ABB 266 MODBUS User Manual page 50

Variations in validation and error budget
Variations in the validation data, within an error budget, are a normal occurrence. However, influences from other factors (leaks
in the system, calibration equipment anomalies, rapid thermal variations on calibration equipment and connections, and other
environmental conditions) are not classified as normal occurrences.
Most of the listed contributing factors, listed above, are outside of ABB control. What is presented here is an example for
calculating an error budget that takes into account a transmitter and a typical digital calibrator. Refer to the 266 MODBUS
multivariable transmitter data sheet, listed under
Error budget calculation example:
Assuming a factory calibrated span (FCS) of 62.5 kPa,
And a validation point of 100% of FCS:
The Device Error
The Calibration Device Error
���������� ���������� = √������������ ����������
Validation point
Device Error
���������� ���������� = √������������ ����������
42 | 266 MODBUS® multivariable transmitter User manual 2105216 Rev. AB
Additional publications (page vii)
of Indicated Value
= 0.04%
of Indicated Value
= 0.05%
2
+ ���������������������� ������������ ����������
= √0.04% 2 + (0.05% + 0.01 ������)
= √0.04% 2 + (0.05% + 0.016%)
= 0.077% ���� ������������������ ����������
of FCS = kPa
= 5% 3.125
= ± (0.04 + 0.002 * [62.5 / 3.125) – 0.02])
2
+ ���������������������� ������������ ����������
= √0.06% 2 + (0.05% + 0.01 ������)
= √0.06% 2 + (0.05% + 0.32%)
= ±0.375% ���� ������������������ ����������
, for device accuracy statements (P/N 2101131).
kPa (typical digital calibrator)
+ 0.01
2
2
2
% of Indicated Value
2
2
2
4 Transmitter start up