Campbell Scientific CS547 Conductivity and Temperature Probe and A547 Interface - Manual (Page 18)

CS547 Conductivity and Temperature Probe and A547 Interface
14
8.2 Temperature Measurement Error
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 8.2-1. For the
range of 0
° to 50°C the interchangeability error is predominantly offset and can be
determined with a single point calibration. Compensation can then be done with an
offset entered in the measurement instruction. The bridge resistors are 0.1%
tolerance with a 10 ppm temperature coefficient. Polynomial errors are tabulated in
Table 8.2-2 and plotted in Figure 8.2-1.
TABLE 8.2-1. 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 8.2-2. Polynomial Error
-40 to +56 <
±1.0°C
-38 to +53 <
±0.5°C
-24 to +48 <
±0.1°C
FIGURE 8.2-1. Error Produced by Polynomial Fit to Published Values