The salt test

[Skeat5353]

Turn the knob on the right two clicks exactly. No more. Then immediately push the button in on the lower left with a pen and hold until the screen blinks. Put back in salt test and it should hit 75%.

I recently had to calibrate a new hygrometer. I bought the Boveda calibration pack -- easier to do because I didn't have to wonder whether I had the right amount of water on the salt.

Tablespoon Salt, Teaspoon Distilled water. Then swirl. 3/1 is the ratio, btw. Whatever ratio you use, just don't oversaturate the salt. All you are doing is creating sodium chloride which in turn only allows 75% of total moisture release as H20 evaporates. You know when you eat too much salt and you get thirsty? Same science at work with salt test. Here's the chart. Look at sodium chloride relative humidity.

http://www.omega.com/temperature/z/pdf/z103.pdf