For DIY or budget solution, use the following parts..
1. Digital Temp / RH / Clock ( cost around RM25-50 only at Jln Pasar )
2. Electronic Moisture Absorber ( I found one around the house used for hanging at clothes closet, so RM0 )
3. A transparent & air-tight box
To be sure the readings are accurate, I have an Arduino microcontoller with DHT11 temp / relative humidity sensors and the measurements are as follows :-
In the room is around 70 RH / 29-30C
In the DIY dry box , the RH drops from 70% to around 40-50% after a few hours
Or for those that do not want to mess with DIY stuff , just get those Karakka box ( google for it ) but it uses analog gauge RH meter..
Dry Box Setting (Photography)