Behind the pH probe holder/front cover there are optical sensors that can detect the reagent drips as they fall into the test beaker below. These consist of black plastic blocks that encase a diode. If the sensors become wet or have deposits building up on them then there is a possibility they will not function correctly. Commonly this will result in an extreme test result or cause instability in the testing. In more severe cases it can also result in a drip sensor error being displayed, however this is more common as a result of air in the reagent line.

To check the sensors remove the pH holder/front cover and observe the sensor blocks for any signs of moisture or deposits. If necessary carefully clean them with a cotton bud and some RO water then dry with some paper towel. If the sensors are wet or have heavy deposits it is worth checking that the dripper nozzle is in position properly, not leaking and that the KH Manager is sitting level. Drops of reagent falling on the sensors can cause permanent damage and will result in the need for them to be replaced.