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Appendix B. Correcting Electrical Conductivity Measurements for System Losses

The temperature effect is described by

(

)

(

)

25T*02.01ECEC

25T

−

∗

[B4]

where is the electrical conductivity at 25ºC and is the electrical

conductivity at other temperatures.

B.2.3 Deriving Calibration Function

Using the K

, ρ

open

and ρ

shorted

values for each probe, the uncorrected electrical

conductivity as measured by the TDR100 can be corrected to give accurate EC

values that account for system losses. To do this, a range of EC values is

chosen for σ

uncorrected

in equation [B5] and σ

corrected

values calculated for the

chosen range of σ

uncorrected

()

puduncorrectepshorteduduncorrecteshortedu

pairuduncorrecteairpuduncorrecte

pcorrected

KZ*K*Z**Z

K*Z**KZ*

−σ+ρ+σρ

ρ+

−

−=σ

[B5]

This equation has a quadratic form. The correction is easier to use if a curve is

fit to the σ

corrected

values for the chosen range of σ

uncorrected.

This quadratic is

implemented in the datalogger program to given the final result that is

corrected electrical conductivity. This must be done for each probe.

0 0.75 1.5

0.75

1.5

uncorrected EC (siemen/meter)

corrected EC (siemen/meter)

FIGURE B-1. Example of corrected and uncorrected electrical

conductivity values.

The fitted equation for this probe is

duncorrecteduncorrectecorrected

35.095.001.0 σ∗+σ∗+=σ

B-3

1 2 ... 16 17 18 19 20 21 22 23 24 25 26

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