Sensors: Types of Industrial Sensors and How They Work

Definition: A sensor is a device that detects a physical condition or property, such as temperature, pressure, vibration, flow, or current, and converts it into a signal that can be measured, recorded, or used to trigger an action. Sensors are the interface between the physical world and the digital systems that monitor, control, and analyze it. In industrial facilities, sensors are the foundation of equipment health monitoring, process control, and safety systems.

How Sensors Work

Every sensor performs two core functions: detection and conversion. The sensing element detects a physical stimulus, and the transduction mechanism converts it into an electrical signal. That signal, typically a voltage, current, resistance change, or digital output, is then processed, transmitted, and interpreted by a connected system.

For example, a temperature sensor contains a sensing element such as a thermocouple, RTD (resistance temperature detector), or thermistor. Each responds to temperature differently: a thermocouple generates a small voltage proportional to temperature, an RTD changes resistance predictably with temperature, and a thermistor has a large resistance change over a narrow temperature range. The signal is conditioned, scaled to engineering units, and output as an analog or digital value.

The same detect-and-convert principle applies to every sensor type. A pressure sensor's diaphragm deforms under applied force. A vibration sensor's piezoelectric element generates charge when accelerated. A flow sensor measures the effect of fluid movement on a sound wave, magnetic field, or rotating element. What changes is the physical phenomenon being detected and the transduction technology used to convert it.

Types of Industrial Sensors

Industrial facilities use a wide range of sensor types. The table below covers the most common categories, with links to detailed pages for the sensor types most relevant to equipment maintenance.

Sensor Type What It Measures Key Maintenance Applications
Vibration sensor Acceleration, velocity, displacement across frequency spectrum Rotating machinery: motors, pumps, fans, compressors, gearboxes
Temperature sensor Surface or ambient temperature (thermocouple, RTD, thermistor, infrared) Bearings, motors, electrical panels, heat exchangers, ovens
Pressure sensor Gauge, absolute, or differential pressure in fluids and gases Hydraulic systems, compressed air, lubrication lines, process pipelines
Flow sensor Rate or volume of fluid moving through a pipe or channel Cooling water, lubricant circuits, compressed air, process lines
Current / power sensor Electrical current draw, power factor, energy consumption Electric motors, drives, compressors, HVAC, energy management
Ultrasonic sensor High-frequency sound waves; detects leaks, bearing wear, electrical discharge Compressed air leaks, slow-speed bearing monitoring, valve condition
Acoustic emission sensor Stress waves from material defects, friction, or crack propagation Slow-speed bearings, gearboxes, structural monitoring
Proximity / position sensor Presence, absence, or position of an object Machine guarding, conveyor position, valve open/close status
Humidity / moisture sensor Relative humidity or moisture presence Electrical enclosures, HVAC systems, storage environments
Gas sensor Concentration of specific gases (CO, H2S, O2, VOCs) Confined space entry, chemical plants, refineries, food production

Sensor Output Types

The output signal a sensor produces determines how it connects to control and monitoring systems. Choosing the right output type is part of sensor selection.

Output Type Description Common Use
4-20mA analog Current loop signal; 4mA = minimum range, 20mA = full range Process instrumentation; long cable runs; noise-resistant
0-10V analog Voltage proportional to measured value HVAC, building automation, simple process monitoring
Digital (on/off) Binary output triggered by a threshold Limit switches, proximity sensors, alarm contacts
HART Digital communication overlaid on 4-20mA; enables remote configuration Process instrumentation in facilities with existing 4-20mA infrastructure
Modbus / Profibus / OPC-UA Industrial digital bus protocols for networked sensor communication Automation systems, PLCs, SCADA integration
Wireless (BLE, LoRaWAN, Wi-Fi) No wiring required; data transmitted to a gateway or cloud platform IIoT condition monitoring; retrofit installations; remote assets

Sensors in Industrial Maintenance

In a maintenance context, sensors serve one primary purpose: giving the maintenance team visibility into what equipment is doing between inspections. Manual inspection rounds capture a snapshot of equipment condition at a single moment. Sensors capture a continuous stream.

