Analog Outputs - Emerson VILTER MicroVission Operation And Service Manual

Section 20 • Auxiliary I/O

Analog Outputs

This screen gives the ability to map any standard analog
input or auxiliary input to any of the five analog auxiliary
outputs. There is page 4 for auxiliary output configura-
tion. see Figures 20-6 and 20-7.
• Active Input: The active Input can be selected from
the available standard analog inputs or auxiliary in-
puts or calculated values list. The selected Active
Input gets mapped to auxiliary output.
• Run Always: "Run Always" option can be selected to
enable the mapped auxiliary output irrespective of
the compressor's run state. If "Run Always" is not se-
lected, then the mapped auxiliary output is enabled
only when the compressor is running.
• Trigger: Trigger configuration is used to enable / dis-
able an auxiliary output according to the configured
trigger input. The trigger input can be selected from
the available standard analog inputs, standard digi-
tal inputs, auxiliary analog inputs or digital inputs.
Trigger value and differential in combination with
trigger type ("enable if above / On" or "enable if be-
low / Off") enables or disables the auxiliary output.
Control Auxiliary outputs can be PID Controlled or
Scalable Controlled.
PID Control
P = Proportional (gain): Used to adjust the auxiliary out-
put in direct proportion to the difference between the
control setpoint and the active input. The proportional
term is a unitless quantity and is used for coarse adjust-
ment. This setpoint should be set to the lowest value
that gives adequate control system response. Increasing
the proportional setting increases the control system's
sensitivity to small process fluctuations and the tenden-
cy to hunt.
I + (Reset): Used to integrate the error over time, to
account for a small error that has persisted for a long
time. This quantity is used for fine adjustment. This set-
point is used to smooth out process variations. When
this setpoint is set / non-zero, integral error will get
accumulated.
Examples:
Case I -
PID Settings
P = 1 Setpoint = 20, I Op. Band = 0
I + (Reset) = 1
I – (Reset) = 1
D = 1 Inverse (20 – 4 mA) = Disabled
20 – 6
Other Settings
Interval = 1 sec
Negative Error = Disabled
MicroVission Controller • Operation and Service Manual • Emerson • 35391MV 1.3
In this case, the integral error will get accumulated when
process variable is below setpoint i.e. 20.
Case II -
PID Settings
P = 1 Setpoint = 20, I Op. Band = 0
I + (Reset) = 1
I – (Reset) = 1
D = 1 Inverse (20 – 4 mA) = Disabled
In this case when negative error is enabled, the inte-
gral error will get accumulated when process variable is
above setpoint i.e. 20.
I - (Reset): Used to remove the error over time, to ac-
count for a small error that has persisted for a long time.
This quantity is used for fine adjustment. This setpoint
is used to smooth out process variations. When this set-
point is set / non-zero, integral error will get removed.
Examples:
Case I -
PID Settings
P = 1 Setpoint = 20, I Op. Band = 0
I + (Reset) = 1
I – (Reset) = 1 Negative Error = Disabled
D = 1 Inverse (20 – 4 mA) = Disabled
In this case, the integral error will get removed from the
accumulated error when process variable is above set-
point i.e. 20.
Case II -
PID Settings
P = 1 Setpoint = 20, I Op. Band = 0
I + (Reset) = 1
I – (Reset) = 1
D = 1 Inverse (20 – 4 mA) = Disabled
In this case when negative error is enabled, the integral
error will get removed from the accumulated error when
process variable is below setpoint i.e. 20.
D = Derivative (rate): Used to account for how fast the
error is changing, positively or negatively.
Other Settings
Interval = 1 sec
Negative Error = Enabled
Other Settings
Interval = 1 sec
Other Settings
Interval = 1 sec
Negative Error = Enabled