The Oakton Instruments WD-37250-10 is a Spring Wound Two-Speed Hygrothermograph that is made of corrosion-resistant acrylic for indoor or sheltered outdoor use. Spring winding keeps the chart running for eight days. Even when the motor begins to run down, a steady chart speed is maintained. It includes one 1-day gear and one 7-day gear, two felt-tipped pens (red and blue), and one 7-day rotation chart.

• Record temperature and humidity on 1 or 7 day rotation