KH Director only reads Zero

[Conor_K]

Welp, time to ask for some help…

Hooked up my new to me KHD a week or so ago.
New doser. Run via P4.

First test went fine. Measured lower than expected at 7.8, but it was just the first test.

Every test since then has resulted in a 0 dKh reading.

I’ve remeasured tubes/recalibrated pumps, calibrated ph Probe multiple times.

Test seems to be running as expected.
Titrating down to 4.3-4.5 pH.
Tubes are filling/clearing as they should.

I feel like this is a software/hardware issue at this point. Anyone expeeience this before?

Appreciate the help. Pics of the test i just ran right before titration began and when it finished.

@Lasse @Vinny@GHLUSA @BeanAnimal

 

[Lasse]

Your pH probe seems be calibrated as it should - around 20 000 between the endpoints. When titration start - do you hear the internal pump working? The tube from the venture connection - does it end in the air? If it end below water surface in the waste container it will suck in water in the chamber when you empty the chamber. I would submit a ticket Use guest log in

Sincerely Lasse

 

[Conor_K]

Internal Pump seems to be working.
I can hear it and feel it running.
Both waste line and emergency vent line are above water line.
Ticket will be the next step.
I was just hoping someone might have gone through this before and it was some setting or something I missed.

 

[Lasse]

If you do a test - look att the pH during titration - it should go down in a steady rate - rather fast to around 5.4 - slow between that and around 4.8 - a little bit faster the last step. I have had zero or rather low values but in that case - pH was erratic up and down. Check also the BNC connection between pH electrode and the director.

Also - the electrode should be insert until it stops and I try to have the text facing up. It means that the gap around the glass will be vertical. Do not know if it matter - but I use to mount it that way. See picture

Sincerely Lasse

 

[Conor_K]

That seems to be the pattern with my PH.
Going to run another now just to be sure.

Check and check on the probe. I actually ready through your thread where you opened one up (amongst any other thread I could find this week looking for an easy answer) and oriented the probe as such.

 

[Lasse]

Is there any strong magnetic or electrical field near the electrode cable (PSU or anything else that can create electrical disturbances?

Sincerely Lasse

 

[meermann]

@Lasse @Vinny@GHLUSA

I’m experiencing the same issue - my KHD consistently shows 0. A month ago, I replaced the main board because the old one was damaged by salt. It worked fine for a month, but now it only measures zeroes.

I’ve recalibrated the pH probe and positioned it as @Lasse recommended. I also moved all the cables away from the sensor cable to avoid signal interference. The internal pump seems to work - at least I can hear it running. Additionally, both vent tubes are positioned above the drain water surface. Previously, I had some incidents where the drain tubes sucked a bit of water back in. While this lowered the measurements, they never dropped to zero.

I did notice something unusual during titration: the pH falls to 4.3. Previously, it never dropped below 4.4 (I believe it stops adding the reagent at 4.45). Could it be adding an excessive amount of reagent? I recalibrated the pumps as well, but there’s a "valve" inside that presses or releases the hose. Could it be malfunctioning?

What else could I check or adjust? Should I replace the probe?

 

[meermann]

@Lasse @Vinny@GHLUSA

Huh, I also read this thread and decided to disconnect all the devices from my P4, then reset the PAB. After that, I reconnected them one by one, and suddenly KHD started measuring correctly again.

However, I noticed the lower limit of the pH is now still 4.3, whereas it used to be 4.4. I also found that the probe reacts to pH changes more slowly than before. It now takes a few minutes to calibrate, whereas previously it was very quick, maybe 20-30 seconds only.

I also remembered that once my Doser got stuck and made an annoying sound. I just pressed "Cancel Current Action" on the KHD. Perhaps the reaction chamber was full of acidic water—I'm not sure 100%. I replaced the Doser within a week or so. Could prolonged exposure to acidic water have affected the probe or made it slower than usual?