DAVIS Weather Monitor II (7440, 7440CS) - Manual (Page 40)

Calibration Numbers
Page 36 Weather Monitor II
7 . C
A L I B R A T I O N
N
U M B E R S
Calibration (CAL) numbers are used to turn raw data from the sensors into
meaningful readings on the display. The standard or default CAL numbers are
automatically entered by the unit when it is first powered up and whenever
power is lost and later restored.
Calibration numbers should not be changed except for certain specialized
applications. This section explains why you may wish to change CAL, the
equations used by the Weather Monitor II, and the default values for CAL
numbers. For instructions on changing CAL, see “Changing Calibration Num-
bers” on page 37.
Note: We do not recommend changing the preset calibration numbers unless you are using a metric rain
collector.
I
NSIDE AND
O
UTSIDE
T
EMPERATURE
Change CAL if you wish to adjust the Weather Monitor II so that is reads the
same as another thermometer. Note that there are individual CAL numbers for
both inside and outside temperature. If you change CAL for outside tempera-
ture, the wind chill reading will also be affected.
C ALIBRATED T EMPERATURE = T EMPERATURE + CAL
Default CAL = 0 (for ˚F); 0 (for ˚C).
W
IND
S
PEED
The four units of measure provided are generally sufficient for most applica-
tions. If you change CAL for wind speed, the wind chill readings will be incor-
rect.
C ALIBRATED W IND S PEED = R EVOLUTION X (1600 / CAL)
Default CAL = 1600 (for mph); 995 (for kph); 1843 (for knots); 3578 (for m/s).
H
UMIDITY
Change CAL if your outside humidity reading is off by a consistent amount. A
CAL number exists for outside humidity only. If you change CAL, dew point
readings will also be affected.
C ALIBRATED H UMIDITY = H UMIDITY + CAL
Default CAL = 0%.