A somewhat older or formal word for thermometer; in modern everyday Japanese, 温度計 (おんどけい) is more common.
See also: 温度計 (おんどけい)
寒暖計で室温を測る。
I measure the room temperature with a thermometer.
昔の学校には、廊下に寒暖計がかかっていた。
In old schools, a thermometer hung in the hallway.
I measured the temperature with a thermometer.
The thermometer shows thirty degrees.