Campbell CS616 Manuel d'instructions télécharger pdf (Page 37)

CS616 and CS625 Water Content Reflectometers

if there are free ions in soil solution, polar solid constituents such as organic

matter or some clay, or conductive mineral constituents.

The general calibration equation for the CS616/CS625 will provide good

results with attenuation equivalent to about 0.5 dS m

-1

bulk electrical

conductivity. Between 0.5 dS m

-1

and 5 dS m

-1

, the CS616/CS625 will

continue to give a well-behaved response to changes in water content but a soil

specific calibration is required. See Section 8, Water Content Reflectomer

User-Calibration, for calibration information.

7.6 Temperature Dependence and Correction

The error in measured volumetric water content caused by the temperature

dependence of the CS616/CS625 is shown in FIGURE 7-4. The magnitude of

the temperature sensitivity changes with water content. Laboratory

measurements were performed at various water contents and over the

temperature range from 10°C to 40°C to derive a temperature correction for

probe output period. The following equation can be used to correct the

CS616/CS625 output period,

uncorrected

, to 20°C knowing the soil temperature,

soil

. See sample datalogger programs. The temperature correction assumes

that both the water content and temperature do not vary over the length of the

probes rods.

( )

τ τ τ

corrected soil

uncorrected soil

uncorrected uncorrecte

T T

= + −

− +20

0 526 0

052 0 00136

* . . * .

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 49 50

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Campbell CS616 Manuel d'instructions Page 37