Drying moisture analyzers are essential for accurately detecting the moisture content of substances in many fields, such as food, chemical industry, agriculture, etc. In order to ensure the reliability and accuracy of its measurement results, it is necessary to carry out rigorous verification work according to relevant regulations. We will follow the JJG658 - 2010 Drying Moisture Analyzer Verification Procedures to discuss the key points of operation in the actual verification.
Environmental and technical conditions
The testing room should be kept clean and tidy, and the moisture analyzer should be placed firmly on a sturdy and stable work table. There must be no vibrations, air currents, corrosive gases, and strong magnetic fields that would interfere with its metering performance. The temperature of the verification chamber should be maintained at 10°C-30°C, the relative humidity should be at 30%-70%, and the verification work should be carried out under stable environmental conditions. For the power supply, the rated voltage is allowed to fluctuate in the range of -15%-+10%, and the power supply frequency varies from -2%-+2% for 50Hz.
Structural principle
Moisture analyzers use the drying principle to directly analyze isolates or microfractions of moisture on the surface of a measured sample. When performing metrological analysis on the residual solids of a measured sample, the meter can also be referred to as a solids analyzer. According to the different display methods and measuring devices, it can be divided into analog display moisture analyzer and digital display moisture analyzer.
Analog display moisture analyzer
These Testers are built on the principle of lever balancing and are equipped with a mechanical measuring device with a differential scale. The common heating elements include tunnel ovens, infrared ceramic heaters, quartz heaters, etc.
Digital display moisture analyzer
The digital display moisture analyzer realizes the digital display of the measurement results with the help of electronic measuring devices, and its heating methods are rich and diverse, including infrared ceramic heaters, quartz heaters, far infrared heaters, halogen lamps, laser technology, microwaves, etc. In the operation preparation stage, it is necessary to confirm that the verification environment strictly meets the requirements of the verification procedures of the drying moisture analyzer, which is the basis for ensuring the accuracy and reliability of the verification results. The exterior of the instrument is then visually inspected for damage or missing parts. Then place the instrument on a solid platform and adjust it to a level, carefully remove the residual powder and sample on the measuring device, and complete the cleaning process; Finally, the analog moisture analyzer needs to be zeroed before verification, and the digital display moisture analyzer needs to be calibrated after the specified warm-up time to ensure that the instrument is in normal working condition.
Sequence and method of operation
Indication error verification
Analog display moisture analyzer
During the verification, a standard weight for the maximum weighing capacity is placed in the weighing pan and adjusted to a balanced state so that the pointer coincides with the zero index line on the scale, or the zero line of the differential scale coincides with the reference line. The load point is selected by the inspector according to the specific condition of the moisture analyzer, but the key load points such as no load, maximum load point of the scale, and maximum weighing capacity must be covered.
Digital display moisture analyzer
During verification, the load starts at zero load, gradually increases to the maximum capacity of the measuring device, and then unloads to zero load point by point. The load point of the test load needs to be selected according to the actual situation of the instrument, but the load corresponding to the no-load, the maximum allowable error conversion point, or the load close to the maximum allowable error conversion point, and the maximum weighing capacity must be included. During loading or unloading, there must be a sufficient number of measuring points, usually no less than 5 points.
Repeatability test
Analog display moisture analyzer
Place the standard weight of the maximum weighing capacity on the weighing pan and adjust the balance, determine its equilibrium position, record the indication error of the Moisture Meter at this time, and repeat this step 3 times to judge whether its repeatability is up to standard.
Digital display moisture analyzer
The test load is selected as a single weight of 80% - 100% of the maximum capacity, measured no less than 6 times, and can be zeroed before each load to determine whether its repeatability meets the requirements in a specific way.
Verification of moisture measurement errors
Analog display moisture analyzer
Place the fiberglass paper on the moisture analyzer sample tray and pre-bake at 105°C for 10 minutes. Turn off the heating device, adjust the weight on the measuring device, let the moisture analyzer indicate the scale back to zero, and record the weight value on the weighing pan at this time. Take away the 5g weight on the measuring device, measure the 5ml sodium chloride solution with a 5ml pipette, drop it evenly on the fiberglass paper, turn on the measuring device, and record the scale mark value and the weight value on the weighing pan after equilibration. Turn on the heating after turning off the measuring unit and raise the temperature to 105°C, turn on the measuring unit after 1 hour, and add or remove the weights on the measuring unit to read the balance position on the display. After the indication value is stable, the mass value of the increased and decreased weights and the final equilibrium position are recorded, and then the sample moisture is calculated according to the corresponding rules.
Digital display moisture analyzer
At a temperature of 105°C, the standard drying program was selected according to the 1mg/60s water loss rate determination method. Fiberglass paper was placed on the specimen tray and also pre-baked using the 1mg/60s water loss rate determination method. After the pre-baking, 5ml of sodium chloride solution was pipetted with a 5ml pipette, dropped on the fiberglass paper as evenly as possible, and then the moisture was determined by the 1mg/60s water loss rate method, and the final moisture value was recorded.
Weight verification
If the simulated moisture analyzer is equipped with a matching weight, it needs to be verified according to the corresponding weight class to ensure the accuracy of the weight, and then ensure the measurement accuracy of the entire Tester.
Rules and precautions for use
The moisture analyzer should be level, and the parts should be performing properly and in the correct position.
Before use, the zero point of the moisture analyzer should be adjusted, and the digital display moisture analyzer should be self-calibrated to ensure the accuracy of the measurement.
The digital display moisture analyzer should be pre-loaded before use, so that the instrument can reach a better working condition.
The heating process of the moisture analyzer should be smooth to prevent the temperature overshoot from causing the sample to scorch and affect the measurement results.
When turning on and off the instrument, the action should be gentle and gentle to avoid damaging the instrument with excessive force.
The operator must hold a professional inspector certificate to ensure the standardization and professionalism of the operation.
Maintenance
Professional responsibility - professionals undertake maintenance and maintenance work to ensure the quality and effect of maintenance work.
Troubleshooting - once a problem is found, it needs to be reported to the relevant departments in a timely manner. After identifying the cause of the failure, the repair can only be carried out with the approval of the competent leader to avoid more serious problems caused by improper maintenance.
All in all, the verification operation of the drying moisture analyzer covers a number of key links, from the preparation of the instrument, the standardized implementation of the operation process, to the precautions in use and subsequent maintenance, each step is closely related, which plays an indispensable role in ensuring the measurement accuracy and reliability of the instrument. Only by operating in strict accordance with the relevant regulations and requirements can we give full play to the performance of the drying moisture analyzer and provide solid and powerful support for the moisture testing work of various industries.
