SECTION 4
SPRING CALIBRATION PROCEDURE
MODEL 286 RHEOMETER
This procedure requires the removal of the Torsion Shaft Assembly, shown in Fig.1, from the
Rheometer, and mounting it in the Calibration Fixture.
A. Torsion Shaft Assembly Removal
1. Disconnect the Rheometer from the power source.
2. Unscrew and remove the Sleeve, Bob, and Dust shield from the Rheometer.
3. Use hex key wrenches loosen the set screws holding the power ON/OFF switch,
the speed selector switch, and the knob for the variable speed control, then
remove these three knobs.
5. Remove the speed selector switch nut and the variable speed potentiometer nut
holding these parts to the stainless steel cover. Use socket wrenches or nut
drivers.
6. Remove two 6-32 x 1/4 long cover to frame screws on the sides near the front of
the Rheometer.
7. Remove two 6-32 x 1/4 long cover to power supply bracket screws in the back of
the Rheometer.
8. Carefully lift the cover up and off Rheometer.
9. Remove flat head screw [79] from top center of dial [60], then carefully lift dial
straight up and remove.
10. Remove printed circuit board by removing screws as follows:
Two 4-40 screws mounting the printed circuit board to the frame. These two
screws go through the circuit board from the top. One is near each side of the
board about 5 inches, (12.7 cm), from the square end.
One 1/4 inch long screw that attaches the power transistor to the frame on the right
side as viewed from the curved front of the Rheometer frame.
One 3/8 inch long screw that attaches the voltage regulator to frame on the left
side as viewed from the curved front of the Rheometer frame.
11. If the heat sink sealer has the power transistor or the voltage regulator stuck to the
frame, pry them loose.
12 Lift the printed circuit board upward and allow it to swing out of the way hanging
near the front left side of the instrument.
Loosen two Zeroing screws that act as set screws against the flat on the Torsion
Body, [item 6, Fig 1] (right hand side of frame) sufficiently to clear and allow
removal of the torsion body.
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