Hygrometers, Humidity, Help!

[bnaz]

I currently have my two Phal. orchids in their own humidity trays and sitting within an uncovered 5.5 gallon fish tank. As of now, there are no stones/water on the tank base, just the orchids in their own little pebble trays. I was wondering if you think this is helping with the humidity levels for my plants. I'm likely going to put pebbles on the bottom of the tank, and a thin layer of water as well.

Also, what kind of hygometer do you use? Are the cheaper ones still accurate and effective? I'd really like to get one for around $10 if at all possible. HERE a link to Amazon's listing for hygrometers, if you see the one you use, could you point it out for me? c:

As always, help is so much appreciated!