VAC V200 Fine Tuning

If the positioner and the feedback have been accurately calibrated but the feedback is not
linear the steps below will help improve feedback linearity. Important Note: A full gauge set
is very helpful when trying to fine tune a positioner and feedback. Being able to see the
pressure movement, and their reaction to signal changes helps you know the positioner is
responding. Check list.
• Make sure air is turned on.
• Will need to make sure you have 2 good loop calibrators.
• One for generating a 4 to 20mA signal
• One for reading a 4 to 20mA signal (BOTH UNITS MUST BE SET TO HAVE A 24V LOOP
SOURCE) IF YOU DO NOT SET THE CALIBRATOR IN THE 24V source SETTING, YOU
WILL NOT READ ANYTHING ON THE FEEDBACK.
• Normal flat head screwdriver
• Tweeker (small screwdriver) for adjusting span and zero trim pots settings on the feedback.
• Check 4mA and 20mA. On the feedback, this will be done by
mechanically moving the valve/actuator as stated below:
• At 4mA make sure that the valve is not open/closed by manually pushing up on the balance
arm that is connected to the spool valve. There should be no movement; this can be seen/read
in the feedback. If you see movement in the feedback, make adjustments to the zero on the
positioner. NOT THE ZERO ON FEEDBACK.
• At 20mA feedback make sure the valve is open/closed by manually pushing down on the
balance arm that is connected to the spool valve. There should be no movement; this can be
seen in the feedback. If you see movement in the feedback, make adjustments to the span on
the positioner, outer silver wheel. NOT THE SPAN ON FEEDBACK.
• Once these adjustments have been made:
• Give positioner a 4mA control signal. Make adjustments to the zero
on FEEDBACK as necessary to get the output close to the 4mA input.
• Give positioner a 20mA control signal. Make adjustments to the span on FEEDBACK as
necessary, to get the positioner input close to the 20mA output.
V200 Fine Tuning

Positioner Feedback