<5. Functions>
128
IM 01E21A02-03EN
When the high and low limit alarms are reset, each has a hysteresis. The hysteresis width should
be set with the percentage (%) for the span of the physical quantity PV-mapped in Subsection
5.1.2. The hysteresis in each case can be specified with the following parameter.
Menu path
Display
--
F
OUNDATION
Fieldbus
Diagnostic ► AI1* ► Device Diagnostics ► Diagnostics/Alerts ► Alert ► Alert Common ►
(see below)
*For AXG, one from Al1 to Al4, and for AXW, one from AI1 to AI3.
Block Name
Relative
Index
Parameter
Description
Display
F
OUNDATION
Fieldbus
AI1 - AI4 (AXG)
AI1 - AI3 (AXW)
24
-
Alarm Hysteresis
Specifies the hysteresis width
for the alarm occurrence and
resetting.
(1) Hysteresis value = Span or max. range x Hysteresis width [%]
(2) Value that causes a high or high-high limit alarm to be reset
= Set high limit or high-high limit - Hysteresis value
(3) Value that causes a low or low-low limit alarm to be reset
= Specified low limit or low-low limit value + Hysteresis value
Example:
Span of volumetric flow rate = 300 m
3
/h,
High limit value = 250 m
3
/h, Low limit value = 50 m
3
/h,
High-high limit = 300 m
3
/h, Low-low limit = 25 m
3
/h,
If Hysteresis width is set to 5 %
In this case, each value is obtained as shown below.
(1) Hysteresis value = 300 [m
3
/h] x 5 [%] = 15 [m
3
/h]
(2-1) Value that causes a high-high limit alarm to be reset
= 300 [m
3
/h] – 15 [m
3
/h]
= 285 [m
3
/h]
(2-2) Value that causes a high limit alarm to be reset
= 250 [m
3
/h] – 15 [m
3
/h]
= 235 [m
3
/h]
(3-1) Value that causes a low limit alarm to be reset
= 50 [m
3
/h] + 15 [m
3
/h]
= 65 [m
3
/h]
(3-2) Value that causes a low-low limit alarm to be reset
= 25 [m
3
/h] + 15 [m
3
/h]
= 40 [m
3
/h]
