Sensors - A Complete Guide (Types, Applications, and Suppliers)

 Welcome to electronicdevicenetwork blog complete guide to the types of sensors, detectors, and transducers available. Below you will find comprehensive information on the types of products, their suppliers and manufacturers, sensor applications in industry, considerations, and important attributes.

Table of Contents

1. What are Sensors, Detectors, and Transducers? 
2. Types of Sensors/Detectors/Transducers
3. Applications and Industries
4. Considerations
5. Important Attributes
6. Related Product Categories

What are Sensors, Detectors, and Transducers?

Sensor/Detectors/Transducers are electrical, opto-electrical, or electronic devices composed of specialty electronics or otherwise sensitive materials, for determining if there is a presence of a particular entity or function. Many types of sensors, detectors, and transducers are available including those for detecting a physical presence such as flame, metals, leaks, levels, or gas and chemicals, among others. Some are designed to sense physical properties such as temperature, pressure, or radiation, while others can detect motion or proximity. They operate in a variety of manners depending on the application and may include electromagnetic fields, or optics, among others. Many applications over a wide range of industries use sensors, detectors, and transducers of many kinds to test, measure, and control various processes and machine functions. With the advent of the Internet Of Things(IOT) , the need for sensors as a primary tool to provide enhanced automation is increasing.

Different Types of Sensors/Detectors/Transducers

Below find a breakdown of the different types of sensors and their uses, as well as detectors and transducers.

List of Sensors

Use this list of sensors below to take you to a particular section:

Vision and Imaging Sensors
Temperature Sensors
Radiation Sensors
Proximity Sensors
Pressure Sensors
Position Sensors
Photoelectric Sensors
Particle Sensors
Motion Sensors
Metal Sensors
Level Sensors
Leak Sensors
Humidity Sensors
Gas and Chemical Sensors
Force Sensors
Flow Sensors
Flaw Sensors
Flame Sensors
Electrical Sensors
Contact Sensors
Non-Contact Sensors

Vision and Imaging Sensors

Vision and Imaging Sensors/Detectors are electronic devices that detect the presence of objects or colors within their fields of view and convert this information into a visual image for display. Key specifications include sensor type and intended application, along with any particular transducer features. 

Temperature Sensors

Temperature Sensors/Detectors/Transducers are electronic devices that detect thermal parameters and provide signals to the inputs of control and display devices. A temperature sensor typically relies on an RTD or thermistor to measure temperature and convert it to an output voltage. Key specifications include sensor/detector type, maximum and minimum measurable temperatures, as well as the dimensions of diameter and length. Temperature sensors are used to measure the thermal characteristics of gases, liquids, and solids in many process industries and are configured for both general- and special-purpose uses.

Radiation Sensors

Radiation Sensors/Detectors are electronic devices that sense the presence of alpha, beta, or gamma particles and provide signals to counters and display devices. Key specifications include sensor type and minimum and maximum detectable energies. Radiation detectors are used for surveys and sample counting. .

Proximity Sensors

Proximity Sensors are electronic devices used to detect the presence of nearby objects through non-contacting means. A proximity sensor can detect the presence of objects usually within a range of up to several millimeters, and, doing so, produce a usually dc output signal to a controller. Proximity sensors are used in countless manufacturing operations to detect the presence of parts and machine components. Key specifications include sensor type, maximum sensing distance, minimum & maximum operating temperatures, along with dimensions of diameter and length. Proximity sensors are generally short-range devices but are available too in designs that can detect objects up to several inches away. One commonly used type of proximity sensor is known as a capacitive proximity sensor. This device uses the change in capacitance resulting from a reduction in the separation distance between the plates of a capacitor, one plate of which is attached to the object being observed, as a means of determining motion and position of the object from the sensor. 

