TA Instruments AR 2000, Operator'S Manual

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AR 2000 Operator's Manual
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CAUTION: The Peltier Plate may be damaged by operating the instrument without a
flow of water through the Peltier system. There is a Peltier Overheat protection
device that will activate if the device becomes too hot.
Sans écoulement d'eau, le système Peltier peut être endommagé. Un dispositif de
protection a été conçu pour se déclencher en cas de surchauffe.
Normal Force Transducer
When a viscoelastic liquid is sheared, a force can be generated along the axis of rotation of a cone or parallel
plate geometry. For this to happen, the structure responsible for the elasticity must not be completely disrupted
by steady shear.
For this reason, colloids, suspensions, etc., although elastic at rest, become effectively inelastic under steady
shear and can show negative normal forces due to inertial effects. However, polymer solutions and melts, and
products incorporating them, are typically elastic under shear because of the long lifetime of the molecular
entanglement.
Normal force measurements are made with cone and plate or parallel plate geometries; therefore, it is important
to use a method to detect the force that does not allow significant changes in the gap. This would result in the
actual shear rate varying with normal force, due to deflections of the force-detecting component.
The AR 2000 Rheometer keeps the upper geometry positioned as accurately as is possible with an air bearing,
and movement is kept to an absolute minimum. This ensures good bearing performance.
The force is detected on the static lower measuring geometry assembly using high sensitivity load cell technol-
ogy. This results in a fast response, wide range signal, which is easy to calibrate, and has a genuine normal
force measurement capability.
CAUTION: During sample loading and measurement, the normal force transducer is
protected from overload. However, take care when cleaning or attaching accessories
to the lower plate that you do not exceed the maximum normal force.
Le capteur de force normale est protégé contre toute surcharge. Cependant, prendre
soin de ne pas dépasser la force normale maximale lors de toute manipulation
(nettoyage, changement de plaque…).