NOTE: Broader ranges of sample types and moisture ranges are available with the MR-G9 Probe, which utilizes different modules for specific moisture ranges.
In order for a capacitance based moisture analyzer to provide accurate moisture information for a given commodity, a series of capacitance readings, over a relevant moisture range for the commodity first have to be taken. For example, if a particular grain generally arrived with between 12% & 18% moisture, capacitance values for a series of samples with different moisture levels, ideally between 11% and 19%, at .5% intervals, would first need to be gathered. The moisture content of each of the samples, needs to be determined by an existing method, generally an oven test.
Proprietary Software then carries out the task of correlating the moisture levels to the capacitance values, in the form of a moisture curve. The next time a like sample is placed in the capacitance analyzer, it again takes a capacitance reading, only this time, it knows the relative moisture percentage.
This COFFEE MOISTURE-MAC (LEFT) Hand held capacitance based, moisture analyzer uses a screw down compression cap to achieve uniform density, instead of a balance, which needs constant calibration. It's low cost and nominal maintenance, make it a perfect choice for field use with grains.
Note: Do not use a compression cap type on brittle materials that will crack readily under slight pressure. Uniform density may be achieved by use of a meter fitted with a sample grinder.
BENEFITS
Oven tests can take many hours to complete for each sample, making it the least productive method for determining moisture levels, especially where multiple, ongoing testing is required. Moisture balances or fluidized bed analytical dryers can reduce the time to minutes instead of hours, but time is still a factor.
Indirect methods like capacitance based moisture analyzers are accurate enough for quick preliminary quality control measures, offering results accurate to within a few tenths of a percent in just seconds.
They are used worldwide for agricultural applications, in grain elevators, processing facilities, exporting centers, etc...
From left to right the (1) AP-6060 uses an oscillating balance to measure a samples mass. The (2) Sinar SP Moisture Probe is designed for insertion in to bulk samples, where it assumes the samples volume. There must be enough uninterrupted sample (Soccer Ball Size) surrounding the sensor for it to work accurately. These sensor types are often used for inline capacitance based moisture determination applications, to help automate processing.The (3) Coffee Pro Compression cap design, assumes a fixed volume with a cup, and achieves uniform density by applying slight pressure with a screw down compression cap. The (4) Sinar DRYPRO uses similar technology to the SP 6600 for inline moisture determination applications. Lastly, the (5) Sinar LSA is a hybrid, designed for seeds or grains that are otherwise to large to fit in a standard sample cell, like Cacao Beans. Crop calibrations can be interchanged between instruments, but bias offsets may be required.