Pressure Sensors

Pressure Sensors/Detectors/Transducers are electro-mechanical devices that detect forces per unit area in gases or liquids and provide signals to the inputs of control and display devices. A pressure sensor/transducer typically uses a diaphragm and strain gage bridge to detect and measure the force exerted against a unit area. Key specifications include sensor function, minimum and maximum working pressures, full-scale accuracy, along with any features particular to the device. Pressure sensors are used wherever information about the pressure of a gas or liquid is needed for control or measurement. 

Position Sensors

Position Sensors/Detectors/Transducers are electronic devices used to sense the positions of valves, doors, throttles, etc. and supply signals to the inputs of control or display devices. Key specifications include sensor type, sensor function, measurement range, and features that are specific to the sensor type. Position sensors are used wherever positional information is needed in a myriad of control applications. A common position transducer is a so-called string-pot, or string potentiometer. 

Photoelectric Sensors

Photoelectric sensors are electrical devices that sense objects passing within their field of detection, although they are also capable of detecting color, cleanliness, and location if needed. These sensors rely on measuring changes in the light they emit using an emitter and a receiver. They are common in manufacturing and material handling automation for purposes such as counting, robotic picking, and automatic doors and gates.

Particle Sensors

Particle Sensors/Detectors are electronic devices used to sense dust and other airborne particulates and supply signals to the inputs of control or display devices. Particle sensors are common in bin and baghouse monitoring. Key specifications include transducer type, minimum detectable particle size, operating temperature range, sample volume, and response time. Particle detectors used in nuclear engineering are referred to as radiation detectors (see above). 

Motion Sensors

Motion Sensors/Detectors/Transducers are electronic devices that can sense the movement or stoppage of parts, people, etc. and supply signals to the inputs of control or display devices. Typical applications of motion detection are detecting the stalling of conveyors or the seizing of bearings. Key specifications include the intended application, sensor type, sensor function, and minimum and maximum speeds. 

Metal Sensors

Metal Detectors are electronic or electro-mechanical devices used to sense the presence of metal in a variety of situations ranging from packages to people. Metal detectors can be permanent or portable and rely on a number of sensor technologies with electromagnetics being popular. Key specifications include the intended application, maximum sensing distance, and certain feature choices like handheld and fixed systems. Metal detectors can be tailored to explicitly detect metal in specific manufacturing operations such as sawmilling or injection molding. 

Level Sensors

Level Sensors/Detectors are electronic or electro-mechanical devices used for determining the height of gases, liquids, or solids in tanks or bins and providing signals to the inputs of control or display devices. Typical level sensors use ultrasonic, capacitance, vibratory, or mechanical means to determine product height. Key specifications include sensor type, sensor function, and maximum sensing distance. Level sensors/detectors can be of the contacting or non-contacting type. 

Leak Sensors

Leak Sensors/Detectors are electronic devices used for identifying or monitoring the unwanted discharge of liquids or gases. Some leak detectors rely on ultrasonic means to detect air leaks, for example. Other leak detectors rely on simple foaming agents to measure the soundness of pipe joints. Still, other leak detectors are used to measure the effectiveness of the seals in vacuum packages. 

Humidity Sensors

Humidity Sensors/Detectors/Transducers are electronic devices that measure the amount of water in the air and convert these measurements into signals that can be used as inputs to control or display devices. Key specifications include maximum response time and minimum and maximum operating temperatures. 

Gas and Chemical Sensors

Gas and Chemical Sensors/Detectors are fixed or portable electronic devices used to sense the presence and properties of various gases or chemicals and relay signals to the inputs of controllers or visual displays. Key specifications include the intended application, sensor/detector type, measurement range, and features. Gas and chemical sensors/detectors are used for confined space monitoring, leak detection, analytical instrumentation, etc. and are often designed with the capability of detecting multiple gases and chemicals. 

Force Sensors

Force Sensors/Transducers are electronic devices that measure various parameters related to forces such as weight, torque, load, etc. and provide signals to the inputs of control or display devices. A force sensor typically relies on a load cell, a piezoelectric device whose resistance changes under deforming loads. Other methods exist for measuring torque and strain. Key specifications include sensor function, number of axes, minimum and maximum loads (or torques), minimum and maximum operating temperature, as well as the dimensions of the sensor itself. Force sensors are used in load measuring applications of all kinds, from truck scales to bolt tensioning devices. 

