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b) c2
9. The following standard Thermocouple coefficients are also produced
unaltered:
Type
Range 1 Coefficients Range 2 Coefficients Range 3 Coefficients
Other
(see above)
Type B c3...c6 c0, c3...c8 N/A N/A
Type E c3...c13 c3...c10 N/A N/A
Type J c3...c8 c0, c3...c5 N/A N/A
Type K c3...c10 c0, c3...c9 N/A N/A
Type N c3...c8 c3...c10 N/A N/A
Type R c3...c9 c0, c3...c5 c0, c3...c4 c3...c9
Type S c3...c8 c0, c3...c4 c0, c3...c4 c3...c8
Type T c3...c14 c3...c8 N/A N/A
Type AuPt c3...c8 c3..c9 N/A N/A
3.8 Methods used for calculating coefficients
The thermometric expressions used by this software are well known expres-
sions and as such are described in detail elsewhere. This section touches on
some specifics as they relate to the methods used to arrive at solutions.
The coefficients for all solutions with the exception of the IPTS-68 platinum
probe are calculated using matrix methods. The IPTS-68 platinum probe solu-
tion is calculated using iteration. The solutions are either exact solutions or
overdetermined solutions depending on the number of set-points used in rela
-
tion to the number of set-points required. Exact solutions result when the exact
number of set-points required for simultaneous solution of sets of equations are
used (i.e., two coefficients from two set-points). Overdetermined solutions re
-
sult when more set-points are used than the unknowns require (i.e., two coeffi
-
cients from three or more set-points).
3.8.1 ITS-90
The ITS-90 is expressed in terms of resistance ratio(W) vs. temperature (K)
rather than resistance (R) vs. temperature. The resistance ratio is defined as the
resistance at a temperature divided by the resistance at the triple point of water,
or:
W
R
R
t
tpw
=
Because ratios are used in the ITS-90, the R
tpw
is required in addition to the re
-
sistance values at the test temperatures, thus, three set-points are required to
9933 TableWare
User’s Guide
44