10
1400500-101 Rev. A
Introduction
(Continued)
Definition of Density
(continued)
“Specific Gravity” (SG) (or “Relative Density” (RD)) is expressed in multiples of the density of some other
standard material, has dimensionless quantity, and usually refers to water or air.
SG=
P sample
P reference
__________
Oscillating U-Tube
The DENSITY4/5 has a built-in reference oscillating U-Tube, which is a new method of measuring density.
Approximately 1.0 ml of sample is needed for a measurement and the device offers very high accuracy
and resolution. Working with an oscillating U-Tube is ultra fast compared to other methods and true density
is provided in the measurement. the system is fully automatic (calculations not necessary), so it is less
vulnerable to human error.
The oscillating U-tube samples the viscosity of a fluid by vibrating a glass tube at a frequency which will
measure the resistance of a fluid that is being deformed by either shear stress or tensional stress. This
sometimes is referred to as the “thickness” of a fluid and it has the following parameters:
•
High viscosity → density over-reading
•
Low viscosity → correct result
Another parameter to consider in the measurement process is the temperature of the fluid. The tem-
perature of the fluid is very important. The built-in high accuracy temperature sensor guarantees precise
measurement utilizing a Peltier-Element (temperature range 5°C to 95°C) to control the fluid temperature.
Some features of the temperature control system are:
• Eliminates temperature drift. After modifying the measuring temperature, the instrument
remains stable as soon as the new temperature is reached.
•
Simplifies measurement at different measuring temperatures.
Using the temperature con-
trol at 20 °C provides consistent data related to one temperature.
(additional adjustment at 40 °C and 60 °C can be performed. for example, once a year to re-adjust tem-
perature characteristics of the DENSITY4/5 sensor).
Figure IS-01, Oscillating U-Tube Detail
