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A sensor is a device that detects and responds to some type of input from the physical environment. The input can be light, heat, motion, humidity, pressure, or any number of other environmental phenomena. The output is usually a signal that is converted to human-readable display at the sensor position or transmitted electronically over the network for reading and further processing.

Sensors play an important role in the Internet of things (IoT). They can create an ecosystem to collect and process data about a particular environment, making it easier to monitor, manage, and control it. Internet of things sensors are used in homes, outdoors, cars, airplanes, industrial environments, and other environments. Sensors bridge the gap between the physical and logical worlds, acting as the eyes and ears of the computing infrastructure, analyzing the data collected from the sensors and processing them.

What are the types of sensors? Sensors can be classified in many ways. A common method is to classify them as active or passive. Active sensor is a kind of sensor that needs external power supply to respond to environmental input and produce output. For example, sensors used in weather satellites usually require some energy to provide meteorological data about the Earth's atmosphere.

On the other hand, passive sensors do not need an external power supply to detect environmental input. It depends on the energy of the environment itself, using energy such as light or heat. A good example is a mercury glass thermometer. Mercury expands and contracts as the temperature fluctuates, causing the liquid level in the glass tube to rise or decrease. The external tag provides a human-readable instrument for viewing the temperature.

Some types of sensors, such as earthquake and infrared light sensors, come in both active and passive forms. The environment in which the sensor is deployed usually determines which type is most suitable for the application.

Another way to classify sensors is based on the type of output generated by the sensor, according to whether they are analog or digital. The analog sensor converts the environmental input into a continuously changing output analog signal. The thermocouple used in gas water heaters is a good example of an analog sensor. The indicator light of the water heater continues to heat the thermocouple. If the indicator is off, the thermocouple cools and sends a different analog signal indicating that the gas should be turned off.

Unlike analog sensors, digital sensors convert environmental inputs into discrete digital signals transmitted in binary formats (1 and 0). Digital sensors have become quite common in all industries and have replaced analog sensors in many cases. For example, digital sensors are now used to measure humidity, temperature, atmospheric pressure, air quality and many other types of environmental phenomena.

Like active and passive sensors, some types of sensors (such as thermal sensors or pressure sensors) come in both analog and digital forms. In this case, the environment in which the sensor is running usually determines which is the best choice.

Sensors are also usually classified according to the type of environmental factors they monitor. Here are some common examples:

Accelerometer. This type of sensor detects changes in gravitational acceleration so that tilt, vibration and, of course, acceleration can be measured. Accelerometer sensors are used in a wide range of industries, from consumer electronics to professional sports to aerospace.

Chemistry. Chemical sensors detect specific chemicals in a medium (gas, liquid, or solid). Chemical sensors can be used to detect soil nutrient levels in farmland, smoke or carbon monoxide levels in rooms, pH levels in water bodies, alcohol levels in someone's breath, or anything else. For example, oxygen sensors in automobile emission control systems usually monitor the ratio of gasoline to oxygen by generating voltage chemical reactions. The computer in the engine compartment reads the voltage and re-adjusts the ratio if the mixture is not optimal.

Humidity. These sensors can detect the amount of water vapor in the air to determine the relative humidity. Humidity sensors usually include temperature readings because the relative humidity depends on the air temperature. These sensors are used in a wide range of industries and environments, including agriculture, manufacturing, data centers, meteorology, and heating, ventilation and air conditioning (HVAC).

Grade. A liquid level sensor can determine the liquid level of a physical substance, such as water, fuel, coolant, grain, fertilizer or waste. For example, drivers rely on their fuel level sensors to make sure they don't end up stuck on the side of the road. Liquid level sensors are also used in tsunami warning systems.

Exercise. Motion detectors can sense physical motion in a limited space (detection area) and can be used to control lights, cameras, parking doors, faucets, security systems, automatic door openers, and many other systems. Sensors usually emit some type of energy-- such as microwaves, ultrasonic waves or beams of light-- and can detect when the energy flow is interrupted by an object entering its path.

Optical. Optical sensors, also known as photoelectric sensors, can detect light waves at different points in the spectrum, including ultraviolet, visible and infrared light. Optical sensors are widely used in smartphones, robots, Blu-ray players, home safety systems, medical devices and a wide range of other systems.

pressure. These sensors detect the pressure of liquids or gases and are widely used in machinery, automobiles, aircraft, HVAC systems and other environments. They also play an important role in meteorology by measuring atmospheric pressure. In addition, pressure sensors can be used to monitor the flow of gases or liquids, usually adjusting the flow rate.

Close. Proximity sensors detect the presence of objects or determine the distance between objects. Proximity monitors are used in elevators, assembly lines, parking lots, retail stores, cars, robots, and many other environments.

Temperature. These sensors can identify the temperature of the target medium, whether it is gas, liquid or air. Temperature sensors are used in a variety of equipment and environments, such as electrical appliances, machinery, aircraft, cars, computers, greenhouses, farms, thermostats and many other equipment.

Touch. The touch sensing device detects physical contact on the monitored surface. Touch sensors are widely used in electronic devices to support touchpad and touchscreen technology. They are also used in many other systems, such as elevators, robots and soap dispensers.

These are just some of the various types of sensors used across environments and devices. However, none of these categories are strictly black and white; for example, a level sensor that tracks the liquid level of a material may also be regarded as an optical or pressure sensor. There are many other types of sensors, such as those that detect load, strain, color, sound, and various other conditions. In fact, sensors have become so common that people hardly notice their use.

This article is from the official account of Wechat: sensor Technology (ID:WW_CGQJS), author:-

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