|
|||||||||||||||||||||||||||||||||||
| Quantity | |||||||||||||||||||||||||||||||||||
| Dynamic
viscosity is a derived physical quantity which defines a
resistance at liquid flow. Dynamic viscosity is defined
as a ratio of shear stress to shear rate. Kinematic
viscosity is defines as a ratio of the dynamic viscosity
to density. |
|||||||||||||||||||||||||||||||||||
| Unit
- dynamic viscosity: Pa·s; kinematic viscosity:
m2·s-1. |
|||||||||||||||||||||||||||||||||||
| Tasks of the laboratory | |||||||||||||||||||||||||||||||||||
| The main
tasks of the laboratory are research and development for
the realisation and dissemination of the unit of
viscosity. |
|||||||||||||||||||||||||||||||||||
| International comparisons | |||||||||||||||||||||||||||||||||||
| ASTM
Project D.02.07.A DUNAMET Project No. D22 EUROMET Project No. 415 - EUROMET.M.V-K3 - key comparison. |
|||||||||||||||||||||||||||||||||||
 |
Available metrological services | ||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||
| Methods of measurement: | |||||||||||||||||||||||||||||||||||
| The
primary standards are calibrated by the step-up method,
using the value of the kinematic viscosity of the
redistilled water at temperature of 20 °C. The
viscometers of higher nominal values are calibrated by
direct comparison with viscometers of lower nominal
value. The lower order standards and working instruments (capillary viscometers) are calibrated by the direct comparison with SMU standard viscometers. Falling Ball and Rotational Viscometers are calibrated by using of certified reference liquids which are traced to the national standard of viscosity. |
|||||||||||||||||||||||||||||||||||
|
Instruments in use | ||||||||||||||||||||||||||||||||||
|
The National standard consists
of two sets of Ubbelohde capillary viscometers with 500
mm capillary length and two sets of Ubbelohde capillary
viscometers with 400 mm capillary length. The measurement
device consists of temperature controlled bath with
accesories (heating circulator and immersion cooler),
Pt25 thermometer, device for water preparation (reference
liquid for derivation of scale of kinematic viscosity),
computer controlled automatic measuring device for efflux
time measurement and measurement control. The standard
device is computer operated and process of measurement is
free programmable and fully automated by the set of
bistabil electromagnetic valves (four valves for each of
8 viscometers in the bath). The efflux time measurement is realized by swiching on/off the counter, when liquid level passes by the position of optical sensors. Sensors position is adjustable to coincide with ring marks of viscometer. |
||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||
