Home >> Science & Nature >> Science

How to Test an Analog Hygrometer

A hygrometer is a device that measures the amount of moisture in the air. Analog hygrometers accomplish this by using a mechanism that changes shape depending on the humidity -- typically a salt-laced paper or a strand of hair, to move the dial. As many hygrometer applications require narrow ranges of humidity, it is important to make sure your hygrometer is functional and properly calibrated to avoid it displaying incorrect measurements.

Things You'll Need

Jar lid
Salt
Water
Paper towels
Airtight sealing container
Screwdriver

Instructions

- 1
  Remove the lid of a plastic or glass jar and thoroughly clean it with warm water. Allow it to dry before proceeding.
- 2
  Place the lid upside down and fill it with salt. Add water to the salt until it is damp, but do not allow water to pool over the salt; use a paper towel to dab any excess water away. Place the lid in an airtight container, such as a large plastic bag. Place the hygrometer in the bag and seal it.
- 3
  Wait eight hours and then check the hygrometer; it should have a reading of about 75 percent humidity.
- 4
  Calibrate the hygrometer if the reading is off. Use a small screwdriver to turn the adjustment screw -- normally on the back of the hygrometer -- until the dial reads 75 percent humidity.
- 5
  Retest and calibrate the hygrometer at least once a year.

Science