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7.4
General
Table 7-3
Symptom
Angle reading does not change or
changes erratically
Unexpected angle readings, but
correct with calibration fluid
101625591
General
Possible Cause
Baffle unscrewed against bob
Bob shaft assembly bent
Torsion magnet touching upper
pivot spring
Bottom vee jewel adjusted too far
down
Debris between torsion magnet and
pivot cap
Dirty vee jewels
Solids caked around torsion spring
or limit stop
Faulty magnetometer
Cell bearings or bushings worn
Rotor speed calibration incorrect
Rotor and magnet holder incorrectly
assembled
Inadequate calibration fluid volume
in cell during calibration
Contaminated fluid during
calibration
Wrong calibration chart used
iX77™ Rheometer User Manual
Revision F
Solution
Tighten baffle and inspect bottom
vee jewel for damage
Straighten
Adjust magnet position and inspect
bottom vee jewel for damage
Inspect for damage and adjust
Clean
Clean and inspect for damage with
microscope
Thoroughly clean torsion spring
module
Call for FANN service
Check pivot bushing, rotor bushing
and angular contact bearing for wear
(0.0156 inch max vertical movement
at rotor edge) and replace as
indicated
Confirm rotor speed with optical
tachometer and adjust motor control
board
Loosen magnet set screw and verify
rotor and magnet holder squarely
seat, tighten set screw
Recalibrate with correct fluid
volume
Clean cell and recalibrate with fresh
calibration fluid
Recalibrate with correct calibration
chart for fluid being used
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