User manual

Columbia Weather Systems, Inc. 39
inches of mercury (in. Hg.) move the Pressure switch on the back panel of the
console to the “inches” position.
2. Millibars Display: For a continuous display of barometric pressure in Millibars,
move the Pressure switch on the back panel of the console to the “millibars”
position.
3. Pressure Trend Indicators: Two LED lights to the right of the barometric pres-
sure display indicate when the pressure is rising or falling.
If there has been no change over a three-hour period (i.e., the pressure conditions
are steady), neither light will be illuminated. The Capricorn II Plus takes a sample
approximately every hour to see if there has been a significant change in barometric
pressure from the reading taken three hours previously. If there has been a change
in the averaged barometric pressure of 0.06 in. Hg (2 mbar) or more over the last
three hours, the Rising or Falling light will illuminate, as appropriate. During the first
three hours of operation, the barometric pressure readings will be compared every
hour with the reading taken at the start.
Since the barometric pressure readings broadcast on radio and television are
frequently several hours old, it is likely that the Capricorn II Plus will not agree with
the broadcast readings during changing weather conditions. Additionally, the Capri-
corn II Plus will differ from broadcast readings if it is not located in the immediate
vicinity or elevation of the broadcast pressure site.
The United States Weather Service measures barometric pressure in Millibars and
converts the readings into inches of mercury (Hg). Use the following chart for con-
version of values:
One inch Hg (mercury) = 33.8639 Millibars
One millimeter Hg = 1.3333 Millibar
One Millibar = 0.02953 inches Hg
One Millibar = 0.750 millimeter Hg
One atmosphere = 760 millimeters Hg
One atmosphere = 1013.3 Millibars
One atmosphere = 29.921 inches Hg
D. WIND SPEED
The Capricorn II Plus measures wind speed by using a precision wind cup anemom-
eter which turns an infrared optical chopper. The unique design of the wind speed
sensor assembly virtually eliminates the effect of friction on the sensor hub. The
mechanical threshold wind speed at which the anemometer starts to turn is 0.5 mph.
Measurable wind speeds range from 0 to 125 mph (0 to 200 km/h or 0 to 108 knots).
Accuracy is +/- 5% (or better) of the wind (gust) speed reading. The displayed wind
speed is the 0.5-second average. A measurement is taken and displayed every 0.5
second.