# General > Member's Lounge > Photography >  How does a camera dry box works?

## carlfsk

I have an old camera dry box at home. With nothing to do, I thought of using the humidity guage to measure the humidity level in my emersed tank setup.

This dry box has a small black box at the back, which I suppose is the controling device to control the humidity level. Behind, there is a wire extended out which is plugged into the socket to supply electrivcity to the controller. However, when I took out the meter guage, I realised it's not in anyway connected to the wire or the controller. The guage is a stand alone device.

So, if the guage is not connected, how is the humidity level controlled in the box? Or is there another humidity meter in the controller?

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## tawauboy

the black box is the humidity controller. it should be an electronics based device and it does not need the gauge to work.
the gauge is there to provide you with a humidity value. and you are the one who "close the control loop".

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## benny

Carl,

What you are looking at is a hygrometer to put in your emersed setup. It can be digital or analogue (does not need batteries). Such meters can be bought from a lot of hardware shops and can come together with thermometers as well.

Cheers,

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## carlfsk

Hey guys, thanks alot. I have placed the hygrometer in my emersed setup, humidity level is at 60 - 70%. Room humidity is 40%.

I am digressing... anyone knows how I can control the humidity level in the tank? I intend to drill a few holes on the cover, and control from there. Will monitor any changes in humidity. 

Any better ways or off-the-shelve product in the market?

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