West Control Solutions N8100 - Manual (Page 13)

NOTE: If, on entry into Set Up Mode, the upper
display initially shows all decimal point
positions illuminated), this indicates that one
or more of the critical configuration
parameters - typically input range or output
use/type - have been altered in value/setting and, as a consequence, all
Set Up Mode parameters have been automatically set to their default
values/settings. To clear this display, simply alter the value/setting of any Set
Up Mode parameter (see below).
2.2 SET UP MODE PARAMETERS
The parameter sequence for view/adjustment in Set Up Mode is shown in Table
2-1. Use the Function key to step through the parameters. In each case, the
legend will be shown in the lower display and the current value/setting will be
shown in the upper display. The value/setting may be altered using the
Raise/Lower keys. A detailed description of each of these parameters is given in
the following Subsections.
2.2.1 Input Filter Time Constant
The Controller input is equipped with a digital filter which is used to filter out any
extraneous impulses on the process variable. This filtered PV is used for all
PV-dependent functions (control, alarms etc.).
CAUTION: If this parameter value is set excessively high, the control quality
may be significantly impaired. The value chosen should be sufficiently
large to attenuate stray noise on the process variable signal but no larger.
2.2.2 Process Variable Offset
This parameter is used to modify the actual process variable value (measured at
the Controller’s input terminals) in the following manner:
Offset PV value = Actual PV value + Process Variable Offset value.
For Controllers fitted with a linear input, the displayed process variable value is
limited by Scale Range Maximum (see Subsection 2.2.30) and Scale Range
Minimum (see Subsection 2.2.31). The offset process variable value is used for all
PV-dependent functions (control, display, alarm, recorder output etc.).
NOTE: This parameter value should be chosen with care. Any
adjustment to this parameter is, in effect, a calibration adjustment.
Injudicious application of values to this parameter could lead to the
displayed process variable value bearing no meaningful
relationship to the actual process variable value. There is no front
panel indication when this parameter is in effect (i.e. has been set
to a non-zero value).
O054-2 2-2
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