VPAD Manual
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Experiments in conditions in which turbulent behaviour can be encountered should be avoided.
The condition should be that of stationary fluid. Accelerations or retarding processes are excluded
from the parameters of measurement.
Spindle immersion
The standard spindle should be submerged to the halfway mark in the axle. An erroneous immersion
can compromise the result of the viscosity measurement.
With the disc spindles you should avoid the creation of air bubbles, which could remain under the disc.
To this end you should insert the spindle laterally and smoothly and bring it over to the centre of the
sample. Once it is there, attach it to the viscometer’s axle.
Precision and Repetition
FUNGILAB viscometers guarantee a precision of
1% from the bottom of the speed/spindle
combination scale and a repetition of
0.2%.
The precision of temperature measurement is ±0.2 ºC.
Getting a viscosity reading
Before working with the viscometer you should make sure of the following points:
The viscometer is properly fastened to the stick and level.
Both spindle and speed are selected. (read attentively the section about speed and spindle selection).
The spindle is carefully placed and fastened.
The instructions and necessary parameters for obtaining a viscosity reading have been carefully read
in the user’s manual.
Once the readings have been initiated, allow some time for stabilization, the length of which will be in
function of the rotational speed during the measurement.
IMPORTANT WARNING
When you wish to obtain viscosity reading with FUNGILAB rotational viscometers, there are two
considerations to take into account:
The obtained viscosity results must be between 15% and 100% of the torque range, for whichever
spindle/rotational speed combination.
The viscosity reading must be executed under laminar flow condition, not turbulent flow conditions.
The first consideration is linked to the precision of the instruments. All of the FUNGILAB rotational
viscometers guarantee a precision of (
) 1% from the bottom of any spindle/rotational speed
combination scale.
Working with less than 15% of the bottom of the scale is not recommended due to that the potential
(
) 1% error in the viscosity is relatively big compared to the equipment reading.
The second consideration has to do with fluid mechanics. All of the rheological measurements of fluid
flow properties must be taken under laminar flow conditions. Laminar flow is when all of the
movements of the fluid particles are in sheets, directed by an external applied force.
The flow lines represent speed and fluid flow direction.
Laminar flow:
“straight” flow lines. Relatively easy to predict. Generally slow.