Flow Sensors

Flow Sensors/Detectors are electronic or electro-mechanical devices used to sense the movement of gases, liquids, or solids and provide signals to the inputs of control or display devices. A flow sensor can be all electronic—using ultrasonic detection from outside a pipeline, say—or partially mechanical—a paddlewheel, for instance, that sits and spins directly in the flow stream itself. Key specifications include sensor/detector type, sensor function, maximum flowrate, maximum working pressure, and minimum and maximum operating temperatures. Flow sensors are used extensively in the processing industries. Some designs for panel mounting allow quick indication of flow conditions to process operators. 

Flaw Sensors

Flaw Sensors/Detectors are electronic devices used in a variety of manufacturing processes to uncover inconsistencies on surfaces or in underlying materials such as welds. Flaw detectors use ultrasonic, acoustic, or other means to identify defects in materials and can be portable or fixed installations. Key specifications include sensor type, detectable defect or thickness range, and intended application. 

Flame Sensors

Flame Detectors are optoelectronic devices used to sense the presence and quality of fire and provide signals to the inputs of control devices. A flame detector typically relies on ultraviolet or infrared detection of the presence of flame and finds use in many combustion control applications such as burners. A key specification is detector type. Flame detectors find applications in safety settings too, such as in under-the-hood fire suppression systems. 

Electrical Sensors

Electrical Sensors/Detectors/Transducers are electronic devices that sense current, voltage, etc. and provide signals to the inputs of control devices or visual displays. Electrical sensors often rely on hall effect detection but other methods are used as well. Key specifications include sensor type, sensor function, minimum and maximum measurement ranges, and operating temperature range. Electrical sensors are used wherever information on the state of an electrical system is needed and are employed in everything from railway systems to fan, pump, and heater monitoring. 

Contact Sensors

Contact sensors refer to any type of sensing device that functions to detect a condition by relying on physical touch or contact between the sensor and the object being observed or monitored. A simple type of contact sensor is used in alarm systems to monitor doors, windows, and other access points. When the door or window is closed, a magnetic switch provides an indication to the alarm control unit so that the status of that entry point is known. Similarly, when a door or window is opened, the contact sensor alerts the alarm controller of the state of that access point and may trigger an action such as engaging an audible siren. There are many uses of contact sensors such as temperature monitoring and as proximity sensors in robotics applications and automated machinery. 

Non-Contact Sensors

In contrast to contact sensors, non-contact sensors are devices that do not require a physical touch between the sensor and the object being monitored in order to function. A familiar example of this type of sensor is the motion detector used in security lights. Detection of objects within the range of a motion detector is accomplished using non-mechanical or non-physical means, such as via detection of passive infrared energy, microwave energy, ultrasonic waves, etc. Radar guns used by law enforcement to monitor the speed of vehicles is another example of a form of non-contact sensor. Other types of devices that fall under the category of non-contact sensors include Hall-effect sensors, inductive sensors, LVDTs (linear variable differential transformers), RVDTs (rotary variable differential transformers), and Eddy current sensors, to name a few. 

Sensor Applications in Industry

A sensor is generally intended to produce a variable signal over some measurement range as opposed to a switch which generally acts in a binary fashion, as in on or off. While this is not always true it helps when it comes to deciding between sensors or switches. For example, a level switch can detect when a certain specified level in a tank has been reached and signal a pump to stop running. A level sensor, on the other hand, can sense changing tank depth and provide signals that can be proportionally displayed on a readout, etc. Thus, where a sump pump could use a level switch to signal a pump to start running at a certain level, a fuel tank level sensor would determine the tank status between empty and full and provide signals to a fuel gage, etc. Some manufacturers refer to this distinction as “point” versus “continuous” sensing.

