GHL KHD

[Coralqueendom]

Recently got the GHL KHD at the first measurement I took read 11.8 when my Hannah checker reads 9.5. I use reef crystals with no problems and have a hard time believing that my tank is running at 10-11DKH. I contacted GHL and they basically said that Hannah is cheap and not as accurate as the GHL which I believe is true but I don’t want to adjust my system to 11.8 if it’s not really that. I ordered reference solution but not Sure how to use it yet I’m sure I can figure it out once it gets here. I know you can adjust the disparity between the testing method you usually use and the GHL but if the GHL is really that much more superior in accuracy than I would prefer to adjust to its levels. I also I’m having a hard time figuring out what adaptive control motors and how to properly set up a dosing schedule so I can completely control my alkalinity.

 

[vangvace]

For the reference solution, you'll pour some of the solution into a container and submerge the sample line into it. Manually run the KHD through a test. The results will tell you how high or low your readings are on the GHL device. Say you are using the default 80ml sample I would recommend 100ml or 120ml of sample fluid just to avoid air in the line.

To use the same reference solution in the Hanna, I want to say it is RO water in the first cuvette, and the reference solution in the second.

For setting up the adaptive control I'm going to ping @Ditto and @Vinny@GHLUSA to chime in for better assistance.

 

[Coralqueendom]

For the reference solution, you'll pour some of the solution into a container and submerge the sample line into it. Manually run the KHD through a test. The results will tell you how high or low your readings are on the GHL device. Say you are using the default 80ml sample I would recommend 100ml or 120ml of sample fluid just to avoid air in the line.

To use the same reference solution in the Hanna, I want to say it is RO water in the first cuvette, and the reference solution in the second.

For setting up the adaptive control I'm going to ping @Ditto and @Vinny@GHLUSA to chime in for better assistance.

Thank you for the advice on the reference solution and checking with the Hannah checker. Do you know what the best way is to set up a dosing schedule? Do I leave it in measurement only mode for a couple of days and just watch how fast it drops and then add up how many milliliters it would take to correct it and divide? And you’re saying that Using a bigger sample of water makes it more accurate and less likely to get bubbles?

 

[Lasse]

First measurements is often out of line. Have ou done more tests?

Sincerely Lasse

 

[Coralqueendom]

First measurements is often out of line. Have ou done more tests?

Sincerely Lasse

It has run about 20 times so far and emptied and flushed and measured again

 

[Lasse]

OK

I would use some titration test in order to have a third opinion on KH. Like Saliferts and Red Seas Pro KH tests, With Red Seas pro test - read exactly when it turns to green and have it stable.

Sincerely Lasse

 

[Coralqueendom]

OK

I would use some titration test in order to have a third opinion on KH. Like Saliferts and Red Seas Pro KH tests, With Red Seas pro test - read exactly when it turns to green and have it stable.

Sincerely Lasse

I tested in comparison to Hannah and Salifert and Hannah reads 9.5 GHL reads 10.8-11.2

 

[vangvace]

Thank you for the advice on the reference solution and checking with the Hannah checker. Do you know what the best way is to set up a dosing schedule? Do I leave it in measurement only mode for a couple of days and just watch how fast it drops and then add up how many milliliters it would take to correct it and divide? And you’re saying that Using a bigger sample of water makes it more accurate and less likely to get bubbles?

I wouldn't feel comfortable answering too many dosing schedule questions as I run a reactor. The only dosing I do is phyto where I have it dose 0.1ml 4x a day.

Oh, what I was saying is when you run the reference solution test, use extra fluid in the test container the sample line is going to draw from to avoid bubbles. You could technically insert the sample line directly into the reference solution bottle, but then it is contaminated if you wanted to test again further down the road.

Lasse does bring up a good point that the first test or two of a new Director is off.

