ROTRONIC MBW 473 - Manual (Page 20)

16 MBW473_MANUAL_E_V2.0
4.2 Selection of indicated Parameters
In the Parameter menu you can choose which parameters you would like to have displayed on the
data lines. When you select parameters for display on any of the four data lines, those selections re-
main valid until you change them again, even after you turn the 473 off. Below you will find the list of
the available parameters.
Parameter Explanation
Dew Point The temperature to which a gas must be cooled to start condensing water vapor to liquid water.
Dew point is pressure dependent and must be stated together with its associated pressure.
Frost Point The temperature to which a gas must be cooled to start deposition of water vapor in the
form of ice. Frost point is pressure dependent and must be stated together with its associ-
ated pressure. Frost point exists only below 0 °C. While not technically correct, it has been
common industry practice to report values below 0 °C as dew point, although frost point is
the correct term. For further explanation on
dew or frost point refer to ‘Dew / Frost Control’
in section 4.5.
%RH The ratio between the amount of water vapor in a sample and the maximum amount possi-
ble at that same temperature and pressure.
%RH WMO The ratio between the amount of water vapor in a sample and the maximum amount possi-
ble at that same temperature and pressure calculated using the World Meteorological Or-
ganization (WMO) formula.
Volume Ratio The ratio between the water vapor volume and the total volume of the sample gas, general-
ly expressed in parts per million by volume, ppm
v
or its numerical equivalent μl/l. Once
determined, ppm
v
has no further pressure dependence. It is also independent of the gas
type or mixture.
Weight Ratio Weight ratio is the ratio between the mass of water vapor and the total mass of the sample
gas, generally expressed in parts per million by weight, ppm
w
or its numerical equivalent
mg/kg. Once determined, ppm
w
has no further pressure dependence, but depends on the
gas type and mixture through the molecular weight of the constituents.
Absolute Humidity The weight of water vapor per unit volume of humidified gas.
Specific Humidity A ratio of the water vapor to the total weight of the humidified gas.
Vapor Pressure The partial pressure exerted by vapor in thermodynamic equilibrium with its condensed
phases (solid or liquid) at a given temperature. It is usually expressed in kPa.
Head Pressure The pressure of the gas sample in the measuring head.
External Temp The temperature measured by the external temperature probe.
Head Temp The temperature measured by the PRT in the measuring head.