Siemens MASS 2100 Operating Instructions Manual page 136

Functions
8.1 Process values
value exceeds the Upper Limit Warning or the Lower Limit Warning. Process value alarms and
warnings are displayed in the HMI as well as at the communication interfaces.
Hysteresis
The hysteresis functions as follows:
Figure 8-1
A: Upper Alarm Limit with hysteresis
The alarm is triggered when the process value overshoots the Upper Alarm Limit (1). The alarm
is cleared when the process value undershoots the Upper Alarm Limit minus hysteresis (2).
B: Lower Alarm Limit with hysteresis
The alarm is triggered when the process value undershoots the Lower Alarm Limit (1). The
alarm is cleared when the process value overshoots the Lower Alarm Limit plus hysteresis (2).
C: Lower Alarm Limit without hysteresis
The alarm is triggered when the process value undershoots the Lower Alarm Limit (1). The
alarm is cleared when the process value overshoots the Lower Alarm Limit (2).
D: Upper Alarm Limit without hysteresis
The alarm is triggered when the process value overshoots the Upper Alarm Limit (1). The alarm
is cleared when the process value undershoots the Upper Alarm Limit (2).
Note
Flow direction warning
The limit function can be used to signal the flow direction by setting the Lower Limit Warning
for the Process Value to 0. A warning will occur in case of negative flow
All alarms and warnings can be signaled on the output if Status Mode is set to Individual alarms,
see Digital output (Page 229).
Limit behavior on the outputs
Process Alarms can trigger Fail Safe behavior on the Signal Output, whereas Process
Warnings are only used as information available in HMI and on the communication. Process
value will bring the Signal output to Fail Safe mode if:
- Signal Output is configured to Current, Pulse or Frequency
- Fail Safe Mode is configure to react on a failure
- Process Alarm occurs on a process value selected on the output
The alarm behavior is described in detail below.
Detail alarm behavior is described in Digital output (Page 229).
136
Hysteresis
MASS 2100 & FC300 (FCT030)
Operating Instructions, 06/2017, A5E39789040-AA