SOWACS: CS616 probe linearity?

[Roland Stenger]

Roland Stenger writes to the sowacs list:
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Recently, Steve Evett wrote that
"Of the two, the CS616 output is linear with water content, while the
Theta probe output is nonlinear with water content. This makes
calibration of the CS616 much easier. Both devices should be
calibrated for the specific soil in which they are to be used."

Is there anyone around who can address my follow-on questions:

1. Has anyone shown that the CS616 probe is linear with water content
for a wide range of soils (different texture, different mineralogy,
different bulk density)?

2. Has anyone on the list experience with field or laboratory
calibration of the predecessor model CS615 and is willing to share it
with the list?

Cheers, Roland

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Steve Evett writes to the sowacs list:
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Craig and all,

The CS616 and the Theta probe are both frequency domain devices, while
the
TDR100 system is a time domain reflectometry system. The TDR100 captures
a wave form from each probe in the system and analyzes it for travel time,

which is then used to estimate water content. Alternatively, the wave
forms can be stored and analyzed separately.

My judgement is that the CS616 works better than the Theta probe. It is
certainly more robust. Of the two, the CS616 output is linear with water

content, while the Theta probe output is nonlinear with water content.
This makes calibration of the CS616 much easier. Both devices should be
calibrated for the specific soil in which they are to be used.

Steve Evett


*******************************************************************
Roland Stenger

Environmental Scientist (Research)
Dr. agr., Dipl. Ing. agr. (TUM, Germany)

Lincoln Environmental
Ruakura Research Centre
Private Bag 3062
Hamilton, New Zealand

Phone: (64)-7-858-4844
Fax: (64)-7-858-4841
Email: stenger@lvlham.lincoln.ac.nz
Homepage:
http://www.gsf.de/iboe/expertn/Authors/stenger/

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Some countries have oil, New Zealand has soil.
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