Portable trace moisture analyzer is a commonly used analytical equipment in the fields of petroleum, chemical, power, environmental protection, etc. It is based on Karl Fischer microcoulometry and can accurately determine trace moisture in liquid, gas, and solid samples. Regular calibration is a key step to ensure the long-term stable operation of the instrument and accurate and reliable data. Here are several practical calibration techniques and precautions.

1、 Preparation before calibration

Before calibration, it is necessary to ensure that the instrument is in good condition. Firstly, check if the interface of the electrolytic cell is sealed properly to avoid calibration errors caused by liquid leakage. Secondly, confirm that the electrolyte is fresh and effective. If the electrolyte changes color or has been used for too long, it should be replaced in a timely manner. At the same time, run the self-test function of the instrument after startup to confirm that there are no open or short circuit alarms on the electrodes and that the circuit system is working properly.

2、 Selection and use of standard substances

It is recommended to use certified reference materials for calibration, such as standard solutions with known accurate water content or aqueous standard samples. During operation, it is necessary to strictly control the injection volume, usually using a microinjector for precise sampling. For the measurement range of the instrument (3 μ g~200mg), different moisture content levels of standard substances can be selected for segmented calibration, such as low moisture content range (3 μ g~1000 μ g) and high moisture content range (>1000 μ g), to comprehensively evaluate the linearity and accuracy of the instrument.

3、 Control points of calibration process

Environmental conditions: Calibration should be carried out in an environment with relatively stable temperature and humidity to avoid airflow interference. The working power supply of the instrument should be stable at AC220V ± 10%. If using a built-in lithium battery for power supply, ensure sufficient battery power.

Blank value calibration: Before formal calibration, a blank test is required, and the sample can only be injected after the instrument background value is stable. The instrument has a balance point drift compensation function, which can reduce errors introduced by baseline fluctuations.

Repeatability verification: Repeat the measurement of the same standard substance at least 3 times to observe the consistency of the results. The instrument resolution can reach 0.1 μ g, and the repeated measurement data should be close. If the deviation is large, the electrolytic cell or electrode status should be checked.

Error assessment: According to the technical parameters of the instrument, the error in the low water section should be controlled within ± 3 μ g, and the error in the high water section should not exceed ± 0.3%. If the calibration result exceeds the tolerance, it is necessary to check the stability of the electrolytic current or perform circuit debugging.

4、 Daily maintenance and data management

After calibration, data should be recorded in a timely manner, and the storage function of the instrument can be used to save historical records with time stamps (up to 10000 records can be stored). In daily use, pay attention to regularly cleaning the electrodes to avoid sample residue affecting sensitivity. If the instrument is equipped with WIFI function, calibration data can be synchronized to a computer or mobile phone for long-term tracking of instrument performance trends.

5、 Precautions

The standby power consumption of the instrument is relatively low (about 4W), but it should be powered off and saved when not in use for a long time.

When carrying or moving instruments, be careful to avoid severe vibrations to prevent leakage of electrolytic cells or damage to circuits.

If there is an abnormal alarm during the calibration process, the fault should be checked according to the instructions, and if necessary, professional personnel should be contacted for maintenance.

Through standardized calibration operations and regular maintenance, the portable trace moisture analyzer can maintain high sensitivity and reproducibility, providing reliable support for trace moisture analysis of various samples. Calibration is not only a technical step, but also an important foundation for ensuring data quality, which deserves full attention from users.