Specifications

Section 4. Sensor Support
4-27
TABLE 4.4-3. Limits of Error on CR1000 Thermocouple Polynomials
(Relative to NIST Standards)
TC
Type Range
o
C Limits of Error
o
C
T -270 to 400
-270 to -200 + 18 @ -270
-200 to -100 ± 0.08
-100 to 100 ± 0.001
100 to 400 ± 0.015
J -150 to 760 ± 0.008
-100 to 300 ± 0.002
E -240 to 1000
-240 to -130 ± 0.4
-130 to 200 ± 0.005
200 to 1000 ± 0.02
K -50 to 1372
-50 to 950 ± 0.01
950 to 1372 ± 0.04
4.4.1.6 Reference Junction Compensation: Temperature to Voltage
Thermocouple instructions TCDiff() and TCSe() utilize the parameter (TRef)
to incorporate the associated reference junction temperature into the
thermocouple measurement. A reference junction compensation voltage is
computed from (TRef) as part of the thermocouple instruction, based on the
temperature difference between the reference junction and 0°C. The
polynomials used to determine the reference junction compensation voltage do
not cover the entire thermocouple range, as illustrated in TABLE 4.4-3 and
TABLE 4.4-4. Substantial errors in the reference junction compensation
v
oltage will result if the reference junction temperature is outside of the
polynomial fit ranges given in TABLE 4.4-4.
The refe
rence junction temperature measurement can come from a
PanelTemp() instruction, or from any other temperature measurement of the
reference junction. The standard and extended (-XT) operating ranges for the
CR1000 are -25 to +50 °C and –55 to 85 °C, respectively. These ranges also
apply to the reference junction temperature measurement using PanelTemp().
Two sources of error arise when the reference temperature is out of the
polynomial fit range. The most significant error is in the calculated
compensation voltage; however a small error is also created by non-linearities
in the Seebeck coefficient.
TABLE 4.4-4. Reference Temperature Compensation Range and
Polynomial Error Relative to NIST Standards
TC
Type Range
o
C Limits of Error
o
C
T -100 to 100 ± 0.001
J -150 to 296 ± 0.005
E -150 to 206 ± 0.005
K -50 to 100 ± 0.01