Sensor glossary: technical terms from A to Z
The most important terms in industrial sensing, explained briefly and clearly. Each entry works as a standalone definition.
A–F
- Absolute encoder
- An encoder that assigns each shaft position a unique value and knows it immediately after power-up, with no reference run. See absolute encoders.
- Analogue signal
- A continuously variable output signal, usually 4–20 mA or 0–10 V, that represents a reading such as pressure or temperature.
- Differential pressure
- The pressure difference between two measuring points, measured by pressure sensors for filter monitoring, for example.
G–N
- Hysteresis
- The gap between a sensor's switch-on and switch-off points, which prevents the output from chattering near the threshold.
- Inductive sensor
- A contactless proximity switch that detects metal only, via an electromagnetic field. See inductive sensors.
- IO-Link
- A standardised digital point-to-point link (IEC 61131-9) for transmitting readings, parameters and diagnostic data. See IO-Link.
- IP rating
- A code for protection against solid objects (first digit) and water (second digit), e.g. IP67 or IP69K.
- Capacitive sensor
- A contactless proximity switch that evaluates the change in capacitance within its fringe field. Besides metal it detects non-conductive materials such as plastic, glass, wood or liquids; what matters is the object's relative permittivity. The achievable switching distance therefore depends heavily on the medium.
O–Z
- PNP / NPN
- Two switching types of digital sensors: PNP switches the load to plus, NPN to ground. The choice has to match the controller input.
- Switching distance
- The distance at which a proximity sensor switches reliably. The nominal switching distance applies to a standardised target; real values depend on the material.
- Normally open / normally closed (NO / NC)
- A normally open contact closes on object detection; a normally closed contact opens it.
- Repeatability
- A measure of how consistently a sensor hits the same switching point under identical conditions.
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