Barometers Realm

Self-registering instruments are technically ingenious devices in which, along with the primary instrument (such as an aneroid barometer, bimetallic thermometer, or hair hygrometer), a clock mechanism hidden inside a drum drives this drum, allowing a recording pen to continuously document any changes in the measured parameters. The mechanical clock hidden within the drum typically has an eight-day movement and requires winding with a key each week, as does the chart, which is also designed for one week of recording.