HOW TO CREATE CUSTOM CALIBRATIONS FOR COMPATIBLE COMMODITIES
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.
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
EQUILIBRIUM MOISTURE- MOISTURE CONTENT AT EQUILIBRIUM WITH A GIVEN PARTIAL PRESSURE OF VAPOR
FREE MOISTURE- MOISTURE IN EXCESS OF EQUILIBRIUM MOISTURE
BOUND MOISTURE- MOISTURE THAT EXERTS AN EQUILIBRIUM VAPOR PRESSURE LESS THAN THAT OF THE PURE LIQUID
UNBOUND MOISTURE- MOISTURE THAT EXERTS AN EQUILIBRIUM VAPOR PRESSURE EQUAL TO THAT OF THE PURE LIQUID
Official methods for moisture determination in grains, dried fruits and vegetables, and feed products, are often time consuming, and prone to human error. Indeed, to conduct an accurate oven test on a commodity like green coffee beans, one must have a solid understanding of drying characteristics in granular, hygroscopic materials. Volatiles are often evaporated along with water, which is why it is referred to as loss of weight with drying instead of loss of moisture with drying. Dried fruits require the sample to be formed in to a paste, prior to being shoved by hand in to a tube that measures electrical resistance of moisture containing substances.
Further complicating things, especially with loss on drying applications, are the different types of moisture (bound and unbound) present in hygroscopic materials.
While it is important to have direct methods of moisture determination available for validation, they are often impractical for routine moisture analysis in a quality control setting, taking days to complete in some cases.
Instead, the majority of grain, seed, and feed companies, utilize an indirect method of moisture determination, by quantifying the electrical storage properties of the water present in a substance, or capacitance.
Actual 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...
THIS MAX MOISTURE BALANCE HAS A SPECIALLY DESIGNED HEAT SOURCE FOR USE WITH AGRICULTURAL APPLICATIONS
THIS SHERWOOD M501 ANALYTICAL FLUID BED DRYER SUSPENDS THE PARTICLES IN THE AIR FOR UNIFORM DRYING
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