noun
self-registering hygrometer; recording hygrometer
A technical instrument that automatically records humidity over time. Used in meteorology, laboratories, and industrial settings.
気象台では自記湿度計を使って湿度の変化を記録している。
At the weather station, they use a self-registering hygrometer to record changes in humidity.
Compound of 自記 (self-recording) + 湿度計 (hygrometer). A straightforward technical term.