This article will help you calculate or measure relative humidity. Relative humidity is an estimate of how saturated the air is with water vapor. Follow these instructions to find out what tools you will need and how to use them.
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Method 1 of 4: Buying a Humidity Meter (Hygrometer)
Step 1. The easiest way to measure humidity is to buy a hygrometer
The hygrometer measures humidity from 0% (dry) to 100% (when there is more dew, fog or rain will appear.)
- Relative Humidity (KR) can vary throughout the day. The cooler air contains less dew so the KR level will be higher at night. This is the reason why air conditioners tend to be very dry.
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The price of a hygrometer can be very cheap to very expensive.
- It is recommended that you purchase a more expensive hygrometer if you are maintaining expensive items or need a more accurate hygrometer. When buying a hygrometer, the price will be according to its use. Forecasters, museum curators, cigarette collectors, tropical lizard owners, HVAC systems technicians, acoustic guitar collectors, and owners of vintage Stradivarius Violins want a high-quality hygrometer to protect their investment.
- You can buy a cheap hygrometer if you just want to make sure your basement doesn't get too wet or make sure someone's room with a fever is comfortable.
- Even if you're okay with cheaper hygrometers being inaccurate, another problem arises: the hygrometer can break and you don't notice it. For example, if you're measuring humidity in your basement, and you never enter it, a broken hygrometer will be a problem.
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Hygrometers are available in both analog and digital forms.
- If you need to build a humidifier system that turns on when the humidity in the room reaches a certain level, then you need a digital hygrometer.
- Many guitar players buy good analog hygrometers to keep in their guitar case. Digital hygrometers will look less good when mounted on an acoustic guitar.
Method 2 of 4: Measuring the Hygrometer's Accuracy Level
Step 1. The simplest way to test the accuracy of the hygrometer is to experiment with a wet cloth
Wrap the hygrometer in a damp cloth and leave for a few hours. The hygrometer will show ~95%.
Wet cloth experiments can show errors for hours or days on a cheaper electronic hygrometer, whereas on a higher quality hygrometer it will be faster until the hygrometer reading is accurate
Step 2. A more accurate way to measure (help calibrate) the hygrometer's accuracy is the “Salt Experiment”
The Salt Experiment is more accurate, but not suitable for more difficult applications.
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Take a sample bag and insert the hygrometer, then face it upwards. Take a bottle cap (2 liter plastic bottle) and pour salt into the bottle cap to taste. Then add distilled water until the salt resembles melted snow. Close the sample bag tightly. After 12 hours the hygrometer will show 75%.
- Suppose the hygrometer shows 80%, then the calibration result is too high 5%.
- You can repeat the experiment for consistent results.
Step 3. You can also combine other related elements for further application
Each experiment will show different results.
For example, you can also use magnesium chloride and lithium chloride instead of table salt (sodium chloride). Magnesium Chloride reaches equilibrium at 33%, while Lithium Chloride at 11%. The composition can be used if you are experienced in the field of chemistry
Method 3 of 4: Measuring Humidity Using a Psychrometer
Step 1. Purchase a psychrometer
You can choose an electronic psychrometer even Dewcheck for further application. Rotary psychrometer is recommended for education because it is fun for students.
Taisho and Bacharach are two leading manufacturers of electronic psychrometers
Step 2. Make your own psychrometer
- Take two thermometers.
- Use either one to record the temperature on the thermometer.
- Place a wet object such as a wet cotton swab over the bulb (bottom end of the thermometer).
- Turn on the fan to flick the thermometer, then wait for the temperature drop to stop and take notes.
- You can also use this method:
Method 4 of 4: Using Dewcheck
Step 1. Dewcheck is an industrially advanced temperature and humidity monitoring device
Generally used in painting and gluing to prevent moisture levels from getting too high.
Step 2. Dewcheck comes with a USB device so data can be exported easily
Dewcheck also has analysis software.
Step 3. Before using Dewcheck, you need to program the durability of this device
The durability of the device depends on the deployment you are using.
