Instruction Manual
KH Director®
EN
2018-02-19
39
7
Measurement accuracy
The KH Director gives you the best possible accuracy for a measuring device of this class.
In lengthy and time-consuming trials, the measurement process, the measurement
electronics and the mechanical design have been optimized to such an extent that the KH
Director can supply very precise measurement results. Nevertheless, small measuring
tolerances, as they occur in all measuring devices, cannot be completely avoided.
You as a user can make a significant contribution to achieving the maximum measurement
accuracy the KH Director can offer by ensuring the following optimal starting conditions:
•
Max.
Water sample
volume (100ml)
•
Careful calibration of the pH electrode at regular intervals (about every 4 weeks)
•
Very accurate calibration of the dosing pumps involved in the measurement
•
Shortest possible tubes between dosing pumps and KH Director as well as between
reagent container and dosing pump
•
Careful ventilation of reagent liquid tubes
Under these optimal conditions, a tolerance of approximately 0.1 ° dKH can be achieved per
measurement.
If not all optimal conditions are met (for example because of smaller sample volume to
consume less reagent), the tolerance becomes slightly higher, typically to about 0.3 ° dKH.
In any case, the measured value resolution is 0.1° dKH.
7.1
What does the measuring tolerance mean in practice?
On closer consideration, it can be concluded that the aforementioned tolerance for the
application does not play a significant role. Why is that?
•
Depending on the source, optimal KH ranges with a range of approx. 1.5 ° dKH are
recommended.
•
Daily KH fluctuations of 2 ° dKH or more are not uncommon and usually do not harm,
whereas exceeding or falling below the optimal range may well be detrimental.
•
Many other conventional measuring methods, e.g. Droplet tests, provide a
reproducibility of 0.5 ° dKH at best under real conditions.
•
When controlling the KH value, it is not important that a certain value of one tenth be
maintained permanently; on the contrary, care should be taken to ensure that the KH
value moves within an optimal range.