Download SMP40 Calibration Calculation

MELTING POINT – SMP40
Technical note: T07-001A
SMP40 Calibration – The SMP40’s Calibration
Calculations
Introduction
To ensure the accuracy of its melting point data the SMP40 automatic melting point apparatus
allows users to perform a single or dual point instrument calibration with suitable, certified melting
point standards. This technical note discusses the calculations and process that are used by the
SMP40 to generate accurate and reliable melting point data.
SMP40 Calibration
The SMP40’s displayed temperature value is calculated using the instrument’s platinum resistance
temperature sensor data and the current calibration equation.
Displayed Block Temperature =
ax2 + bx + c
(where x = Instrument’s PRT Temperature Value)
When a new calibration procedure is performed the instrument
requires the original PRT temperature values in order to
accurately calibrate the instrument and calculate the values of
a, b and c in the calibration equation. This is done by
performing a quadratic regression through zero on a graph of
the expected melting point values verses the original PRT
temperature values. The instrument reports the calculated b
term as the Calculated Calibration Factor and as the
regression curve is forced through zero, the c term in the
instrument’s calibration equation will always equal zero.
Figure 1: Calibration Data Entry Screen
The original PRT temperature values are calculated from the measured melting point data using a
modified form of the standard quadratic formula:-
PRT Temperature Value =
-b +
b2 + 4a(y)
2a
where a and b are taken from the SMP40’s current calibration equation and (y) equals the
measured melting point of the certified melting point standard.
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