Emerson Vilter Vission 20/20 Operation And Service Manual Download

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Section 18

•

Auxiliary Input / Output

Vission 20/20 • Operation and Service Manual • Emerson • 35391SC 2.7

Digital Outputs

The digital outputs section of the Auxiliary I/O screen

allows an operator to configure the auxiliary digital

outputs, see Figure 18-2. The digital output can be con-

figured to activate (go High, 120VAC) based on either a
digital input or a specified level on an analog input. Every

digital and analog input in the Vission 20/20 is made
available to control a digital output.

Analog Input:
•

Selecting the Analog Input radio button fills the

Active Input drop-down box with all available analog
inputs. One of the analog inputs can then be selected
to control the digital outputs.

Digital Input:
•

Selecting the Digital Input radio button fills the

Active Input drop-down box with all available digital
inputs. One of the digital inputs can then be selected
to control the digital outputs.

Run Always:
• Selecting this checkbox enables the function that

controls the digital output to operate only when the
compressor is running or runs all the time.

• N/O & N/C:

• Choosing the Normally Open (N/O) or

Normally Closed (N/C) radio buttons defines

what the output will be above or below the trig-
ger value. In the N/O setting, the output will be
off (0VAC) while the input value is below the
trigger value. In the N/C setting, the output will
be high (120VAC) while the input value is below
the trigger value.

Analog Trigger:
• The analog trigger toggles the digital output based

on a specified value plus the specified differential val

ue. These options will be available only when Analog
Input is selected.

Analog Trigger value:
•

This defines the specified value in which the output

will toggle. This is an absolute value and not based
on units. For example, 100 could mean temperature
or pressure depending on the type of input selected.

Differential:
• This is the differential around the trigger value. For

example, if a trigger value of 100 is entered with a
differential of 1, then as the value increases to 101,
the output will be triggered. If the value decreases
to 99, then the output will be toggled in the oppo-
site direction.

Enable Timer:
• Selecting this checkbox enables the function that

controls the digital output when activated on the ba-
sis of ON Time and OFF Time.

Timers:
• ON Time:

•

This defines the ON Time for the digital out

put when it is activated.

• OFF Time:

•

This defines the OFF Time for the digital out

put when it is activated.
• For example, if an analog input is selected
with a trigger value of 100 and differential of 1
and ON Time and OFF Time of 1 min each and
N/O setting, then as the analog input value in-
creases to 101, the output will be high (120VAC)
for 1 min and then the output will be low (0VAC)
for 1 min. The output will keep on toggling from
high to low and then low to high until the analog
input value decreases to 99.

Analog Inputs

The Analog inputs section of the auxiliary I/O screen al-

lows an operator to define the function of an instrument

connected to the Vission 20/20. For Auxiliary Analog
Inputs Screens, see Figure 18-3, 18-4 and 18-5. The ana-

log inputs can be configured to simply monitor an input

for informational purposes or used as a control input for
the auxiliary digital and analog outputs. The analog in-

puts can also be configured to alarm, trip, and inhibit on
specified values.

• Alarm / Trip:

• This drop-down box allows the operator to
select whether the analog input should gener-
ate an alarm, trip, or both when the input value
exceeds the limits entered into the alarm and
trip entry boxes.

• Inhibit:

• Selecting this checkbox will prevent a start if
the input value exceeds the alarm limit values.

• Low Alarm:

•

This defines the lower limit of the input value

that when exceeded will generate an alarm.

• High Alarm:

•

This defines the upper limit of the input value,

that when exceeded will generate an alarm.