Mastering Industrial IoT Series: Selection of Sensors, Transducers, And Switches

The Industrial Internet of Things (IIoT) and industrial automation projects have gained significant momentum in recent years, revolutionizing how industries operate, optimize processes, and maintain equipment. The global IIoT market is expected to reach $263.4 billion by 2027, growing at a CAGR of 16.7% from 2020 to 2027 (Allied Market Research). This rapid growth is driven by the increasing need for real-time data analytics, predictive maintenance, and more efficient resource management across sectors.

Sensors, actuators, controllers, and communication networks are fundamental for every IIoT project. The success of any automation project depends largely on the right selection of these fundamental components. By carefully evaluating factors such as functional operation, integration with existing systems, cost, and ease of operation, organizations can ensure the success of their projects, ultimately resulting in improved performance and a stronger competitive edge in the market.

However, often people may use the terms Sensors, Transducers, and Switches interchangeably, even though they are functionally different. Therefore, understanding the differences and functionalities and selecting an appropriate component is crucial for successful implementation. Our article is aimed at assisting automation engineers and enthusiasts in selecting the right component for their application.

Upon completing the article, you will be able to:

1. Understand the key differences between sensors, transducers, and switches and their specific roles in IIoT and industrial automation projects.
2. Evaluate the factors that influence the selection of the appropriate components.
3. Identify common misconceptions and mistakes when selecting components, and learn how to avoid them to ensure the success of your project.

Sensors, Transducers, and Switches:

A sensor’s primary function is to detect or measure a physical, chemical, or process change and convert it into a signal, while a transducer converts one form of energy into another, often as part of a sensor or actuator system. Whereas a switch only opens or closes a circuit based on specific threshold conditions. Let us formally define the three and then compare them with various factors to help you decide the best component for your automation application:

#A. Sensor:

Detects or measures physical, chemical, or process changes and converts them into electrical signals.

Common Sensor Types, Examples, and Applications in Industrial IoT:

1. Temperature sensors: Thermocouples, RTDs (Resistance Temperature Detectors), and thermistors are used to measure temperature changes in various industrial processes.
2. Pressure sensors: Piezoelectric, capacitive, and strain gauge pressure sensors monitor pressure levels in pipelines, tanks, or other systems.
3. Proximity sensors: Inductive, capacitive, and ultrasonic proximity sensors detect the presence or distance of objects for positioning, counting, or collision avoidance.
4. Humidity sensors: Capacitive and resistive humidity sensors measure the relative humidity in controlled environments or weather monitoring applications.

#B. Transducer:

A transducer is a device that converts one form of energy into another, often as part of a sensor or actuator system. For example, a thermocouple (a temperature transducer) converts temperature changes into an electrical voltage, while a piezoelectric transducer transforms mechanical energy (pressure or vibration) into electrical signals.

Common Transducer Types, Examples, and Applications in Industrial IoT:

1. Strain gauge transducers: These transducers measure mechanical deformation or strain, often used in structural health monitoring, load cells, or torque sensors.
2. Piezoelectric transducers: Used for generating and detecting ultrasonic waves, these transducers have applications in non-destructive testing, medical imaging, and ultrasonic cleaning.
3. Linear Variable Differential Transformers (LVDTs): These electromagnetic transducers measure linear position or displacement with high accuracy in machine tooling, robotics, and hydraulic systems.
4. Thermocouples: A type of temperature transducer that converts temperature changes into an electrical voltage, used in various industrial temperature sensing applications.

#C. Switch:

Device that opens or closes a circuit based on specific conditions or variables. Switches can be mechanical, electrical, or solid-state and are commonly used for on/off control, safety, and system protection.

Common Switch Types, Examples, and Applications in Industrial IoT:

1. Limit switches: Mechanical, inductive, or optical switches used to detect the position of moving parts, often found in assembly lines or robotic applications.
2. Pressure switches: These switches monitor and control system pressure in HVAC systems, hydraulic systems, or other pressurized equipment.
3. Safety interlock switches: Designed to ensure that safety doors, guards, or barriers are in place before a machine can operate, these switches protect workers from potential hazards.
4. Relay switches: Electromechanical or solid-state switches that control high-power circuits using a low-power signal, often used in control systems and automation.

Each component – sensor, transducer, and switch has its unique advantages and limitations, the following section lists the differences between each component.

Note: Transmitters are different from Transducers. Transmitters are often inbuilt in sensors, transducers, and switches to transfer the data over long distances.