PDA

View Full Version : KH Director Measurements



mlandscape
20.04.2020, 15:21
I set up my new KHD yesterday having followed the 3 part Youtube videos.

The first test failed "OK Error: Titration takes too long " which I wasnt too concerned about.

The second test read 8.4 and subsequently dropped at the next measurement to 8.3 from where it has remained on a schedule of 4 measurements over 24 hours.

Firstly I was not expecting the reading to be over 8 and so stable as my regular Hanna readings have been 7.7 to 7.4 and my last ATI lab test two months ago was 7.74.

I don't have a problem with it being 8.3 and so stable in fact it is preferable but I need to be certain that it is measuring accurately

Despite following the videos on Youtube about the length of the water sample tube I have subsequently found on this forum that I should have also included the tube length from the doser pump to the KHD which it doesn't mention in the videos.

I have now corrected that measurement in the setup but apart from altering the sample tube volume to 21 ml, there is no change in the measurement still reading 8.3 and steady.
I would expect at least some change in measurement over a 24 hour period.

Can someone please advise their thoughts on this, please

Vinny
20.04.2020, 22:09
Hi there,

The measurement of the dosing tube is mentioned at 5:05 in part 3 of the setup video. That is when it tells you the length of that tube.

If you are 100% sure the length of the water sample tube (including the 7ml from water filter) is correct, then I'd suggest verifying that by temporarily disconnecting the water sample tube that is going INTO the KHD. Manually run that pump head so that both ends of the tube are completely filled with water. Once filled, take the tube out of the sump and let it hang out in the air. Manually run the pump again and measure how much water comes out of the tube. That amount should match what was calculated. If it does not, enter in the provided amount.

Another thing to check is your KHD probe calibration.
Did you dip the probe in each pH 4 and 7 fluids to see if the displayed value is within +/- 0.2?
If not, I would try this.
If the displayed value is outside of the acceptable range (+/- 0.2), recalibrate the probe.

Hanna checkers have shown to provide varying values depending on the age of the reagent powder. A two month old ATI test would not carry much significance here since you're testing today and does not factor-in daily KH swings.

After you've done the above, if the readings are still "off" and you would rather see numbers you're more accustomed to, use the adjustment tool.

mlandscape
20.04.2020, 22:39
Hello Vinny and thanks for the reply. Firstly can I just say that ideally I dont want to use the adjustment tool as I happy to use the measurements from the KHD as long as I am sure that they are accurate and the fact that they are always the same is not the sign of a problem - another measuremet just took place and now gone from 8.3 to 8.4 which is the first alteration since the start.

I have watched the video a number of times and unless I am mistaken it doesn't specifically mention to add the tube length from the pump to the KHD and certainly doesnt mention what you have just mentioned ie adding 7ml for the filter so can I just clarify it all to be absolutely clear that I am measuring correctly. I have the filter part way along the tube from the sump to the doser. So I should measure the length of tube from the sump end to the filter connection, then from the other side of the filter to the doser, then add 4.7 inches for the tube in the doser head, then from the doser to the KHD. When I have added all those together I place them in the calculator to get the result and whatever that is I add 7ml to it for the filter??

Depending on your clarification on that point if needed I will go through your other suggestion.

I must admit I did not check the calibration which I can do.

Many thanks

Vinny
20.04.2020, 22:50
You have to measure all external tubing which is involved in the water sample line. Otherwise, the KHD won't know how many ml is actually in the tube.

From sump to filter
From filter to pump
Dosing tube inside head (4.7")
From pump head to KHD
Add 7ml to calculated total for water filter

mlandscape
20.04.2020, 22:54
OK Vinny thanks for clarifying all that. I will recheck tomorrow and adjust if necessary and also check probe calibration in both solutions

Thanks for your help

mlandscape
21.04.2020, 14:00
Hello Vinny. Firstly having reread your last post about which lengths to measure I assume you meant on line 2 "From filter to pump"

I have firstly recalibrated the probes and after checked in each solution. In solution 4 it read 3.97 and solution 7 it read 7.01 I know that the 4 solution is marginally outside of the 0.2 acceptable range but due to time I had at that stage did not recalibrate further. This I can do if you really feel it is a major problem.

I then measured the sample tube length:- ( I should add that in these measurements I have included any tubing length that overlaps onto the connectors to the filter, pump and KHD rather than to where the connector starts.)

From sump to filter 7.5 in
From Filter to pump 44.5 in
Dosing tube inside head 4.7 in
From pump head to KHD 6.3 in which is the length I was advised to use in the video.

This gives a total length of 63 in which I then put into the calculator which gave a sample tube volume of 20ml to which I added 7ml for the filter and saved. That gave a sample tube volume of 27mm with a subsequent reading of 8.8 which is even higher than 8.4 at 10 pm last night and 4 am this morning.

I then decided to complete your verification check process to establish how much water was in the sample tubing and that surprisingly only gave me 22ml so I changed the 27ml volume to 22ml and carried a further measurement which was 11.3 !!! which is no way correct.

I have now changed it back to the 27 ml as per the calculator and it is measuring 8.4 which is back to where it was before I recalibrated and remeasured the sample water tubing.

Maybe it was alright in the first place? From what you have read do you feel able to give me some reassurance that all is operating OK and readings are as accurate as you would expect from the KHD? I have always understood to expect some variation in measurement over a 24 hour period - would you expect that yourself?

Many thanks

Vinny
21.04.2020, 18:00
Yes, it should have read "pumps". :)

As long as the KHD values are consistently testing within +/- 0.2 dkH of each other, the device is providing stable results.

mlandscape
21.04.2020, 18:20
Thanks - so just to be clear are you saying that you wouldn't expect the dkH to vary +/- 0.2 over a 24hr period?

Vinny
21.04.2020, 18:25
I'm saying the acceptable tolerance is +/- 0.2 which means whatever value the KHD provides may actually be +/- 0.2 higher or lower. Any swing is possible with the tank itself since multiple variables are at play.

mlandscape
21.04.2020, 18:28
Right OK, thanks Vinnie for your help.

I have a number of other questions/queries that has come over the last few days since I have been using GHL so I will send you an email with those in rather than keep adding different questions on here. Is that OK Thanks

Vinny
21.04.2020, 18:44
If they are all related to the same product and requires technical assistance, please create a support ticket.

mlandscape
21.04.2020, 19:19
They are more general questions about P4 display icons, GHL ID's and GCC Devices.

Vinny
21.04.2020, 19:42
Okay so you can post them in the forum then. :)

mlandscape
22.04.2020, 10:58
OK will do in due course