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FAQ - Answer 2 (A)
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| How do AquaFlux TEWL measurements compare
with Delfin VapoMeter measurements ? |
The AquaFlux and the VapoMeter use different
closed-chamber measurement methods, as follows:-
1. VapoMeter = Unventilated-chamber method
This method was first used in the 1960s for measuring water loss from
plant leaves [1]. Its use for TEWL measurement was first described
by Miller et al [2]. Water vapour is captured in a closed measurement
chamber, causing the humidity of the trapped air to rise. Water vapour
flux is determined from the rate of rise of humidity with time.
2. AquaFlux = Condenser-chamber method
This measurement principle is unique to the AquaFlux [3]. The closed
chamber is equipped with a condenser cooled to below the freezing point
of water, which acts as a sink for the water vapour. Water vapour flux
is determined using Nilsson's diffusion gradient principle [4].
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References |
| [1] |
EF Wallihan: Modification
and use of an electric hygrometer for estimating relative stomatal apertures. Plant Physiol. 39,
86-90, 1964.
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| [2] |
DL Miller, AM Brown & EJ Artz: Indirect
Measures of Transepidermal Water Loss. In Bioengineering and the Skin (R
Marks & PA Payne Eds), 161-71, MTP Press Lancaster, 1981.
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| [3] |
RE Imhof, EP Berg, RP Chilcott, LI Ciortea and FC Pascut:
New instrument for measuring water vapour flux
density from arbitrary surfaces.
IFSCC Magazine. 5(4), 297-301, 2002.
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| [4] |
GE Nilsson, Measurement
of Water Exchange through Skin.
Med Biol Comput. 15, 209-18, 1977. |
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