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Materials that can absorb moisture change their properties in the electric field depending on the moisture content. Moisture analyzers that determine the capacitance work quickly and non-destructively. The measurements can be repeated as often as required at the same or neighbouring point. Measurement depth and results are influenced by both the type and structure of the material. They can be altered by foreign materials as well as by salts embedded in the measuring area. For known materials and defined environmental conditions, reliable measurement results are possible. For other conditions, these devices are good for quick determination and isolation of the areas with increased moisture.

As the moisture content increases or decreases, so does the electrical resistance or conductivity. However, since these electrical values are also influenced by temperature and material composition, some important points must be taken into account when using this method. The influence due to temperature differences can be compensated for some models via sensors, special components or manual settings. Stored reference lines for materials or material groups allow a higher accuracy for the selectable materials. However, only a few moisture analyzers with resistance measurement offer the option of storing their own reference lines.

Moisture analyzers with resistance or conductivity measurement offer fast results during the non-destructive measurement. The values allow the moisture deviations to be detected and their extent to be narrowed down. Partially insulated probes are suitable for determining the values at different depths. This allows conclusions to be drawn as to whether there is more moisture inside than outside. This facilitates the assessment of the drying out behaviour and the causes of the moisture.

The moisture content of many materials depends on the temperature and humidity of the environment. If the material can absorb moisture from the air and release it back into the air, a certain material moisture will be established after some time as a compensating moisture for a certain ambient climate. This means that moist materials release moisture in a dry environment and, conversely, dry materials absorb moisture in a moist environment. With the measurements according to the KRL method, it can be determined whether moist materials have already reached their compensation moisture and whether materials or components show increased moisture values due to the influences other than the ambient climate. The measurement is repeatable, so that the statements on the course of drying or moisture absorption are possible.

The determination of the corresponding air humidity can be carried out with the help of material samples, in bulk materials, as well as in boreholes or on the material surface. The samples are placed with the sensor in airtight containers or foil bags. During the measurements in boreholes or on surfaces, air exchange must also be prevented by airtight masking. The German Adhesives Industry Association (Industrieverband Klebstoffe e.V.) describes in TKB Report 2 "The KRL Method for Determining the Moisture in Screeds" the procedure for taking samples of moist screeds analogous to the calcium carbide method. In the case of screeds, it is mandatory to determine the residual moisture before tiling or flooring work to prevent damage to the flooring due to subsequent moisture equalisation.

If the moisture values of the material are above those of the characteristic compensation moisture, the relative humidity of the enclosed air increases until the material no longer releases any moisture into it. If, on the other hand, the material is drier than usual for the prevailing ambient conditions, it absorbs moisture from the enclosed air and its humidity decreases.

Microwaves of certain wavelengths are influenced by water molecules and vice versa. They can be used not only to heat food containing water, but also for targeted moisture analysis. The microwaves that hit water molecules are slowed down, damped and partly reflected. These changes can be measured. The water content of electrically non-conductive substances can thus be determined precisely, quickly and non-destructively. Depending on the number of the water molecules in the examined substance, the resonance frequency, transmittance and reflection of the microwave radiation become higher or lower. However, the strength of the change is not only dependent on the water content, but also on other influences. Therefore, the moisture analyzer that works on the basis of the microwave technology must be adjusted to the material and the concrete measuring conditions by the reference measurements.

In general, only low microwave power is required for the measurement, so that the material is hardly heated or influenced in any other way by the measurement. The measurement can be repeated as often as desired at the same position, provides very fast results and also works with moving material. This is why the moisture analysers with microwave technology are often used for inline moisture measurements in manufacturing, drying and storage processes. For sensitive products, very short measuring intervals in milliseconds and accuracies of 0.1 moisture percent are possible. Analogue or switching interfaces can be used to ensure that the countermeasures are taken very quickly in the event of moisture deviations.

When buying grain by weight, verified scales and verified moisture analyzers must be used. For most grains, a moisture content of 14.5 percent is considered the base value; for canola, the base value is 9 percent. Deviations from these basic values for the water content are taken into account in the price via factors as surcharges or discounts. Necessary drying measures are additionally invoiced.

As a rule, construction timber is not invoiced by weight, but by volume. However, it is very important to determine the moisture content of the wood with a moisture analyzer, because wood that is too moist can be destroyed by fungi and insects. In addition, wood changes its dimensions when moisture content changes. It swells when it absorbs water and shrinks during the drying process. In the process, shrinkage cracks and curvatures can form. For this reason, various standards require that the moisture content of wood be limited. According to DIN 18 334, solid wood components in insulated roofs may have a maximum wood moisture content of 20 percent during installation, and a maximum of 18 percent in wooden house construction. In contrast, a maximum wood moisture content of 15 percent applies to glued components.

Moisture analyzer scales function in principle independently of the material. They can be used in the laboratory to test a wide variety of samples. However, as with the original kiln-drying method, the temperatures used for drying must be adapted to the material. With many of the moisture analyzer scales, the parameters for different test sequences can be permanently stored. The stored drying programs can be easily recalled later when the samples of the same material are to be tested again.

Most models of the moisture analyzer scales are designed for very small sample quantities. The small quantities shorten the drying time and thus allow a quick statement on the moisture content. For larger sample quantities, several individual measurements can be performed. It is important for the validity of the measurement that the sample does not change its moisture content until the measurement is started. The material samples should therefore arrive at the laboratory as quickly as possible, at a constant temperature and packed in an airtight container.

If the moisture measurements are required for the ongoing production process or for quality assurance, the measurements should be carried out as soon as possible after sampling. If the factory laboratory is too far away, it is recommended that an additional testing station be set up. The space requirement and the requirements for the moisture analyzer scales for the installation site are hardly higher than those for the letter scales.

In food production and processing, moisture content is important for both shelf life and processability. Everyone knows that fresh food has a limited shelf life. Anyone who occasionally buys too many potatoes or carrots also knows that they are difficult to peel if they have lost too much water. To ensure that food can be used for a long time, it should be stored under special conditions or processed and preserved as quickly as possible.

Before and during processing, the moisture content of food can be determined with the moisture analyzer suitable for this purpose. In highly automated processes, inline moisture sensors are usually used to transmit the current moisture data directly to the process control station. This allows the temperature and the duration of drying or the addition of water to mixtures to be automatically adjusted to the measured moisture.

Regardless of whether the moisture analyzer is used for continuous or single measurements, special hygiene requirements must always be observed in the food industry. In particular, if the measurements are not made on taken samples but directly in the material to be processed, it must be possible to clean the contact surfaces in accordance with the relevant hygiene regulations. Many models of the moisture analyzers are therefore designed so that the contact surfaces can be sterilized with liquids as well as with high temperatures.