One may ask, why calibrate water quality monitors at all? In fact, the reason is very simple, because the calibration of the detection equipment has a great relationship with the measurement data, if not timely calibration will lead to more and more errors in the detection results. In this chapter, water quality online monitoring instrument manufacturers will understand the calibration problems of water quality testing equipment together with you in the future.

When the instrument is used for a long time, the instrument detection data is likely to have errors. For example, small physical changes in the glass surface on a PH sensor will alter the response and lead to inaccurate pH readings. However, calibration can offset these changes in the water quality online monitoring equipment. In addition, when using a single calibration water quality online monitoring equipment, it is necessary to use a value close to the water quality standard, the farther away from the standard value, the lower the data accuracy of the water quality monitoring instrument industry. The factors that determine the inaccuracy of the results become linear features, generally referring to the change in the response of the instrument as the concentration changes.

However, not all water quality on-line monitoring equipment and analytes have linear behavior, and not all instruments are linear at all ranges. Usually linearity is slightly different, and these are important reasons for determining effective calibration. If the device does not exhibit linear behavior over a range, then two calibration criteria are chosen that closely surround the expected values, which will offset the inaccuracies caused by nonlinearities.

All in all, the concentration and number of points used to calibrate the equipment will have a certain impact on the results of the water quality monitor, so the user should carry out regular calibration of their equipment.