1. What is humidity anyway?
Humidity is the amount of water in the air. It's made up of invisible water droplets suspended in the air.
High humidity means there is a lot of water in the air, and low humidity means there is less water in the air.
Humidity sensing point
You can actually feel the humidity on your skin.
- When the humidity is high, the air becomes sticky and sweat does not dry easily.
- When humidity is low, the air becomes dry and your throat and skin tend to become dry.
What is the appropriate humidity?
It is said that the ideal humidity for humans to be comfortable is around 40% to 60%.
- If it is lower than 40%, the air will be too dry, making you thirsty and your skin dry.
- If it's higher than 60%, the air becomes too humid and mold grows easily.
That's why it's important to measure the humidity level in your home and use humidification or dehumidifier to maintain an appropriate level of humidity.
2. How to measure humidity?
There are two main ways to measure humidity:
- How to use a wet and dry bulb thermometer (psychrometer)
- The humidity is calculated from the difference between the readings of a dry-bulb thermometer and a wet-bulb thermometer (a thermometer wrapped in a damp cloth).
- Uses the principle that when the air is dry, the water in the wet bulb evaporates and the temperature drops
- The relative humidity is calculated by comparing the difference between the dry bulb and wet bulb temperatures with a humidity chart.
- How to use a temperature/humidity hygrometer
- Use a dedicated measuring device equipped with a humidity sensor such as a bimetal or hair.
- There are two types: digital and analog. The digital type gives you an accurate reading of the humidity level.
- The best location to install it is one that is not exposed to direct sunlight and has no wind currents.
- While a wet and dry bulb thermometer is a convenient way to measure humidity, a temperature/humidity is easier and more accurate.
3. Purpose of measuring humidity
To maintain a comfortable living environment
Proper humidity has a significant impact on human health and comfort.
- If the humidity is too high, it becomes muggy and sticky, and if it is too low, it becomes dry and causes sore throats and skin.
- Generally speaking, humans feel comfortable with a humidity level of around 40-60%.
- Use a hygrometer at home and adjust the humidity with a humidification or dehumidifier to maintain a comfortable indoor environment.
To manage the storage conditions of items
Proper humidity control is important because humidity can affect the deterioration and transformation of items.
- In art galleries and museums, humidity is controlled to prevent deterioration of paintings and ancient documents.
- When storing food or medicine, excessive humidity can easily cause deterioration or mold.
- Humidity control is also carried out in warehouses and factories to maintain product quality.
To maintain a proper working environment
In some workplaces, humidity needs to be controlled as it can affect work efficiency and product quality.
- In printing factories, the humidity of the paper is controlled because it affects the print quality.
- Humidity control is used as a countermeasure against static electricity at electronic component manufacturing sites.
- Humidity control is also carried out in warehouses and factories to maintain product quality.
In this way, humidity measurement plays an important role in various situations, such as maintaining a comfortable living environment, properly storing items, and managing the work environment.
4. Types of hygrometers and how to choose them
The main points to consider when choosing a hygrometer are:
- Use and installation location
- For home use, ease of viewing and additional functions (clock/alarm/ back-lit illumination display etc.) are convenient
- For commercial use, high accuracy that can handle a wide range of temperature/humidity is suitable.
- accuracy
- For general household use, an error of about ±5% is acceptable.
- When precision is required, it is preferable to have a precision within ±2%.
- Installation Method
- Choose a stand-type, wall-mounted, magnetic, or other type that can be installed in a variety of ways.
- Install in a location that is not exposed to wind or direct sunlight.
- Integrations
- If it can be linked to a smartphone app, remote monitoring is possible.
- If there is a function to notify you of abnormalities, you can avoid danger in advance.
As such, it is important to choose an appropriate hygrometer by taking into consideration the purpose, installation location, and required accuracy.
5. Make your own hygrometer
Making your own hygrometer is relatively easy.
- How to use a resistance humidity sensor
- Lithium chloride electrolyte method
- How to use hair
The sensor value is read by a microcontroller and converted into humidity by a program.
6. Humidity and perceived temperature
Even if the temperature is the same, if the humidity is high, the perceived temperature increases and you are more likely to feel uncomfortable. If the humidity is low, the perceived temperature decreases and you feel comfortable.
- A 20% increase in humidity will increase the perceived temperature by approximately 1°C.
