62
•
Total
(Input + Input 2)
•
% Difference
[(Input - Input 2) / Input]
• This selection could be used to calculate % Rejection in RO applications, for example
Virtual Input Details
The details for any type of virtual input include the current value calculated, alarms, the status, and the input type.
Settings
Touch the Settings icon to view or change the settings related to the virtual input.
Alarms
Low-Low, Low, High and High-High Alarms limits may be set.
Deadband
This is the Alarm Deadband. For example, if the High Alarm is 7.00, and the deadband
is 0.1, the alarm will activate at 7.01 and deactivate at 6.90.
Input
Select the physical input whose value will be used in the calculation shown above as
the Input in the formula.
Input 2
Select the physical input whose value will be used in the calculation shown above as
the Input 2 in the formula.
Calculation Mode
Select a calculation mode from the list.
Alarm & Datalog
Suppression
If any of the relays or digital inputs are selected, any alarms related to this input
will be suppressed if the selected relay or digital input is active. At the same time,
all datalogs and graphs containing the input will show no data for the duration of
the activation.
Low Range
Set the low end of the normal range for the calculated value. A value below this will
trigger a Range Alarm and deactivate any control output using the virtual input.
High Range
Set the high end of the normal range for the calculated value. A value above this will
trigger a Range Alarm and deactivate any control output using the virtual input.
Smoothing Factor
Increase the smoothing factor percentage to dampen the response to changes. For ex-
ample, with a 10% smoothing factor, the next reading shown will consist of an average
of 10% of the previous value and 90% of the current value.
Name
The name used to identify the input may be changed.
Type
Select the type of input; either Calculation or Not Used.
5.2.18
Virtual Input – Redundant
A Redundant type Virtual Input is not a physical sensor; it is a value that is calculated from two physical sensor
inputs. The redundant sensor algorithm compares the readings from two sensors, and chooses which sensor to use.
The value of the virtual input is the value of the sensor chosen by this comparison.
If the difference between the two exceeds a programmable amount, a deviation alarm is set, but control continues.
If one of the sensors goes into a range error or a fault alarm, the other sensor will take over. If both sensors give
invalid readings, an input alarm is set and any outputs using the virtual input for control are disabled.
The analog values that can be used for each type of calculation are selected from a List of all defined sensor inputs
and analog inputs.
There are three modes:
• Primary/Backup – The primary sensor (selected as the Input) value, as opposed to the backup sensor
(selected as Input 2) value, is chosen as the virtual input value, assuming it has a valid reading.
• Minimum Value – The sensor that has the lower reading of the two sensors is chosen as the virtual
