West Control Solutions ProVU 4 - Manual (Page 146)

ProVU4 Controller, Profiler & Recorder/Controller - Product Manual
59407, Issue 1 – March 2008 Glossary Page 145
Manual Mode
If Manual Mode is enabled/disabled (from the control configuration sub-menu, or the
Auto/manual screen in operation mode if it is available) it causes a controller to enter or
leave manual control mode. Manual Mode can also be selected using a digital input if one
has been fitted and has been configured for this function. Switching between automatic and
manual modes is achieved using “bumpless transfer”.
Manual Mode operates as follows:
The setpoint legend is replaced by the word MAN and setpoint value is replaced by a %
output power value. This value may be adjusted using the  or  keys. The power value
can be varied from 0% to 100% for controllers using single control type, and -100% to +100%
for controllers using dual control type. It is possible to use a controller as a permanent
“Manual Station” by selecting Manual Control in the control configuration sub-menu.
Caution: Manual Mode should be used with care because the power output level is set by
the operator, therefore the PID algorithm is no longer in control of the process. The operator
MUST maintain the process at the desired level manually. Manual power is not limited by the
Power Output Limits.
Also refer to: Bumpless Transfer, Control Configuration, Control Type, Operation Mode, PID,
and Power Output Limits.
Master & Slave Controllers
The terms master and slave are used to describe the controllers in multi-zone applications
where one instrument controls the setpoint of another. These can be simple Setpoint
Master/Slave applications where the master controller transmits its setpoint to the slaves via
serial communications, or retransmits it as an analogue DC linear output signal. If serial
comms are used, the master controller must be able to act as a communications master
device and the slave must have a compatible communications option fitted. If DC linear
retransmission is use, the slave controller must have a matching a remote setpoint input. It is
possible to apply an offset to each zone if the slave has a Setpoint offset parameter or by
offsetting it’s remote setpoint input (or adjusting the scaling of this input).
Cascade Control is a type of Master & Slave application where the slaves setpoint is set
using the master controllers PID power output.
The terms Master and Slave are also used in a different context in relation to serial
communications.
Also refer to: Cascade Control, Linear Output, Retransmit Output, Remote Setpoint, Auxiliary
Input Offset, Serial Communications and Setpoint.
Minimum Duration Of Change
A form of alarm hysteresis unique to the Rate Of Change Alarm. It is the minimum time that
the rate of change in the process variable must be above the alarm threshold, before the
alarm will change state (from on to off, or off to on).
Settings = 1 to 9999 secs.
Default value = 1sec.
Caution: If the duration is less than this time, the alarm will not activate no matter how fast
the rate of rise.
Also refer to: Alarm Hysteresis, Alarm Types and Rate Of Change Alarm.