Online Moisture Analyzer

An online moisture analyzer is an instrument that continuously monitors product moisture during production and displays it in real time; it is also called an online moisture monitor or online moisture monitoring system. The current market mainly offers near-infrared (NIR) online moisture analyzers and microwave online moisture analyzers. As the instruments evolve, online moisture monitors are becoming increasingly intelligent and user-friendly — with features such as upper/lower limit exceedance alarms, data logging, and uploading to user management platforms — helping enterprises maintain stable production and playing a vital role in production activities.

According to on-site production conditions, online moisture analyzers can be installed in various ways, such as non-contact installation (e.g., over conveyor belts), insertion installation (e.g., in tanks), communicating-vessel installation, and in-pipe installation.

In the near-infrared region of the spectrum, these bands are particularly strong for water molecules, and the instrument can more easily emit, filter, and receive this energy. Specific wavelengths of near-infrared light energy are used to deliver the right amount of energy to the moisture in the product being measured. The wavelengths generally used for moisture measurement remain in the 1 to 2.5 micron range.

Absorption depends on water molecules encountered and absorption strength—proportional to moisture. As a reflectance method it is also affected by the material's reflectance and absorption; NIR measurement is non-destructive, non-contact, and real-time.

The signal strengths of the two channels combine into: R/M X M1/R1=ratio

Where: R--reference channel of the product beam

M--measurement channel of the product beam

M1--measurement channel of the compensation beam

R1--reference channel of the compensation beam

If drift occurs, M and M1 shift equally, canceling out in the ratio and preserving stability.

Microwave attenuation and phase shift depend on the medium's dielectric constant and loss tangent—far higher for polar water than ordinary media. Moisture is calculated from received attenuation and phase shift.

Microwaves penetrate fully, measuring all physical moisture—surface and internal—with high accuracy unaffected by color or structure. Applications span coal, sinter mixes, iron ore, chemicals, bauxite, nickel ore, sugar, tobacco, bagasse, grain, silicon, wood, wool, food, sand, polymers, cotton, and other non-conductives.

The probe measures 150-200 mm deep, analyzing total (core and surface) moisture; deep penetration means surface dirt does not matter.

The variation of relative permittivity is the key principle; simply:

Water's εr≈80 versus ~1-10 for most materials (sand/gravel 3-4)—a large measurable difference.

Moisture is measured directly from this difference and output as a mass-percentage standard signal.

In other words: the more water a material contains, the closer its relative permittivity εr approaches 80.

Signals are obtained as material passes the sensor—even on fast lines; stationary bulk materials can also be measured.

Whether on conveyor belts, open vessels, pipelines, tanks, mixing equipment, or open pools, an online microwave moisture analyzer can be used for moisture detection. The specific installation method requires the supplier to provide a professional solution based on the user's on-site production conditions. For example:

In-Material Installation:The probe must protrude at least 8 cm. Pay attention to the mounting position — avoid proximity to the inlet to reduce damage to the sensing rod from material impact during feeding. If the moisture analyzer must be near the inlet, install a protective baffle above the instrument.

Pipeline Installation:The online microwave moisture analyzer can be mounted on a pipeline to monitor the moisture content of the material inside in real time.