Chapter 2 ___________________________________________________________ Product Overview
VAISALA ________________________________________________________________________ 15
Output Parameters Explained
Table 4
Parameters Supported by HMW90 Series
Parameter Symbol
Unit(s)
Description
Temperature T
°C
°F
Temperature in Celsius or
Fahrenheit scale.
Relative
humidity
RH
%
Ratio of the partial pressure of
water vapor in the air to the
saturation vapor pressure of air
at the current temperature.
Dewpoint
Td
°C
°F
Temperature at which the water
vapor in the air will condense into
water at the current pressure.
Dewpoint
Tdf
°C
°F
Same as Td, except when the
dewpoint is below 0 °C, the
transmitter outputs frostpoint (Tf)
instead of dewpoint.
Dewpoint
depression
dTd
°C
°F
Difference between ambient
temperature and dewpoint (Tdf).
Wet bulb
temperature
Tw
°C
°F
The minimum temperature that
can be reached by evaporative
cooling in the current conditions.
Absolute
humidity
a
g/m3
gr/ft3
Quantity of water in a cubic meter
(or cubic foot) of air.
Mixing ratio x
g/kg
gr/lb
Ratio of water vapor mass per
kilogram (or pound) of dry air.
Enthalpy
h
kJ/kg
btu/lb
Sum of the internal energy of a
thermodynamic system.
NOTE
Humidity parameters are not measured by TMW92, TMW93, and
TMW90 transmitters even though the parameters can be selected using
the service port (serial line and MI70 indicator use).
