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Example 3:
A PRT was calibrated to ITS-90 and its calibration certificate states values for
coefficients R(273.16K), a6, b6, c6, and d. Set the 1502A parameters with val
-
ues from the certificate as follows:
6.4.4
Callendar-Van Dusen (RTD) Conversion
The RTD conversion uses the Callendar-Van Dusen equation:
[]
()
rt C
Rt
tt
t
Rt
°=
+− −
÷
≥
+
0
0
1
100 100
10
1
αδ
α
−−
÷
−−
÷
÷
δβ
tt t t
100 100
1
100
1
100
3
<
t
0
The coefficients
R
0
, α, β , and δ can be set by the user. They are indicated as
“r0”, “ALPHA”, “bEtA”, and “dELtA” on the display. For IEC-751 or DIN-43760
sensors, the coefficients for “r0”, “ALPHA”, “bEtA”, and “dELtA” should be
100.0, 0.00385, 1.507, and 0.111 respectively.
Some probes may be provided with A, B, and C coefficients for the
Callendar-Van Dusen equation in the following form:
[]
()
()
()
[]
rt C
RAtB
RAtBtCt t
t
t
°=
++
++ + −
≥
<
0
2
0
23
1
1 100
0
0
The A, B, and C coefficients can be converted to α, δ, and β coefficients using
the following formulas:
αδ β=+ =−
+
=−
+
AB
A
B
C
AB
100
100
100
1
10
100
8
6.4.5 IPTS-68 Conversion
The IPTS-68 characterization converts resistance to temperature according to
the International Practical Temperature Scale of 1968. The applicable coeffi
-
cients are
R
0
(“r0”), α (“ALPHA”), δ (“dELtA”), a
4
(“A4”), and c
4
(“C4”). You can
also select the temperature scale (“SCALE”) as IPTS-68 (“68”) or ITS-90
20 Manual Rev. 952801 Hart Scientific
6 General Operation
1502A Coefficient Certificate Value
R0.01 R(273.16K)
Aa6
Bb6
Cc6
Dd
A4 0.0
b4 0.0
Table 4 Setting Coefficients R(273.16), a6, b6, c6, and d
1.888.610.7664 sales@GlobalTestSupply.com
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