PhiAlpha1857:Going for a digital hygrometer. Are they all the same or are some more precise/accurate than others?
JDH:I have a Western Caliber II digital, and I highly recomend these.
The Sniper:Any hygrometer will work my friend - as long as you calibrate it. Just depends on what you want to spend on one. While the suggestions you've gotten so far are all good ones, an el cheapo that you cant adjust will work just fine. Use the salt test, find out how far off 75% RH it is, and write that on the hygro with a sharpie.
IE: Lets say when you do your salt test, the hygro is reading 79%. Just write "Add 4" on the hygro, and voila! You're in business.
If you do want to come off a little change for one, I recommend the ROUND style hygro from Xikar. They tend to hold calibration for a long time with no variance, and the one-touch calibration adjustment cant be beat!
Hope this helped. :-)
Lasabar:I just found that my hygro was off by 4% after a salt test, one of my humi's was a tad dry over the holiday weekend. I am currently salt testing two Xikar rectangle Hygros and they are pretty nice. Superb build quality and are adjustable... I'm impressed with them so far.