PASCO Xplorer GLX, User Manual

Page: 78 / 152

72 C a l i b r a t i o n
Two points, Pt 1 and Pt 2, define the line. In the two-point calibration procedure,
each point is reset by associating a known standard value (for instance, the pH of
a buffer solution) with a raw input measurement that the sensor sends to the GLX
when it is in that standard. In a one-point calibration, only one of the points is
reset by the user.
Types of Calibration
There are three types of calibration: two-point, one-point slope, and one-point
offset. Any of these calibrations can be performed on a single sensor, or simulta-
neously on multiple similar sensors; however, for any given sensor, the GLX will
automatically select the most typical calibration type as the default setting.
Two-Point
In a two-point calibration, you reset two points to define a new line.
This type of calibration affects both the slope and the offset. For step-by-step
instructions on the two-point calibration procedure, see page 75.
Two-point calibration; two points are set to redefine the line
One-Point Slope In a one-point slope calibration, you reset only one point.
The slope of the line changes so that the line intersects the new point, while the
offset (or Y-intercept) does not change. For step-by-step instructions on the one-
point slope calibration procedure, see page 76.
One-point slope calibration; the line changes its slope to intersect the new point
Input Dat
a
Output Data
Offset
Pt 1
Pt 2
D Output
D Input
Slope =
D Input
D Output
Pt 2
Pt 2
old
calibration
new
calibration
Pt 1
Pt 1
Input Dat
a
Output Data
old
calibration
new
calibration
Offset
does not
change
Input Dat
a
Output Data
new
point
old
point
slope changes