Example3:A PRTwas calibrated to ITS-90 and its calibration certificate states values forcoefficientsR(273.16K), a6, b6, c6, and d. Set the 1502A parameters with val-ues from the certificate as follows:6.4.4 Callendar-VanDusen (RTD) Conversion
The RTDconversion uses the Callendar-VanDusen equation:[]
()
rtC
Rt
tt t
Rt
°=
+− −
⎛
⎝
⎜⎞
⎠
⎟
⎡
⎣
⎢⎤
⎦
⎥
⎧
⎨
⎩
⎫
⎬
⎭≥
+
0
0
1100 100 10
1
αδ
α−−
⎛
⎝
⎜⎞
⎠
⎟−−
⎛
⎝
⎜⎞
⎠
⎟⎛
⎝
⎜⎞
⎠
⎟
⎡
⎣
⎢
⎢
⎤
⎦
⎥
δβ
tt t t
100 100 1100 1100
3
⎥
⎧
⎨
⎩
⎪
⎫
⎬
⎭
<
⎧
⎨
⎪
⎪
⎩
⎪
⎪t0
The coefficientsR0,α,β,andδcan be set by theuser. They are indicated as“r0”, “ALPHA”, “bEtA”, and “dELtA” on the display.The ALPHA coeffi-cientis scaled by a factor or 1000 to allow adequate resolution. For IEC-751 orDIN-43760 sensors, the coefficientsfor “r0”, “ALPHA”, “bEtA”, and“dELtA” shouldbe 100.0, 0.00385055, 1.49979, and 0.1086 respectively.Some probes may beprovided with A, B, and C coefficients for theCallendar-VanDusen equation in the following form:[]
()()
()
[]rtC 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,andβcoefficientsusingthe following formulas:αδ β=+ =−
+
=− +
AB A
B
C
AB
100 100
100 1
10
100
8
1502A Thermometer Readout
User’s Guide
20
1502ACoefficient CertificateValue
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