Principle of determination
The halogen moisture meter works based on the principle of thermal weight loss. Its core component is a halogen heating unit that quickly generates radiant heat to evenly heat the specimen placed in the sample tray. The moisture in the sample evaporates when heated, and the high-precision balance built into the instrument monitors and records the mass loss during the heating process in real time. The moisture content of the sample can be calculated directly by calculating the mass difference between the sample before and after heating and combining it with the initial mass. The process can usually be completed in a matter of minutes, significantly improving efficiency compared to traditional oven methods.
Moisture content (WThe formula for calculation is as follows:
W = (m1 - m2) / m1 × 100%
Among them,m1represents the initial mass of the sample before heating,m2Represents the mass of the sample after heating to a constant weight.
Instrument structure
A typical halogen moisture meter consists of a halogen radiant heating device, a precision load cell, a sample tray, a temperature control system, and a microprocessor unit. As a heat source, halogen lamps have the characteristics of rapid heating and uniform energy distribution, which can achieve rapid drying of samples. The temperature control system allows users to set and precisely control the heating temperature based on sample characteristics, preventing overheating and causing sample decomposition. The microprocessor controls the entire measurement process, collects data and automatically calculates the results.
Its main technical features include: fast measurement speed, suitable for rapid testing on the production site or in the laboratory; Small sample volume required; Easy operation and high degree of automation; It has data storage and transmission functions. It is important to note that the suitability of the method needs to be evaluated for samples that contain volatiles (other than water) or are prone to degradation by heat.
Operation process
Standardized operating procedures are the basis for ensuring reliable results. First, the instrument needs to be preheated and calibrated. Subsequently, a representative appropriate amount of sample was taken and evenly laid on the sample tray. Set the appropriate drying temperature and program (e.g. timed heating or automatic determination of the end point) on the instrument operation interface. After starting the measurement, the instrument automatically completes the heating, weighing, calculation process, and displays the final moisture content result on the screen.
The key parameters of the method mainly include:
| Sample preparation | Make sure the sample is homogeneous and representative. |
| Sampling volume | It is determined according to the instrument range and the expected moisture content of the sample. |
| Drying temperature | Set according to the thermal stability of the sample to avoid decomposition. |
| Drying procedure | You can choose between timing mode or automatic end judgment mode. |
Applications:
Halogen moisture meters are widely used in industries that require rapid monitoring of moisture content, such as: moisture detection of grains, starches, meats in food processing; moisture control of powders and granules in the chemical industry; moisture analysis of ceramics and building materials raw materials; fiber raw material testing in the paper and textile industries, etc.
The following matters should be paid attention to during use: the instrument should be placed in a stable and vibration-free environment; The sample tray should be kept clean to avoid cross-contamination; For samples with different properties, the optimal temperature and time parameters should be determined through experiments. The instrument's weighing unit and measurement accuracy are regularly verified using standard weights and moisture content reference materials.
Comparison of methods
Compared with the traditional oven method (such as referring to GB/T 28731, ISO 18134 and other relevant standards), the halogen moisture meter method has obvious advantages in terms of ease of operation and detection speed, but its results may be systematically different from those of the oven method. Therefore, when establishing a rapid assay method, it is recommended to conduct comparative experiments with reference methods, establish correlations or determine correction factors through a large amount of data, so as to ensure the accuracy and acceptability of the rapid method results. The laboratory should formulate corresponding operation instructions to clarify the scope of application, steps and acceptance criteria of the method.