West Control Solutions 8700+ - Manual (Page 143)

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Glossary 59305, Issue 7 – March 2014
When tuning a cascade system, first set the master to manual mode. Tune the slave
controller using proportional control only (I & D are not normally required) then return the
master to automatic mode before tuning the master. The result is quicker, smoother control
with minimum overshoot and the ability to cope with load changes, whilst keeping the jacket
temperature within acceptable tolerances.
Also refer to Manual Mode, Master & Slave, PID, Remote Setpoint, Remote Setpoint Lower
Limit, Remote Setpoint Upper Limit, Setpoint, Setpoint Select and Tuning.
Communications Write Enable Type: General Definition
Enables/disables the changing of parameter values via the RS485 communications link, if
the communications option is installed. Possible settings are read only or read/write.
Display code =

, default setting = (read/write).
Control Type Type: Controller Parameter
Defines if a controller has one or two control outputs. Single outputs can drive the PV in one
direction only (e.g. heat only, cool only, increase humidity etc). Dual outputs can force the PV
to increase or decrease (e.g heat & cool, humidify and dehumidify etc).
Dual control is not possible on Valve Motor Drive controllers
Display codes =

and

, default value =

.
Also refer to PID, Primary Proportional Band, Process Variable, Secondary Proportional
Band and Valve Motor Control.
Controller Type: Controller Definition
An instrument that can control a Process Variable, using either PID or On-Off control
methods. Alarm outputs are also available that will activate at preset PV values, as are other
options such as PV retransmission and Serial Communications.
Also refer to Alarm Operation, Indicator, Limit Controller, On-Off Control, PID, Process
Variable, Retransmit Output and Serial Communications.
CPU Type: General Definition
This stands for Central Processing Unit and refers to the onboard microprocessor that
controls all of the measuring, alarm and control functions of the instrument.
Current Proportioning Control Type: Controller Definition
Current proportioning control can be implemented on units configured with linear current or
voltage output(s). It provides a 4 to 20mA, 0-20mA, 0 to 5V, 0 to 10V or 2 - 10V DC PID
output. On-Off control should not be used with Current proportioning control.
Also refer to On-Off Control, PID, Primary Proportional Band, Rate, Secondary Proportional
Band and Time Proportional Control.
Cycle Time Type: Controller Definition
For time proportioning outputs, it is used to define time period over which the average on vs.
off time is equal to the required PID output level.

,

and

are available when
option slots 1, 2 or 3 are defined as time proportioning output types. The permitted range of
value is 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256 or 512 seconds. Shorter cycle times will give
better control, but at the expense of reduce life when used with an electromechanical control
device (e.g. relays or solenoid valves).
Display codes =

,

and

, default value = 32.
Also refer to PID and Time Proportioning.
Deadband Type: Controller Parameter
- Refer to Overlap/Deadband.