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digit will flash. Use the U and D buttons to change a digit. Once the sign and
digits are correct, press Enter to accept the number. If you decide to cancel any
changes you have made, you may do so by pressing the Ω/Exit button. This
will immediately skip to the next coefficient.
If the coefficient also requires an exponent, it will appear after setting the num
-
ber as follows:
E -04
Increase or decrease the exponent using the U and D buttons. Once the expo
-
nent is correct, press Enter to accept it.
6.4.3 ITS-90 PRT and Coefficients
The ITS-90 option is for PRTs calibrated and characterized using the Interna
-
tional Temperature Scale of 1990 equations. The parameters that appear when
ITS-90 is selected are “R0.01", ”A", “b”, “C”, “d”, “A4", and ”b4". These
should be set with the corresponding values that appear on the calibration cer-
tificate for the PRT. The parameter “R0.01" takes the triple point of water resis-
tance, often labeled ”Rtpw" or “R(273.16K)” on the certificate. Parameters
“A”, “b”, “C”, and “d” take the an,bn,cn, and d coefficients where n is a num-
ber from 5 to 11. Parameters “A4" and ”b4" take the a4 and b4 coefficients or
the a5 and b5 coefficients on the certificate. Any ITS-90 parameter of the
1502A that does not have a corresponding coefficient on the PRT’s certificate
must be set to 0.
The following table shows which parameter to set for each of the coefficients
that may appear on the certificate. The examples that follow demonstrate how
to set the ITS-90 parameters for certain cases. (Note: If the certificate has two
sets of coefficients, one set for “zero-power” calibration and one set for 1 mA
calibration, use the coefficients for the 1 mA calibration.)
1502A Thermometer Readout
User’s Guide
18
1502A ITS-90 Coefficient Certificate Value
A a5, a6, a7, a8, a9, a10, or a11
b b5, b6, b7, b8, or b9
Cc6orc7
dd
A4 a4 or a5
b4 b4 or b5
Table 2 Matching Certificate Values to 1502A ITS-90 Coefficients