AR 2000 Operator's Manual
27
Auto GapSet Mechanism
The auto gap set facility has three major functions, as follows:
• Automatic setting of gaps via software
• Programmed gap closure
• Thermal gap compensation.
These features are described in more detail on the following pages.
Zeroing of the Gap
It is important that you use a reproducible gap zeroing technique to reduce errors from such factors as operator-
to-operator techniques. The automation of gap zeroing on the rheometer minimizes these errors.
Closing the Gap
Once you have set the gap and loaded the sample, the head is lowered. The velocity and deceleration of the
head as it is lowered is controlled via the 'automatic gap options' set in the Rheology Advantage software.
There are four closure options available with the AR 2000 Rheometer-—Standard, Linear, Exponential, and
Normal Force. The options available are described in detail in the online help for the rheology software.
CAUTION: Keep hands and fingers away from the plate during head move-
ment.
S'assurer que les mains ou doigts ne soient pas entre le peltier et la
géométrie lors du mouvement de la tête de l'instrument.
Thermal Compensation
When a wide temperature range is used for an experiment, the metallic rheometer parts and the measurement
geometries can heat or cool causing expansion or contraction of the measurement system gap. A typical expan-
sion value for stainless steel geometries is 0.5 µm°C
-1
. The auto gap-set facility compensates for these changes.
Therefore, regardless of temperature, you can be confident that the gap remains constant.
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