Bumpless Transfer; Loop Alarms - Automation Direct DL05 User Manual

Bumpless Transfer

The DL05 loop controller provides for bumpless mode changes. A bumpless transfer from
manual mode to automatic mode is achieved by preventing the control output from changing
immediately after the mode change.
When a loop is switched from Manual mode to Automatic mode, the setpoint and Bias are
initialized as follows:
Position PID Algorithm
SP = PV
Mx = M (Control Output)
The bumpless transfer feature of the DL05 is available in two types: Bumpless I and Bumpless
II (see page 8-26). The transfer type is selected when the loop is set up.

Loop Alarms

The DL05 allows the user to specify alarm conditions that are to be monitored for each loop.
Alarm conditions are reported to the CPU by setting up the alarms in DirectSOFT 5 using
the PID setup alarm dialog when the loop is setup. The alarm features for each loop are:
• PV Limit – Specify up to four PV alarm points.
High-High
High
Low
Low-Low
• PV Deviation Alarm – Specify an alarm for High and Low PV deviation from the setpoint (Yellow
Deviation). An alarm for High High and Low Low PV deviation from the setpoint (Orange
Deviation) may also be specified. When the PV is further from the setpoint than the
programmed Yellow or Orange Deviation Limit the corresponding alarm bit is activated.
• Rate of Change – This alarm is set when the PV changes faster than a specified rate-of-change limit.
• PV Alarm Hysteresis –
using threshold values. When the absolute value or deviation exceeds the threshold,
the alarm status becomes true. Real-world PV signals have some noise on them, which
can cause some fluctuation in the PV value in the CPU. As the PV value crosses an
alarm threshold, its fluctuations will cause the alarm to be intermittent and annoy
process operators. The solution is to use the PV Alarm Hysteresis feature.
Velocity PID Algorithm
SP = PV
PV rises above the programmed High-High Alarm Limit.
PV rises above the programmed High Alarm Limit.
PV fails below the Low Alarm Limit.
PV fails below the Low-Low Limit.
The PV Limit Alarms and PV Deviation Alarms are programmed
DL05 Micro PLC User Manual, 6th Edition, Rev. A
Chapter 8: PID Loop Operation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
A
B
C
D
8–13