OPERATION
Page 51
MANUAL
CT
Controllers
CALIBRATION SUBMENUS
X.2 - Calibration Options
The CALIBRATION Submenu is common to all the functions
that require sensor calibration. This includes Conductivity, pH,
Temperature and ORP. Pressure and Flow have only direct 1-
point calibration.
The CALIBRATION OPTION Submenu X.2 is used to select
the number of calibration points desired. Most applications
require only 1- Point calibration but any number up to three can
be selected. If more than 1-point calibration is selected, the
operator needs to use calibrated buffer solutions. These
sample solutions must be spaced sufficiently from one another
to yield meaningful calibration values.
X.2.1 - One-Point Calibration
When using 1-Point calibration, the conversion curve for the
sensor readings is a straight line using the standard (default)
slope built in the program.
1-Point calibration should be satisfactory for most applications.
The operator places the sensor in a single water sample and
tests it with an appropriate test kit. The value obtained is then
entered on the calibration screen as the new display value.
The controller uses the calibration value that has been entered
by the operator to calculate the origin “a” of the representative
linear equation:
DISPLAY = a + SLOPE * INPUT
X.2.2 - Two-Point Calibration
With 2-Point calibration, the operator needs to use two different
solutions with values that are spaced widely enough to show
significant differences in the slope of the calibration curve.
The controller uses these values to compute the origin “a” and
slope “b” in the equation:
DISPLAY = a + b * INPUT
X.2.3 - Three-Point Calibration
With 3-Point calibration, the representative straight line is
replaced by a second-degree polynomial curve. The operator
needs three different solutions, again with values that are
spaced widely enough to show differences in the curvature of
the polynomial.
The controller uses these values to compute the origin “a”,
slope “b” and curvature “c” in the equation:
DISPLAY = a + b * INPUT + c * INPUT*INPUT
Submenu X.2
Submenu X.2.1
Submenu X.2.2
Submenu X.2.3
CALIBRATION OPTIONS
1 Point (zero)
2 Point (slope)
3 Point (curve)
Use 1, 2 or 3 points depending
on accuracy needed
1-PT CALIBRATION
Point 1
7.5
2-PT CALIBRATION
Point 1
7.5
Point 2
10.0
3-PT CALIBRATION
Point 1
4.0
Point 2
7.5
Point 3
10.0