Brookfield LFRA Texture Analyzer Instrukcja Użytkownika Pobierz pdf (Strona 18)

Brookeld Engineering Labs., Inc. Page 18 Manual No. M/05-370-B0507

Withinaprobecategory,variationsofgeometrycanbesignicant.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Brookeld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.4 Recommendations

The results of a texture measurement are very dependent on both sample preparation and the test

method.Whendevelopingamethod,Brookeld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signi-

cant detail. This will ensure good repeatability of results and good comparison with others who

attempt to duplicate your method.

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