Classification of sensors and their purpose

Sensors are sophisticated devices that are often used to detect and respond to electrical or optical signals. The device converts the physical parameter (temperature, blood pressure, humidity, speed) into a signal that can be measured by the device.

The classification of sensors in this case may be different. There are several basic parameters for the distribution of measuring devices, which will be discussed later. Basically, this separation is associated with the action of various forces.

This is easy to explain using temperature measurement as an example. The mercury in the glass thermometer expands and compresses the liquid to convert the measured temperature, which can be read by an observer from a calibrated glass tube.

Criterias of choice

There are certain features that must be considered when classifying a sensor. They are listed below:

1. Accuracy.
2. Environmental conditions - usually sensors have restrictions on temperature, humidity.
3. Range - the measuring range of the sensor.
4. Calibration is necessary for most measuring instruments, as the readings change over time.
5. Cost.
6. Repeatability - variable readings are repeatedly measured in the same environment.

Categorization

Sensor classifications are divided into the following categories:

1. Primary input number of parameters.
2. Principles of transduction (use of physical and chemical effects).
3. Material and technology.
4. Destination.

The principle of transduction is a fundamental criterion that is followed for the effective collection of information. Typically, the logistics criteria are selected by the development team.

The classification of sensors based on properties is distributed as follows:

1. Temperature: thermistors, thermocouples, resistance thermometers, microcircuits.
2. Pressure: fiber optic, vacuum, liquid-based elastic pressure gauges, LVDT, electronic.
3. Flow: electromagnetic, differential pressure, positional displacement, thermal mass.
4. Level sensors: differential pressure, ultrasonic radio frequency, radar, thermal displacement.
5. Proximity and offset: LVDT, photoelectric, capacitive, magnetic, ultrasonic.
6. Biosensors: resonance mirror, electrochemical, surface plasmon resonance, light-addressing potentiometric.
7. Image: charge-coupled devices, CMOS.
8. Gas and chemistry: semiconductor, infrared, conductivity, electrochemical.
9. Acceleration: gyroscopes, accelerometers.
10. Others: humidity sensor, speed sensor, mass, tilt sensor, strength, viscosity.

This is a large group of subsections. It is noteworthy that with the discovery of new technologies, sections are constantly replenished.

The purpose of the classification of sensors based on the direction of use:

1. Control, measurement and automation of the production process.
2. Non-industrial use: aviation, medical products, automobiles, consumer electronics.

Sensors can be classified according to power requirements:

1. Active sensors are devices that require power. For example, LiDAR (light detection and range finder), a photoconductive cell.
2. Passive sensors are sensors that do not require power. For example, radiometers, film photography.

These two sections include all devices known to science.

In current applications, the purpose of the classification of sensors can be divided into groups as follows:

1. Accelerometers - based on microelectromechanical sensor technology. They are used to monitor patients who include pacemakers. and dynamic vehicle systems.
2. Biosensors - based on electrochemical technology. They are used to test food, medical devices, water and the detection of dangerous biological pathogens.
3. Image Sensors - Based on CMOS technology. They are used in consumer electronics, biometrics, traffic monitoring and safety, as well as on computer images.
4. Motion detectors - based on infrared, ultrasound and microwave / radar technologies. Involved in video games and simulations, light activation and security detection.

Sensor Types

There is also a main group. It is divided into six main areas:

1. Temperature.
2. Infrared radiation.
3. Ultraviolet.
4. Sensor
5. Approach, movement.
6. Ultrasound.

Each group may include subsections, if the technology is even partially used as part of a specific device.

1. Temperature sensors

This is one of the main groups. The classification of temperature sensors unites all devices that have the ability to evaluate parameters based on heating or cooling of a particular type of substance or material.

