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. It's low cost and nominal maintenance, make it a perfect choice for field use with grains.
Note: Do not use a compression cap style moisture analyzer on materials that will crack readily under slight pressure like roasted coffee beans, or materials where compression changes the packing density, like tobacco leaves.
Although loss on drying and Karl Fischer are two of the most popular test methods for determining moisture, they both have severe drawbacks when it comes to routine moisture checking in a quality control setting, or wherever frequent or routine testing is carried out.
Oven tests can take many hours to complete for each sample, making it probably the least productive method for determining moisture levels. Moisture balances or laboratory dryers can reduce the time to minutes instead of hours, but 15 minutes can turn in to hours, with enough samples.
Karl Fischer Moisture analysis, another preferred direct method, requires a high degree of operator training, as well as sophisticated and expensive instrumentation.
Indirect methods like capacitance, and NIR, provide usable accuracy in seconds, require very little operator training, and are non destructive to the sample.
All methods of determining moisture, are chosen for suitability based on the physical characteristics of the sample. For example if one was to want to obtain the amount of water in a sample of oil, it would be easier to add a liquid chemical to the oil that would react relative to the amount of moisture, than to heat the oil, and try to drive off the water that way, so Karl Fischer is what is used in petrochemical moisture determination. For a sample of coffee beans, it is easier to heat them up to drive off moisture, that to try to arrange for a chemical reaction, where the sample would first need to be homogenized, to help ensure the chemical reaches the areas where the moisture is.
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.
DIFFERENT SENSOR TYPES AND DESIGN VARIATIONS TO ACCOMODATE UNIQUE SAMPLE CHARACTERISTICS
G-9 DIGITAL PROBE (Radio Frequency Loss of Signal) FOR INSERTION IN TO SACKS. ALSO USEFUL FOR POWDERS, GRANULAR MATERIALS, GELATIN CAPSULES, AND WOOD CHIPS
EQUIPMENT FOR QUALITY CONTROL AND R&D APPLICATIONS
NIR (NEAR INFRA-RED) ANALYZERS are most often associated with inline applications, because they read surface moisture without
having to come in contact with the sample. They only slightly penetrate the samples surface, so the surface moisture has to be representative of the moisture throughout the rest of the sample. They work well on powders or ground products, but not as well on granular products where the surface moisture may not accurately reflect the total moisture.
This portable ZX 50 measure moisture , oil, and protein.
THE MR910ST NIR Analyzer can be used in lab or inline for moisture determiination
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