Bailey Infi 90 IMHSS02, Instruction, Page: 35 / 64

CALIBRATION
INITIAL CALIBRATION
4 - 2 I-E96-315B
®
are fast cycle times and are not recommended if the turbine is
on-line.
3. Go to the block address specified in S3. Set the calibration
command bit to 1. This places the HSS in the calibrate mode.
4. Read the value of S8 with the valve in the 0 percent posi-
tion (closed).
5. If the value of S8 is between 0 and - 9 VDC, remove the
HSS and increase the demodulator gain (switch 6) one posi-
tion. For example, if the gain is 2 (position 8 closed), change
the gain to 5 (close position 7, open position 8).
6. Reinsert the HSS in the MMU.
7. Continue reading S8 and increase the demodulator gain
until S8 displays a value of - 9 VDC to - 10.0 VDC. Record the
final gain value in the space provided in Table
3-6 .
8. Go to the block address specified in S5. Set the LVDT null
bit to 1.
9. Go to the block address specified in S4. Set the GO/HOLD
select bit to 1.
10. Monitor the output block (n+1) until it has a value of 1.
This indicates the actuator is at the null point.
11. Make the necessary adjustments to the servo valve and the
LVDT position to adjust the actuator to its mechanical null
position.
For maximum LVDT linearity, the LVDTs null point should
occur at the actuators mid travel position. When S4 is in the
GO mode, the actuator ramps to and holds at the LVDT null
point (LVDT secondaries have equal voltages). While the actua-
tor is held at the LVDT null point, the mechanical zero on the
LVDT can be adjusted until the actuator is at its mid-travel
position.
12. After LVDT zeroing, turn the null check mode off (S5=0).
The HSS drives the actuator to the 100 percent position at the
selected stroke time (S6). While the actuator is held against the
100 percent end of travel, function code 150 stores the LVDT
differential voltage at 100 percent in specification (S9).
After recording the 100 percent reading, the HSS drives the
actuator to the 0 percent actuator position at the selected
stroke time. While the actuator is held against the 0 percent
end of travel stop, function code 150 records the LVDT differ-
ential voltage at 0 percent in specification (S8). After recording
the 0 percent reading, the actuator moves at the selected
stroke time to the position demand from the MFP. The 100