Honeywell R0512 manual Trend Hysteresis, Example of alarm hysteresis

ATTRIBUTES EXCEL 50/100/500/600/800

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 = [10-2to (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"

EN2B-0092GE51 R0512 22