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 Post subject: Calibrating TDS
PostPosted: Fri Dec 30, 2011 2:01 am 
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Does anyone know if it's ok to use pure RO water to calibrate my TDS meter, or do I need to buy the calibration fluid???


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 Post subject: re: Calibrating TDS
PostPosted: Fri Dec 30, 2011 6:21 am 
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Isn't that doing it kinda backwards? How do you know your RO is 0 TDS if your meter isn't calibrated to test it? I would use the solutions as they only cost a few dollars.

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 Post subject: re: Calibrating TDS
PostPosted: Fri Dec 30, 2011 6:29 am 
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Hi BrainDevil,

I think I know what has happened here. You were wanting to do some water maintenance now during the Christmas break and you all of a sudden discovered that you did not have the calibration solution and all the agents were closed, right?

Well, unfortunately, as TTA says, you do need the calibration fluid. If you use RO water the only thing that it tells you is that the reading is 0, but you need a solution that has a fixed value in order to get the meter to measure other solutions in relation to that one.

If it is a broad scale measurement that you are after, you can always leave the meter as it was calibrated before, and go ahead as before. Unless the meter has gone seriously wrong, it should not really be out of calibration that much. If you get calibration solution again, you can say measure the TDS of your aquarium first, then calibrate the meter, and measure it again and then you can see if the error was very large or not. This is inaccurate, but perhaps a solution for your immediate problem.

Bless Bonny Scotland from me, I visit Edinburgh ever so often.

Kind regards,

Dirk

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 Post subject: re: Calibrating TDS
PostPosted: Sun Jan 01, 2012 12:01 am 
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And your R/O may not necessarily be producing 0ppm water, I mean, that's the ideal, but a well used membrane can produce higher ppm water.
No better way put than said by TTA.
Ed

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 Post subject: re: Calibrating TDS
PostPosted: Sun Jan 01, 2012 1:15 am 
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Hi, and thanks for all your replies. I was just checking up on some information that was passed onto me by a supposedly expert(from another forum), and I thought i would get it checked over by the real experts.
My tds meter is working fine and when i come to recalibrate I will buy the calibration fluid. All the things you said make total sense.

Thanks again for all your help. :)


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 Post subject: Re: re: Calibrating TDS
PostPosted: Mon Jan 02, 2012 12:27 am 
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Hi BD.

There's an interesting question or two in there somewhere


One such question could be: "Which kind of calibration fluid is to be used for my purposes, and why that kind ?


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 Post subject: re: Calibrating TDS
PostPosted: Mon Jan 02, 2012 9:43 am 
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Hi BD,

Just in case you were wondering about rag's post, I just want to indicate that rag is one of our very valued moderators who sees to it that not a single scientific theory is not subjected to the utmost scrutiny.

Rag raises a very relevant question and that is that TDS is a measure of how much salt is dissolved in water. TDS is how this is measured in the USA, Canada and the UK, but in Europe it is measured as conductivity. This is a measure of how different ions in solution will allow a current to be conducted by it. Well what we know is that an amount of salt (Sodium chloride) in solution will give a reading of X when we measure this using a TDS meter or a conductivity meter. However, when we take the same amount of potassium chloride (and I mean in terms of the number of potassium chloride ions, i.e. molarity), then the TDS or conductivity measure will not be the same.

So TDS or conductivity measurements give an idea of the contents of water, but the measurements are not able to tell us which ions are actually responsible for the measurements of TDS or conductivity, so this is giving us a glorious average, which is valuable because we do not have to do separate measurements of the contents of each of the salts, but has to be interpreted with care.

Am I interpreting your comment correctly, Dave (rag) or have I missed something?

Kind regards,

Dirk

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 Post subject: re: Calibrating TDS
PostPosted: Mon Jan 02, 2012 7:28 pm 
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My understanding was that the inner workings of a TDS meter are the same as for a conductivity meter but the TDS meter then used a formula which took into account the water temp and converted the micro Siemens into a TDS reading. Of course there is no universal conversion number that really works perfectly especially under different conditions.

Where I find mine most useful is in being able to change TDS for dry and rainy seasons. It also helps to see the difference between what is going into and coming out of my RO/DI unit.

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 Post subject: Re: re: Calibrating TDS
PostPosted: Tue Jan 03, 2012 1:31 am 
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Dirk Bellstedt wrote:
Hi BD,

Just in case you were wondering about rag's post, I just want to indicate that rag is one of our very valued moderators who sees to it that not a single scientific theory is not subjected to the utmost scrutiny.

