4 Ways to Calculate Humidity

2024 Author: Samantha Chapman | [email protected]. Last modified: 2023-12-17 09:13

This article will help you calculate or measure relative humidity. Relative humidity is an estimate of how saturated the air is with water vapor. To understand what kind of tool you need and how to use it, just follow these steps.

Steps

Method 1 of 4: Buying a Moisture Meter (Hygrometer)

Step 1. The simplest way to measure humidity is to purchase a hygrometer

Hygrometers measure humidity from 0% (dry) to 100% (when the extra humidity precipitates or turns into fog.)

• Relative humidity (RH) can vary throughout the day. The colder air holds less moisture, so the RH level will usually be higher at night. It is also the reason why conditioned environments tend to be drier.

• The prices of hygrometers can range from very cheap, to very high figures.

  • A more expensive hygrometer is recommended if you have to use it to protect expensive things or if you need more accurate readings. When you buy a hygrometer, you receive the equivalent of what you pay, within reasonable limits. Meteorologists, museum curators, cigar collectors, owners of tropical lizards, technicians working on HVAC (heating, ventilation and air conditioning) systems, collectors of acoustic cabinet guitars, and owners of antique violins Stradivari want high quality hygrometers to protect their investments.
  • If you just want to make sure the basement isn't too humid, or that a room is comfortable when someone is cooled, a cheap hygrometer will suffice.
  • While the poor accuracy of a cheap hygrometer may be fine with you, there is another problem: cheap hygrometers can break, and you may not notice. For example, if you are measuring the humidity in the basement and never go to the basement, a broken hygrometer could be a problem.

• There are analog and digital hygrometers.

  • If you need to create a system where a humidifier turns on when the humidity reaches a certain level, you need a digital hygrometer.
  • Many guitarists will buy a nice analog hygrometer to put in their guitar case. The digital ones would be awful paired with an acoustic cabinet guitar.

Method 2 of 4: Measure the accuracy of your hygrometer



Step 1. The easiest way to test the accuracy of a hygrometer is to use a damp cloth

Simply wrap a damp cloth around the hygrometer and leave it there for a couple of hours. It should mark approximately 95%.

Note that for less expensive electronic hygrometers, the wet cloth test can give erroneous readings for hours or even days. Higher quality devices need a very short time to reach the approximately correct value



Step 2. A more accurate way to measure the accuracy of a hygrometer (or to help calibrate its accuracy) is the "Salt Test"

The Salt Test is more accurate, but is not suitable for applications that require maximum precision.

• Take an airtight bag and put the hygrometer in the bag, with the reader facing upwards. Then take the cap of a bottle (the cap of a 2-liter plastic bottle 2 is fine) and pour standard table salt into the cap. Then add a small amount of distilled water, until the salt has the consistency of muddy snow. Close the bag carefully. After twelve hours, the hygrometer should indicate 75%.

  • If the hygrometer indicates 80%, for example, it means that it is calibrated by 5% in excess.
  • It may be necessary to take more than one reading to confirm that the value is reliable.

  

  Step 3. For advanced applications, you can use the salt test with other similar items, each of which has its own readings

  For example, you could also use Magnesium Chloride and Lithium Chloride rather than table salt (Sodium Chloride). Magnesium Chloride gives as a reading 33%, Lithium Chloride 11%. Other compounds can be used based on your experience with chemistry

  Method 3 of 4: Measure humidity with a psychrometer

  

  Step 1. Purchase a psychrometer

  For more advanced applications, you can choose an electronic psychrometer, or even a dew point meter (Dewcheck). For educational purposes, Slingshot Psychrometers are recommended because they are fun for students.

  There are very reputable manufacturers of electronic psychrometers including Fieldpiece and General Tools

  

  Step 2. Make your own sling psychrometer

  • Get two thermometers.
  • Use one of the thermometers to take the current temperature and write it down.
  • Put something moist like wet cotton on the bulb of the other thermometer (the bottom tip of the thermometer).
  • Turn on a fan by directing the jet of air against the thermometer, wait for the temperature to stop dropping and then record it.
  • Go to the website https://www.fb.u-tokai.ac.jp/WWW/hoshi/env/humid.html and use their relative humidity table to calculate your relative humidity.
  • You can also use these programs here:

  Method 4 of 4: Using a Dewcheck Meter

  

  Step 1. The Dewcheck is a very advanced temperature and humidity monitoring device used for industrial applications

  It is often used for paints and epoxy resins, to avoid problems resulting from humidity levels that are too high.

  

  Step 2. The Dewcheck is equipped with a USB device, so the data can be easily exported

  It also has analytics software.

  

  Step 3. Before using the Dewcheck, tolerances must be programmed

  Depending on the application, these may differ.