This device collects temperature information from a source and converts it into a form that is understandable to other equipment or a person. The best illustration of a temperature sensor is mercury in a glass thermometer. Mercury in the glass expands and contracts depending on temperature changes. Outside temperature is the starting point for measuring the indicator. The position of mercury is observed by the viewer to measure the parameter. There are two main types of temperature sensors:

1. Contact sensors. This type of device requires direct physical contact with an object or medium. They control the temperature of solids, liquids, and gases over a wide temperature range.
2. Contactless sensors. This type of sensor does not require any physical contact with the measured object or carrier. They control non-reflective solids and liquids, but are useless for gases because of their natural transparency. These instruments use Planck's law to measure temperature. This law applies to the heat emitted by a source for measuring a benchmark.

Work with various devices

The principle of operation and classification of temperature sensors are also divided into the use of technology in other types of equipment. These can be dashboards in a car and special production plants in an industrial workshop.

1. Thermocouple - modules are made of two wires (each from different homogeneous alloys or metals), which form a measuring transition by connecting at one end. This measuring unit is open to the elements being studied. The other end of the wire ends with a measuring device, where a support transition is formed. Current flows through the circuit, since the temperature of the two compounds is different. The resulting millivolt voltage is measured to determine the temperature at the junction.
2. RTDs are types of thermistors that are made to measure electrical resistance when the temperature changes. They are more expensive than any other temperature measuring device.
3. Thermistors. They are another type of thermal resistor in which a large change in resistance is proportional to a small change in temperature.

2. IR sensor

This device emits or detects infrared radiation to determine a specific phase in the environment. As a rule, thermal radiation is emitted by all objects in the infrared spectrum. This sensor detects a type of source that is not visible to the human eye.

The main idea is to use infrared LEDs to transmit light waves to the object. Another IR diode of the same type should be used to detect the reflected wave from the object.

Operating principle

The classification of sensors in the automation system in this direction is common. This is due to the fact that the technology makes it possible to use additional tools to evaluate external parameters. When an infrared receiver is exposed to infrared light, a voltage difference occurs on the wires. The electrical properties of the IR sensor components can be used to measure the distance to the object. When the infrared receiver is exposed to light, a potential difference occurs through the wires.

Where applicable:

1. Thermography: according to the law on the radiation of objects, you can observe the environment with or without visible lighting using this technology.
2. Heating: Infrared radiation can be used to prepare and heat food. They can remove ice from the wings of an airplane. Converters are popular in the industrial field, such as printing, plastic molding and polymer welding.
3. Spectroscopy: this method is used to identify molecules by analyzing constituent bonds. The technology uses light radiation to study organic compounds.
4. Meteorology: measure the height of the clouds, calculate the temperature of the earth and surface is possible if meteorological satellites are equipped with scanning radiometers.
5. Photobiomodulation: used for chemotherapy in cancer patients. Additionally, the technology is used to treat herpes virus.
6. Climatology: monitoring the exchange of energy between the atmosphere and the earth.
7. Communication: An infrared laser provides light for optical fiber communication. These emissions are also used for short-distance communications between mobile and computer peripherals.

3. UV sensor

These sensors measure the intensity or power of the incident ultraviolet radiation. The form of electromagnetic radiation has a longer wavelength than x-rays, but is still shorter than visible radiation.

An active material known as polycrystalline diamond is used to reliably measure ultraviolet radiation. Instruments can detect various environmental effects.

Criteria for choosing a device:

1. The wavelength ranges in nanometers (nm) that can be detected by ultraviolet sensors.
2. Working temperature.
3. Accuracy.
4. Weight.
5. Power range.

Operating principle

An ultraviolet sensor receives one type of energy signal and transmits another type of signal. To observe and record these output streams, they are sent to an electric meter. To create graphs and reports, indicators are transferred to an analog-to-digital converter (ADC), and then to a computer with software.

It is used in the following devices:

1. Ultraviolet phototubes are radiation-sensitive sensors that monitor the processing of air in the ultraviolet, the treatment of water in the ultraviolet and exposure to the sun.
2. Light sensors - measure the intensity of the incident beam.
3. UV sensors - are charge-coupled devices (CCDs) used in laboratory images.
4. UV light detectors.
5. Germicidal UV detectors.
6. Photo stability sensors.

4. Touch Sensor

This is another large group of devices. The classification of pressure sensors is used to evaluate external parameters that are responsible for the appearance of additional characteristics under the action of a particular object or substance.

