Brookfield LFRA Texture Analyzer - Manual (Page 18)

Brookfield Engineering Labs., Inc. Page 8 Manual No. M/05-370-B0507
Within a probe category, variations of geometry can be significant. It may require a larger force
to drive a cone of shallow angle as compared to a cone of steep angle. Similarly, a cylinder of
large diameter may require a larger force than a cylinder of small diameter. The selection of the
probe (type and size) will affect the test result.
IV.3 Test Parameters
The LFRA Texture Analyzer will require the setting of several parameters depending upon the
test method selected (see Table III.1). In general, the following relationships will hold true for
Speed and Distance.
1) The measured load will increase as the test speed increases.
2) The measured load will increase as the compression distance increases. An exception to
this could be a material with an outer layer such as an apple.
The Trigger Point establishes the minimum load required to begin the test. This is how the
LFRA knows when the probe is touching the sample. This parameter should be set to a low
value for a material with a very delicate outer layer. In general Brookfield recommends a value
of 4 grams.
The Hold Time allows for monitoring the response of a material to a constantly applied position.
Normally, an increase in the Hold Time will result in a lower measured value.
The Cycle Count provides a way of working a material prior to measurement by applying the
same test method (speed, distance, probe) to a sample repeatedly.
IV. Recommendations
The results of a texture measurement are very dependent on both sample preparation and the test
method. When developing a method, Brookfield recommends that each parameter be varied in
turn to determine its effect on the results. (Note: vary only one parameter at a time) Once this
information is considered and a method established, the method should be documented in signifi-
cant detail. This will ensure good repeatability of results and good comparison with others who
attempt to duplicate your method.