Thanks Bros...
At least I have a guide where to search!!!
My room's air-con on for night time only.
When the air-con not on, the "hygrometer" in the dry cabinet read between 50 to 60 %.
But After The Air-con on after two hour, let the dry cabinet's door open, the reading will go down to 45%, Is this sound strange?
i scared that the built in hygrometer didn't work properly, so i need a better hygrometer to confirm the condition. if $30 can get a ZHUN one, it will be great!!