West Control Solutions 8700+ - Manual (Page 149)

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Glossary 59305, Issue 7 – March 2014
Manual Mode Enable Type: Controller Parameter
Determines whether operator selection and de-selection of manual control is enabled. If the
mode is enabled in Set-Up mode, pressing the AM key in Operator Mode will normally
activate or deactivate manual control mode. However, disabling

in whilst manual
control mode is active will lock the controller into Manual Mode and pressing the Auto/Man
key will no longer cause a return to PID (automatic) control. To exit from Manual Mode,

must temporarily be re-enabled to allow PID control to be re-established.

can then be
safely disabled.
It is possible to use a controller as a permanent “Manual Station” by disabling

to
deliberately lock it into Manual Mode.
Manual Mode can also be selected using a digital input if one has been fitted and configured
for this function. When in Manual Mode, the MAN LED indicator flashes.
Display code =

, default setting =

Also refer to Manual Mode and PID
Master & Slave Type: Controller Definition
The terms master & slave are used to describe the controllers in applications where one
instrument controls the setpoint of another. The master controller can transmit the setpoint to
the slave using an analogue DC linear signal. The slave controller must have a matching a
remote setpoint input. Some Profile Controllers can transmit their setpoint via serial
communications serial communications. For this method, the Profiler must be able to act as a
communications master device and the slave must have a compatible communications
option fitted.

Also refer to Cascade Control, Retransmit Output, Remote Setpoint, Serial Communications,
Setpoint
Minimum Motor On Time Type: VMD Controller Parameter
This defines the minimum drive effort needed to initiate valve movement, if the valve was
previously stationary. This parameter is used primarily to ensure that valve frictional and
inertial effects do not cause controller drive to be ignored by the valve.
If Self-Tune is

, this parameter can be used to influence valve activity. Larger values
reduce valve activity but increase the risk of the process oscillating. Self-Tune monitors on-
control valve activity and will minimise it automatically.
Too large a value of Minimum Motor On Time can impair the effectiveness of the Self-Tune
facility; if process variable oscillations persist whilst Self-Tune is running, it may be for this
reason
Display code =

, default setting =

Also refer to Motor Travel Time, Self-Tune and Valve Motor Drive Control.
Modulating Valve Type: VMD Controller Definition
A valve that can be positioned anywhere between fully closed and fully open by means of an
incorporated motor. A typical application would be controlling temperature in a furnace
heated by gas burners. A Valve Motor Drive (VMD) Controller is used to move the valve to
the desired position in order to control the gas valve. Some modulating valve motors require
linear (mA or VDC) signals to position the valve. These require standard Process Controllers
(using PI control) instead of VMD types.
Also refer to Motor Travel Time, PI Control and Valve Motor Drive Control.
Motor Travel Time Type: VMD Controller Parameter
The Motor Travel Time parameter is the time the valve takes to travel from one physical end
stop to the other. This parameter is used by the Valve Motor Drive control algorithm when