Thermo Scientific Orion Versa Star Pro, Руководство пользователя

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Appendix A

Channel Specific Settings and Features
132
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Orion Versa Star Pro Meter User Manual Thermo Scientific
Linear Regression
Versa Star Pro meters with pH, pH/ISE and pH/LogR modules offer a linear regression feature
for pH and ISE calibration curves. Linear regression determines how the slope will be
implemented after a multi-point calibration is performed.
The default setting is linear regression off, which implements a traditional, segmented slope
with point-to-point lines. The segmented approach is the most accurate and precise.
Using the linear regression off setting, straight-line segments are drawn between each
successive pair of calibration points. Separate slope and E
0
values are calculated using the
adjacent pair of calibration points. For example, in a five point calibration, four slopes and four
E
0
values are calculated to correspond to the four line segments that connect the calibration
points. pH or concentration values for samples are calculated according to the segment that
their mV potential values fall into. Those above or below the range of calibration are calculated
by extrapolation from the top or bottom most segment. The displayed slope is an average slope
of the separate segments. The slope may be outside the range normally expected for an
electrode. For example, if the slope of one segment is low, then the average will be lower than
theoretical, even though the response may be Nernstian over most of the range.
Setting the linear regression on will implement a single best fit line for the calibration curve and
can be beneficial if pH measurements vary greatly over a large range.