Industrial sensors are a critical component of factory automation and Industry 4.0. Motion, environmental, and vibration sensors monitor equipment health, including linear or angular positioning, tilt sensing, leveling, and impact or fall detection. Specialized industrial motion sensors based on micro-electro-mechanical system (MEMS) components are suitable for Industry 4.0 applications, featuring wide mechanical frequency sensing bandwidth, high reliability, measurement stability, and accurate operation up to 105°C.
Industrial Automation Sensors
Industrial sensors are a critical component of factory automation and Industry 4.0. Industrial sensor systems are typically powered by 24V DC, which differs significantly from sensors in consumer systems powered by 3V or 5V supplies. Consequently, industrial sensor systems require additional power management to effectively drive the sensors. They utilize digital outputs, such as IO-Link, which connects directly to microcontrollers or even wireless transceivers. Analog data outputs are usually conditioned by operational amplifiers and linked to analog-to-digital converters (ADCs) within microcontrollers.
1. Environmental Sensors
In factory automation environments, environmental sensors measuring temperature, relative humidity, pressure, and audible noise are typically powered by 24V DC. These sensors commonly employ the IO-Link communication protocol to output data in digital format.
2. Image Sensors
As the core of machine vision systems, image sensing is primarily deployed in applications that compute physical objects, calculate their weight and volume, and inspect their shape. High Dynamic Range (HDR) image sensors provide a suite of critical features, including autofocus (AF) drivers and lens shading correction (LSC) algorithms, to support the design of high-performance industrial image sensors.
3. Motion and Vibration Sensors
Motion and vibration sensing and detection play a vital role in factory automation applications, including linear or angular positioning, tilt and leveling, motor condition monitoring, and impact and fall detection. Typically powered by a 24V DC rail, inertial sensors commonly use the IO-Link communication protocol to output data in analog or digital formats.
4. Proximity Sensors
Proximity sensors detect the presence or distance of nearby objects without physical contact. They can be constructed using various principles, including capacitive or inductive changes in response to metal targets or infrared light, or by measuring the time-of-flight (ToF) of photons within a light beam.
ST offers a range of MEMS motion and environmental sensors, 8-bit STM8 and 32-bit STM32 microcontrollers, and extensive connectivity solutions (wired or wireless, including IO-Link) to help sensor system designers successfully address these challenges.
Industrial automation sensors come in various types, including:
1. Temperature Sensors
Temperature sensors range from positive temperature coefficient devices to negative temperature coefficient devices and RTDs (Resistance Temperature Detectors).
Positive Temperature Coefficient (PTC) thermistors are resistors with a positive temperature coefficient, meaning their resistance increases as temperature rises. These are typically made of silicon to provide linear characteristics. In contrast, switch-type PTC thermistors exhibit a nonlinear temperature measurement curve. As the thermistor heats up, its resistance decreases until reaching a critical temperature, after which it increases.
They are used with monitoring relays in motor windings within industrial equipment to provide overheat protection against insulation damage. The nonlinear response curve causes the resistance to increase sharply at the maximum allowable winding temperature, triggering the relay to prevent overheating. It can then be linked to a wireless sensor network.
Negative Temperature Coefficient (NTC) thermistors exhibit decreasing resistance with rising temperature. They maintain accuracy across a broad temperature range of 0°C to 70°C with ±0.1°C or ±0.2°C tolerance, featuring excellent long-term stability.
These thermistor probe assemblies are commonly deployed throughout IIoT and smart factories for fault diagnosis. Thermistor sensor elements can monitor diverse systems and link wireless sensor networks back to the cloud.
Analog and Digital Temperature Sensor ICs
2. Proximity Sensors
Inductive proximity sensors detect nearby metals, enhancing human-machine interface (HMI) safety. Available in 2-wire and 3-wire DC versions, as well as sensors with separate amplifiers for high-speed operation.
Laser ranging (lidar) sensors enable object detection in one-dimensional topologies, such as infrared motion sensors on conveyor lines. 2D LiDAR sensors function as position sensors to identify component locations on production lines.
Proximity and Time-of-Flight (ToF) Sensors
3. Vibration Sensors
Vibration sensors utilize MEMS accelerometer elements or piezoelectric crystals to measure vibration frequency and tune to the harmonics of monitored systems. They provide critical data for fault diagnosis, while accelerometers serve as motion sensors for tilt, drop, and impact measurement. Accelerometers, Gyroscopes, Inertial Measurement Units (IMUs), Electronic Compasses
4. Other Sensors: Pressure, pH, Flow, Humidity, Ultrasonic, PIR, Photoelectric Sensors
Other sensors used in automation include pressure sensors, pH sensors for measuring liquid acidity, and flow sensors, humidity sensors, and ultrasonic sensors for monitoring actuators. PIR sensors, photoelectric sensors, and rotary encoders can serve as limit switches for threshold measurements in industrial automation systems.
All these IoT sensors connect to gateways via industrial sensor networks (wired or wireless), which then link to the IoT for real-time analytics and condition monitoring. ST's proprietary industrial sensors.
Industrial Wireless Sensors and Networks
Industrial wireless sensor networks utilize a wide range of protocols, from short-range Bluetooth and Zigbee to Wi-Fi.
For long-range industrial wireless sensor networks (IWSN), low-power sub-GHz LoRa wireless communication can be employed.
Cellular modems represent a higher-cost option for wireless sensor networks but offer the reliability of telecommunications networks. This is significant for the higher data rates provided by machine vision systems. As part of the IoT, video can be sent back to the cloud for analysis.
Power consumption is a critical consideration for industrial sensor networks, as thousands of sensor nodes and their wireless transceivers consume substantial power. Some wireless routing protocols inherently consume less energy, primarily through lower duty cycles. Higher power is sometimes required in heavy-load applications to overcome interference, ensuring reliable data collection and network reliability.