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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 ,andδ can be set by the user. They are indicated as
“r0”, “ALPHA”, “bEtA”, and “dELtA” on the display. The ALPHA coeffi
-
cient is scaled by a factor or 1000 to allow adequate resolution. For IEC-751 or
DIN-43760 sensors, the coefficients for “r0”, “ALPHA”, “bEtA”, and
“dELtA” should be 100.0, 0.00385055, 1.49979, and 0.1086 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,andβ coefficients using
the following formulas:
αδ β=+ =−
+
=−
+
AB
A
B
C
AB
100
100
100
1
10
100
8
1502A Thermometer Readout
User’s Guide
20
1502A Coefficient Certificate Value
R0.01 R(273.16K)
Aa6
Bb6
Cc6
Dd
A4 0.0
b4 0.0
Table 5 Setting Coefficients R(273.16), a6, b6, c6, and d