VVP10 HART
HART
®
VALVE POSITIONER
INSTALLATION, OPERATION, CONFIGURATION AND MAINTENANCE MANUAL
______________________________________________________________________________________________________________________________
32
3.8.
CALIBRATION
VVP10 HART allows user to calibrate several variables according to their own measurement standards to suit their
system perfectly. The variables that can be calibrated with their respective procedures are described below.
POSITION
It allows user to take advantage of the largest possible range of the measurement system by the magnetic sensor
related to the physical limits of the valve, by performing previously explained procedures: Automatic Travel Calibration
or Manual Travel Calibration. Both procedures can be found in the
Specific/Calibration
directory and will perform both
lower and upper position calibrations, based on the physical limits (valve seating).
If user wishes to calibrate those positions outside valve's physical location, the Trim (
Lower Position Trim
and
Upper
Position Trim
) functions must be used. Those can be found under
Trim/Sensor
directory.
For lower position, user must perform the
Lower Position Trim
function, where the positioner will send the actuator to
the previously calibrated lower position. From there, via configurator, user must position system in the desired position,
entering the step to be given by the positioner (on display or HART monitoring), since it is lower thano 10%.
For example, with the valve in 0%, execute Lower Position Trim, sending the value (-5%). The valve will go to 5% and
the user can confirm the new position, which will become the new 0% (lower reference) of the stroke course.
For the upper position, the process is repeated, only changing reference from lower to upper.
For example, with the valve in 100%, execute Upper Position Trim, sending the value (105%). The valve will go to 95%
and the user can confirm the new position, which will become the new 100% (upper reference) of the stroke course.
CURRENT
The positioner has two calibrations for 4-20 mA current: the return current from control position and the input loop
current. Calibrations are independent and work differently. Both can be found under
Trim/Current
directory.
Calibration of the position return current functions as the calibration common to the transmitters, but with HART
®
commands specific for the positioner. The positioner also provides specific commands to execute methods that
automatically set the output current to 4 mA and 20 mA according to the calibration point to be executed (zero or span,
respectively).
After generating the fixed current through the positioner, with an ammeter connected in series (see figure 3.17), user
can check the actual current generated and send it by means of HART
®
commands to the equipment, which will
perform the internal calibration and generate the corrected current, allowing user to see the new current in the
connected ammeter, automatically.
The calibration of loop current works with standard HART
®
commands and routines, since the positioner will only
perform the adjustment of the measurement being carried out on the input current (with the help of an ammeter - figure
3.18) so that user is sure of the correct current supplied to the positioner.
Both procedures can be repeated as many times as the user deems necessary, until the currents are perfectly
calibrated at both ends (4 mA and 20 mA).
WARNING
With these two calibrations, the positioner will have its references of 0% and 100% for changed system
positioning, in relation to the physical valve settlement limits.
If the user wants to return to the calibration of the system settlement positions, simply perform the automatic
position calibration again.
