This section provides an overview for environmental sensors as well as their applications and principles. Also, please take a look at the list of 11 environmental sensor manufacturers and their company rankings.
An environmental sensor is a sensor used to detect external environmental information. An environmental sensor can be used for natural or human subjects, such as weather information (temperature, humidity, light, etc.).
Although environmental sensors are sometimes used by themselves to display information, they are mainly used to detect external environmental information for the purpose of controlling other devices or equipment. Environmental sensors should be selected based on the object to be measured. The following are some examples of environmental sensors in use:
This section describes the principle of environmental sensors. Environmental sensors are used to detect information about the external environment. They target external inputs (weather information, light, obstructions, sound, etc.). Some sensors have the ability to amplify weak signals and output them, or to convert the unit of measurement. Some typical environmental sensors are introduced below. There are many other types of sensors, such as temperature/humidity sensors that detect temperature and humidity, and optical sensors that detect light such as infrared and ultraviolet rays, but temperature/humidity sensors are the most familiar and widely used in homes and businesses alike.
1. A temperature/humidity sensor is a sensor that measures temperature and humidity. Although they are often integrated as a device, temperature and humidity are measured separately.
Thermocouple type: A thermocouple is a measuring end consisting of two different metal wires connected to form a ring-shaped circuit, and temperature is detected at the contact point. The temperature is detected at the opposite contact point B, and the result of comparing the thermal electromotive force between the contacts is converted to temperature.
Thermistor type: The temperature is detected by a resistive element composed of a metal wire and a metal oxide semiconductor. It utilizes the property of metal oxide semiconductors to have a pronounced change in electrical resistance with temperature change. Among several types of thermistors, NTC thermistors are widely used because of their easy-to-understand relationship between temperature and resistance, and because the resistance of NTC thermistors decreases as the temperature rises. The temperature is calculated by measuring the amount of change in the potential difference at this time.
Non-contact method: Detects infrared radiation emitted from an object. The infrared light is converted into an electrical signal through a lens, and the difference from the environmental temperature is compared and converted into a temperature. It is applicable to cases where the object has only a small heat capacity.
Capacitance type: It measures changes in the capacitance of a semiconductor; the distance between the electrodes opens as the moisture-sensitive material sandwiched between two electrodes absorbs moisture, detecting changes that reduce the capacitance. It is highly sensitive, but requires attention to noise processing and is costly due to its complex structure.
Resistance change type: It measures changes in semiconductor resistance. The electrodes are spread out at equal intervals, like a comb, and a moisture-sensitive material is applied on the electrodes in the form of a sheet. With a charge applied to the electrodes, the moisture-sensitive material absorbs moisture, causing the ions of the water molecules in the material to increase. The increase in ions increases conductivity, and the decrease in resistance between the electrodes is detected. Although inferior to the capacitance method in terms of sensitivity and accuracy, it is less susceptible to noise and has a relatively simple structure, making it relatively inexpensive.
Recently, CO2 sensors, a type of environmental sensors, are sometimes used as an indicator of room ventilation. CO2 sensors mainly measure the concentration of carbon dioxide produced by human respiration, and can be used in places where many people gather, such as conference rooms and hospital waiting rooms.
One of the air quality standards in the Building Environmental Sanitation Management Standard specifies the carbon dioxide content as one of the air quality standards. The standard for indoor air quality is to keep the carbon dioxide content below about 1000 ppm. Since there is no standardization for crowded places, it is up to each individual to decide how to ventilate the room.
Cram schools, classrooms, and other places where many people gather. In addition, if the carbon dioxide concentration is too high, it is said to affect human concentration, which is expected to improve work efficiency.
As technology has advanced in recent years, environmental sensors has become smaller and smaller. Some of the smallest environmental sensors are less than 1 cm in size, and are used in a variety of fields, including medicine, agriculture, and manufacturing.
There are also USB-based environmental sensors. They are smaller than a typical USB memory stick and can be powered by USB for constant operation, and can be connected to a network via USB or Bluetooth for transmission of measurement data. However, when connected to a PC's USB port, the temperature sensor may not be able to measure temperature values correctly due to the heat of the PC itself, so it is recommended to use an extension cable.
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