The mason's hygrometer is a wall-mounted wet and dry thermometer for determining relative humidity.

The classic masons hygrometer with wet and dry bulb hygrometer and a large water reservoir. One thermometer bulb is in air and the other is wrapped in a wick kept moist from a water reservoir. The difference between the two readings is used to give an accurate calculation of humidity. Complete with wet and dry bulb tables. Centigrade & Farenheight.

The hygrometer is housed in a robust case that measures 310 x 77 x 32mm.