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Also refer to: Display Configuration; Operation Mode;
Main Menu and PC Software.
Display Resolution
The maximum number of digits that can be displayed
and/or the maximum number of decimal places. Nu-
meric values (e.g. process variable, setpoints etc) are
limited to no more than 5 digits. The maximum number
of decimal places is selectable from 0 to 3 places, but
the overall 5-digit limit means that larger values reduce
the number of decimal places shown. For example,
values >99.999 will show no more than 2 decimal plac-
es (e.g. 100.00).
Also refer to: LSD.
Effective Setpoint
- Refer to Actual Setpoint.
Engineering Units
The Process Variable and Setpoint displays can as-
signed engineering units to describe the signals con-
nected to the process inputs. The engineering units for
linear inputs can be: °C; °F; K; bar; %; %RH; pH; psi or
none. For temperature inputs (RTD or Thermocouples)
they can be °C; °F or K.
Also refer to: Linear Input; Process Input; Process Vari-
able RTD and Thermocouple.
Ethernet
A networking technology for local area networks
(LANs). Used to link computers and other equipment
in order to share data or control such devices. If fitted
with an Ethernet communications module in option slot
A, this instrument can connect as a slave to a Modbus
TCP master device via a wired Ethernet LAN connec-
tion.
Also refer to: Modbus TCP and Serial Communications.
Gain Scheduling
Gain scheduling bumplessly switches between pre-set
PID values automatically at successively higher set-
point or process values. This allows optimal control
across a wide range of process conditions, or if the
controller is used in several different applications. It is
especially useful if the process conditions change sig-
nificantly during use, such as a process that becomes
exothermic as the temperature rises.
Also refer to: Bumpless Transfer; PID; PID Sets; Pro-
cess Variable and Setpoint.
Indicator
An instrument that displays process values, but lacks
control features. Typically, alarm outputs are available
that will activate at pre-set PV values.
Also refer to: Controller; Limit Controller and Process
Variable.
Input Configuration
A sub-menu of configuration mode, used to adjust the
parameters that relate to the process and auxiliary in-
puts (type, engineering units, decimal places, scaling,
filtering etc.).
Also refer to: Auxiliary Input; Configuration Mode and
Process Input.
Input Filter Time Constant
This parameter is used to filter out extraneous impuls-
es affecting process variable values. The filtered PV is
used for all PV dependent functions (display, control,
alarm etc). Use this parameter with care as it will also
slow the response to genuine process changes.
Also refer to: Process Variable.
Input Range
This is the overall process variable input range and
type as selected by the Process Input Type parameter.
This range can be scaled using the Scale Input Upper
& Lower Limits.
Also refer to: Input Span; Process Input; Scaled Input
Lower Limit and Scaled Input Upper Limit.
Input Span
The measuring and display limits, as defined by the
Scale Input Lower and Scaled Input Upper Limits. The
trimmed span value is also used as the basis for cal-
culations that relate to the span of the instrument (e.g.
proportional bands).
Also refer to: Input Range; LSD; Primary Proportional
Band; Scaled Input Lower Limit; Scaled Input Upper
Limit and Secondary Proportional Band.
Integral Action
Integral action biases the proportional control output
to compensate for process load variations. Their com-
bined values adjust the correcting variable, until the
control deviation error is zero, at which point the inte-
gral value is held constant. Decreasing the integral time
constant increases the integral action. Integral action is
also known as “Automatic Reset”.
Integral
Time
Power
Response
begins to control
deviation step
Time
Summary of Contents for Chromalox 4081
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