So what is it?

A hygrometer is an instrument that measures the moisture in an environment by using a metric known as relative humidity. Besides being used in humidors, meteorologists use them to measure the weather and they are also used in greenhouses and industrial areas. How do I choose one? First you must decide if you want a digital or analog style hygrometer. The digital models are usually more expensive than analog style, but are easier to read. Once you chose between digital and analog it really comes down to personal choice. Just chose the one you think looks the coolest, is the cheapest or best matches your humidor.

How do I calibrate it?

Once you get your hygrometer home there are a few things you need to do in order to make sure it is functioning correctly.

1. Take a teaspoon of salt in a small cup and drop in a few drops of water without dissolving the salt.
2. Place the wet salt and the hygrometer in a sealable see through jar. Let sit for atleast 6 hours.
3. If your hygrometer is calibrated correctly it should read 75%. If it reads another number such as 71% than you know when trying to get the humidity levels you will need to add 4%. In the case of a humidor, which should be 70%, your hygrometer would read 66%.
4. If you have an analog hygrometer then you can just adjust it yourself to be accurate. Just change it to 75%. There should be way to adjust it on the back with a screwdriver or by turning a dial, depending on the model you have.