GE FVP110 - Function Diagram of AR Function Block

FVP 110 Fieldbus Valve Positioner Manual
154
GE Energy
The major functions of the block are shown in Figure 69.
Figure 69 Function Diagram of AR Function Block
The range extension function has a graduated transfer, controlled by two constants
referenced to IN. An internal value, g, is zero for IN less than RANGE_LO. It is one when
IN is greater than RANGE_HI. It is interpolated from zero to one over the range of
RANGE_LO to RANGE_HI. The equation for PV follows:
PV = g * IN + (1-g) * IN_LO
If the status of IN_LO is unusable and IN is usable and greater than RANGE_LO, then set
g to one. If the status of IN is unusable, and IN_LO is usable and less than RANGE_HI,
then g should be set to zero. In each case the PV should have a status of Good until the
condition no longer applies. Otherwise, the status of IN_LO is used for the PV if g is less
than 0.5, while IN is used for g greater than or equal to 0.5. An optional internal hysteresis
can be used to calculate the status switching point.
Six constants are used for the three auxiliary inputs. Each has a BIAS_IN_i and a
GAIN_IN_i. The output has a BIAS and a GAIN static constant. For the inputs, the bias is
added and the gain is applied to the sum. The result is an internal value called t_i in the
function equations. The equation for each auxiliary input is the following:
t_i = (IN_i + BIAS_IN_i) * GAIN_IN_i
The flow compensation functions have limits on the amount of compensation applied to
the PV, to assure graceful degradation if an auxiliary input is unstable. The internal limited
value is f.