It is not heat, it is moisture! “It’s sultry!” Have you ever heard someone say such a thing on a hot day?
To understand humidity, you must first realize that there is water in the air around you. “But I’m not wet!” You may be right. Most of the air around you has water in the form of gas called water vapor.
Let’s understand moisture through a few things:
What is humidity?
What is the dew point?
How to measure humidity?
What is humidity?
Moisture that is easily expressed is simply the amount of water vapor held in the air. Water vapor is a gaseous state of water. As the temperature rises, more water vapor can be retained, as the molecules move at higher temperatures to prevent condensation.
There are three main measurements of humidity: relative, absolute and specific. Humidity measurement
Absolute humidity:
Absolute humidity is the measurement of the actual amount of water vapor in the air, regardless of air temperature. The higher the amount of water vapor, the higher the absolute humidity. For example, a maximum of about 30 grams of water vapor can be present in one cubic meter of air volume with temperatures in the mid-1980s. (Units are hot water vapor per cubic meter of air volume)
relative humidity:
Relative humidity, expressed as a percentage, is a measure of the amount of water vapor that air holds in comparison to the amount that it can hold at a certain temperature. Hot air can have more water vapor (humidity) than cold air, so with the same amount of absolute / specific humidity, the air will have a higher relative humidity. 50% relative humidity means that the air on that day (specific temperature) holds 50% of the water needed to saturate the air. Saturated air has a relative humidity of 100%. Humidity measurement
The relative humidity of a mixture of air and water is also defined as the ratio of the partial pressure of water vapor in a mixture to the pressure of water vapor saturated at a certain temperature (see what is vapor pressure). Therefore, the relative humidity of the air is a function of water content and temperature.
Specific humidity:
Specific humidity refers to the weight of water vapor per unit weight (amount) of air (expressed in grams of water vapor per kilogram of air). Absolute and specific humidity are quite similar in concept.
What is the dew point?
Dew point is the temperature at which air is saturated with water and condensation begins. The higher the dew point, the higher the humidity.
How to measure humidity?
Since many things are affected by humidity, it can be said that humidity must be measured and different methods can be used to measure it. Some of the main methods are as follows:
Types of hygrometers:
The following types of hygrometers are used to measure humidity.
Relative humidity sensor (electrical impedance):
Hygrometer is a relative humidity sensor based on an electronic component that absorbs water vapor according to the humidity of the air and changes the electrical impedance (resistance or capacity). The device is usually in the form of a “probe” that is connected directly or via a cable to an electronic unit to display relative humidity.
Density-based hygrometer:
Hygrometer uses cooling to induce controlled compaction. The stable temperature at which this occurs is measured and reported as the dew point or ice point. A typical format is a cooled mirror with optical density detection, which is used as feedback to control the temperature of the mirror.
Dew point probe:
Hygrometer based on electronic sensor that changes the electrical capacity in water absorption and is able to measure small levels of water vapor in very dry gases. It is often scaled in units of dew point (or freezing point).
Psychrometer (wet and dry bubble hygrometer)
Hygrometer Using an evaporative coolant as a humidity measure, a dry thermometer is compared to a thermometer coated in a wet wick in moving air. Paired temperature values can be used to find humidity using tables or calculations (sometimes internally calculated and displayed directly by modern hygrometers).
Mechanical hygrometer:
Using a hair length modifier (hair hygrometer) or other organic material to measure moisture, some types of hygrometers record on a graph driven by clock wheels or batteries. Very primitive varieties are not fed at all. Electronic sensor-based hygrometers are usually now preferred, but many mechanical hygrometers are used to monitor the room.