What is the RF dielectric technology of a moisture analyzer
This method relies on a higher water dielectric constant compared to most solids.
Many technologies have been developed to determine the dielectric, including radio frequency, microwave, and time-domain reflectometry. In order to measure the relative dielectric constant of a material, it is necessary to electrically couple the material to the sensing circuit. This operation can be achieved by placing the material between two parallel electrodes, but it is not convenient for online application. If the sensing circuit operates at RF, it is easy to propagate RF energy through the material, thus coupling to the product without physical contact. The planar edge field electrode provides a unilateral measurement structure with minimal impact on the process.
The electrical analogy of solid products is capacitors connected in parallel with leakage conductivity. These components are all affected by moisture, but the dielectric constant is very predictable, while the loss factor is not. The combined components represent a complex impedance that can be easily measured, but it may be influenced by variables other than humidity.
Real dielectric moisture meters are rare because most low-cost instruments do not attempt to separate the dielectric and loss components. The lowest cost instruments rarely or never attempt to measure combined impedance with any long-term stability and repeatability.
It is a penetration measurement that can measure heterogeneous products.
It has a large measurement area and can provide a more representative overall average moisture content for the product.
Compared to other online technologies, it is relatively inexpensive.
It is very reliable, sturdy, and has no wear or damage to moving parts.
Various mechanical sensor designs are suitable for various process conditions and can be used in high-temperature environments.
Infrared technology
Near infrared reflectance (NIR or IR) technology is a widely used technology for online moisture testing. Its popularity is largely due to its ease of use.
Align the light source (usually a quartz halogen bulb) and filter it to a specific wavelength. A filter installed on a rotating wheel cuts light into a series of pulses of specific wavelengths. The filtered beam directly illuminates the surface of the product to be measured. A portion of the light is reflected back to the detector (usually lead sulfide). Light of a specific wavelength is absorbed by water. If a filter is selected so that one wavelength will be absorbed by water (sample beam) and one wavelength will not be affected by water (reference beam), the amplitude ratio of the two reflected wavelengths will be proportional to the amount of water in the water.
Easy to apply. Usually installed 6 to 10 inches above the product. Moderate product height changes have little impact on measurement.
The small measurement area is combined with the scanning frame to provide product contours.
You can choose a specific wavelength to measure variables other than humidity.
