified current carrying capacity of the signal output. If a certain current value is exceeded, the short-circuit protection triggers. If the overload is very large, the ambient temperature of the sensor's installation space must not be high, even if the temperature is still within the temperature range specified in the data sheet.
Stainless steel. V2A stands for the X12CrNi18-8 alloy type, or alternatively 1.4300. No longer produced. These days, the designation V2A is used for the successor material 1.4301 (X5CrNi18-10).
Stainless steel, similar to V2A. However, it also contains 2% molybdenum (Mo) that makes it more resistive to corrosion due to media containing chlorides such as found in salt water, swimming pools, the chemical industry etc. The general designation for V4A is 1.4401 (X5CrNiMo17-12-2).
Reverse polarity protection
The conductors can be connected wrongly without risk of damage to the sensor – but it will not function or not function correctly. If the connection fault is then corrected, the sensor will work properly.