Model 35 Viscometer Instruction Manual
208878
Revision N, February 2013
27
Readings outside the specified limits are indications that the instrument should be
either calibrated or repaired. (See Section 6.3 for the procedure to calibrate the
spring.)
After completion of the calibration check, carefully wipe clean the rotor surfaces
(inner and outer), bob, thermometer, sample cup, and work area
.
6.3
Torsion Spring Calibration
Refer to Figure 5-4 for identification of parts.
Make sure that the bob shaft is not bent before adjusting the
torsion spring.
1.
Remove dust cap [A], and then loosen set screw [C] about one-half turn.
2.
Insert the calibration tool into the spring and rotate the adjustable mandrel
(inside the spring) slightly. Turn the mandrel counterclockwise if the dial
reading is too low, or turn the mandrel clockwise if the dial reading is too high.
Before tightening set screw [C], check the top of the center
mandrel and be sure that it is flush with the top of the clamp [E].
To accomplish this, it may be necessary to adjust the spring by
slightly compressing or stretching the spring.
3.
Tighten the set screw [C]. The slot in the top of the adjustable mandrel should
line up with clamping set screw [C].
4.
Loosen the set screw [F] to zero dial under index, then rotate knob [G] as
required for alignment, then adjust knob [G] vertically to allow the spring to be
clamped in a "free" position, neither stretched nor compressed.
5.
Tighten the set screw [F] and replace the dust cap [A].