What puzzles many people is that this degradation usually happens very slowly. The device is not yet powered on normally, is still calibrated, and is still producing measurement results, so it's difficult to notice the abnormality until image errors start affecting the work.
Even when measuring the same water sample, the results vary each time
A glass of water is kept constant, the temperature remains unchanged, and the measurement procedure is the same, yet the screen displays significantly different values between consecutive tests. The first test shows 125 ppm, then increases to 140 ppm, and then drops to 115 ppm, even though the water sample is completely unchanged.
A difference of a few units is still within the normal range for many handheld devices. A difference of tens of ppm is a different story. In this case, the electrodes often no longer maintain their initial stability, causing the received signal to change continuously even under the same measurement conditions. This situation is quite common in RO, DI systems, or applications requiring constant water quality monitoring.
The calibration was completed, but the error returned
Many people believe that simply recalibrating will resolve all discrepancies. This is true for errors arising from normal use, but it becomes ineffective if the electrode itself has begun to age.
A readily apparent sign is that the device completes the calibration process perfectly, even with fairly good results immediately afterward. However, within a few days or weeks, errors reappear and continue to increase.
The sensor surface changes in physical properties after prolonged use. Standard solutions can help the device re-establish the reference value, but they cannot restore the electrode to its original state. This is also why specialized devices like the HI98199 allow for the replacement of only the HI763063 electrode without replacing the entire unit.
The screen took a long time to stabilize
A good electrode usually responds quite quickly. After immersing it in the water sample, the displayed value will quickly stabilize and remain almost constant.
If it previously took only a few seconds but now requires tens of seconds or more to record the final result, the sensor's responsiveness has significantly deteriorated.
This sign is often overlooked because the degradation process is gradual. Everyday users find it difficult to notice the small changes between measurements. Only when placed next to a new electrode or another device of the same type does the difference become apparent.
Regular electrode cleaning did not improve accuracy
Mineral deposits on sensors are a common occurrence in water sources with high hardness, such as well water or industrial wastewater. After each cleaning, measurement results usually improve significantly if the cause is solely due to surface deposits.
However, there are cases where electrodes are cleaned correctly but errors persist. Measurement results continue to fluctuate, response speed remains slow, and stability remains almost unchanged.
This usually indicates that degradation has occurred within the sensor structure itself. Once the electrode surface loses its original properties, conventional cleaning methods will no longer yield noticeable results.
Two measuring devices used to test the same water sample yielded significantly different results
This is a method used by many laboratories and water treatment plants to assess electrode condition.
With the same water sample, measured at the same time, and under the same operating conditions, the results between two devices can differ significantly. If one device has just been calibrated, its electrodes are new, or it has a more stable operating history, the error is likely originating from the other electrode.
This comparison method is particularly useful in water quality control systems, where every operational decision is based on measured data.
How often should the electrodes in a TDS meter be replaced?
Electrode lifespan depends on frequency of use, working environment, and the quality of the water in contact with it daily. An electrode used in a laboratory with proper maintenance procedures can maintain performance for many years. Field applications or environments containing high levels of minerals often lead to significantly faster degradation.
Therefore, the time for replacement should be assessed based on actual performance rather than just the number of years of use. Unusual fluctuations, slow response times, repeated errors after calibration, or significant discrepancies when compared to other equipment are all more concerning signals than any fixed timeframe.
Read more: What TDS level is safe to drink? Understanding TDS correctly before assessing water quality
Conclude
The electrode directly determines the accuracy of all EC/TDS measurements. Most deviations that occur after prolonged operation are related to sensor degradation rather than the device itself.
Early detection of abnormalities helps maintain the reliability of water quality control and avoids costly misdiagnosis of the cause of the problem. With devices that support electrode replacement, such as the HI98199, the simplest solution often lies in a new probe compatible with the existing equipment.
