KH Director reading is variable

[ss162400]

Hi all,

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

I have recalibrated the pumps multiple times, and have also recalibrated the ph probe multiple times.

Have also flushed unit, vented regent etc. The regent tube is well under 70cm.

The readings are consistently variable, Salifert reading is consistently 7.7;

When I finish the sample pump calibration, KH Director reading is 7.7, but once its readings changed into 8.3, after I recalibrated the sample pump, the reading returned to 7.7. Sometime its reading changed into 7.4 or more low. I need often recalibrated the sample pump, so that I get the right reading.

Basically I need to check the sample pump every three days so that I can guarantee that the reading is correct. What should I do?

By the way, I have 2 units GHL Doser 2.1, I changed the Dosers, but the issue still stand here.

[ss162400]

From the perspective of high-speed performance, Maxi must be better than Doser 2.1, but which one is more stable at high speed? If they are consistent, or MAXI is better. I think I can buy another MAXI to improve my current predicament. Which expert can tell me the actual situation? Thank you!

[Thilo]

The dosing amount is stable on both Doser versions. But the Doser maxi can't be used for the KH Director, because it's dosing amount is too much for the KHD.

Is the KHD measuring 7.7 dKH at the first measurement after calibrating only and the measures 8.3 at each measurement?
You're sure that the measurement cell is empty before every measurement?

[AQUA-digital]

hello.-)
today i check my khd with the dkH reference and it is 7,5 and the second messuring is 7.6. i calibrate the pumps and ph on the 1st of march.
great system.

[ss162400]

The dosing amount is stable on both Doser versions. But the Doser maxi can't be used for the KH Director, because it's dosing amount is too much for the KHD.

Is the KHD measuring 7.7 dKH at the first measurement after calibrating only and the measures 8.3 at each measurement?
You're sure that the measurement cell is empty before every measurement?

Hi Thilo,

Thanks for your timely reply! I am sorry for my late reply.

The KHD measuring reading is 7.7 dKH at the first measurement after calibrating only and Salifert reading also is consistently 7.7dKH.
but the measureing is variable rather than 8.3 dKH at each measurement. sometime it is 8.3 or 7.4 dKH, which is not the definite measurement reading after a few days

I clearly saw that the measurement cell is empty before every measurement.

Every few days, I need the calibrating to be sure the measuring reading is right. I am very confuse.

At once I bought a new GHL Doser 2.1 Pumps Maintenance Set to solve the issue, but the problem remains.

I think the unstable output of Doser 2.1 pump causes the result.

[Thilo]

Hi,

to solve this issue, I think it would be best to continue in our ticket system: https://www.aquariumcomputer.com/support/tickets-enquiries

[ss162400]

Hi,

to solve this issue, I think it would be best to continue in our ticket system: https://www.aquariumcomputer.com/support/tickets-enquiries

I have submit my ticket， and Ticket #596。

[otimer]

Hi,
Have you resolved this problem?
For the reference to others, I'd like to write my experience here.
The symptoms my KHD were very similar with those explained in this thread.

First of all, I calibrated pH probe, and each pump with an accurate mass cylinder.
I performed 1 minute measurement 5 times and devided by 5 to get accurate pump flow rate.
Then I installed a ferite core on the pH probe cable to eliminate any possible electronic noise.
Also, the cable is sagregated from power cables.
And then, I cleaned the three rollers and tube in the pump haed for all 3 pumps.
They were contaminated with some dark dust.

Now it measures in total difference of about 0.3dkh against Hanna ppm alakalinity checker HI755.
My Hanna checker has about 3ppm deviation on measurements of single reagent with 2 vials.
It's same 3 ppm deviation even if same water sample with multiple measurements are performed.
Besides, KHD readings are about 0.3dkh total deviation on multiple measurements one after another.

One thing strange is the offset value +/- 30%.
To make similar readings with those from Hanna checker, the KHD reading changes very small
such as +16% offset changes only 0.2dkh from 6.5dkh(6.5-->6.7) when it is going up,
but only -0.5% offset changes more than 1.0dkh from 8.0dkh (8.0-->7.0) when it is going down.
I expect this is debugged in the future F/W update.

Hope this is helpful to KHD users having similar problem in the future.
Son

[ss162400]

Hi,
Have you resolved this problem?
For the reference to others, I'd like to write my experience here.
The symptoms my KHD were very similar with those explained in this thread.

First of all, I calibrated pH probe, and each pump with an accurate mass cylinder.
I performed 1 minute measurement 5 times and devided by 5 to get accurate pump flow rate.
Then I installed a ferite core on the pH probe cable to eliminate any possible electronic noise.
Also, the cable is sagregated from power cables.
And then, I cleaned the three rollers and tube in the pump haed for all 3 pumps.
They were contaminated with some dark dust.

Now it measures in total difference of about 0.3dkh against Hanna ppm alakalinity checker HI755.
My Hanna checker has about 3ppm deviation on measurements of single reagent with 2 vials.
It's same 3 ppm deviation even if same water sample with multiple measurements are performed.
Besides, KHD readings are about 0.3dkh total deviation on multiple measurements one after another.

One thing strange is the offset value +/- 30%.
To make similar readings with those from Hanna checker, the KHD reading changes very small
such as +16% offset changes only 0.2dkh from 6.5dkh(6.5-->6.7) when it is going up,
but only -0.5% offset changes more than 1.0dkh from 8.0dkh (8.0-->7.0) when it is going down.
I expect this is debugged in the future F/W update.

Hope this is helpful to KHD users having similar problem in the future.
Son

Based on the current output accuracy of GHL Doser 2.1, multiple calibration averages are the only effective measure to approach real readings.