he KH Director (KHD) was designed for maximum accuracy and operational reliability.
It is essential that you download and follow the latest KHD instructions in our download area.
Hints for achieving maximum accuracy (in addition to the instructions)
- Calibrate the associated dosing pumps as exactly as possible. More here.
- Calibrate the pH electrode carefully and regularly. For a max. accuracy we recommend a calibration interval of max. 4 weeks.
Then check the calibration: Immerse the electrode sequentially in the two calibration liquids (pH 4 and 7) and observe the measured pH value (visible on the KHD page in new GCC versions, if necessary, update GCC). The value should differ max. 0.1 each.
- The shorter and the lower the height differences of the tubes involved, the better. The reagent tube should not be longer than 70cm in total (without pump).
- To avoid bubbles in the reagent tubes, be sure to use the supplied Flex PVC tubing. You are welcome to contact us directly if you do not have it.
- The waste water tube must not hang in the water, it must hang freely over the water surface.
(These are partly repetitions of the manual, due to the importance and the experience that the instructions are not always fully followed, they are mentioned again)
Possible problems and causes
Error message “Titration takes too long”
This message appears when the KHD failed to complete a measurement. The measurement is stopped after a certain time if the pH value could not change sufficiently.
If this error occurs, you should watch the progress of the pH value during the measurement for further diagnosis (visible on the KHD page in new GCC versions, if necessary, update GCC). Does the pH value change? From what value to what value?
- Reagent empty – top up and vent system
- Internal circulation pump does not run (pump should be heared during measurement and water circulation in the measuring cell is visible after removing the housing cover) – Contact Service
- Internal reagent tube is clogged or pinch valve is not open (can be seen after removing the housing cover) – Contact Service
- Measuring cell is not (sufficiently) filled with sample water, as result the pH electrode is not submerged – Find and eliminate the cause
- pH electrode defective, can be found out by calibration – Replace pH electrode
Error message “Leakage alarm”
The KHD has an internal (in-device) leakage sensor to shut down the system in case of water penetration for safety reasons.
If this error occurs, the device must be unpowered immediately and must not be used. After removing the housing cover, you can determine whether there are traces of water inside the unit – contact Service
Measurements do not meet expectations
Although everything was done correctly and all calibrations are correct for sure, the readings of the KHD differ from your expectations.
According to our investigations and observations of many customers, the measured values of various test procedures (test kits, optometric measurements, KHD) are up to 2°dKH apart.
These deviations are product and user dependent, not exceptional and usually no reason for a complaint.
The KHD offers the maximum possible accuracy if the instructions and the points mentioned here have been observed.
If one nevertheless prefers to see other values - e.g. because you are used to the values of a certain test kit, you have the option of trimming the values displayed by the KHD in the range +/- 30% (see setting option on KHD page).
(Please also note the detailed explanations in the manual for this topic)