Supported Modes; Alarm Types; Mode Handling; Status Handling - GE FVP110 Maintenance Manual

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Simple HTG compensated level
Where PV is the tank base pressure, IN_1 is the top pressure, IN_2 is the density
correction pressure, and GAIN is the height of the density tap.
func = (PV -t_1) / (PV - t_2)
After the value of func is calculated, it is multiplied by GAIN, and then BIAS is added to
the result. Finally, high and low output limits are applied, and the result is the term
PRE_OUT. If the mode is Auto, PRE_OUT becomes OUT.
Difficulties with the function, such as division by zero and roots of negative numbers,
should be handled gracefully, without disturbing the status of OUT, or the mode. Division
by zero produces a large number of the proper sign. Infinity cannot be used, as it has a
special meaning for unused limits. Roots of negative numbers produce the root of the
absolute value, with a negative sign. The output has absolute high and low limits.

Supported Modes

O/S, Man, and Auto.

Alarm Types

Standard block alarm.

Mode Handling

The algorithm never changes the mode, even when inputs go bad.
If the mode is changed to Man, an internal value is set to the difference between OUT and
the output of the selected function. When the mode is changed to Auto, the difference
value exponentially decays to zero with a time constant of BAL_TIME.
The output of the calculation function appears in PRE_OUT.

Status Handling

The INPUT_OPTS bit string controls use of auxiliary inputs with less than good status.
The status of unused inputs are ignored.
The status of the output is that of the worst of the inputs used in the calculation after
applying INPUT_OPTS.

Initialization

Standard.

Power Failure Recovery

Standard.
FVP 110 Fieldbus Valve Positioner Manual
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