Why is there a deviation between the TDS value measured by the TDS pen and on the Mijia Smart Water Purifier N800G?

The TDS probe in the Mijia Smart Water Purifier N800G and the TDS pen are calibrated using the same water quality analyzer, so in theory, they should give similar readings for the same water.
If a deviation occurs, it is related to the measurement method:
  1. If air bubbles adhere to the probe of the TDS pen during measurement, the result can deviate from the actual value.
  2. The TDS pen measures static water, whereas the purifier measures flowing water, which can cause slight differences.
  3. If the purifier has not been used for an extended period, the initial TDS of the output water can fluctuate, causing discrepancies between the TDS pen and the real-time reading on the device.
  4. A deviation within 10% is generally considered normal.
Therefore, when measuring water TDS with a TDS pen, follow the instructions carefully to minimize errors.

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