Infrared Moisture Meter

Infrared moisture meters are divided into two major categories:Infrared Heating Loss-on-Drying Type (Laboratory Benchtop)、Near-Infrared Spectroscopy Type (Online / Handheld, non-contact), the principles of the two are completely different, and many people easily confuse them.

I. Two Principles

1. Infrared Heating Moisture Meter (Thermogravimetric Method)

Benchtop laboratory instrument, similar in principle to halogen moisture meters, with infrared lamps as the heating source / Infrared tubes.

• Principle: Infrared radiation heats the sample, moisture evaporates, and the built-in balance measures the weight difference before and after heating to calculate moisture content.
• Testing Time:315 min。
• Advantages: Low price, simple operation;
• Disadvantages: Sample is destroyed; other volatile substances in the sample are counted as moisture, leading to higher results; not suitable for materials that decompose at high temperatures.

2. Near-Infrared Spectroscopy Moisture Meter (NIR, Industrial Online / Handheld)

Non-contact, non-destructive, most commonly used on production lines.

• Principle: Water molecules OH Key to specific near-infrared wavelengths (1.94 μm etc.) have strong absorption; the instrument emits multi-wavelength infrared light onto the material and measures the reflected light intensity; usingDual / Three-Wavelength CompensationEliminate interference from material color and roughness, convert to moisture content.
• Features:Does not contact the sample, does not destroy the sample, millisecondsOutput in seconds, can monitor continuously online。
• Disadvantages:Must be calibrated, different materials require corresponding calibration models; affected by material thickness and surface condition; can only measure surface moisture at a certain depth.

II. Instrument Classification

1. Benchtop Infrared Heating Moisture Meter: Laboratory, grains, feed, plastic pellets, medicinal herbs, pastes; sampling testing, sample is dried and destroyed.
2. Handheld Near-Infrared Moisture Meter: On-site rapid spot checks, non-destructive.
3. Online near-infrared moisture meter: Conveyor line probe type, installed above the conveyor belt, real-time output 420mA/RS485 Signal, can link with drying equipment for closed-loop production control, papermaking, tobacco, coal, food, building materials, chemical powders.

III. Main Industry Applications

• Grain and Feed: Cereals, Flour, Feed Pellets
• Food and Tobacco: Tea, Milk Powder, Tobacco Shreds, Baked Goods
• Papermaking and Textiles: Paper, Paperboard, Textiles
• Building Materials and Chemicals: Coal Powder, Ore, Fertilizers, Various Powders and Pellets
• Medicine: Traditional Chinese Medicine Slices, Granular Materials

IV. Comparison of Advantages and Disadvantages

Infrared Heating (Loss on Drying)

✅Advantages: Simple principle, close to oven method, no complex modeling required; low price.❌Disadvantages: Slow testing; sample destruction; volatile substance interference; can only sample and test in the laboratory, cannot be used online.

Near-Infrared Spectroscopy Type

✅Advantages:Non-destructive, extremely fast, can measure continuously online, sample can be retained and reused。 ❌Disadvantages: High procurement cost; each type of material needs calibration against the oven method; affected by surface, dust, and steam; measures surface moisture only.

V. Key Precautions

1. Calibration is the core: Near-infrared models must be calibrated using the oven method (national standard); recalibration is required when changing materials; universal curves have large errors.
2. Online probe: Avoid strong light, steam, dust; clean the lens regularly; material thickness should be uniform, and the light spot should completely cover the material surface; install the probe at the height specified in the manual.
3. Heating Type: Spread sample evenly with uniform thickness; heating chamber is high-temperature, beware of fire and burns; use with caution for volatile and heat-sensitive samples.
4. Environment: Avoid direct strong light, large vibrations, voltage fluctuations; fully preheat before testing after power-on.