How to Test a Hygrometer to Measure the Humidity Levels
Hygrometers are precision instruments used to measure relative humidity. Relative humidity is the percentage of water vapor actually in the air at a specific temperature, as compared to the maximum amount of water vapor the air could hold at that temperature. Relative humidity is important to people with asthma, in chicken hatcheries, in exotic pet terrariums and even in humidors containing expensive cigars. You should check mechanical and electrical hygrometers for accuracy at least once a year. If necessary, you can manually adjust your hygrometer or apply a correction.
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Instructions
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Add the salt and water to the mug. Mix to form a wet paste with the spoon.
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Place the hygrometer and the mug containing the salt and water paste in the plastic bag.
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Seal the plastic bag with the rubber band.
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Place the plastic bag out of drafts or bright sun and let it sit undisturbed for eight to 12 hours.
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Read the hygrometer while it is still in the sealed plastic bag. If it is accurate, the hygrometer will read 75 percent.
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Adjust your hygrometer to read 75 percent, if necessary, using the adjustment screws on the back of the case. If you cannot manually adjust your hygrometer, add or subtract the amount the reading differed from 75 percent to each subsequent humidity reading. For example, if it read 73 while in the plastic bag, you would add 2 percent to each humidity reading.
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Tips & Warnings
Make your readings with the hygrometer out of direct sunlight or wind, as they can affect accuracy.
It can take as long as two hours for a hygrometer to adjust to changes in humidity, so let it sit at least that long before taking a reading.
To prevent damage, keep the salt and water mixture from touching your hygrometer.
References
- Photo Credit hygrometer and barometer image by Richard J Thompson from Fotolia.com
