SOWACS: TDR and below zero temperatures

[Kailash Thakur <K.Thakur@irl.cri.nz>]

Kailash Thakur writes to the sowacs list:
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TDR recognises the electrical property of material which is permittivity
(dielectric constant and loss factor).  Since water has very high value of
dielectric constant (~78) compared to that of dry soil, its presence in soil
changes the effective value of dielectric constant.

Ice on the other hand is electrically different from water.  Dielectric
constant of ice is around 3.  When there is transformation of liquid water
to ice, the dielectric constant drops a lot giving a low value of moisture
content.

-kailash

-----Original Message-----
From: Johannes Deelstra [mailto:johannes.deelstra@jordforsk.no] 
Sent: Tuesday, 18 March 2003 21:17
To: brooz@pobox.com
Subject: SOWACS: TDR and below zero temperatures


"Johannes Deelstra" writes to the sowacs list:
===8<============== Is there
anyone who can tell me about how TDR-equipment functions when soil
temperatures drop below zero. I have continuous readings with TDR-equipment
in addition to soil temperatures. During the winter season when the soil
temperature drops below zero, one can notce a sudden drop in moisture
conten. TDR measures the water but can one say that the reading provided by
the TDR-equipment when soil temperatures are below zero is the water content
or is it influenced by the ice content. 


regards

Johannes (Hans) Deelstra

Jordforsk
Frederik A. Dahls vei 20,
1432 ‰s

tel: +47 64948100(8173)
fax: +47 64948110

johannes.deelstra@jordforsk.no
www.jordforsk.no

===8<==============
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