Hygrometers come in a number of different styles and are used mainly to determine the humidity of wine cellars, cigar boxes, and greenhouses to keep your moisture-loving products in top condition. This is an important job and it is not wise to sacrifice quality for a bargain.
If you plan on using a hygrometer for just the outdoors check out weathershop for a variety of weather assessment devices.
If you want to use your hygrometer for controlled environments you have two main choices:
The National Park Service uses hygrometers for national park services and museum collections.
* The recommendation? "In order for humidity-sensing instruments to accurately sense and record conditions, they require routine calibration. Instruments using hygroscopic sensing elements have a tendency to drift from a set point. It is recommended that hygrometers and hygrothermographs be calibrated at least quarterly, preferably monthly. When environmental conditions change rapidly or dramatically in an area being monitored, it may be necessary to check calibration even more often."
* In light of this, the calibration-free digital hygrometers seem to be the best option on the market.
One More Question
If you're buying for a cigar-purpose, would you like your hygrometer built in to your humidor? It's really a matter of personal preference. Would you like a strealined humidor or one with all the bells and whistles?