KH Readings Low

Hi all,

I am having problems with the reading from my KH director.

The readings are consistently low, KH director is 6.3, Hanna checker is 8.68. I have also check with Redsea manually.

I previously had the KH director attached to my profilux 3ex and it worked fine as far the readings compared to the hanna.

I have now swapped the 3 over to the 4.

I have recalibrated the pumps multiple times, remeasured the tubing and have double checked the tubing calculator and have also measured what is in the supply line.

Have also recalibrated the ph probe multiple times and have confirmed the calibration reading back in the solution.

Have also flushed unit, vented regent etc. The regent tube is well under 70cm and has no visibleAttachment 11432Attachment 11433 bubbles.



Pics of setup and control centre.

Anyone got any ideas on whats going on?

If the readings are consistent, the KH Director is working correctly. What are the flow rates of the pumps?

You could ajdust the displayed measured value with the input at the top right of the KH Director settings page.

hi,

pump 1 is 40ml (Fast), pump 2 is 4ml (slow), pump 3 is 39ml (fast).

Yes I guess i could change the displayed measurement, although would be good to understand why it is not correct without such a large adjustment.

I think it's the calibration of the dosing pumps. With a flowrate of 4ml/min. at slow speed, it should be near 32ml/min. at fast speed.
We recommend using a very precise measurement tool. A micro scales would be a good option.

Very interesting that you mention after switching from P3 to P4 you getting lower reading!! I am having exactly the same problem! pump calibrated several times using digital scale. So this is not a calibration error. Order reference solution from GHLL USA 8 days ago and still my order hasnt been shipped yet:(
I suspect internal issue with DKH:((

Quote:

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Originally Posted by mshur

Very interesting that you mention after switching from P3 to P4 you getting lower reading!! I am having exactly the same problem! pump calibrated several times using digital scale. So this is not a calibration error. Order reference solution from GHLL USA 8 days ago and still my order hasnt been shipped yet:(
I suspect internal issue with DKH:((

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And you also have recalibrated the pH-probe?

Of course ! Probe calibrated and show correct PH calibration fluid


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When measuring and calculating the sample hose length for volume, are you including the 4" for the line in the dosing pump head?
Also make sure to mine the tubing ID, the hose GHL provides is 4mm ID, if you use RO or US Vinyl/Poly Vinyl tubing, it may be 1/8"(0.125") ID ... 3.175mm ID

Are the flowrates you've measured while calibrating the soing pumps the same as on the ProfiLux 3?

Quote:

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Originally Posted by Thilo

Are the flowrates you've measured while calibrating the soing pumps the same as on the ProfiLux 3?

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First pump is different since i change length of the tubing. others are the same

And which flowrates do you actually have set on the pumps?

Quote:

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Originally Posted by Thilo

Are the flowrates you've measured while calibrating the soing pumps the same as on the ProfiLux 3?

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https://uploads.tapatalk-cdn.com/201...9c0c86fdb8.jpg
https://uploads.tapatalk-cdn.com/201...97dd24be72.jpg
https://uploads.tapatalk-cdn.com/201...5f0f84818b.jpg



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Thanks for the Screenshots. The flowrates seem to be ok.
Is the Firmware of the ProfiLux 4 and the Doser 2 up to date?

Yes of course .



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I guess, that the flowrate of the water sample or reagent pump is not 100% correct, a slight deviation can cause this issue. But to avoid another calibration, I recommend using the "Adjust displayed measured value"-function, if the deviation is steady.

Hi,

Unfortunately I need to report the similar behaviour of KH director, something that makes "adjust displayed measured value " correction hard to use. Specs of the installation below:
- Reagent tube length 70cm, using the one which came with the 3x1000ml reagent set
- Total sample tube volume 27ml and testing volume 80ml
- pH probe double calibrated and afterwards tested in calibration fluids to give exactly 4 and 7
- Flowrates have been triple calibrated for sample and reagent (37ml and 4.8ml/min, respectively)

With this setup I do get consistently low values. I have been now repeatedly testing ATI reference solution (7.5 dKH) and my aquarium system water (as drawn from quite sump region). I have tested everything with Salifert KH test as well.

Reference solution (7.5dKH)
Salifert: 8.3 dKH
Director: 6.3 dKH

Aquarium water:
Salifert: 6.1 dKH
Director: 5.5 dKH

All tests have now been done triple over couple of days. Aquarium test results naturally vary a bit as there is very heavy use of alkalinity. However, same tendency continues. Director gives constantly low values, and it seems, Salifert goes over. Where is acceptable truth... that is troubling. Most troubling is that director is off by (-)1.2dKH when compared to reference solution. Is this just something to be accepted and put like +19% correction into the GHL control center which means that reference solution would give 7.49dKH. Problem is that Salifert and director seem to differ more if the sample to be tested has higher KH. If I implement that +19% into GHL control center and test aquarium water director would give 6,5 whereas Salifert gives 6.1... meaning that correction would cause director to shoot over even Salifert which otherwise always seems to go over. Therefore... what would be reasonable correction if one cannot deduce it from reference solution?

