Classification of Sensors by Measurand (What They Measure) with Examples

A sensor is commonly classified by its measurand—the specific physical quantity the sensor responds to (e.g., temperature or pressure). This measurand-based view is a practical way to organize sensor families used in instrumentation and control, as noted in common sensor classification references.2

Footnotes

1. Sensors and Transducers: Principles Explained - Notes that sensors are classified by the physical quantity (measurand) they measure. ↩

2. Sensors and Transducers Classification - Discusses classification methods and states measurand-based classification as common and practical. ↩

Key measurand groups (what to remember)

Typical measurand categories include: thermal (temperature), fluid (pressure/flow/level), mechanical (displacement/position; velocity; acceleration), force & strain (load; stress), optical (light), chemical (gas/ions), and radiation/acoustic quantities. Several “list of sensors” references explicitly group sensors by these measurement categories (e.g., temperature, pressure, flow, position, optical, chemical, radiation, and vibration/sound).

This section will walk through the major measurand categories and give representative real-world examples for each.

Footnotes

1. Sensors and Transducers Classification - Discusses classification methods and states measurand-based classification as common and practical. ↩

1) Thermal measurands: temperature / heat

Temperature sensor measures temperature or thermal energy effects (often called heat).

Common sensor examples:

• Thermocouple: high-temperature industrial measurement.
• RTD: precision temperature measurement.
• Thermistor: fast, compact temperature sensing.
• IR (infrared) thermometer: temperature measurement of moving targets.

Thermal categories are explicitly represented in sensor lists under “Thermal, heat, temperature.”

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

2) Fluid pressure measurands

Pressure sensor measures pressure or vacuum (negative pressure). Pressure is a dominant measurand in instrumentation and appears as its own sensor category in general sensor lists and guides.2

Representative examples:

• Piezoresistive pressure sensor: common in transducers for industrial pressure ranges.
• Strain-gauge pressure transducer: robust and accurate for many process pressures.
• Diaphragm-based sensors: widely used in compact sensors.

Pressure measurement references describe use of piezoresistive sensing elements and compensation approaches in typical devices.

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

2. Pressure measurement - Wikipedia - Describes common pressure sensor principles including piezoresistive pressure sensors and compensation. ↩ ↩² ↩³

3) Fluid flow measurands (flow rate / velocity in fluids)

Flow sensor detects flow or flow-related quantities like volumetric flow rate.

Examples by measurand category:

• Differential pressure (DP) flow measurement: used in orifice-plate type methods.
• Turbine flow meter: measures flow through mechanical rotation.
• Vortex shedding meter: used for many industrial liquids and gases.
• Ultrasonic flow meter: clamp-on or inline options.

Flow is explicitly called out as a common sensor category (“Flow, fluid velocity”) in sensor listings. Instrumentation sources also describe flow measurement approaches in terms of fluid velocity and pressure/force/constriction concepts.

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

2. Instrumentation measurement principles | PPSX (Slideshare) - Includes descriptions of flow measurement concepts and meter examples (orifice/DP, turbine, vortex, ultrasonic, etc.). ↩

4) Liquid/gas level measurands

Level sensor measures level.

Representative examples:

• Float level switch: simple on/off level detection.
• Capacitive level sensor: works with many liquids and granular solids.
• Ultrasonic level sensor: contactless level measurement.
• Radar level sensor: high accuracy for industrial tanks.
• Hydrostatic level sensor: uses pressure at the bottom to infer height.

Sensor lists explicitly separate “Force, density, level” as a category. Instrumentation guidance also highlights common level sensor technologies (radar/float/ultrasonic/hydrostatic).

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

2. Pressure, level, temperature and flow instrumentation - Mentions level sensing technologies such as radar, float, ultrasonic, and hydrostatic sensors. ↩

5) Mechanical displacement & position measurands

Position sensor captures displacement and position.

Examples:

• Potentiometer: common for analog displacement/position.
• Optical encoder: accurate rotational position.
• Inductive proximity sensor: non-contact position/proximity.
• Hall-effect position sensors: robust for machinery and automotive sensing.
• LVDT: high-resolution analog displacement.

