Cannon CMRV-5000 Instruction & Operation Manual

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Cannon CMRV-5000 Instruction & Operation Manual Manual pdf 119 page image

CANNON® Mini-Rotary Viscometer CMRV-5000 Instruction & Operation ManualVersion 1.0b—August, 2011; CANNON® Instrument Company2139 High Tech Road • State College, PA • 16803 • USA110Kinematic viscosity and temperatureKinematic viscosity is an extremely temperature-sensitive measurement -a change of 1°C can sometimes lead to a viscosity change of 10 percentor more. Therefore, it is not surprising that temperature measurement andcontrol are the most common problems encountered by laboratoriesperforming accurate kinematic viscosity measurements.Although capillary viscometers typically measure kinematic viscositywith a precision of several tenths of one percent, measurements accurateto within one tenth of one percent (0.1%) are possible. To achieve this,temperatures must be measured with an accuracy of 0.01°C, and bemaintained within a range of ± 0.01°C.Thermometers CANNON® Instrument Company recommends the Dostmann DigitalThermometer as an alternative to the liquid in glass (i.e., mercury)thermometers. The Digital thermometer offers temperature data docu-mentation via RS-232 to the PC and is available in a dual probed configu-ration.ASTM Thermometers Each ASTM kinematic viscosity thermometer measures only 3 degreeson a scale subdivided into 0.05°C units (equivalent thermometers areavailable with Fahrenheit scales). These thermometers contain an ice-point scale which allows recalibration by determining the ice-pointtemperature.Thermometer Calibration Calibration of the thermometer is very important. Often the true tempera-ture of a liquid differs markedly from that shown on the thermometerscale. It is not uncommon for kinematic viscosity thermometers to givereadings varying as much as 0.1°C from the actual temperature. The trueliquid temperature is obtained by applying the proper correction (asnoted on the original calibration certificate) to the reading showing onthe thermometer scale and including any difference obtained in a recentice-point measurement of your thermometer.Thermometer Immersion Proper thermometer immersion is critical for viscosity measurements.Even a calibrated thermometer will read incorrectly if it is improperlyimmersed in the bath. “Total immersion” kinematic viscosity thermom-eters should be used with the bulb and entire mercury column beneaththe surface of the liquid, but with the emergent stem above the surface atambient temperatures.NOTE Different thermometers have different installation requirements. Refer tothe information included with the thermometer in use for specific installa-tion instructions.CHAPTERC APPENDIX C— THERMOMETRY