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ATTRIBUTES EXCEL 50/100/500/600/800
EN2B-0092GE51 R0512 22
Fig. 11. Example of alarm hysteresis
The “normal” and “alarm” states as defined by the attribute "Alarm Hysteresis" are
the determined using the appropriate values in the formula given above:
Range = [10
-2
to (Max1 -Min1)] = [0.01 to 2]
Table 7 lists the resulting alarm conditions for the chosen hysteresis value of 0.05:
Table 7. Alarm conditions for alarm hysteresis
limit normal to alarm condition alarm to normal condition
Max 1 4.00 4.00 - 0.05 = 3.95
Max 2 5.00 5.00 - 0.05 = 4.95
Min 1 2.00 2.00 + 0.05 = 2.05
Min 2 0.5 0.5 + 0.05 = 0.55
Trend Hysteresis
Trend hysteresis (V1.5.x) The attribute "Trend Hysteresis" is available for the trend functions “Local Trend
Data” and “Trend Setup Data”. The attribute "Trend Hysteresis" prevents new
values from being written to the trend buffer unless the datapoint value changes
(positively or negatively) at more than the specified trend hysteresis. The minimum
hysteresis value is 10
-a
(a = number of decimal places set in the attribute
"Engineering Unit"). The CARE default value (i.e. 1% of actual value and no less
than 0.2) for this attribute is 0. Access to "Trend Hysteresis" is also possible via
RIA/WIA.
This value can be edited from an operator interface (XI581 (not with XCL5010,
Excel 100C), XI582, XL-Online, or Excel 50 MMI) via the B port (XC5010C/XC6010)
or the serial port, the system bus (XBS 1.3.3 and higher and XFI 1.6.1 and higher)
and CARE RIA/WIA statements. The password level for this attribute is determined
by the attribute "Access" (default initialization value in CARE is 0).
Fig. 12. Example of the attribute "Trend Hysteresis"