Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 295

■Variation rate check
During the variation rate alarm check time (CTIM), this function block compares input changes with the variation rate alarm
value (DPL) every execution cycle T and checks variation rate alarms.
Alarm occurred
Variation rate
Basing
alarm value
point
[%] (DPL)
a
Input
Execution
cycle (ΔT)
Item
Alarm (ALM)
DPL: Variation rate alarm value (%)
m: Variation rate monitoring counter = CTIM/T
T: Execution cycle
CTIM: Variation rate alarm check time
Xn: Reference value
■Engineering value conversion
This function block converts a process variable (%) into an engineering value.
RH-RL
PV= × Input value (%) + RL
100
RH: Engineering value high limit, RL: Engineering value low limit, PV: Process variable
■Disable alarm detection
This function block sets whether to detect alarms (ALM) or not in the high high limit/high limit/low limit/low low limit checks and
variation rate check.
Item
Disable alarm detection by setting tag data
Disable alarm detection by loop stop processing
■Loop stop processing
When the stop alarm (SPA) of the alarm (ALM) or the tag stop (TSTP) of the monitor output buffer (DOM) is TRUE, this
function block performs the following processing.
• The output (PVPO) is as follows.
PV-RL
PVPO= ×100(%)
RH-RL
• The control mode is automatically switched to MANUAL.
• When HHA, LLA, PHA, PLA, DPPA, or DPNA of the alarm (ALM) has occurred, the HHA, LLA, PHA, PLA, DPPA, or DPNA
is reset.
• No alarm is detected in the high high limit/high limit/low limit/low low limit checks and variation rate check.
Alarm
Alarm
recovered
b c d
Variation rate alarm check time
(CTIM)
Positive variation rate (DPPA)
Negative variation rate (DPNA)
DPL
New basing point
CTIM
Input condition of when an alarm occurs
TRUE (Detected)
(Xn + m) - Xn  DPL
(Xn + m) - Xn  -DPL
Disable alarm detection processing
If the following bits in the disable alarm detection (INH) are TRUE, HHA, LLA,
PHA, PLA, DPPA, or DPNA of the alarm (ALM) will not be detected.
• ERRI
• HHI
• LLI
• PHI
• PLI
• DPPI
• DPNI
Page 293 Loop stop processing
10 LOOP CONTROL OPERATION
10.19 High/Low Limit Alarm Check (M+P_PHPL)
FALSE (Reset)
Other than the left range
Other than the left range
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