The final thing to also double check is the volume of water in the sample hose by using a graduated cylinder. To preform the check:

1. Disconnect the sample line from the KHD input screw fitting.
2. On the doser, manually activate the pump to fill the tubing completely.
3. Remove the sample line input from the tank.
4. Place the sample line output disconnected in step 1 into the graduated cylinder.
5. On the doser, manually activate the pump to empty the tubing completely.
6. Verify cylinder volume matches in the GHL app.
7. return the sample tubing to normal

 

[Lasse]

I would also do a new calibration of the pH meter. Many pH meters I have used normally change a little after the first time. I always re-calibrate a new pH probe after one week of running. What do your Salifert show? I also use a scale in order to calibrate the pumps. I do at least three calibrations in a row and take the average of them.

Sincerely Lasse

 

[robbyg]

On a side note, there is no way the Hanna is off by that much. Many people have compared the Hanna to other standards and it does not vary by a full 2 dKH. Seeing a .3dKH to .5dKH difference would be the most I would expect.

 

[Coralqueendom]

On a side note, there is no way the Hanna is off by that much. Many people have compared the Hanna to other standards and it does not vary by a full 2 dKH. Seeing a .3dKH to .5dKH difference would be the most I would expect.

Yes that is exactly what I thought as well. And my Hannah is calibrated. It is a major disparity and when I contacted GHL and I asked them about it after I had calibrated three times and checked three times they said to go with the reading that was coming off of the GHL because it wasn’t more than .2 off of each reading from the GHL. But Hannah continued to read low

 

[Coralqueendom]

I would also do a new calibration of the pH meter. Many pH meters I have used normally change a little after the first time. I always re-calibrate a new pH probe after one week of running. What do your Salifert show? I also use a scale in order to calibrate the pumps. I do at least three calibrations in a row and take the average of them.

Sincerely Lasse

I have calibrated each pump multiple times and I get the same measurements each time so I know that they are properly calibrated

 

[robbyg]

He is saying that you should recalibrate the pH probe not the pump. If the probe is not calibrated properly all your readings will be consistently off.

 

[AquaPhilNJ]

The reagent pump needs to be very accurate, and should be set to the slowest settings. For calibration to even be possible for this pumps you would need a 5 ml graduated cylinder capable of measuring tenths of an ml.
For water sample dosing pump (where fastest settings is 50ml per minute) accuracy is less important, nonetheless make sure your water sample settings is accurate. Instead of measuring with a ruler try pinching tube then releasing water over and into a graduated cylinder thus measuring volume of water more accurately.

 

[Lasse]

For calibration to even be possible for this pumps you would need a 5 ml graduated cylinder capable of measuring tenths of an ml.

Ore a scale showing 0.1 g and multiply calibration in a row. Without reading for each calibration. If you had the pump run for - as an example - 5 times * 1 minute - take the result and divide with 5.

Sincerely Lasse

 

[Ditto]

When calibrating the pumps I did exactly what Lasse did. I did each one on the KH based on the settings of the pump. I ran each one 5 times and the. Divided the results by 5 and put the number in. I then at the end ran 5 more test After I set the pump and took the readings if they were all the same I knew I had nailed the settings and done the calibration correctly.

Ones my KH was up and running and let it monitor the tank for almost 3 months before turning on any form of adaptive controls.

I started at adaptive control but at the end settled on add on control. I determine how much I needed to raise my KH by 1 divided that by how many doses a day my tank does and placed the value into the value.

I like adaptive but I had some swinging during water changes that I felt add on did a better job controlling. Again each tank is different so I tell people try the one they feel will work better for them.

On my qt tank adaptive is used, because the changes are so so tiny on it.

Hope this helps

 

[KenO]

What is the flow rate and speed setting of your reagent Pump? I had something similar happening with my one KHD and the flow rate was off. The other possibility is your measurement setting for the sample line with the filter. I also had the number incorrect on my other khd and was getting a high KH reading. Now a third possibility is the mixing pump inside the KHD. I had a mixing pump go bad. How noisy is your unit? Since I have 2 KHD’s it was easy to hear the difference. I have a video

Here are the flow rates and speed settings of my reagent lines.