BYK CAP 1000+, Manual, Page: 20 / 32

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Repeatability / Making Viscosity Measurements
III.2 REPEATABILITY
The CAP 1000+ Viscometer is repeatable to ±0.5% of the full scale viscosity
range (FSR). Due to shear heating considerations which occur in high shear rate
instrumentation, the measurement of NIST Viscosity Standard Fluids at rotational
speeds above 900 RPM will show a de- crease in viscosity with an increase in
rotational speed (shear rate).
Normal forces due to the shearing of a viscoelastic fluid (such as paint) are
accounted for in the CAP Series Viscometers by weight on the spindle column of
3.4 Newtons (340,000 Dynes) total force. This is done to avoid having the cone lift
off the plate, thereby changing the cone plate geometry and producing incorrect
viscosity readings. For normal forces greater than 3.4 Newtons (340,000 Dynes)
total force, additional externally mounted weights are required. However, more
weight means more wear on the cone and plate. Additional weights should only be
considered when definitely required and removed when not required.
Contact BYK-Gardner or your local BYK-Gardner Representative for details on the
above information.
III.3 MAKING VISCOSITY MEASUREMENTS
The following procedure is recommended for making a viscosity measurement.
With the viscometer on a clean, level surface, connect it to the proper power supply
(Section I.4).
1. Turn the power switch
ON (Section II.1).
The procedure assumes that the following list has been done:
a) If the viscometer has been “off” for an extended period (i.e., overnight) a
“warm up” period of 30 minutes is suggested. The default temperature
(25°C) is used for low temperature instruments (i.e., L). The
default temperature for high temperature is 50°C (i.e., H). If a cone
calibration is to be done immediately after the warm up period, temperature
should be set to 60°C (calibration temperature for high temperature
instruments) to save some time.
b) The cone calibration procedure (Appendix B) should have been done for all
cones which are used with the instrument. Cone calibration is only required
when a new cone (i.e., replacement for lost/damaged cone) is used, or when
calibration check fails.
c) When making measurements with low temperature instruments (L),
the solvent trap may not be required (for the containment of solvents and/or
prevention of sample “drying”). The trap should be used for all measurements
with high temperature instruments (H).
d) If a printer is to be used, it should be connected (AC power & viscometer to
printer cable). The will print automatically when a reading is taken if
the printer is connected and “on line.”
Select and attach the cone (Section II.2).