AZI Sales/Customer Service 800-528-7411 or 602-470-1414 or support@azic.com Page 16 of 26
5. MOISTURE ANALYSIS TESTING
The Computrac
®
MAX
®
Series loss-on-drying moisture analysis system takes advantage
of computer technology to reduce test times and increase precision over standard
vacuum oven or convection oven drying procedures.
Prior to testing, a Test Program is created with the parameters to be used for testing the
sample. The instrument then controls the test using this Test Program. Within each Test
Program, the test temperature can be programmed between normal room temperature
(25 ºC) and 225 °C (275 °C on a MAX
®
4000XL). Using the linked test functionality
available on the MAX
®
4000XL, a multi-step temperature contour can be setup across
several linked Test Programs.
In the test chamber, an aluminum sample pan rests on a pan support coupled to a
sensitive electronic force balance. The sample is added to the sample pan and the force
balance registers the initial weight of the sample before testing. The heater located on the
underside of the test chamber’s lid then heats the sample, and a Resistance Temperature
Device (RTD) monitors the temperature in the test chamber. The temperature readings
from the RTD are sent to the microprocessor, and under the microprocessor's control, the
heater element is cycled on and off to bring the test chamber to the programmed
temperature.
As the sample is heated according to the Test Program selected for the test, it loses
weight due to moisture evaporation. The balance records that weight loss and transmits
the data to the microprocessor for evaluation. The balance readings are averaged to
eliminate signal interference or erroneous data. The sample's decreasing weight is
compared to the initial sample weight and the calculated moisture concentration appears
on the display. When using the Predict ending criteria, the microprocessor interprets the
information and compares the sample's weight loss to a standard drying curve. The final
moisture concentration is extrapolated from the drying curve and results are available
within minutes.
The MAX
®
4000 is an extremely flexible instrument. This flexibility means that some time
is required to determine the best set of parameters for a particular application. The
determination of the proper parameters requires a series of tests and good laboratory
procedure. Call your AZI technical sales representative for assistance developing Test
Programs for your samples.
5.1. Performing a Test
A Test Program for your material must be developed prior to using the MAX
®
4000 for
production testing:
• See section 6.1 Test Programs on page 20 for basic information on setting up a Test
Program. Refer to the manual for extensive details on determining the proper test
temperature, ending criteria, sample size, and other parameters.
• The Parameter Expert feature automatically selects most test parameters based on
your reference method results and then guides you through a series of tests to
determine the proper test temperature and ending criteria. See the manual for details.
• AZI technical sales can develop Test Programs for your material.
After a new Test Program is developed, run 5 or more tests to obtain reliable information
about the standard deviation of a typical result. Each test result is automatically saved,
and the instrument can calculate the mean, standard deviation, and relative standard
deviation through the Test Results menu.
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