Humidity

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Originally Posted by paperaith

Slightly OT, but how do you calibrate the analog ones?

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Some higher quality analogue hydrometers have an adjustment knob on them. the analogue ones sold at pet stores do not have this feature.

Good analogue ones have 2 things in common metal face cards and a calibration screw on the back. They inexpensive ones use a bi metal spring and the screw just re tensions them it is a very robust simple system. The digital version has a calibration dial that allows the changing of the RH value. I have tried 2 different digital ones but the dial is on the face and easily moved and with both the ones I had the snake managed to move it. Digital units can be tested but the standard salt test is hard on the digital sensors. They are very frail and sensitive to dust dirt and any and all contaminants. I would suggest a calibrate-able hygrometer is the way to go. Sadly calibrating digital units is likely to shorten the life so when they are wrong it is easier to toss them, and replace it.

My brand of choice is this one...

http://www.amazon.com/Analog-Hygrome.../dp/B0007VWEQA