Quote Originally Posted by TheSnakeGuy View Post
All of those round analog thermometers are unreliable. Digital with a probe is the only way to go. ...

I too recommend the exact hygrometer. I calibrate instruments as part of my job. Yes there are digital units that have higher accuracy than the posted analogue. They are generally called PSYCHROMETERS and are fragile and hand held, The cheap ones that have an accuracy of 2-6%RH generally run in the 200$ range better ones with a 1% accuracy are in the 500$ range. They are fussy and frail (dropping it is often the end of the unit) I would not suggest them ever. The cheap digital hygrometers are cheap. The use a micro resistance to detect the change in RH and most common ones are 5-10% accuracy. To me 10% up or down from correct seems a bit much some have even worse at 20% which is about the same as licking your finger and timing the time it takes to dry.

The little analogue dial one posted has a METAL face card. This is the issue with the junk ones the card warps in humid conditions and jams the needles swing. The unit posted also has a calibration screw. I have own 25 of these units and have owned 30 digital units the best digital unit is 3% RH off the worst is 55% off (low it got peed on and that is all she wrote.) The worst of the analogue was 3% and I then corrected it. I test them every 6 months with a salt test and adjust them as needed they almost always are spot on the test which is only accurate to 1% so all average 1% error.

So 10$ analogue buys you 1% accuracy, and 500$ buys you a digital unit with 1% accuracy. I tend to feel that robust and cheap beats fragile and expensive. Don't believe me test them your self. You can do a salt test (google) on the analogue and buy a test kit for the digital (salt tests are hard on them digital are fragile and cannot be dusty dirty or damaged)