What is a hygrometer? And what are its uses?
Hygrometer, which is also called humidity gauge, is a device used to measure humidity or the amount of water vapor in the air. Hygrometers are valuable devices that calculate and calibrate changes in pressure and temperature, when these factors are added together, the resulting percentage is the humidity of the air.
Types of hygrometers
- Mechanical hygrometer:
In this type of hygrometers, organic materials are used, especially finer materials such as human hair, which contract and expand in response to humidity. Contraction and expansion in the mechanical hygrometer causes the spring to move the needle on the scale plate and the amount of air humidity is determined by it.
- Digital hygrometer:
This type of hygrometers, which are often used in industrial places, work based on measuring the change in electrical resistance. These hygrometers measure humidity changes using a thin layer of lithium chloride and a semiconductor.
- (Psychrometer) Psychrometer
Psychrometer is a hygrometer that consists of two thermometers – one with a wet bulb and the other with a dry bulb. In this type of hygrometers, evaporation is used to determine humidity. The end of the wet bulb thermometer is covered by a large cloth and by rapidly rotating both thermometers or by blowing air on the bulbs, the temperature of the wet bulb thermometer becomes cooler than the dry bulb thermometer. The temperature difference between wet and dry bulb thermometers can be used to calculate the amount of water vapor in the air
- Capacitive hygrometer:
For applications where cost and resistance to breakage are important, capacitor moisture meters are used, which have a lower price and accuracy. In capacitive hygrometers, the effect of humidity on the dielectric constant, which is a polymer or metal oxide material, is measured. If these hygrometers are calibrated, their accuracy will double to three times. Capacitive sensors are resistant to effects such as condensation and temporary high temperature. Capacitive hygrometers lose their accuracy if they are constantly exposed to contamination and wear, however, they are suitable for many applications.
- Thermal hygrometer:
Thermal hygrometers work based on measuring the change in thermal conductivity of the air caused by humidity. These types of hygrometers measure absolute humidity instead of relative humidity.
- Optical hygrometer:
The optical hygrometer works based on the amount of light absorption by water in the air. In this type of hygrometers, there is a light emitter and a light detector with a volume of air between them.
- Most hygrometers have the ability to measure dew point and wet point, and some of them have a separate sensor to measure humidity, which makes it easier to measure humidity in different places. Hygrometers have different accuracy and measurement range, and according to that, they are used in different places.
- In addition to measuring air humidity, hygrometers can also measure relative humidity, air temperature, surface temperature, and wind speed. A hygrometer is a useful tool for offices, homes, and especially production and industrial processes such as factories, refineries, petrochemicals, research laboratories, etc. These areas need to ensure that the humidity does not change because the change in humidity may affect the production of materials and output products as well as their quality.
- Hygrometers play an important role in firefighting because the lower the relative humidity, the more intensely the fuel can burn. In residential environments, hygrometers are used to help control humidity (too little humidity can damage the human skin and body, while too much humidity promotes the growth of mold and dust mites).
- Almost every product imaginable is directly affected by humidity or performs differently at different relative humidity levels, which is why hygrometers are valuable tools for measuring ambient air humidity. The amount of humidity in the environment and industrial processes affects the performance of materials, so that minor changes in humidity levels can have significant effects on industrial processes. In order to obtain and know the exact amount of this humidity, sensors must measure variables such as pressure and temperature of the environment. take and be in control. Therefore, the two factors of pressure and temperature have a significant effect on the measurement of humidity.
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