Gill Instruments Ltd
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MaxiMet
Page 40
Issue 1
Doc. No. 1957-PS-000x
March 2015
There are drop down menu selectable parameters available depending on the MaxiMet model
(see pages 5 and 8 to10).
These are:-
WINDSTAT
Outputs Status codes relating to Wind Sensor Data (see Page 65).
PRECIPS
Outputs Precipitation (Rain) Status as No (N) or Yes (Y).
Changes N to Y when total precipitation is incremented.
Changes Y to N when total precipitation has not incremented in the last 60
seconds.
CSPEED
Outputs Corrected Speed if a GPS unit is fitted.
PASL
Outputs Barometric Pressure at Sea Level if HASL figure set (see page 38).
p
0
= p
1
.exp( (g.h) / (R.T) )
where
p
0
= air pressure at sea level (Pa)
p
1
= air pressure at sensor (Pa)
h = sensor altitude above sea level (m)
R = specific gas constant
T = air temperature as measured
g = acceleration due to gravity
PSTN
Outputs Barometric Pressure at Station if HAS figure set (see page 38).
Pressure at station shall be computed as:
where:
Pb = static pressure (pascals)
Tb = standard temperature (K)
Lb = standard temperature lapse rate (K/m) in ISA
h = height above sea level (meters)
hb = height at bottom of layer b (meters; e.g., h1 = 11,000 meters)
R = universal gas constant for air: 8.31432 N·m /(mol·K)
g0 = gravitational acceleration (9.80665 m/s2)
M = molar mass of Earth's air (0.0289644 kg/mol)
AH
Outputs Absolute Humidity.
Absolute humidity shall be computed as
H = C · P
w
/T
where
H = absolute humidity
C = Constant 2.16679 gK/J
Pw = Vapour pressure in Pa
T = Temperature in K
