Sinar Technology specializes in manufacturing scientific instrumentation, used primarily for the evaluation of specific properties in agricultural commodities, like moisture determination. Because moisture determiination plays such an important role in the quality, shelf life, and transportation costs of such goods, the Sinar Family of moisture analyzers have become internationally recognized as the workhorse of quick and accurate moisture determination.
Although the technology and logic differs slightly with the different types of Sinar Moisture Analyzers, they all do essentially the same thing, the primary difference being how the sample comes in to contact with the sensors on the instrument, which is based on the samples size and density characteristics. Capacitance based analyzers generally have to collect information on a samples mass, density, chemical composition, and temperature, to be able to provide an accurate moisture reading.
For hygroscopic, free flowing, sample types, the speed, accuracy, and relative low cost of capacitance type analyzers, make them an increasingly popular choice.
FIRST STEP
The first step is to determine if the commodity being tested is compatible with a capacitance based analyzer. As long as the commodity is hygroscopic (picks up or gives off moisture readily) , free flowing, and of somewhat uniform density and chemical composition, it should be suitable.
Grains, seeds, feeds, and even some plastic products are examples of such commodities.
To determine suitability, you just need two samples with different moisture contents. Place each sample in the analyzer, and take at least three, preferably more, raw data readings, (numerical value that the analyzer assigns in its' own scale) emptying and refilling the analyzer each time.
If the readings for the two samples differ, and all readings fall within the accuracy parameters of the analyzer, the material is suitable.
SECOND STEP
Next a collection of samples, with known and varying moisture contents, needs to be obtained. Place each sample in the analyzer, and obtain a raw data reading (Referred to as Code 0 Reading with SINAR). Then the collection of raw data readings, and corresponding moisture percentage values, are entered in to the instruments software (MNET) via a computer. (See right)
FIG 1 FIG 2 FIG 3
While working with hygroscopic samples be sure to store them in sealed glass jars with as little head space as possible.
It's not uncommon to hear about unusual readings, only to find that a sample has been stored in an open
plastic bag inside a refrigerator.
Ensure that all samples are roughly at room temperature when creating a calibration curve.
When obtaining moisture values for the different samples, either by oven, moisture balance, or Karl Fischer,
be sure to use a representative sample. The larger the sample, (within reason) the better the results will be.
Example: You can't really take one raisin out of a box, and expect it to be representative of the whole box. Moisture levels vary
within a sample to some extent. The moisture in the middle of a pile is likely to be higher than at the top.
If using a loss on drying type of reference method, try to ensure uniform drying by preparing the sample.
Nuts and grains can be ground.
Before starting, be sure to check with us if we already have a calibration for your commodity.
EXAMPLE
SAMPLE # OVEN % CODE 0
1 12.5 24.9
2 13.5 27.3
3 16.5 37.2
NOTE: The more data points you have the more accurate the moisture curve. Before entering the data in to MNET, it sometimes helps to put the values in to an ExCel File, with two columns.Then by using the chart function,
you can create an X,Y Chart.
This helps in editing out stray data points, and in forecasting the curve out past known values.Then by applying the curve formula to the X Values, a new set of data points reflecting the ExCel Curve will be available for entry in to MNET.
The weight corrected capacitance type of instrument, like this Sinar AP 6060, uses an internal balance to determine mass. Samples with less than 3/4" particle diameter, and uniform density, work best in this type of benchtop unit. Examples are coffee beans, some animal feeds, and grains.
The probe type of instrument, like this Sinar SP 6600, is designed for field use where it is possible to cover the sensor with about a 12" Diameter amount of sample, like the back of a grain truck. or by inserting in to a commodity sack. This technology assumes a fixed volume in order to determine mass.
For larger diameter sample types like cocoa beans, or large nuts, this variation of the probe type of instrument, the Sinar LSA works best, again by assuming a fixed volume to determine mass.
What distinguishes Sinar Instruments from many other types of moisture analyzers, is the availability of MNET user software, that allows the user to create and customize their own proprietary calibrations, instead of having to send samples in to the manufacturer.
CREATING SAMPLE MOISTURE CURVES FOR CAPACITANCE ANALYZERS
A popular primary or reference method by which moisture is often determined, is known as loss on drying, or thermogravimetrics.
A sample is weighed, and then placed in an oven at a very low temperature, over a fairly long period of time (Sometimes as much as 24 hours), to help reduce inaccuracies resulting from volatiles (oils and other evaporative compounds) being driven off along with the water.
After repeated heating and weighing, the rate of evaporation will change, and slow down substantially, as the critical moisture point is reached. It should be noted, that it is the residual or surface (chemically unbound) moisture that is generally being measured here. The sample is then weighed, and the result subtracted from the original weight, giving the moisture as a percentage of the total weight.
In a busy manufacturing environment, this process quickly becomes cumbersome. Moisture balances can produce superior results, in a reduced time frame, but great care still has to be exercised in regards to volatiles. Most have automatic modes with relatively high heat settings, that stop heating the sample when the rate of weight loss changes beyond pre-programmed parameters. This may causes sample burn, and generally leaves the bound moisture in place.
SINAR INSTRUMENTS uses an indirect method of determining moisture. Most capacitance based analyzers emit some type of electrical signal, ie...radio frequency, X-ray converted to electrical, or other, and it's the electrical storage properties of the sample, and how they react with that electrical signal, that provides the reading. The popularity of these instruments is based on their ability to achieve useable accuracy in a substantially reduced time frame, in the case of Sinar, usually around six seconds
Although the instrument reads the reaction of the electrical signal as it comes in to contact with moisture, it doesn't have the intuition to convert the reading in to a useable moisture percentage reading. So we have to do it.
ThisCOFFEEPRO MOISTURE-MAC Coffee moisture analyzer uses a fixed volume sample cell, along with a screw on compression cap to help achieve uniform density
SINAR TECHNICAL INFORMATION & PROGRAMMING MOISTURE CURVES
A sample can be stored briefly in small jar, inside an air tight container like this cigar jar (FIG 1), with water at the base to elevate a samples moisture content, or alternatively dehydrated to create a sample with lower moisture. Using the included coarse sieves, and some other components from the Grind sizer, fitted with PVC, a ball valve, and some hose clamps, a crude but effective fluid bed dryer (FIG 2) can be constructed using the low setting on a standard hair dryer to provide the heated air flow. Very advanced fluid bed dryers (FIG 3) are now able to dry materials while simultaneously plotting a moisture curve. Fluid bed dryers operate by suspending the particles in a heated and agitated air pattern, which allows for uniform drying.
