Water quality monitoring relies on a variety of analytical methods. Errors may occur throughout the water quality testing process due to multiple factors. This article, together with Modi, introduces several causes of errors generated by water quality analyzers, which are mainly categorized as follows:

1. Gross errors

Such errors stem from improper human operation during testing, which distort measurement results. Typical cases include using the wrong sample, incorrect reagent dosing, unclean or defective lab-ware, and improper operation.

The key to eliminating gross errors lies in operators. Staff should stay focused and meticulous, and continuously improve theoretical knowledge and operational skills. Measurement data containing gross errors usually appear as outlier values, which can be removed via statistical tests for outliers.

2. Random errors

Random errors are triggered by random influencing factors during measurement.

To reduce random errors, test conditions shall be strictly controlled and all operations performed in compliance with specifications. Besides, random errors can be mitigated by increasing the number of tests, leveraging their compensating property.

3. Systematic errors

Systematic errors refer to the deviation between the average measured value and the true value, caused by certain constant influencing factors. Increasing measurement times cannot reduce systematic errors.

Four measures help minimize systematic errors:

① Calibrate equipment before use;

② Conduct blank tests;

③ Carry out comparative analysis;

④ Perform recovery tests.

In summary, errors in water quality analyzers may arise from the limitation of finite digits to represent measured values, insufficient understanding of testing principles and constraints of technical capabilities. As a result, inaccuracies may appear when assessing water quality based on monitoring results. Therefore, efforts should be made to reduce errors and guarantee valid test data, supporting reliable evaluation of water safety.