Flowserve AF-17 Electronic Positioner - Manual (Page 6)

6 AF-17 Electronic Positioner: Installation, Operation and Maintenance WCAIM2031
2.0 ELECTRONIC CIRCUIT BOARD (120/240 VAC)
2.1 General
Figure 1 defines the location of major components and wires from the positioner to terminal strip connections. The #18 gauge
white wire is the AC power unit “neutral” (or common) in the case of DC input wire. The #20 gauge white/black wire is one of the
connections between the feedback pot and the terminal block (TB-1) on the circuit board.
2.2 Circuit Board Configurations
The positioner board is factory supplied for one of the seven input signal options.
NOTE: Field changes to the positioner board are not advised. Consult Flowserve before attempting any modification.
2.3 LED Indicators
Light emitting diodes (LED) marked LD1, LD2 and LD3 are in the output circuits of amplifier U4. LD1 is tied to pin #13, LD2 to pin
#14, and LD3 to pin #1, and they are each associated with their respective opto-coupler U1, U2 and U3 and indicate when the
input side of the opto-coupler is energized.
2.4 Controls
Three adjustment potentiometers are provided, located on the top side of the board and marked “Range”, “Zero”, and “AH”. See
Figure 1.
2.4.1 Range
The “Range” Control adjusts the positioner’s feedback circuit to cover the same span of voltage as generated by the input
signal.
2.4.2 Zero
The “Zero” adjustment is basically an offset adjustment in that essentially all input signals start at other than a zero signal
condition, i.e., 1, 4 or 12 milliamps.
2.4.3 A-H
The “AH” Control is used primarily to balance the positioner to the dynamic characteristics of the device and media being
controlled. Functionally, it varies the amount of input signal that must be applied to the positioner to cause the actuator to
reverse its direction of rotation. In effect it varies the deadband of the positioner on a reversing signal condition only. The
deadband — the percent change in input signal change that must be applied to initiate a movement of the actuator — on a
signal that is constantly increasing or decreasing, is relatively unaffected by the “AH” control.
The “AH” control can vary the balance point deadband from approximately .3% to 4.0% of signal span. It can therefore be
used to help decrease the effects of signal noise, with a tradeoff in accuracy/sensitivity.
2.5 AC Power Control
The AC output circuits are controlled by solid-state switches (triacs Q1, Q2, Q3), which will provide trouble-free operation for the
life of the equipment they are used with, AS LONG AS THEY ARE OPERATED WITHIN THEIR RATINGS.
The ratings for the solid-state switches used in the Worcester AF-17 Positioner are listed in Part 6.3.
Flow Control Division
Worcester Controls