Infrared Moisture Meter

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

I. Two Principles

1. Infrared Heating Moisture Meter (Thermogravimetric Method)

Desktop laboratory instrument, similar in principle to halogen moisture meter, with infrared lamp / infrared tube as heating source.

• Principle: Infrared radiation heats the sample, moisture evaporates, built-in balance weighs the difference before and after heating to calculate moisture content.
• Test time: 315 min.
• Advantages: Low cost, 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: The OH bond of water molecules has strong absorption of specific near-infrared wavelengths (1.94 μm, etc.); the instrument emits multi-wavelength infrared light to irradiate the material and measures the reflected light intensity; usingDual / triple wavelength compensationEliminates interference from material color and roughness, converts to moisture content.
• Features:Non-contact, non-destructive to samples, output in milliseconds to seconds, continuous online monitoring possible。
• Disadvantages:Must be calibrated, different materials require establishing corresponding calibration models; affected by material thickness and surface condition; can only measure moisture at a certain depth on the surface.

II. Instrument Classification

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

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 Granules
• Pharmaceuticals: Traditional Chinese Medicine Slices, Granular Materials

IV. Pros and Cons Comparison

Infrared Heating (Thermogravimetric)

✅Advantages: Simple principle, close to oven method, no complex modeling needed; low cost. ❌Disadvantages: Slow testing; sample damage; interference from volatile substances; only sampling and laboratory testing, not 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 requires calibration against the oven method; affected by surface, dust, 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, and general curves have large errors.
2. Online probe: Avoid strong light, steam, dust; clean lens regularly; material thickness uniform, light spot fully covers material surface; probe installation height according to 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.