Campbell Scientific Sentek TriSCAN® Manual v 1.2a - Manual (Page 43)

TriSCAN Manual Version 1.2a
Copyright © 1991 – 2004 Sentek Pty Ltd All rights reserved Page 36
For very sandy soils, the %CLAY can be assumed to be close to zero (0).
Note: If the samples are tested in separate batches for ease of handling, then a couple of quality control
(QC) samples, should be added to each batch. These samples are then used to make a correction for inter-
assay variation.
Adjusting the Salinity scale from Volumetric Ion Content (VIC)
units to EC or EC
e
units
To determine the relationship between VIC and EC, plot the average VIC output recorded by the TriSCAN in
the field (over 10 minutes) against the measured EC or EC
e
in a spreadsheet based software program.
Perform a linear regression to derive the equation that best describes the relationship between VIC and EC
or EC
e
.
This equation can then be applied to the data recorded by the TriSCAN sensors in the field to convert VIC to
EC or EC
e
using either a programming change in the data logger, or using a spreadsheet program. An
example of this is shown in Figure 8. In this example, four treatments were used to collect the data.
In this example only the following relationship applies:
ECe = 1,095.5 x VIC – 50,157
This relationship will be different for each soil.
Figure 8: Field Correlation: Volumetric Ion Content vs. ECe
It is up to the operator’s discretion to apply the most accurate mathematical relationship to the field data.
y = 2E-05x + 0.0191
R
2
= 0.8376
0
0.05
0.1
0.15
0.2
0.25
0 2000 4000 6000 8000 10000 12000
Volumetric Ion Content
EC 1:5 (dS/m)