Recording hygrothermographs
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A recording hygrometer is an instrument that records temperature and humidity by inscribing the levels with pens on a paper chart fastened to a rotating drum. The drum can be powered by clockwork, battery, or directly from an electrical power supply. There are various designs, but all feature charts that are marked into hours, days, and weeks. The pens are attached to levers, which are activated by metallic thermometer and hair bundles or diaphragms. The hair or diaphragm stretches or contracts to measure humidity, while a pen records the level and rate of fluctuation on the moving chart. |
The advantage of the recording hygrothermograph
is that, if properly used, it provides a graphic
and long-term record of conditions. Maintenance
can be onerous and must be performed assiduously
if an accurate record is to be kept. The paper
charts must be collected and changed every week,
the two pens charged with ink, the hair bundles
or diaphragm regularly replaced because of wear
and tear. At least monthly, calibration with a
psychrometer must be done.
Next: Psychrometer
