Cannon Instrument CMRV-4500 - Manual (Page 39)

33
CANNON ® Mini-Rotary Viscometer CMRV-4500 Instruction & Operation Manual
Version 1.1e—October, 2011 • CANNON ® Instrument Company
2139 High Tech Road • State College, PA • 16803 • USA
CHAPTER
7
CALIBRATING THE CMRV
TEMPERATURE PROBE
The CMRV temperature probe must be calibrated before performing the
initial cell calibration or running temperature profiles. A complete
calibration session involves setting temperature offsets in the VISCPRO
software for key temperature checkpoints beginning at 80°C, then 50°C,
then other temperatures at 5-degree increments from 0 to -40°C. The
calibration process ensures that temperature probe readings are correctly
interpreted by the CMRV hardware and software. This ensures accurate
temperature control throughout the temperature profile.
There is a 10-minute equilibration time at each calibration temperature.
The entire calibration procedure requires at least 3 hours and requires
operator input at each temperature plateau. Thereafter, the probe should
be calibrated at the user's discretion, particularly when viscosity data is
suspect, the instrument exhibits poor repeatability, or the probe tempera-
ture on the display does not correspond with the calibrated thermometer
reading.
Both the CMRV probe calibration and cell calibration procedures should
be completed shortly after initial installation of the CMRV software.
Probe calibration must precede cell calibration to ensure accurate tem-
perature control during the cell calibration process. Periodic probe
calibration will enhance the accuracy of test results.
Probe calibration procedure
1. After preparing the CMRV instrument (see Chapter 6), place 10 ml ± 0.1
ml of any clean generic oil sample into each of the viscometric cells
being calibrated. Carefully place the rotors into their corresponding
viscometric cells and secure each rotor in position with the rotor pin.
Checking temperature probe 2. Make sure that the thermistor probe sheath is securely seated in the
cylindrical opening on the rear of the CMRV housing.
3. Using the VISCPRO ® software, click Service/MRV/Temperature Probe
Calibration. The Temperature Probe Calibration window will open.
NOTE In preparation for the heating phase of the calibration procedure, remove
the calibrated -46°C to +30°C thermometer from the CMRV block to
prevent separation of the mercury column. Reinsert the calibrated
thermometer when CMRV block temperature is within its range.
4. Select the desired temperature for calibration by clicking on the
thermometer graphic or selecting the temperature from the drop-
down box. Then click the
Calibrate button to begin the calibration