Campbell-scientific CS547A-L Conductivity/Temperature Probe and A547A Manuel d'utilisateur télécharger pdf (Page 23)

CS547A Conductivity and Temperature Probe and A547 Interface

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

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 29 30

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Campbell-scientific CS547A-L Conductivity/Temperature Probe and A547A Manuel d'utilisateur Page 23