The touch sensor acts as a variable resistor in accordance with the place where it is connected.

The touch sensor consists of:

1. Fully conductive substance such as copper.
2. Insulated intermediate material such as foam or plastic.
3. Partially conductive material.

There is no strict separation. The classification of pressure sensors is established by selecting a specific sensor, which evaluates the emerging voltage inside or outside the studied object.

Operating principle

Partially conductive material counteracts the flow of current. The principle of a linear position sensor is that the current flow is considered more opposite when the length of the material through which the current must pass is longer. As a result, the resistance of the material is changed by changing the position at which it comes into contact with a fully conductive object.

The classification of automation sensors is based entirely on the described principle. It also involves additional resources in the form of specially designed software. Typically, the software is associated with touch sensors. Devices can remember the “last touch” when the sensor is turned off. They can register the “first touch” as soon as the sensor is activated and understand all the meanings associated with it. This action is similar to moving the computer mouse to the other end of the mat to move the cursor to the far side of the screen.

5. Proximity Sensor

Increasingly, modern vehicles use this technology. The classification of electrical sensors using light and sensor modules is gaining popularity among automotive manufacturers.

The proximity sensor detects the presence of objects that are almost without any points of contact. Since there is no contact between the modules and the perceived object and there are no mechanical parts, these devices have a long service life and high reliability.

Different types of proximity sensors:

1. Inductive proximity sensors.
2. Capacitive proximity sensors.
3. Ultrasonic proximity sensors.
4. Photoelectric sensors.
5. Hall sensors.

Operating principle

The proximity sensor emits an electromagnetic or electrostatic field or a beam of electromagnetic radiation (such as infrared) and awaits a response signal or changes in the field. The detected object is known as the target of the recording module.

The classification of sensors according to the principle of operation and purpose will be as follows:

1. Inductive devices: there is a generator at the input, which changes the loss resistance to the proximity of the electrically conductive medium. These devices are preferred for metal objects.
2. Capacitive proximity sensors: they convert the change in electrostatic capacitance between the detection electrodes and ground. This occurs when approaching a nearby object with a change in the oscillation frequency. To detect a nearby object, the oscillation frequency is converted to a DC voltage, which is compared with a predetermined threshold value. These appliances are preferred for plastic objects.

The classification of measuring equipment and sensors is not limited to the above description and parameters. With the advent of new types of measuring instruments, the general group grows. Different definitions are approved to distinguish between sensors and transmitters. Sensors can be defined as an element that receives energy in order to produce a variant in the same or another form of energy. The sensor converts the measured value into the desired output signal using the conversion principle.

Based on the received and generated signals, the principle can be divided into the following groups: electrical, mechanical, thermal, chemical, radiating and magnetic.

6. Ultrasonic sensors

An ultrasonic sensor is used to detect the presence of an object. This is achieved by emitting ultrasonic waves from the device head and then receiving a reflected ultrasound signal from the corresponding object. This helps in detecting the position, presence and movement of objects.

Because ultrasonic sensors rely on sound rather than light to detect, they are widely used for measuring water levels, medical scanning procedures, and the automotive industry. Ultrasonic waves can detect invisible objects, such as transparencies, glass bottles, plastic bottles and flat glass, using their reflective sensors.

Operating principle

The classification of inductive sensors is based on the scope of their use. It is important to consider the physical and chemical properties of objects. The movement of ultrasonic waves varies depending on the shape and type of medium. For example, ultrasonic waves travel directly in a homogeneous medium and are reflected and transmitted back to the boundary between different media. The human body in the air causes significant reflection and can be easily detected.

The technology uses the following principles:

1. Multireflection. Multiple reflection occurs when waves are reflected more than once between the sensor and the detection object.
2. Limit zone. The minimum operating distance and maximum operating distance can be adjusted. This is called the limit zone.
3. Detection zone. This is the interval between the surface of the sensor head and the minimum detection distance obtained by adjusting the scanning distance.

Devices equipped with this technology allow scanning of various types of objects. Ultrasonic sources are actively used in the creation of vehicles.