The Ford viscosity cup is a simple
gravity
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
device that permits the timed flow of a known
volume
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). ...
of
liquid
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, ...
passing through an orifice located at the bottom. Under ideal conditions, this
rate of flow would be proportional to the
kinematic
Kinematics is a subfield of physics, developed in classical mechanics, that describes the motion of points, bodies (objects), and systems of bodies (groups of objects) without considering the forces that cause them to move. Kinematics, as a fie ...
viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the int ...
(expressed in stokes and centistokes) that is dependent upon the
specific gravity
Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its dens ...
of the draining liquid. However, the conditions in a simple flow cup are seldom ideal for making true measurements of viscosity. It is important when using a Ford Cup and when retesting liquids that the temperature of the cup and the liquid is maintained, as ambient temperature makes a significant difference to viscosity and thus flow rate.
The original Ford Cup was based on Imperial (UK) measurement of the aperture.
Many other types of
flow cups are being used, depending on the industry or region.
Din Cup 4 mm., standard DIN 53211 (cancelled)
ISO Cup 2, 3, 4, 5, 6, 8 mm. standard ISO 2431
AFNOR Cup 2,5, 4, 6, 8 mm. standard NF T30-014
ASTM Cup 1,2,3,4,5 standard ASTM D1200
See also
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Flow measurement
Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. The common types of flowmeters with industrial applications are listed below:
* a) Obstruction type (differential pressure or variable area ...
*
Viscometer
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. Thus, a rheometer can be considered as a spe ...
*
Zahn cup
*
Din cup
*
Afnor cup
*
Flow cups
Notes and references
Fluid dynamics
Viscosity meters