Patent No. 6,766,028 - OFI Testing Equipment, Inc.
OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: 832-320-7300 / Fax: 713-880-9886 / www.ote.com 49
Appendix
Adjusting the P Value
The P value represents the position of the transducer. In order to provide
accurate readings, the P value must be between 20,000 and 21,000. At the
beginning of each calibration (in standalone mode), you will be asked to verify
the P value. If it is out of range, use the following instructions to adjust it.
The P value must also be adjusted any time the internal components of the
viscometer are disassembled. This includes replacing the main bearings,
bob shaft bearings, or torsion spring.
1. Follow steps 1 - 6 on page 40 to expose the transducer.
2. Loosen the screws on the Transducer Clamp. Refer to the photo on page
46.
3. Turn the bob shaft counterclockwise and hold it rmly against the stop.
4. While holding the bob shaft against the stop, turn the transducer until the
P value reads approximately 17,000.
The P value can be viewed either on the display screen on the keypad or
in the ORCADA
®
software. To view it in the ORCADA
®
software, open the
“Calibrate Shear Stress” screen and nd the “Shear Stress Raw” eld.
5. Tighten the screws on the Transducer Clamp.
6. Carefully place the Spring Mounting Plate onto the three standoffs and
secure it in place with the hex screws. Be careful not to bend the spring.
Refer to page 40 for photos.
7. Loosen the two set screws that hold the Zero Calibration Knob onto the
Spring Mounting Plate.
8. Tighten the set screw that holds the spring in the Zero Calibration Knob.
9. Slowly rotate the Zero Calibration Knob until the P value is approximately
20,500.
10. Tighten the set screw in the Zero Calibration Knob.
11. Reassemble the Model 900.
12. Turn the unit off and then on to make sure the P value does not drift.
13. Calibrate the viscometer with uid.
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