Analog hygrometers will do the job, but after a while, they become inaccurate, and calibrating one is a clumsy operation. With the Hygro-Set Adjustable Digital Hygrometer, assuring the accuracy of the unit is as easy as turning a dial. On top of that, it has an easy-to-read display and it also shows the temperature. Oh, and the round unit should fit where your old analog hygrometer did. It's also available as a rectangular device or there's one for external hygrometers.