They have been discontinued for some time they will become impossible to get soon. I have never liked them myself. I believe in a decent accuracy sadly there is really two ways to get it. Spend lots of money, or buy a handful of cheap ones. I use very inexpensive probe types, they are poor accuracy so you need to buy a few (at least 3 and more, 5) Lay all out together and keep the ones that read the same. I use an accurate analogue hygrometer, they need to have a METAL face card and most have a calibration screw as well. The digital hygrometers usually do not have good accuracy anyway. Calibratable analogue types often come very good out of the box. If they test out to be incorrect they can be adjusted. As a bonus they stand up to dust dirt and being dunked in water.
http://www.ebay.ca/itm/LCD-Digital-F...item415ade2f7d
http://www.amazon.com/Analog-Hygrome...5305482&sr=8-1
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