Expert: James Yee - 6/17/2008

Question
QUESTION: Should it be a level teaspoon or a mound teaspoon when calibrating your hygrometer?.

Thanks, Charles

ANSWER: Hi Charles,

For the salt test, it should be approximately 1 teaspoon of table salt and a few drops of distilled water.  It doesn't have to be a precise teaspoon measurement and when mixed with the water, the mixture should have a crumbly texture.

Regards,
James

---------- FOLLOW-UP ----------

QUESTION: Tip 1: Take a wet towel (not dripping wet, but wet enough) and wrap it completely around your hygrometer. Wait about half an hour, the reading should be of 98 % or more, if this is so, your hygrometer is calibrated and you do not need to re-calibrate.

Tip 2: If the reading is off, turn the screw on the back of the hygrometer until it reads 98 %. You have properly calibrated your hygrometer.

Is this a valid way?, it seems much quicker.

Thanks, Charles

ANSWER: Hi Charles,

Yes, that is also a good method for calibrating your hygrometer.  Both methods are equally effective at testing your hygrometer but most people prefer using a salt test.

Either method is fine so it's purely personal preference.

Regards,
James



---------- FOLLOW-UP ----------

QUESTION: If i know my hygrometer is out of sync, can i just put it to 98% streight away or does the process of the wet towel have an effect.

Answer
Hi Charles,

The purpose of the salt test/wet paper towel is to determine exactly how much your hygrometer is out of sync.  Once you find out how much the hygrometer is out of sync, you can adjust it accordingly.  For example, the salt test should achieve a reading of 75% humidity.  If your hygrometer reads more or less than 75% during the salt test, it is out of sync so you should adjust the pin so that it reads 75% exactly.  A wet paper towel over the hygrometer should create 98-100% humidity.  If it doesn't read 98-100%, adjust the hygrometer needle so that it does.

When calibrating your hygrometer, it's important that you test it with either the wet towel or salt test method.  If you just set the hygrometer to 98% without using the wet towel, it will still be out of sync.

Regards,
James