Table 2 shows the various ITS-90 subranges with the temperature range and co-
efficients. All subranges also include R(TPW) (the resistance at 273.16K) as a
coefficient. For details about the ITS-90 see
NIST Technical Note 1265, Guide-
lines for Realizing the International Temperature Scale of 1990.
Subrange
Number
Temperature Range
Coefficients
Low Range
1
13.8033 to 273.16K
a
1
, b
1
, c
1
-c
5
2
24.5561 to 273.16K
a
2
, b
2
, c
1
-c
3
3
54.3584 to 273.16K
a
3
, b
3
, c
1
4
83.8058 to 273.16K
a
4
, b
4
5
234.3156 to 302.9146K
a
5
, b
5
High Range
6
273.15 to 1234.93K
a
6
, b
6
, c
6
, d
6
7
273.15 to 933.473K
a
7
, b
7
, c
7
8
273.15 to 692.677K
a
8
, b
8
9
273.15 to 505.078K
a
9
, b
9
10
273.15 to 429.7485K
a
10
11
273.15 to 302.9146K
a
11
7.4.3.2.2
IPTS-68
The IPTS-68 option is for probes calibrated to the International Practical Tem-
perature Scale of 1968. IPTS-68 probes are often only calibrated over a limited
temperature range and some of the coefficients may not be available (e.g. a
3
,
b
3
). Enter 0.0 for unused coefficients. You can select the ITS-90 scale conver-
sion by setting the SCALE parameter to T90. This causes the temperature to be
adjusted by an amount equal to the difference between the IPTS-68 and ITS-90
temperatures. (The accuracy of the scale conversion is ±0.001°C between 0 and
630°C, ±0.002°C between –200 and 0°C, and ±0.003°C between –259 and
–200°C.)
7.4.3.2.3
Callendar-Van Dusen
The Callendar-Van Dusen (CVD) conversion can be used with some industrial
probes such as those that conform to the DIN-43760, IEC-751, or ASTM
E1137 standards. The Callendar-Van Dusen equation is shown below. The stan-
dard coefficients for DIN-43760, IEC-751, or ASTM E1137 are shown in Table
3.
1575/1590 Thermometer Readout
User’s Guide
48
Table 2
ITS-90 Subranges and Coefficients
