®
Wireless Weather Sensor with GPS
Wireless GPS Sensor
6
013-15518A
is reported in units of g/m
3
. The sensor calculates
Absolute Humidity with the formula:
where RH is Relative Humidity (as a percentage), and T
is Temperature in °C.
Dew Point
Dew Point is the temperature to which air must be
cooled at constant pressure for water vapor to
condense. Dew Point is reported as a temperature on
the Celsius and Fahrenheit scales. The sensor
calculates Dew Point (in °C) with the formula:
In this formula,
is the
saturation water vapor pressure, RH is Relative
Humidity (as a percentage), and T is Temperature in °C.
Wind Chill
Wind Chill (or Wind Chill Index) indicates a combined
effect of temperature and wind speed. It is reported as
an apparent temperature on the Celsius and Fahrenheit
scales. The sensor calculates Wind Chill (in °F) using
the formula:
where T is air temperature (in °F) and V is wind speed
(in miles per hour).
Wind Chill is defined for temperatures at or below 50° F
and wind speed above 3 miles per hour; outside of those
limits, the sensor reports a value equal to Air
Temperature.
Heat Stress Index (Humidex)
Heat Stress Index (Humidex) indicates a combined
effect of temperature and humidity. It is reported as an
apparent temperature on the Celsius and Fahrenheit
scales. The sensor calculates Humidex (in °C) using the
formula:
where T is ambient air temperature in °C, and e is the
water vapor pressure in kPa.
Sea-level Corrected Pressure
A typical weather station does not report the actual
measured barometric pressure. Rather, it reports a
“sea-level corrected” value. Use this formula to calculate
the sea-level corrected pressure (in mbar):
[Barometric Pressure (mbar)]+1013*(1-exp(-h/7000))
where h is the sensor’s elevation in m. To have this
calculation done automatically, enter it in the calculator
of the data collection software.
Wireless GPS Sensor
The Wireless GPS Sensor uses signals received from
the Global Positioning System (GPS) to determine its
latitude, longitude, altitude and horizontal velocity
anywhere on earth. Use it alone or in conjunction with
other sensors for outdoor experiments in environmental
science, physics, and other subjects.
Data from the Wireless GPS Sensor is relayed by Blue
-
tooth to the PASCO data collection software on a com
-
puting device such as a computer or tablet.
Theory of Operation
To determine its
position, the sensor
must receive data from
at least three satellites.
When the sensor is first
powered on, it searches
the sky for available
satellites. This process
typically takes between
30 seconds and 2
minutes. Once
satellites have been
identified, the sensor
actively tracks them
and acquires new
satellites as they come
into view.
The Wireless GPS Sensor performs best outdoors with a
clear view of the sky.
Absolute Humidity
13.24 RH
T
273.15
+
----------------------------
17.42
T
T
239.7
+
-----------------------
exp
=
Dew Point
430.22
–
237.7
SatVP RH
100
-----------------------------
ln
+
SatVP RH
100
-----------------------------
ln
–
19.08
+
----------------------------------------------------------------------------------------
=
SatVP
6.11
7.75
T
237.7
T
+
10
=
Wind Chill (°F)
35.74 0.6215
T
35.75
V
0.16
–
0.4275
T
0.16
+
+
=
A
C
1.3
–
0.92
T
+
2.2
e
-------------------------------------
=
