Weems and Plath Endurance II 135 Barometer/Thermometer - Manual (Page 11)

VI. Barometer Instructions
When your barometer left the factory, it was set at standard sea level.
To calibrate your barometer to the atmospheric pressure in your area:
1) Find the current atmospheric pressure by checking local televison station
or weather website such as NOAA.
2) On back side of instrument, use standard screwdriver and turn the slot
head screw to correct position. Never turn this screw in either direction more
than one full rotation as it could cause movement damage. (For Endurance
135 series, turn the fastener on the porthole door of the instrument counter-
clockwise to release the hinged bezel and open. Then adjust screw on
back of movement as above.) For every 100 feet in altitude, an adjustment
of 0.11 inch is required (1,000 ft. = 1.1 inches). The movement used in this
barometer is adjustable up to an altitude of 3,500 feet.
3) The movable pointer (memory hand) at the center of the glass crystal
should be set to the present atmospheric pressure by superimposing it upon
the barometer needle. This will allow you to return to the barometer after
some time has passed and determine if the atmospheric pressure has risen or fallen.
PLEASE NOTE: A barometer is an instrument used to predict a change in
weather by measuring variations in atmospheric pressure, or the weight of the
air around us. The barometer will normally predict changes in weather 12
to 24 hours in advance. It is not an indicator of present weather conditions.
Your barometer is an aneroid or holosteric type which measures atmospheric
pressures mechanically without use of liquids.
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