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A humidistat or hygrostat is an electronic device analogous to a thermostat but which responds to relative humidity, not temperature. A typical humidistat is usually included with portable humidifiers or dehumidifiers. It can also be included with combined air cleaner or humidifier units to control a home's humidity level or any other indoor space. [1]
Humidistats are used in a number of devices including dehumidifiers, humidifiers, and microwave ovens. In humidifiers and dehumidifiers, the humidistat is used where constant relative humidity conditions need to be maintained such as a refrigerator, greenhouse, or climate-controlled warehouse. When adjusting the controls in these applications the humidistat would be what is being set. In microwaves they are used in conjunction with smart cooking one-button features such as those for microwave popcorn. Humidistats employ hygrometers but are not the same. A humidistat has the functionality of a switch and is not just a measuring instrument like a hygrometer is.
For heating, ventilation, and air conditioning (HVAC) of buildings, humidistats or humidity sensors are used to sense the air relative humidity in the controlled space and turn on and off the HVAC equipment. [2]
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.
The dew point of a given body of air is the temperature to which it must be cooled to become saturated with water vapor. This temperature depends on the pressure and water content of the air. When the air is cooled below the dew point, its moisture capacity is reduced and airborne water vapor will condense to form liquid water known as dew. When this occurs through the air's contact with a colder surface, dew will form on that surface.
Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation as HVAC&R or HVACR, or "ventilation" is dropped, as in HACR.
A dehumidifier is an air conditioning device which reduces and maintains the level of humidity in the air. This is done usually for health or thermal comfort reasons, or to eliminate musty odor and to prevent the growth of mildew by extracting water from the air. It can be used for household, commercial, or industrial applications. Large dehumidifiers are used in commercial buildings such as indoor ice rinks and swimming pools, as well as manufacturing plants or storage warehouses. Typical air conditioning systems combine dehumidification with cooling, by operating cooling coils below the dewpoint and draining away the water that condenses.
A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
A hygrometer is an instrument which measures the humidity of air or some other gas: that is, how much water vapor it contains. Humidity measurement instruments usually rely on measurements of some other quantities such as temperature, pressure, mass and mechanical or electrical changes in a substance as moisture is absorbed. By calibration and calculation, these measured quantities can lead to a measurement of humidity. Modern electronic devices use the temperature of condensation, or they sense changes in electrical capacitance or resistance to measure humidity differences. A crude hygrometer was invented by Leonardo da Vinci in 1480. Major leaps came forward during the 1600s; Francesco Folli invented a more practical version of the device, while Robert Hooke improved a number of meteorological devices including the hygrometer. A more modern version was created by Swiss polymath Johann Heinrich Lambert in 1755. Later, in the year 1783, Swiss physicist and Geologist Horace Bénédict de Saussure invented the first hygrometer using human hair to measure humidity.
A humidor is a humidity-controlled box or room used primarily for storing cigars, cigarettes, cannabis, or pipe tobacco. Either too much or too little humidity can be harmful to tobacco products; a humidor's primary function is to maintain a steady, desirable moisture level inside; secondarily it protects its contents from physical damage and deterioration from sunlight. For private use, small wooden boxes holding a few dozen or fewer cigars are common, while cigar shops may have walk-in humidors. Many humidors use hygrometers to monitor their humidity levels.
HVAC equipment needs a control system to regulate the operation of a heating and/or air conditioning system. Usually a sensing device is used to compare the actual state with a target state. Then the control system draws a conclusion what action has to be taken.
An evaporative cooler is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning systems, which use vapor-compression or absorption refrigeration cycles. Evaporative cooling exploits the fact that water will absorb a relatively large amount of heat in order to evaporate. The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants.
A humidifier is a household appliance or device designed to increase the moisture level in the air within a room or an enclosed space. It achieves this by emitting water droplets or steam into the surrounding air, thereby raising the humidity.
The piano requires various forms of maintenance to produce its best sound. Maintenance is also important for the appearance of the piano.
An air handler, or air handling unit, is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. An air handler is usually a large metal box containing a blower, furnace or A/C elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to a ductwork ventilation system that distributes the conditioned air through the building and returns it to the AHU, sometimes exhausting air to the atmosphere and bringing in fresh air. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served without ductwork
Building automation (BAS), also known as building management system (BMS) or building energy management system (BEMS), is the automatic centralized control of a building's HVAC, electrical, lighting, shading, access control, security systems, and other interrelated systems. Some objectives of building automation are improved occupant comfort, efficient operation of building systems, reduction in energy consumption, reduced operating and maintaining costs and increased security.
A motion detector is an electrical device that utilizes a sensor to detect nearby motion. Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area. They form a vital component of security, automated lighting control, home control, energy efficiency, and other useful systems.
HVAC is a major sub discipline of mechanical engineering. The goal of HVAC design is to balance indoor environmental comfort with other factors such as installation cost, ease of maintenance, and energy efficiency. The discipline of HVAC includes a large number of specialized terms and acronyms, many of which are summarized in this glossary.
Water activity (aw) is the partial vapor pressure of water in a solution divided by the standard state partial vapor pressure of water. In the field of food science, the standard state is most often defined as pure water at the same temperature. Using this particular definition, pure distilled water has a water activity of exactly one. Water activity is the thermodynamic activity of water as solvent and the relative humidity of the surrounding air after equilibration. As temperature increases, aw typically increases, except in some products with crystalline salt or sugar.
A dedicated outdoor air system (DOAS) is a type of heating, ventilation and air-conditioning (HVAC) system that consists of two parallel systems: a dedicated system for delivering outdoor air ventilation that handles both the latent and sensible loads of conditioning the ventilation air, and a parallel system to handle the loads generated by indoor/process sources and those that pass through the building enclosure.
A humistor is a type of variable resistor whose resistance varies based on humidity.
Midea Group is a Chinese electrical appliance manufacturer, headquartered in Beijiao town, Shunde District, Foshan, Guangdong and listed on Shenzhen Stock Exchange. As of 2021, the firm employs approximately 150,000 people in China and overseas with 200 subsidiaries and over 60 overseas branches. Midea Group is listed on Shenzhen Stock Exchange since 2013. It has been listed on the Fortune Global 500 since July 2016. Midea produces lighting, water appliances, floor care, small kitchen appliances, laundry, large cooking appliances, and refrigeration appliances. It is the largest microwave oven manufacturer, and acts an OEM for many brands. It also has a long history in producing home and commercial products in heating, ventilation and air conditioning (HVAC). It is the world's largest producer of robots and appliances.
The 'ten agents of deterioration' are a conceptual framework developed by the Canadian Conservation Institute (CCI) used to categorise the major causes of change, loss or damage to cultural heritage objects. Also referred to as the 'agents of change', the framework was first developed in the late 1980s and early 1990s. The defined agents reflect and systematise the main chemical and physical deterioration pathways to which most physical material is subject. They are a major influence on the applied practice of conservation, restoration, and collection management, finding particular use in risk management for cultural heritage collections.