NPTEL-style sensor taxonomy highlights measurand-based grouping such as “Displacement, position and proximity sensors,” including potentiometer, capacitive elements, eddy-current proximity, optical encoders, and Hall-effect sensors. General sensor lists also explicitly reference “Position, angle, displacement, distance, speed, acceleration.”

Footnotes

1. Module 2: Sensors and signal processing Lecture 1 (NPTEL PDF) - Shows measurand-based sensor grouping (e.g., displacement/position/proximity) with example sensor types. ↩

2. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

6) Motion, velocity & acceleration measurands

Acceleration sensor and velocity sensor fall under dynamic mechanical measurands.

Examples:

• Accelerometer: phone IMUs, vibration monitoring.
• Gyroscope (angular velocity): inertial navigation and stabilization.
• Doppler-based velocity sensing: some fluid/target velocity measurement systems.
• Radar speed sensor: vehicle speed measurement.

“Position, angle, displacement, distance, speed, acceleration” and “Flow, fluid velocity” both appear as explicit categories in sensor listings.

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

7) Force, load, strain & stress measurands

Force sensor measures force and related quantities like strain and stress.

Examples:

• Strain gauge: used for strain/force/weight measurement.
• Load cell.
• Torque sensor.

Sensor listings explicitly include “Force, density, level” and include strain gauge/load-cell type sensors as common examples.2

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

2. Sensors and Transducers Classification - Discusses classification methods and states measurand-based classification as common and practical. ↩

8) Optical measurands: light intensity, imaging, presence

Optical sensor measures light-related measurands such as light intensity or uses imaging for spatial information.

Examples:

• Photoresistor (LDR): ambient light detection.
• Photodiode: fast light sensing.
• Phototransistor: switching and detection.
• Camera/CMOS imaging sensor: machine vision.
• PIR sensor: motion detection.

Sensor catalogs list optical categories (“Optical, light, imaging, photon”) explicitly.

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

9) Chemical measurands: concentration, pH, ions, oxygen, gases

Chemical sensor measures chemical measurands such as gas concentration, ion activity, or pH.

Examples:

• Electrochemical oxygen sensor: exhaust gas control.
• Gas sensor (MOS/chemiresistors): air quality monitoring.
• pH sensor: water/food/process monitoring.
• Biosensor: medical diagnostics.

Sensor lists explicitly include chemical-related sensor categories (chemical/ionizing/gas categories) and “Environment, weather, moisture, humidity” among others. Wikipedia also discusses chemical sensing as a significant sensor theme.

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩

2. Sensor - Wikipedia - Discusses chemical sensing and examples of sensors for chemical properties and analytes. ↩

10) Radiation & acoustic measurands (sound/vibration and ionizing radiation)

Acoustic / vibration / sound

Vibration sensor measures dynamic motion in structures. Examples:

• Piezoelectric vibration sensors (common in monitoring)
• Microphones for sound intensity

Sensor lists explicitly separate “Acoustic, sound, vibration.”

Ionizing radiation

Radiation sensor measures radiation such as alpha/beta/gamma or subatomic particle events. Example categories:

• Geiger-Müller counters
• Scintillation detectors

Sensor listings include “Ionizing radiation, subatomic particles.”

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩ ↩²

Consolidated reference table (measurand → sensor examples)

Footnotes

1. List of sensors - Wikipedia - Provides a categorized overview including thermal, pressure, flow, position/speed/acceleration, optical, force/level, chemical, acoustic/vibration, and ionizing radiation groups. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

2. Pressure measurement - Wikipedia - Describes common pressure sensor principles including piezoresistive pressure sensors and compensation. ↩

3. Instrumentation measurement principles | PPSX (Slideshare) - Includes descriptions of flow measurement concepts and meter examples (orifice/DP, turbine, vortex, ultrasonic, etc.). ↩

4. Pressure, level, temperature and flow instrumentation - Mentions level sensing technologies such as radar, float, ultrasonic, and hydrostatic sensors. ↩

5. Module 2: Sensors and signal processing Lecture 1 (NPTEL PDF) - Shows measurand-based sensor grouping (e.g., displacement/position/proximity) with example sensor types. ↩

6. Sensor - Wikipedia - Discusses chemical sensing and examples of sensors for chemical properties and analytes. ↩