That difference is what makes predictive maintenance possible. A bearing that is developing a fault will show changes in its vibration signature weeks or months before it fails. A heat exchanger that is fouling will show a gradual rise in outlet temperature over days or weeks. A hydraulic pump that is wearing internally will show a slow decline in system pressure. None of these trends are visible in a weekly inspection round. All of them are detectable with continuously monitoring sensors.

When sensor data is aggregated into a condition monitoring platform, the system establishes baselines for each asset and alerts the team when readings deviate from those baselines. The alert is the signal to investigate. The sensor trend is the evidence that guides the diagnosis.

Connected Sensors: Industrial IoT

Traditional sensors output a signal that requires local wiring to a controller, PLC, or data logger. Industrial IoT sensors add wireless communication, allowing sensor data to be transmitted to cloud or edge platforms without dedicated cabling. This makes it practical to deploy sensors on assets that were previously too remote, too numerous, or too difficult to wire for continuous monitoring.

The key difference from traditional sensors is not what they measure but how the data gets to the people and systems that need it. An IIoT vibration sensor measures the same parameters as a hardwired vibration transmitter, but the data is accessible from anywhere, in real time, without manual retrieval.

Selecting the Right Sensor

Choosing a sensor for an industrial application requires matching several technical parameters to the operating environment and measurement requirements.

  • What needs to be measured: Start with the failure modes or process parameters you need visibility into. The measurement requirement determines the sensor type.
  • Operating environment: Temperature range, presence of chemicals, dust, moisture, vibration, and electrical noise all affect which sensor technologies and housings are appropriate.
  • Accuracy and range: The sensor must cover the full expected range of the parameter with sufficient accuracy for the decisions being made from the data.
  • Output and integration: The signal type must be compatible with the system receiving the data, whether that is a PLC, SCADA system, or IIoT platform.
  • Power source: Wired sensors need power supply infrastructure. Battery-powered wireless sensors trade some capability for deployment flexibility.
  • Maintenance of the sensor itself: Calibration schedules, cleaning requirements, and expected service life all factor into total cost of ownership.

Sensors that install in minutes and start delivering insights immediately

Tractian's industrial sensors monitor vibration, temperature, and other parameters on your critical assets and connect directly to the Tractian platform for real-time condition monitoring. No complex wiring. No specialist installation.

See Tractian condition monitoring

Frequently Asked Questions

What is a sensor?

A sensor is a device that detects a physical condition or property, such as temperature, pressure, vibration, or light, and converts it into a signal that can be measured, recorded, or used to trigger an action. Sensors are the interface between the physical world and the digital systems that monitor, control, and analyze it.

What is the difference between a sensor and a transducer?

A transducer converts one form of energy into another. A sensor is a type of transducer that specifically converts a physical condition into an electrical signal. In industrial practice the terms are often used interchangeably, but technically all sensors are transducers, while not all transducers are sensors.

What types of sensors are used in industrial maintenance?

The most common types in industrial maintenance are vibration sensors, temperature sensors, pressure sensors, flow sensors, current and power sensors, and ultrasonic sensors. Each targets specific failure modes: vibration sensors detect bearing and machinery faults, temperature sensors identify overheating, pressure sensors monitor fluid system integrity, and current sensors flag electrical anomalies in motors and drives.

How do sensors support predictive maintenance?

Sensors provide the continuous data stream that predictive maintenance depends on. By monitoring equipment parameters in real time and trending them over time, sensor data reveals gradual changes in equipment behavior that precede failures. When a reading deviates from its established baseline, the monitoring system generates an alert before the failure occurs, allowing the maintenance team to plan an intervention rather than respond to an emergency.

The Bottom Line

Sensors are how industrial facilities get eyes and ears on their equipment. Without them, equipment condition is only known at the moment someone walks past it. With them, the data is continuous, available remotely, and can feed analytics systems that detect developing problems long before they become failures.

The value of sensors is not in the devices themselves but in what becomes possible when equipment health data is available continuously and at scale. Predictive maintenance programs, condition-based work orders, and energy efficiency monitoring all start with sensors measuring what is actually happening on the plant floor.

Related terms