Bailey infi 90 IMHSS03, Instruction

Page: 78 / 93

FUNCTION CODE 150 CALIBRATION
INITIAL CALIBRATION
B - 2 I-E96-322A
®
seconds 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 module in the calibrate
mode.
4. Read the value of S8 with the valve in the 0% position
(closed).
5. If the value of S8 is between 0 and -8.5 VDC, remove the
HSS module and increase the demodulator gain (dipswitch S2)
to the next higher value. For example, if the gain is 2 (pole 8
closed), change the gain to 5.5 (close pole 7, open pole 8). Table
3-2 lists the gain associated with each dipswitch pole.
6. Insert the HSS module in the module mounting unit.
7. Continue reading S8 and increase the demodulator gain
until S8 displays a value of -8.5 VDC to -10.0 VDC. Record the
date, time, demodulator gain and names of personnel tuning
the demodulator gain in the space provided in Table
B-1 .
Update the information every time the demodulator gain is
tuned.
8. Go to the block address specified in S5. Set the linear vari-
able differential transformer (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 LVDT null point should
occur at the actuators midtravel 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 transformer 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 module drives the actuator to the 100% position at
the selected stroke time (S6). While the actuator is held against
the 100% end of travel, function code 150 stores the LVDT dif-
ferential voltage at 100% in specification S9.
After recording the 100% reading, the HSS module drives the
actuator to the 0% actuator position at the selected stroke