To determine the accuracy of water quality testing instruments, it is not necessary to rely on a single indicator, but to ensure the reliability of the results through cross validation of three core dimensions: calibration verification, data comparison, and verification of usage conditions.

1、 Core premise: do a good job in instrument calibration and verification

Instrument calibration is the foundation for ensuring the accuracy of detection data, and all detection work must be carried out on the premise of effective instrument calibration.

Regular calibration operation: It is necessary to strictly follow the specifications in the instrument manual and use the corresponding type of standard solution (such as forpHCalibrate the buffer solution used for detection and the standard solution used for conductivity detection. It is recommended to perform the calibration process before each formal test or at fixed intervals (such as monthly or quarterly) to ensure that the readings displayed on the instrument are consistent with the established values of the standard solution.

Blank test investigation: Select pure water (such as distilled water, ultrapure water) that meets the testing standards as the test sample for testing. If the test results show residual impurities or significant abnormalities in the values, it indicates that the instrument may have been contaminated. The instrument needs to be cleaned first and then recalibrated.

Quality control sample validation: Use quality control samples purchased from authorized institutions with known concentrations for testing. If the detection result obtained by the instrument is within the allowable error range of the quality control sample label (the conventional allowable error is ±)5%To ±10%）This indicates that the accuracy of the instrument meets the requirements.

2、 Key means: Conduct data comparison and validation

By comparing and analyzing with external data, the impact of instrument errors or improper operation can be effectively eliminated, further verifying accuracy.

Third party laboratory comparison: Take water quality samples from the same batch and test them separately using the instruments to be tested and the professional testing equipment of the third-party laboratory. If the deviation between two sets of test data is less than the maximum allowable error indicated in the instrument manual (e.gpHAllowable deviation of value ±0.1TheTDSAllowable deviation of value ±5%）It can be determined that the accuracy of the instrument is reliable.

Parallel sample testing: continuous testing of the same water quality sample3-5Perform repeated testing and calculate the relative standard deviation of the test results（RSD）. If calculatedRSDValue ≤5%This indicates that the instrument has good repeatability in detection, which indirectly reflects the stability and accuracy of the instrument meeting the standard; ifRSDIf the value exceeds the standard range, it may be due to insufficient instrument accuracy or improper operation process.

3、 Basic guarantee: Verify the usage conditions of the instrument

The compliance of the instrument's usage environment is an important prerequisite for ensuring the accuracy of the test results. It is necessary to focus on the following two aspects of verification:

Environmental compatibility check: Confirm that the instrument's operating environment meets the requirements of the instruction manual, including temperature control (usually maintained at15-30℃), humidity control (relative humidity should be<85%）At the same time, ensure that the usage environment is free from strong electromagnetic interference. These environmental factors will directly affect the reaction efficiency of instrument electrodes and the detection accuracy of sensors. If the environment does not meet the standards, it is easy to cause distortion of detection data.

Core component maintenance check: Carefully inspect whether the core components of the instrument (such as detection electrodes and various sensors) are intact. If aging of the electrodes or scratches or contamination marks are found on the surface of the sensor, the damaged parts should be replaced in a timely manner, otherwise it will directly affect the accuracy of the instrument's detection and lead to result deviation.

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