Weems and Plath Endurance 125 Clock - Manual (Page 16)

Comfortmeter Operating Instructions
This Comfortmeter is a combination of both temperature and humidity
indicators. Calibration and positioning of hands are designed to indicate
perfect comfort conditions when both hands cross in a limited area of the
dial, the C O M F O R T Zone.
Both temperature and humidity indicators are accurately calibrated at the
factory and normally require no adjustment.
Hygrometer
The Hygrometer will indicate the relative humidity of the atmosphere. While
indoor and outdoor barometric pressure are identical, this is not true of the
relative humidity. Therefore, remember that this instrument when used in
the home indicates the humidity of room atmosphere which has no relation
to the outdoor humidity readings announced on weather reports.
Adjustment of the Hygrometer
Adjustment of the hygrometer is not necessary. However, it is
recommended that hygrometers kept in permanently low humidity areas
(i.e. Central heating/air conditioning, etc.) should be wrapped in a damp
cloth for 24 hours to reactivate "lazy" dried out coils. To maintain accuracy
of the instrument, it is advisable to perform this procedure every six
months.