A viscometer (also called viscosimeter) is an instrument used
to measure the viscosity of a fluid. For liquids with
viscosities which vary with flow conditions, an instrument
called a rheometer is used. Viscometers only measure
under one flow condition.
TYPES OF VISCOMETERS:-
There are different types of Viscometers given below.
rotational viscometer gathers data on a material’s viscosity
behavior under different conditions.The rotational
viscometer basically consists of two parts - a head unit
with a motor and a spindle that is driven by the motor. The
viscosity is determined by measuring the resistance of a
spindle rotating in the sample.
Rotational viscometers can be used for the
accurate measurement of viscosity for both
Newtonian and non-Newtonian fluids. Newtonian
fluids are those that are affected by temperature,
such as water, kerosene,mineral oils etc. NonNewtonian fluids are those that change viscosity
when stirred, shaken or otherwise agitated.
These include paint, gels, inks, milk,ketchup etc.
Why use a rotational viscometer?
Rotational viscometers are ideal for determining
viscosity of liquids which do not depend solely
on temperature and pressure.The behaviour of
non-Newtonian liquids can also be tested and
Viscosity is a measure of the resistance of fluids to flow. A
vibrational viscometer is used for continuous direct
measurement of viscosity in pipes and/or tanks.
The instrument works by creating a special kind of wave in
the fluid.There are many kinds of vibrational waves but
viscosity can only be accessed under shear conditions so we
use shear waves.
To the naked eye nothing moves but when the element is
submerged in the liquid and moves back and forth
microscopically at high frequency the surface of the sensor
shears through the liquid & energy if lost.
The viscosity of the liquid is derived by the measurement og
this lost energy by the instrument .Vibratory Visco.m are
better suited to measure non-newtonian liquids
Electromagnetic viscometer or EMV viscometer.
A viscometer for bedside blood measurements was developed, consisting of an
The oscillating piston viscometer technology has been adapted for small sample
viscosity and micro-sample viscosity testing in laboratory applications.
Measurements are taken when a sample is first introduced into the measurement
chamber where the piston resides.
Electronics drive the piston into oscillatory motion within the measurement chamber
with a controlled magnetic field.
A shear stress is imposed on the liquid due to the piston travel & the viscosity is
determined by measuring the travel time of the piston.
The travel distance of the piston are used to calculate the viscosity according to
Newton’s Law of Viscosity.
It has been adapted to measure high pressure & high temperature viscosity
measurements in both laboratory and process environments
Falling Piston Viscometers
The principle of viscosity measurement in this rugged
and sensitive industrial device is based on a piston
and cylinder assembly. The piston is periodically raised
by an air lifting mechanism, drawing the material being
measured down through the clearance (gap) between
the piston and the wall of the cylinder into the space
which is formed below the piston as it is raised. The
time of fall is a measure of viscosity, with the clearance
between the piston and inside of the cylinder forming
the measuring orifice. The viscosity controller
measures the time of fall (time-of-fall seconds being
the measure of viscosity) and displays the resulting
viscosity value. Falling Piston viscometers operate on
similar principles as the falling sphere viscometers,
except that they measure resistance to a piston
moving through a fluid. These devices are very longlasting and simple to operate, and require little
falling sphere viscometer
A viscometer is an instrument used to measure the
viscosity of a fluid. The falling ball viscometer is based
on Stokes’ Law. This type of viscometer consists of a
circular cylinder filled by the liquid under investigation.
A standard ball is allowed to fall down this tube over a
calibrated distance of 100 mm. The falling time is
recorded and then utilized to determine the viscosity at
a preset temperature. This device has the capability of
providing a more accurate, low time-consuming and a
more user-friendly means of measuring viscosity in a
laboratory environment. This device with a few
modifications can be used as an alternative setup to
the present falling sphere viscometer setup used in the
undergraduate laboratory experiment for the
measurement of viscosity, as it provides the necessary
accuracy and precision required for this experiment.