Trying to setup a brand new KHD with doser 2.1 SA and connect to a Profilux 4. Everything is connected and setup as instructed in manual, doser set as slave of course, and setup mechanically. Khd/doser performs test - but values are to low according to ref solution.

With ref solution (7,5 dkh) I get 5.8-5.9 - the value is constant - I've used almost 1000 ml to perform multiple test in a row and cant figure out why it wont give me correct value.

So far..

Probe - calibrated several times.

Water sample hose - I have different diameters on some of the tubes so I filled the entire hose incl pipes, filter, doser hose etc and measured the volym. This is the volym I've entered into GCC when registering "sample tube volym" - it's 46 ml.

Doserheads are all calibrated several times.

Cleaned rolls on doser pump 3 since it made alot of noise and got stuck. Based on my observations it works fine now.

Sample volum is set to 100 ml.

What else could I try to get more accurate test results?

When measuring aquarium water the margin is 0,9-1,1 – For example KHD sats 7,7 when all other tests says 8,6-8,8

How is this possible?

Tests are done after fresh calibration session and the only thing in between is emptying cell and flushing cell with «new» liquid (the same that are going to be tested).

I assumed margin of error would be bigger with aquarium water than ref soution since it could bring some problems as micro bubbles etc could «polute» the test water.

/ Andre.