Campbell Scientific CR10TCR Thermocouple Reference - Manual (Page 5)

1
CR10TCR THERMOCOUPLE REFERENCE
1. GENERAL
The Model CR10TCR Probe contains a
thermistor for measuring temperature and is
used as a reference temperature for
thermocouples measured with the CR10. It is
installed between the two terminal stripes in the
wiring panel. After all the thermocouples are
wired, the wiring panel cover is installed to
minimize temperature gradients on the terminal
strip.
1.1 SPECIFICATIONS
Temperature Measurement Range: -35
° to +50°C
Thermistor Interchangeability Error: Typically
<
±0.2°C over 0°C to 60°C ±0.4 @ -35°C.
Polynomial Linearization Error: <
±0.5°C over
-35
°C to +50°C.
2. ACCURACY
− TEMPERATURE
SENSOR
The overall probe accuracy is a combination of
the thermistor's interchangeability specification,
the precision of the bridge resistors, and the
polynomial error. In a "worst case" all errors
add to an accuracy of ± 0.4
°C over the range of
-24
° to 48°C and ±0.9°C over the range of
-38
°C to 53°C. The major error component is
the interchangeability specification of the
thermistor, tabulated in Table 1. For the range
of 0
° to 50°C the interchangeability error is
predominantly offset. The bridge resistors are
0.1% tolerance with a 10 ppm temperature
coefficient. Polynomial errors are tabulated in
Table 2 and plotted in Figure 1.
TABLE 1. Thermistor Interchangeability
Specification
Temperature
Temperature (
°C)
Tolerance (
±°C)
−40
0.40
−30
0.40
−20
0.32
−10
0.25
0 to +50 0.20
TABLE 2. Polynomial Error
-40 to +56 <
±1.0°C
-38 to +53 <
±0.5°C
-24 to +48 <
±0.1°C
FIGURE 1. Error Produced by Polynomial Fit to Published Values