Quote:

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Originally Posted by samwise

Hi,

Unfortunately I need to report the similar behaviour of KH director, something that makes "adjust displayed measured value " correction hard to use. Specs of the installation below:
- Reagent tube length 70cm, using the one which came with the 3x1000ml reagent set
- Total sample tube volume 27ml and testing volume 80ml
- pH probe double calibrated and afterwards tested in calibration fluids to give exactly 4 and 7
- Flowrates have been triple calibrated for sample and reagent (37ml and 4.8ml/min, respectively)

With this setup I do get consistently low values. I have been now repeatedly testing ATI reference solution (7.5 dKH) and my aquarium system water (as drawn from quite sump region). I have tested everything with Salifert KH test as well.

Reference solution (7.5dKH)
Salifert: 8.3 dKH
Director: 6.3 dKH

Aquarium water:
Salifert: 6.1 dKH
Director: 5.5 dKH

All tests have now been done triple over couple of days. Aquarium test results naturally vary a bit as there is very heavy use of alkalinity. However, same tendency continues. Director gives constantly low values, and it seems, Salifert goes over. Where is acceptable truth... that is troubling. Most troubling is that director is off by (-)1.2dKH when compared to reference solution. Is this just something to be accepted and put like +19% correction into the GHL control center which means that reference solution would give 7.49dKH. Problem is that Salifert and director seem to differ more if the sample to be tested has higher KH. If I implement that +19% into GHL control center and test aquarium water director would give 6,5 whereas Salifert gives 6.1... meaning that correction would cause director to shoot over even Salifert which otherwise always seems to go over. Therefore... what would be reasonable correction if one cannot deduce it from reference solution?

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Have you tried cross-checking the reference solution itself with another test kit?
Maybe the test kit is expired or reference solution is contaminated. This however, cannot be verified unless you try testing with another kit or use a fresh bottle of solution.

As for the KHD, you mention the flow rates of your sample and reagent, but not the waste water pump. This is an important variable too.

• Flow rate of waste water pump?

What is the total length of the water sample tube?

Did you include all 3 pieces of tube when measuring?

• From tank to water sample pump
• Tube that goes around the pump head itself
• From sample pump to KHD

Lastly, what is the actual water sample size you are using to test with?

Hi, and thanks for your answer.

No I don't have direct access to another test kit, but this is not expired one. It is valid until end of 2020 and opened just few months ago. And I did not notice any drastic change in KH when previous kit ran out and I opened this one, so I don't have any reason to suspect it to be different from previous kit. And reference solution contamination, well, it is brand new just opened to test and calibrate KHD. I can look for possibility to cross-check it. However, even if it would be "wrong" like some mistake in producing that solution it would not solve this puzzle because it would still have some specific KH value and does not change the fact that Salifert and Director fundamentally differ in their opinion what that value is. Like they differ in their opinion about my tank KH value. Thus logically this requires two failures, both in either Salifert kit or KHD, and in addition "contaminated" reference. I would say this is not most probable answer. Also given the fact that both Salifert and Director react nicely when I add NaHCO3 to the tank, both report about equivalent increase, means that in principle they work but they differ in "base line". But yeah, there are not very many logical possibilities here, multiple things need to fail.

KHD waste water pump has been calibrated and does have same flowrate as default: 40ml/min

And I do test the default 80ml, haven't touched that at all.

Total sample tube length 161cm which equals to volume of 20ml and inline filter adds 7ml. This includes tube from sump to inline filter, from filter to doser head and from head to KHD. HOWEVER, I haven't added the length of tube around the doser head. English version of manual does not say anything about that. Manual tells that inline filter is 7ml and is also reminds to take into account the tube betwee doser and KHD, but is does not say anything about the tube around doser head. I though of this when I did the setup, and considered to measure the tube inside doser head, but then I figured that its inside diameter is not going to be 4mm anyhow (like other tubes) because of its strong ability to contract, and because manual doesn't say anything about it and it will always be present in all installations this is likely thought to be constant and built in the internal math of KHD or be within error tolerance. So now that you ask it, it is clear that it should be added but how much that is? Length I can measure with reasonable precision but what is the inner diameter? On average it must be less than 4mm?

Hello Sami,

in order to get this sorted out, open a support ticket, where we can go into detail and help you much better setting things up correctly.
You can also provide your controller configuration as backup file (Settings.par) and attach it there.

https://www.aquariumcomputer.com/sup...ets-enquiries/

I have the same issue.
Reading kh director 7.8
Hanna 9.6
Salifert 9.6
All have checked with reference liquid

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