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6.5
VIRTUAL CHANNEL CONFIGURATION
This allows the configuration of maths channels, totalizers and counters. The configuration is divided into the
following areas: 'Main', 'Trend', 'Alarm 1*' and 'Alarm 2*'. Items appearing in the 'Trend', Alarm 1' and 'Alarm 2'
areas are identical with the equivalent items described in Section 6.4 (Input channels), above.
Note: * Virtual channels 16 to 30 (supplied with Modbus Master and EtherNet/IP options only) come
without alarms
6.5.1 Maths channel configuration
The following maths functions are available (listed in up-arrow scroll order)
Off, Add, Subtract, Multiply, Divide, Group Average, Group minimum, Group maximum, Modbus input, Copy,
Group minimum (latch), Group maximum (latch), Channel maximum, Channel minimum, Channel Average,
Configuration revision, Off.
Figure 74 shows a typical maths channel configuration.
Descriptor
Type
Operation
PV
Status
Resolution
Units
Input1
Input 2
Reset
Time Remaining
Period
September 18
FEC920: USER GUIDE
Virtual Channel.1.Main
Descriptor
Operation
Resolution
Figure 74 Maths channel configuration (typical)
Allows the user to enter a descriptor (20 characters max.) for the maths channel
Math selected for this example. See Section 6.5.2 and Section 6.5.4 for totalizers and
counters respectively.
Allows the user to select the required maths function. See 'Maths Functions', below.
Read-only. Shows the dynamic value of this channel in the units entered in 'Units' below.
Read-only. Shows the status of this channel, reflecting the status of the input sources.
Enter the number of decimal places required
Allows a five character string to be entered to be used as the channel units.
The value of input 1. May be entered manually, or it may be wired from another parameter
(Section 9). Uses the resolution of the source.
As for 'Input 1', Appears only when the operation requires two inputs.
Allows the user to reset latching functions (e.g. Channel Max) or averaging functions (e.g.
Channel Avg). Reset is carried out by setting the field to 'Yes', then operating the scroll
key. The display returns to 'No'. Alternatively the function can be reset by another
parameter wired to 'Reset'.
The period of time remaining before the virtual channel performs its operation. For
example, the time remaining for the maths channel average operation to sample the input
before performing the calculation.
For averaging functions, this allows a period to be entered, over which the value is to be
averaged. Selectable periods are: 0.125, 0.25, 0.5, 1, 2, 5, 10, 20, 30 seconds, 1, 2, 5, 10,
20, 30 minutes, 1, 2, 6, 12, 24 hours.
A5E45696052A Rev-AA
VirtualChan1
Type
Math
Add
PV
180.36 Units
Status
Good
2
Units
Units
Input1
93.49°C
Input2
86.8°C
Page 81
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