
17 Appendix
Pl = | + 0.25 C | (accuracy of standardisation ) |
Pz = | + 0.25 C | (zero accuracy ) |
Pd = | 0 | (no zero offset) |
Pm calculation :
Slope calculation at 240C : 321 +
V/
C Pm = 210 / 317 = + 0.66
C
Max. total accuracy:
Pt = + 0.25 + 0.25 + 0.66 = + 1.16C
17.4. Accuracy class index of class
This is one of the essential concepts of the C.E.I. recommendation: it is intended to alleviate the listing of the specifications. In order to do so, it introduces the concept of ACCURACY CLASS, which is determined here as CLASS C INDEX.
The normalised values of the index of class are: C = 0.1 ; 0.25 ; 0.5 and 1.
The intrinsic error (in the reference conditions) does not exceed C % (the manufacturer can also specify this limit of the intrinsic error as an absolute value (for example
5 microvolts) for the first ranges).
When one of the influence variable varies within the nominal range of use, variations (of the measured value) do not exceed:
-C % for the position, for the magnetic induction from outer origin and for spurious voltages
-0.5 C% for the power supply
-0.3 C% according to the class index for the room temperature (0.15 % for the 0.25 class).
Moreover, the range of insensitivity must not exceed:
-C% in the reference conditions
-1.5 C% for the maximum resistance of the outer circuit of measure
-2 C% for the spurious voltages
-
Eventually, no overvalue should exceed 2 C% (4 C% for the limits of the power supply).
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