5-10
Chapter 5. Functions
PV limiting and PV low/high limit alarm
The PV low and high limits are specified for each PV input range No. In principle,
−10 % FS is the low limit and +110 % FS is the high limit of the PV.
Operation when a PV input error occurs (p.11-4)
The PV is limited to falling within the range.
If the PV before the PV ratio, PV bias, and PV filter are applied is greater than the
PV high limit, a PV high limit alarm (AL01) is generated. If it is less than the PV
low limit, a PV low limit alarm (AL02) is generated.
Handling Precautions
• If the temperature unit is Fahrenheit, the PV low limit for ranges 41–44 is
−235 °F.
A PV low limit alarm (AL02) is generated between −300 and −235 °F,
which is within the PV range.
To control a process below −235 °F, set the output operation at PV alarm
(C15) to “0” (continue the control calculation) or set the temperature unit
(C02) to “0” (Celsius (°C)).
Note that if the output operation at PV alarm (C15) is set to “0” (continue
the control calculation), control will continue also when an abnormality
such as a PV high limit alarm (AL01) occurs.
PV range No. Range PV low limit PV high limit
41, 42 −300 to +900 °F −235 °F +1020 °F
43, 44 −300 to +400 °F −235 °F +470 °F
To Next Page
Loading...
