DHR Series Getting Started Guide Page 33
The Interfacial Double Wall Ring (DWR)
The patented Interfacial Double Wall Ring (DWR) measuring system measures the viscous and linear vis-
coelastic properties of the interface between liquid-liquid and liquid-air. It consists of a thin, square-edged
ring and a Delrin
®
trough with a circular channel. The ring and support legs are constructed from a plati-
num/ iridium (Pt/Ir) alloy, for chemical inertness, ease of cleaning, and wettability. The ring support is
made of stainless steel.
A non-return (check) valve is fitted to the trough below the level of the interface. Together with the
supplied tubing and syringe, this can be used to adjust the lower fluid level, or to add an active ingredient.
Figure 15 Interfacial DWR.
The Du Noüy Ring
The Du Noüy Ring measuring system is mainly used to determine the linear viscoelastic properties of the
interface between liquid and air. It consists of a thin wire ring and a Duran glass dish. The ring is con-
structed from a platinum / iridium (Pt/Ir) alloy for chemical inertness, ease of cleaning, and wettability. It is
important that the ring and dish are aligned concentrically, and a locating ring is provided that fits over the
Peltier plate to ensure this. Two dishes are available; the outer diameter of the standard dish is 70 mm and
the outer diameter of the small dish is 50 mm.
Figure 16 Du Noüy Ring measuring system schematic.
Trough
Geometry
holder
DWR geometry
Check valve
Glass window
Du Noüy Ring
Interface
Fluid
Dish
R1: Ring radius
R2: Dish inner radius
üy Ring
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