GMH 3331
Bases for measurement | 6
B-H77.0.01.DB2-1.0
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6.2.2 Environmental temperature T1
Temperature measured in the probe tip. 0.1°C or 0.1°F resolution. Additional display
values are calculated according to the Mollier diagram of the product:
6.2.3 Dewpoint temperature Td
Cold air can absorb less water vapour than warm air. Consequently, as the temperat-
ure decreases, the relative air humidity increases. If 100% is reached, the air is satur-
ated with water vapour, and additional cooling has the effect that part of the water va-
pour condenses into water and is visible as mist or precipitation (dew).
The dewpoint temperature indicates the temperature at which 100% saturation is
reached and from which dew should be expected.
6.2.4 Enthalpy h
Enthalpy indicates the energy content of the air. This value is based on dry air at 0 °C
and 0 % relative air humidity. In other words, air with 0 % relative air humidity and 0 °C
has the energy content 0 kJ/kg. The warmer the air is and the higher the relative air
humidity is, the greater the energy content will be. As a result, it is apparent that more
energy is required to heat up humid air than dry air.
NOTE
All display values calculated from the humidity and temperature measurements are
based on normal air pressure of 1013 mbar. The deviations for measurement of atmo-
spheric air are negligible. The values must be corrected based on suitable tables for
measurements in pressure vessels and similar equipment.
6.2.5 Surface temperature T2
Surface temperatures, etc. can be measured with the second temperature channel.
6.2.6 Dewpoint distance Δ Td
This measurement relates to measurements T1, T2 and the relative air humidity.
The environmental air is measured with the combination probe and the dewpoint Td is
calculated from its status.
Now surfaces in this environmental air can be measured with the surface probe,
wherein ΔTd indicates the temperature difference from the dewpoint.
Example:
The measurement of the room air provides a Td of 5 °C. As long as the surface tem-
perature of a pane is >5 °C (ΔTd is positive), the pane is not misted over. If the sur-
face temperature is less than 5 °C (ΔTd is negative), the pane will mist over.
Additional application examples:
Locating damp corners, monitoring of heat exchangers or weather forecasting.
6.3 Measurements with the STS 005 / STS 020 flow
measuring probes
There are two types of measuring probes available for measurement of flow speed:
– STS 005 measures the flow of water