- When the temperature is 30°C and the humidity is 80%, the perceived temperature is approximately 33°C.
- When the temperature is 30°C and the humidity is 30%, the perceived temperature is approximately 25°C.
7. Humidity and mold
High humidity environments are prone to mold growth.
- Mold requires a humidity level of 60% or higher to grow.
- When moisture accumulates on walls and furniture due to dew condensation, it becomes an opportunity for mold to grow.
8. Humidity and cold
Humidity itself does not cause colds, but it can have the following effects:
- Low humidity dries out the mucous membranes of the nose and throat, making it easier for viruses to enter the body.
- Extremely low or high humidity makes it easier for viruses and bacteria to grow.
9. Humidity and static electricity
Static electricity is more likely to occur in low humidity environments.
- When the human body or objects become dry, static electricity becomes more likely to occur.
- Electrostatic discharge can cause equipment to malfunction or malfunction.
10. Humidity and Instruments
Different types of instruments have different optimum humidity ranges.
- For wooden instruments, about 50-60% is suitable.
- For metal instruments, around 40-50% is appropriate.
- If the humidity is too high, the instrument may be damaged by mold or rust.
11. Humidity and plants
Proper humidity is important for plant growth.
- High humidity increases the risk of disease and pests.
- Low humidity increases transpiration and causes plants to dry out more easily.
- Generally, the ideal humidity for plant growth is said to be around 50 to 70%.
- Different types of plants have different optimum humidity ranges.
12. Humidity and food
Proper humidity control is essential to maintaining food quality.
- High humidity makes it easier for mold and bacteria to grow.
- Low humidity causes food to dry out and lose quality.
- Generally, the ideal humidity for storing food is considered to be around 60 to 70%.
13. Humidity and medicines
Humidity control is also important for maintaining the quality of pharmaceuticals.
- High humidity can cause chemicals to deteriorate or mold to grow.
- Low humidity can cause tablets to soften and capsules to break.
- The suitable humidity range for storing pharmaceuticals is generally considered to be 20 to 60%.
14. Humidity and Electronics
Humidity control is essential to prevent electronic devices from malfunction.
- High humidity can cause mold, short circuits, and corrosion on components.
- Low humidity can cause static electricity to build up, which can damage components.
- Generally, the ideal humidity range for electronic devices is considered to be around 30 to 60%.
15. Humidity and precision machinery
Humidity control is also important for maintaining the performance of precision machinery.
- High humidity can cause mechanical parts to rust and insulation problems.
- Low humidity can cause static electricity that can damage precision components.
- The humidity range suitable for precision machinery is generally considered to be around 40 to 60%.
16. Humidity and air pressure
The relationship between humidity and air pressure is as follows:
- The higher the air pressure, the more water vapor vapor (absolute humidity) can be contained in the air.
- However, relative humidity remains constant regardless of air pressure.
- For example, in mountainous regions at high altitudes, the air pressure is low, so the absolute humidity is low.
17. Humidity and dew point
The dew point temperature is the temperature at which water vapor in the air becomes saturated and begins to dew condensation.
- The higher the humidity, the higher the dew point temperature.
- dew condensation occurs when the indoor temperature falls below the dew point temperature.
- To prevent dew condensation, proper dehumidification or humidification is necessary.
18. Humidity and heat stroke
Hot and humid environments increase the risk of heatstroke.
- High humidity reduces the evaporation of sweat, making it easier for body temperature to rise.
- The Japanese Society of Biometeorology proposes the wet bulb globe temperature (WBGT) as a guideline for preventing heatstroke.
- In environments where the WBGT is 31°C or higher, care must be taken to avoid heatstroke.
19. Humidity and energy conservation
Proper humidity control also helps save energy.
- In the summer, dehumidifying and lowering humidity will make the room more comfortable at a lower temperature setting.
- In winter, if humidification and increase the humidity, you will feel warmer even at a higher set temperature.
- By adjusting the humidity in this way, the air conditioner's set temperature can be brought closer to energy-saving operation.
20. Humidity and IoT
With the development of IoT, humidity control is becoming more advanced.
- The sensor can measure humidity in real time and collect and analyzing the data.
- Optimal humidity control is possible using AI.
- IoT humidity control is being used in smart homes and building management systems.
