Two-Speed Hygrothermograph from Oakton Instruments
Spring wound- no batteries required!
Made of corrosion- resistant acrylic for indoor or sheltered outdoor use. Spring winding keeps chart running for eight days. Even when the motor begins to run down, a steady chart speed is maintained. Includes one 1-day gear and one 7-day gear, two felt-tipped pens (red and blue), and one 7-day rotation chart.