Table of Contents
Advertisement
The process of selecting a spindle and speed for an unknown fluid
is normally trial and error. An appropriate selection will result in
measurements made between 10-100 on the instrument % torque
scale. There are two general rules that will help in the trial and error
process:
•
Viscosity range is inversely proportional to the size of the spindle.
•
Viscosity range is inversely proportional to the rotational speed.
In other words: to measure high viscosity, choose a small spindle
and/or a slow speed. If the chosen spindle/speed results in a reading
above 100%, then reduce the speed or choose a smaller spindle.
Experimentation may reveal that several spindle/speed combinations
will produce satisfactory results between 10- 100%. When this
circumstance occurs, any of the spindles may be selected.
Non-Newtonian fluid behavior can result in the measured viscosity
and yield stress changing if the spindle and/or speed is changed. See
our publication, "More Solutions to Sticky Problems", for more details.
When viscosity data must be compared, be sure to use the same test
methodology: namely the same instrument, spindle, speed, container,
temperature and test time.
DVNext LV Rheometers are provided with a set of four spindles
and a narrow guard leg; DVNext RV Rheometers come with a set
of six spindles and a wider guard leg; DVNext HA and DVNext HB
Rheometers come with a set of six spindles and no guard leg. (See
Appendix G for more information on the guard leg.)
The spindles are attached to the rheometer by screwing them onto
the coupling nut on the lower shaft (see Figure 2I-4). Note that the
spindles have a left-hand thread. The lower shaft should be secured
and slightly lifted with one hand while screwing the spindle to the left.
The face of the spindle nut and the matching surface on the lower
shaft should be smooth and clean to prevent eccentric rotation of the
spindle. Spindles can be identified by the number on the side of the
spindle coupling nut.
The motor should be OFF whenever spindles are being removed or attached.
M19-2101 REVISION 2.0
D V N E X T R H E O M E T E R - O P E R AT I O N A L M A N U A L
Figure 3-4
Figure 3-5
31
Advertisement
Table of Contents
