Yokogawa DAQWORX - Manual (Page 68)

2-38 IM WX103-01E
Note
When using computation channel alarms, do not disconnect the MX100 and the PC software.
Computation channel alarms will not occur because the computation function does not work
when using only the MX100.
Explanaton
Alarm Types
There are six types of alarms.
When not using difference input on measurement channels, select OFF, High, or Low.
When using difference input, select OFF, dHigh, or dLow.
On math channels, select OFF, High, Low, rHigh, or rLow.
• Upper Lmt Alarm (Hgh)
An alarm occurs when the measured/computed value exceeds the alarm value.
• Lower Lmt Alarm (Low)
An alarm occurs when the measured/computed value falls below the alarm value.
• Dfference Input Upper Lmt Alarm (dHgh)
An alarm occurs when the difference input (difference between the measured value of
its own channel and that of the reference channel) exceeds the alarm value.
• Dfference Input Lower Lmt Alarm (dLow)
An alarm occurs when the difference input (difference between the measured value of
its own channel and that of the reference channel) falls below the alarm value.
Alarm value
Alarm reset
Measured value or
computed value
Alarm occurrence
Upper-limit alarm/difference input
upper limit alarm
Lower-limit alarm/difference input
lower limit alarm
Measured value or
computed value
Alarm reset
Alarm value
Alarm occurrence
• Rate of Change Upper Lmt Alarm (rHgh)
An alarm occurs if the amount of change in the computed value in the rising direction
exceeds the alarm setting value within the rate-of-change detection interval.
• Rate of Change Lower Lmt Alarm (rLow)
An alarm occurs if the amount of change in the computed value in the falling direction
exceeds the alarm setting value within the rate-of-change detection interval.
Change in the
computed value
T
Time
Interval
1
T 2
t 1 t 2
2 1
Amount of change in
the setting
T
Time
2
T 1
t 1 t 2
Computed value
Change in the
computed value
t –t
Interval
2 1 t –t
2 1 T –T
High limit on rate-of-change alarm Low limit on rate-of-change alarm
Computed value
Amount of change in
the setting 1 T –T 2
The rate-of-change detection interval is equal to measurement interval x measurement
count. Select the measurement count (1 to 15) using the Interval of rate-of-change alarm
box.
2.6 Settng Alarms