Rag raises a very relevant question and that is that TDS is a measure of how much salt is dissolved in water. TDS is how this is measured in the USA, Canada and the UK, but in Europe it is measured as conductivity. This is a measure of how different ions in solution will allow a current to be conducted by it. Well what we know is that an amount of salt (Sodium chloride) in solution will give a reading of X when we measure this using a TDS meter or a conductivity meter. However, when we take the same amount of potassium chloride (and I mean in terms of the number of potassium chloride ions, i.e. molarity), then the TDS or conductivity measure will not be the same.

So TDS or conductivity measurements give an idea of the contents of water, but the measurements are not able to tell us which ions are actually responsible for the measurements of TDS or conductivity, so this is giving us a glorious average, which is valuable because we do not have to do separate measurements of the contents of each of the salts, but has to be interpreted with care.

Am I interpreting your comment correctly, Dave (rag) or have I missed something?

Kind regards,

Dirk
Dirk, I had occasion to explore some contentious and absurd claims earlier on wrt conductivity vs TDS meters.

My approach is to determine which questions we are asking of the meter; what is it that we wish to know ? Surely in the hobby, it has very little to do with electricity - it likely has to do with "hardness" in freshwater. It could have to do with "dirtiness" of tankwater.

The meter therefore would read in the range we deal with, and we are often dealing with fish originating in what is called "Natural" - normal or natural river or lake water ( that is, not a bog, not a volcano lake or brackish type of water). As well, often we have natural river/lake water from the municipal water plant.

Different rivers and lakes have different concentration levels, but generally a not dissimilar mix of salts.

The term "Natural", here, is used in reference to 442 solution developed by Myron L. lab, for testing normal water.


http://www.myronl.com/products/solutions.htm

So if we have natural river/lake water and we determine the TDS, we actually have a good idea of which salts and how much, then of how much of any particular salt is in the water ( just as a point of interest ).


Last edited by rag on Tue Jan 03, 2012 1:40 am, edited 2 times in total.

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 Post subject: re: Calibrating TDS
PostPosted: Tue Jan 03, 2012 1:38 am 
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Interesting Info on Link Rag.


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 Post subject: re: Calibrating TDS
PostPosted: Wed Jan 04, 2012 12:26 am 
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Location: Toronto Canada
BD,


Yes, the MyronL link offers good angles to consider for theoretical fun or at least to dispel wrong notions.
In practice, supposing requirments are met for right type of meter, correct calibration, and so on ( one might even get a report from the municipal water authority giving some info on the salts in the water),
it still might come down to just getting the answer for a question like "Is my tank dirtier than it used to be ?"or "Am I making a big change when I add this chemical?"




The answesr to these questions, are of course, relative - not really concerned with absolute values.

Dave


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 Post subject: re: Calibrating TDS
PostPosted: Fri Jan 27, 2012 3:23 pm 
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Most of the meters are dual function; you can toggle between either TDS or EC and some meters display both results simultaneously.
Very cheap meters may only display TDS. I recommend using the dual mode meters. I use this HM Digital EC/TDS Meter
http://www.airwaterice.com/product/HMCO ... Combo.html

Extreme Typhoon III RO/DI Unit 150 gpd info. This kit contains everything except the RO water reservoirs to build an automated shut off RO production system.
http://www.airwaterice.com/product/1EXT ... Meter.html

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 Post subject: re: Calibrating TDS
PostPosted: Sun Jan 29, 2012 6:56 am 
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Other than for those with excess disposable income, I strongly recommend getting the very cheapest meter available that has an auto shut off.
It makes absolutely zero difference whether read as Conductivity or TDS, and all the meters are accurate , far more accurate than we are in our tasks.


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 Post subject: re: Calibrating TDS
PostPosted: Sun Jan 29, 2012 7:32 pm 
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...plus, with a $12 meter, you can replace it easily, so it's an easy choice. Instead of buying a new battery you can buy a new meter.


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 Post subject: re: Calibrating TDS
PostPosted: Sun Jan 29, 2012 7:48 pm 
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Larry, as a point of interesting inquiry; why do you want to know anything about electrical conductivity of the water ?
Is it not so that you may translate the answer into an answer regarding what you are actually asking about ?
Certainly what you are interested in finding out, is not really even about conductivity - right ?
It's about hardness or salt content, or about dirtiness of tank...not conductivity.

The preference of conductivity reading over TDS seems widespread in the discus crew - likely due to the marketing schema.


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