Microwave Moisture Analyzer for Paper and Board

What is the Microwave Moisture Analyzer for Paper and Board?

A microwave moisture analyzer measures the attenuation of microwaves passing through a paper stack, bale or sheet and converts it into a moisture value. It penetrates deeper than electrical hand meters and suits warehouse and bale measurements.

Overview

Water molecules absorb microwave energy much more strongly than cellulose, so transmission attenuation depends mainly on the water mass in the path of the beam. The transmitter and receiver are placed on opposite sides of the sample, which means measurements can be made through bales, reels or stacks without penetrating probes, and the large measurement volume reduces the influence of local variation. Readings are affected by basis weight, thickness, density, additives and temperature, so a calibration is needed for each material class and the sample thickness or mass must be within the calibrated range. Instruments are available as laboratory benches for specimens and as portable units for warehouse use, and both should be verified periodically against oven or Karl Fischer reference results.

How does it work?

All moisture methods compare the mass of water in the sample with either the wet mass or the dry mass, and the chosen reference must always be reported because moisture content and dry matter content give different numbers. The reference method dries a specimen to constant mass in an oven at a specified temperature and calculates the mass loss. Halogen drying performs the same measurement quickly on a built-in balance, using a halogen radiator for faster and more uniform heating, and requires correlation with the oven method for each paper grade. Karl Fischer titration is a chemical method: iodine reacts quantitatively with water, and the endpoint is detected electrochemically, so it measures water specifically and is unaffected by other volatile substances. Microwave and near-infrared instruments measure indirectly through absorption or dielectric response and need calibration against a reference method.

What are the key features?

• Transmission measurement through the sample
• Deep penetration for bales and reels
• No probe insertion required
• Calibration per material class
• Portable and bench-top versions
• Thickness or mass range enforcement

What are the technical specifications?

A typical microwave moisture analyzer for paper and board configuration offers measurement principle of Microwave transmission attenuation, moisture range of 2–25% depending on material, resolution of 0.1%, accuracy after calibration of ±0.5% typical, sample thickness range of Up to about 300 mm for stacks and calibration curves of Multiple material classes. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Microwave Moisture Analyzer for Paper and Board is used in bale and reel moisture measurement in warehouses, recovered paper delivery verification, board and heavy paper moisture checks and rapid screening before converting or printing. Across the wider Moisture Testing class, laboratories also deploy it for incoming moisture checks on pulp and recovered paper, machine-direction moisture control during papermaking and finishing and converting moisture verification.

Which standards and certifications apply?

Relevant standards and methods include ISO 287, ISO 638, ISO 760, TAPPI T412, ASTM D644, ASTM D6869 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Sample handling dominates the uncertainty because paper equilibrates with the surrounding air within minutes. Cut sealed specimens, weigh them quickly in a closed container, and record the temperature and relative humidity of the laboratory, since the standard equilibrium condition defines the moisture of a well-conditioned sheet. Oven temperature, drying time and the use of a desiccator before weighing must follow the method, and the balance should be checked with certified masses. For indirect instruments, recalibrate whenever furnish, coating, grade or basis weight changes, and keep the reference results used to build the calibration. Store paper samples away from heat and direct sunlight before testing.

How do I select the right Microwave Moisture Analyzer for Paper and Board?

Select a microwave instrument when measurements must be made through thick samples, bales or reels without probes, or when a larger measurement volume is needed to smooth out local variation. Confirm the calibrated thickness and moisture range covers your materials, and establish correlations with the oven method for each grade class before using the instrument for acceptance decisions.

How does it compare with other Moisture Testing variants?

Choose the reference oven method when a specification value is required, since almost all paper moisture standards are written around it. Select a halogen instrument for routine control where speed matters, but establish and document the correlation with the oven method for each grade, including for coated and highly filled papers. Karl Fischer titration suits samples where volatile substances other than water are present, such as papers containing solvents, and can be combined with an oven accessory for solid samples that do not disperse. Microwave and near-infrared instruments are chosen for production use: the near-infrared systems mount on the machine and measure across the full web width continuously, while microwave instruments suit bale and stack checking on the floor.