4 Transmitter start up
42 |
266 MODBUS® multivariable transmitter User manual 2105216 Rev. AB
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
Additional publications (page vii)
, for device accuracy statements (P/N 2101131).
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
= 0.04%
of Indicated Value
The Calibration Device Error
= 0.05%
of Indicated Value
+ 0.01
kPa (typical digital calibrator)
𝑉𝑎𝑙𝑢𝑒 𝐸𝑟𝑟𝑜𝑟 = √𝐷𝑒𝑣𝑖𝑐𝑒 𝐸𝑟𝑟𝑜𝑟
2
+ 𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝐷𝑒𝑣𝑖𝑐𝑒 𝐸𝑟𝑟𝑜𝑟
2
= √0.04%
2
+ (0.05% + 0.01 𝑘𝑃𝑎)
2
= √0.04%
2
+ (0.05% + 0.016%)
2
= 0.077% 𝑜𝑓 𝐼𝑛𝑑𝑖𝑐𝑎𝑡𝑒𝑑 𝑉𝑎𝑙𝑢𝑒
Validation point
=
5%
of FCS =
3.125
kPa
Device Error
= ± (0.04 + 0.002 * [62.5 / 3.125) – 0.02])
% of Indicated Value
𝑉𝑎𝑙𝑢𝑒 𝐸𝑟𝑟𝑜𝑟 = √𝐷𝑒𝑣𝑖𝑐𝑒 𝐸𝑟𝑟𝑜𝑟
2
+ 𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝐷𝑒𝑣𝑖𝑐𝑒 𝐸𝑟𝑟𝑜𝑟
2
= √0.06%
2
+ (0.05% + 0.01 𝑘𝑃𝑎)
2
= √0.06%
2
+ (0.05% + 0.32%)
2
= ±0.375% 𝑜𝑓 𝐼𝑛𝑑𝑖𝑐𝑎𝑡𝑒𝑑 𝑉𝑎𝑙𝑢𝑒
Summary of Contents for 266 MODBUS
Page 163: ......
