Cannon Instrument CAV-2000 - Manual (Page 8)

CANNON ® Automatic Viscometer Models CAV-2100 and CAV-2200 with VISCPRO ® Instruction & Operation Manual
Version 2g — May, 2009; CANNON ® Instrument Company
2139 High Tech Road • State College, PA 16803 • USA
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Measuring kinematic viscosity
Kinematic viscosity is a measure of the internal resistance to flow of a
fluid under gravity with the pressure head being proportional to the
density of the fluid. For any particular viscometer, the time of flow of a
fixed volume of fluid is directly proportional to its kinematic viscosity.
Units of measure An accepted unit of kinematic viscosity is one centimeter squared per
second, which is called one stoke. The centistoke (which is equivalent to
1 mm
2 /s) is the unit of measure most frequently used.
Methodology
ASTM Methods D 445 and D 446, included with this manual, describe
appropriate test methodologies and instruments for glass capillary
viscometry.
Manual viscometers Sections 9-11 of ASTM D 445 provide detailed instructions for using
manual viscometers. ASTM D 446 suggests a minimum flow time of 200
seconds for nearly all the glass capillary viscometers (see tables in ASTM
D 446).
Automatic viscometers For automatic viscometers, ASTM D 445 Section 6.1.2 states, “Auto-
mated apparatus may be used as long as they mimic the physical condi-
tions, operations or processes of the manual apparatus they replace ... The
automated apparatus shall be capable of determining kinematic viscosity
of a certified viscosity reference standard within the limits stated ...”
Thus, automated viscometers can be used with flow times less than 200
seconds, as long as the kinetic energy correction and precision require-
ments are met.
CAV tube characteristics
Each standard viscometer tube has three bulbs, each of which has its own
calibration. The normal flow times for each bulb are 60-400 seconds.
Each tube has a hundredfold measurement range (for example, range
from 2-200 cSt or 20-2000 cSt for each tube).
NOTE CANNON ® Instrument Company has not recommended the use of
longer flow times with the CAV, as shorter flow times allow greater
productivity. With longer flow times, the data throughput would be
significantly reduced. However, the viscometer and software design does
permit longer efflux times (up to 600 seconds) as desired by the user.
Safety cautions
Please observe the following safety procedures and notices for proper
operation of the CAV:
Make sure that your unit is operated only by qualified personnel.