Calibration
Before the new M3500 viscometers were shipped to you, they were calibrated for both temperature measurement and torque measurement. And you should find a sheet of “Calibration report” coming with a new unit.
Accuracy Check
Accuracy check should always be performed before any calibration. Accuracy check should only be done with Newtonian certified calibration fluids. Calibration Fluids are available in nominal 20, 50, 100, 200, and 500 cP. All are traceable to ASTM standards and each bottle of fluid is furnished with a viscosity temperature chart certifying that batch of fluid.
1. The instrument being checked must be clean before immersing the rotor and bob into the calibration fluid. If necessary, remove the rotor and thoroughly clean the bob, bobshaft, and rotor. Make sure the bob shaft and rotor are straight and have not been damaged.
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CAUTION
The batch number on the label of the calibration fluid must match the number on the viscosity/temperature chart. |
2. Fill the sample cup to the scribed line with calibration fluid and place it on the instrument stage. Elevate the stage so that the rotor is immersed to the proper immersion depth. Refer to Fig. 1.
3. Place a thermometer into the sample until the bulb touches the bottom and then secure it to the side of the viscometer to prevent breakage.
4. Setup a test sequence, in which the first step operates the instrument at 300 rpm for three (3) minutes. This will equalize the temperature of the bob, rotor and the fluid.
5. Then run 10 seconds each step for 100 rpm, 200 rpm 300 rpm and 600 rpm. Review or download the results depending on whichever the model you have. Also record the temperature from the thermometer to the nearest 0.1° C,(0.15° F).
Compare the thermometer reading to the M3500 measurement, the difference should be within ±2 °F. The viscosity from the temperature chart at the recorded thermometer temperature should be within ±2 cP of the 300 rpm reading. Twice the cP viscosity from the chart should be within ± 3 of the 600 rpm reading. Please also be careful that the readings of shear stress or “Fann® angle” have not reach the maximum reading. Plot the Shear Stress vs. Shear Rate chart, zero, 100 rpm, 200 rpm, 300 rpm and 600 rpm reading should be linear. If zero, 300 and 600 points do not fall in a straight line, probably either the rotor, bob or bobshaft is bent or other eccentricity exists. Readings outside the specified limits are indications that the instrument should be either calibrated or repaired. Refer to below or our Internet training center to calibrate the spring. After completion of the calibration check, carefully wipe clean the rotor inner and outer surfaces, the bob, the thermometer, the sample cup, and work area.
Calibration
After calibration check, if a calibration is necessary, the following steps can be followed to perform a calibration.
1. Remove the sleeve, bob and dust shield as outlined in Section 3.2 "Start & Stop Testing".
2. Prepare a stand about 10"-12" high, put it at the right hand side of M3500 viscometer when looking from the front.
3. Take off top cover by unscrewing 10 screws, which secure the top cover to the frame.
4. Carefully take off the top cover and put it on the stand as shown in appended picture.
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WARNING
After taking off the top cover, at power-on condition, exposed wire, connectors and components
might contain high voltage. DO NOT TOUCH ANY PARTS WITH BARE HANDS. |
For a M3500-1 viscometer, continue from step 5 to step 10; for a M3500-5 viscometer, continue from step 11 to 16.
5. Power the unit on, setup a test sequence with only one testing step, which is 2000 seconds, 40 F and 150 rpm.
6. Pour 200 cp calibration fluid into sample cup. Put on shield, bob and sleeve. Raise the stage to be ready for a test. Refer to Section 2.1 “Test Preparation” and Section 3.2 "Start & Stop Test" for detailed description.
7. Push keypad button "1" to start the test. Wait 3 minutes.
8. Use a thermometer to record the temperature to the nearest 0.1° C,(0.15° F). Locate the correct viscosity of the calibration fluid at this temperature.
9. Turn the petentiometer R4, untill the digital reading of the shear stress is as below:
Shear Stress Reading =
Viscosity (cp) * 5.11 / 2.0
10. If initially the shear stress reading before calibration is too far away from correct reading (>30 dyn/cm2), power down the unit, then repeat step 5 to 9.
(The following is for a M3500-5 viscometer.)
11. Power the unit on, setup a test sequence with only one testing step, which is 2000 seconds, 40 F and 600 rpm.
12. Pour 200 cp calibration fluid into sample cup. Put on shield, bob and sleeve. Raise the stage to be ready for a test. Refer to Section 2.1 “Test Preparation” and Section 3.2 "Start & Stop Test" for detailed description.
13. Push keypad button "1" to start the test. Wait 2 minutes.
14. Use a thermometer to record the temperature to the nearest 0.1° C,(0.15° F). Locate the correct viscosity of the calibration fluid at this temperature.
15. Turn the petentiometer R4, untill the digital reading of the shear stress is as below:
Shear Stress Reading =
Viscosity (cp) 5.11 * 2.0
16. If initially the shear stress reading before calibration is too far away from correct reading (>30 dyn/cm2), power down the unit, then repeat step 11 to 16.
At last, turn off the power and put back the top cover, being sure that no connectors or cable are jammed underneath the top cover.
* Fann® is the registered trade mark of Fann Instrument Company
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