Sensors are arranged by what is being sensed: pressure, temperature, proximity, etc. The intended application makes a good place to search for specific situations where a specifier might not know the sensor/transducer type. For example, if a gear tooth sensor is needed for building a zero-speed detector, selecting this will produce several products for gear tooth detection, some of which rely on hall effect and others that use magnetics to sense a passing tooth. Picking the value “zero-speed” will produce similar results. Likewise, selecting values from the sensor/detector/transducer function will search across the many sub-categories to produce matches from the range of transducer types. Picking the value “speed” here will produce sensors of the optical and hall effect varieties. Speed sensors can also be magnetic or infrared-based.

Transducer type is another way to search for particular sensors. Selecting “infrared,” for example, will produce leak detectors, flame detectors, speed sensors, etc. all of which use infrared as their sensing means.

There is some overlap among the sub-categories. For instance, while gear tooth sensors detect metal, metal detectors are also available as complete units designed to detect metal on food processing conveyor lines, injection molding lines, etc. Selecting the sub-category Metal Detectors will not show any gear tooth sensors because these are found under Motion sensors.

Industrial Sensors - Considerations

Infrared sensors use infrared light in various forms. Some detect the infrared radiation emitted by all objects. Others cast infrared beams that are reflected back to sensors that look for interruptions of the beams.

Temperature sensors generally rely on RTDs or thermistors to sense changes in temperature through the change in electrical resistance that occurs in materials.

Non-contacting proximity sensors often use hall effect phenomena, eddy currents, or capacitive effects to detect the nearness of conductive metals. Other methods are used as well, including optical and laser. Where proximity sensors can be used to detect small changes in the positions of targets, simple on/off proximity switches use the same methods to detect, for instance, an open door.

Ultrasonic sensors measure the time between the emission and reception of ultrasonic waves to determine the distance to a tank’s contents, for example. In another form, ultrasonic sensors detect the ultrasonic energy emitted by leaking air, etc.

Force and pressure sensors typically use strain gages or piezoelectric devices which change their resistance characteristics under applied loads. These changes can be calibrated over the linear ranges of the transducers to produce measures of weight (force) or pressure (force per unit area).

Vision sensors typically rely on CCD, infrared, or ultraviolet cameras to produce images that can be interpreted by software systems to detect flaws, sense barcodes, etc.

Important Attributes

Types of Sensors/Detectors/Transducers

Sensor types are common among many of the various subcategories. For example, Hall effect sensors are found in proximity sensors, level sensors, motion sensors, and so on. Infrared sensors are used for level sensing, flame detection, etc. Sensing a fuel level in a tank, say, can be achieved through a number of sensor types.

Intended Application

Picking an intended application can help narrow choices for specific instances. Proximity sensors for pneumatic cylinders, for example, are designed to attach directly to a cylinder’s tie rods, and thus have specific mounting arrangements, as shown at right.

Output Types

Many control sensors use 4-20 mA current loops, where 4 mA represents the low side of the analog signal and 20 mA represents the high side. Digital switches are used as well, among them NPN/PNP, USB, etc.

Response Time

Many sensors have response times measured in milliseconds, while sensors for gases, leaks, etc. may have their response times measured in seconds or even minutes.

Features

Sensors designed to function in extreme environments, hazardous locations, etc. can be selected here.

Related Product Categories

Encoders are electromechanical devices that are used to convert linear or rotary motions to analog or digital output signals.

Load Cells are mechanical or electronic devices designed to convert forces, either compressive, tensile, torsional, or shear, into electrical signals.

Monitors  typically electronic devices used to remotely or conveniently view information as required.

Data Acquisition Systems (abbreviated DAQ or DAS) collect analog signals from sensors measuring real-world samples and transduce them into digital formats that are processed by

Data Loggers are electronic data storage devices used to gather and record various data-over-time measurements.

Switches are electromechanical devices that are used in electrical circuits.

Thermocouples are mechanical devices formed of dissimilar metal wires welded together and used for the measurement of temperature.

Controls and Controllers see our Controls and Controllers Buyer’s Guide