How do you calibrate a hygrometer?
A hygrometer measures humidity, which is very important for a healthy indoor climate and essential on board a ship. At Studio Maritime, we sell hygrometers with classic hair mechanisms or modern synthetic fibers. Whatever you have: occasional calibration is wise to ensure accurate readings.
What exactly is calibration?
Calibrating means comparing your hygrometer's reading to a known, reliable value. This can be done using another (calibrated) hygrometer, or with simple home methods such as a salt solution or a wet sponge. You don't have to change anything on the device itself—unless the deviation is too large, in which case you can adjust it (if possible).
Please note: a small deviation is normal. Many hygrometers have an accuracy of ±3%, so a difference of 5-6% between two measurements is often still acceptable.
Why calibrate?
Over time, hygrometers can become inaccurate. This can happen, for example, because they have been in dry air, transported, or simply aged. Hair hygrometers are particularly susceptible to this: the hair dries out, which affects the measurement. Therefore, it's wise to check your hygrometer once or twice a year, for example, after winter or after transport.
Method 1: Calibrating with a salt solution (±75% humidity)
What do you need?
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Table salt (preferably without additives)
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A small bowl
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A well-sealable plastic bag or container
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Your hygrometer
How to do it:
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Mix salt with a little water to form a thick paste.
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Place this in the bag or container with the hygrometer.
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Leave it for at least 6 hours at room temperature.
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The humidity in the bag should now be around 75%.
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Is your hygrometer off by a few percent? No problem. Is it significantly off? Then you can adjust it.
Additional info: with pure salt (e.g., sodium chloride without iodine/anti-caking agent) and distilled water, you can achieve an accuracy of ±0.5%. But with ordinary table salt in tap water, you'll already be close.
Method 2: The wet sponge (±95–98% humidity)
What do you need?
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A damp, clean sponge
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A well-sealable plastic bag
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Your hygrometer
How to do it:
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Wet the sponge (not dripping).
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Place the sponge and hygrometer together in the bag.
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Leave it for at least half an hour.
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The meter should now point towards 95–98%.
Tip: you can adjust the hygrometer while it's still in the bag. Use a small screwdriver and adjust to ±98%.
How do you adjust the hygrometer?
Many hygrometers have a small adjustment screw on the back or side. Carefully turn this until the value is correct during one of the test methods above. If in doubt, check the manual or contact us.
Please note: only adjust after the hygrometer has acclimatized to the test environment for at least an hour, otherwise you will be adjusting it based on a snapshot.
What else should you pay attention to?
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Always calibrate at a constant temperature (not next to a heater or in the sun).
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Ensure your hygrometer is upright.
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Even temperature differences of 1°C can already cause a 2–7% difference in humidity.
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Want even more precise measurements? Use two methods (e.g., salt and sponge) and check if your hygrometer measures consistently between those points.
Which hygrometer is right for you?
At Studio Maritime, you will find both hair hygrometers with a classic look and modern versions with synthetic fibers. Both have their charm and function, and are suitable for use on board or indoors.
👉 View our hygrometers
👉 Want to know more? Contact us
