Found this posted on another site. Never thought of taking apart a hygrometer so found this to be a little interesting:

https://m.youtube.com/watch?feature=youtu.be&v=ae8jxXXGWU0

Ha...........very interesting.
All that technology, and my vintage analog French hygro is still as reliable as any of my digitals...................heck.......might even be a horse hair model.......heh

Big Clive has a very interesting channel. He recently reviewed a blasting charger and a solid state dehumidifier chip that was really interesting.

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DC....or... AC....from the batteries?