Went out to buy a dry cabinet today. Mostly motivated for  more storage space than actually needed to keep dry. 

Ended up with a Digi-Cabi DB-036 (it's a 30L) from John 3:16 for $118/-.

The relative humidity stayed at 20% after running it for a day, that's even when the door was left opened for a couple of hours. That convinced me that the psychrometer is not working. True enough, took it apart and immediately saw one piece of resistor like part has came out. Made a random guess and "plugged" it back into one of the many set of holes, and viola, it worked!