Gehaka G939, User Manual

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Grain Moisture Meter – Model G939
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Ice or Snow
Samples containing ice or snow will not be satisfactorily measured. Frozen samples may
be analyzed provided they are left to heat up in a hermetically closed container to get
closer to room temperature. Use the average value of 3 or more readings. Below the
temperature range of 5ºC, perform 3 readings and use the average value.
Surface Moisture
Grains from a warmed warehouse when getting in touch with humid air develop surface
moisture. The same occurs with some cereals uncovered during a rainfall, which will
keep surface moisture for some days unless an artificial heat is applied for drying them.
Surface moisture presents very low impedance to the high-frequency current flow, thus
incorrect readings will be obtained.
Moisture Measurement Processes
There are two methods for measuring moisture in cereals. The primary one and the
secondary one. The primary method consists on a procedure using the vented oven.
This procedure is time-consuming and would not obviously be convenient for use on
grain reception. For this reason, the secondary method was developed, so that using the
cereal electrical properties, quick measurements can be made.
Although many research works have been carried out in the field of electronics and
also on the properties of cereals, it is not possible to analyze a cereal without some
variations. Some of the involved facts are discussed below:
We recommend that the product to be measured by the G939 shall be clean and free from
impurities that could interfere in the moisture measurement. We should considered
that, in the instrument calibration process with the oven, it was always used the product
clean.
Unfortunately, a cereal cannot be measured until the harvest is completed and the
calibration cannot be modified until the measurement of a sufficient number of samples,
in order to be able to determine the change in the cereal electrical properties.
The size of the seed does also affect the test quality. Corn is an example of a difficult
cereal to be measured, due to the irregular size and shape of the seed. In fact, there are
nearly 400 different varieties, maturing in 90 to 125 days. It is evident that, the issue
of precision in moisture measurement is the on-going increase in the variation of the
electrical properties.
3.5 Extreme conditions