tds/conductivity

[DonW]

Is there standard conversion between the two or is it just based on the meter. Is there a dilution formula to measure seawater on a low range us/cm 1-1999 meter.

Thanks
Don

 

[Boomer]

Yes Don there is, KINDA . Converting TDS or uS is a complicated non- linear equation. Meaning, that as there is an increase in conductivtiy the conversion to TDS is different. For seawater levels it is about 66 % of the uS or mS level. In general, for lake stream waters it is about 50 %. And as you get to RO/DI it is less than 50 %, all ythat based on the NaCl scale. If you choose the 442 scale it is even different, which is the scale we should be using for TDS for any water we are measuring, as it is a natural waer scale. But 99% of the people in this hobby have meters set to NaCl, which is the industry std for TDS. However, the seawater std is set to a KCl scale, so all your measurements should be based on KCl for dilution but you could use any of the scales, as long as you know where you are at.

As far as dilution goes no, never seen or heard of any. However, one could make-up a converison by testing. Such a conversion would only be for you only and your choice of salt.

If you look at this you will see what I mean. Take note of Table 2

What is TDS?
http://www.reefkeeping.com/issues/2004-04/rhf/feature/index.php

 

[Scooterman]

I like how he starts off with yea Kinda, then jumps in Hanging around in case I learn something

 

[DonW]

Thanks boomer,
To make a long story short I figured out that the first 700 ml comming from my rodi system actualy had a tds of 55. Since I had it hooked to a ato in the sump it would only dose 500ml at a time due to the sensitivity of the float switch and the small sump return area. I thought cool I had this under control with a automated dump based on tds. Wrong, the initial pressure would push the water in so fast the tds controller would always see 0 and had not time to calculate the tds. Going back over the tracking, it worked only once in a blue moon. I accidently destroyed that tds controler along with a bucket full of other controlers and swapped it out for a real conductivity controller set to 0. Needless to say it now dumps every cycle for exactly 750ml. The only reason I figured this out was that my tank just out of the blue started doing great. All I did was replace the sump to one with no baffles and temporarily remove the ato. My tds lesson learned the hard way.
Now I looking more uses for the conductivity controllers I have in the attic.

Don


Don

 

[Scooterman]

Don what type of TDS controller are you using?. How does it work, does it stop making water when you get too high of a reading?

 

[DonW]

Don what type of TDS controller are you using?. How does it work, does it stop making water when you get too high of a reading?

I'm using hanna mini panel and omega mini panel conductivity not tds. Basicly the conductivity controller triggers two solenoids. One goes to waste the other to the sump. If cond. is not zero then it goes to waste else it goes to the sump. No automation controller need for this part. Very simple.

Don

 

[Boomer]

Yes Don EC meters need a steady flow or at least the probe has to be in water constantly otherwise they go to zero. Expensive one are more forgiving and can read faster, something called "response time" .Matter of fact, a way to check your EC or TDS meter, is to pull the probe out of water and shake it off or air dry it and it should read zero. Sometimes just pulling the probe out of water will make it say zero.

How come your RO/DI TDS is so high 55 ppm TDS


Also you said you bought a " real conductivity controller "are you sure Real ones are big bucks and use "cells" Or do you mean it is in uS and not TDS or can be switched to uS ? I wish we could get people into uS, mS, that way we all would be on the same page.

Here is a short not to deep article on EC

http://www.wileywater.com/Contributor/Sample_2.htm

Here is another one that is much longer
http://www.jp.horiba.com/story_e/conductivity/conductivity_02.htm

I might add that most of the hand-held TDS meters people use in this hobby for tap, RO, RO/DI water belong in the attic or should be filed under "G". Meaning, they can only be used to test for RO/DI output. So, if reads anything other than zero it is time to change the DI. They are about useless for doing tap, RO. Why ? Their accuracy is 1- 2 % full scale, so if the meter goes to say 1, 000 ppm TDS, it may be off 10-20 ppm, no matter what water it is in, other than Pure RO/DI. So, it is only good if it reads zero The only one that is worth a dam is the new HM Digital COM-100 for about $65.

http://www.tdsmeter.com/products/com100.html

On another note; I have been doing some looking for "real" seawater refracts and have found 2. One is $200 the other just less than $100. A friend of mine will be selling the $100 ones maybe by next week. No, I get no kicks-backs, I do things for free He can get those HM Digital COM-100 also but I do know what the price will be. That would be thefilterguys.

 

[Boomer]

Ok, Don I see you have a Hanna and a Omega. More than likely that Omega was made by Hanna. Omega makes nothing, they are just like Cole-Parmer.

Are these the ones ?

http://www.omega.com/ppt/pptsc_lg.asp?ref=CDCN201&Nav=

http://www.davis.com/showpage.asp?L3ID=1839

 

[Scooterman]

Boomer I hear you on the hand held, If I get any reading on my hana, I usually start changing filters, my water outlet pressure usually drops about the same time, so then I change the pre & carbon filters & retest & may then change the DI if necessary, regardless of what color it is because I'm about half color blind when it comes to these anyway. I'm looking for something I should use like the one you just posted the com 100, I saw that one last week, should I also install the HM for the RO/DI in-line also?

 

[DonW]

Ok, Don I see you have a Hanna and a Omega. More than likely that Omega was made by Hanna. Omega makes nothing, they are just like Cole-Parmer.

Are these the ones ?


http://www.omega.com/ppt/pptsc_lg.asp?ref=CDCN201&Nav=

http://www.davis.com/showpage.asp?L3ID=1839

Yup! those are the ones. I've got 3 of each. By real ones I mean us/cm not tds. Not really "us" but I dont know how to make the proper symbol on a keyboard. You always get high tds water at first start up of a rodi then it falls to zero. But when all I was adding was the initail shot (5-700ml) of high tds its was kind of a waste.

Don

 

[Boomer]

Ok Don, you did good those are fine. And "real ones", just the probe is $400 :lol:

Scoot

should I also install the HM for the RO/DI in-line also

That is up to you, just so you know that it is 2% of scale or the potiental of a 20 ppm error. These or cheap meters are only good if you look at the numbers given as meaninless values and you are just looking for a shift in the number. Again, on the DI output, if it goes higher than 0 ppm TDS time to change the resin. Don's are the same, 2% of FS ( Full Scale of Scale). You will never get better than 1 -2% full scale (or selected scale if it has more than one scale) unless you get a really expensive one which are like 2% Of Reading (OR). Meaning if it read 10 ppm, on a 10 ppm scale, it may be off 2% of 10 ppm or .2 ppm. But you are talking $1,000 - $2,000 and these are "cell" units.

Like this one for almost 2 grand

 

[Scooterman]

Nope Don't think I need to spend 2K to make the same decision, usually I change them when I get a reading other than "0" & from what it seems I'll stick to that. Thanks For the info. Boomer!

 

[Boomer]

That HM COM-100 will tell you about anything you need. On its low scale it may be in error 1-2 ppm and has a "real" temp probe. It does no play with air temp like the others

 

[Scooterman]

Using the Com-100 TDS meter?
Quote:
Originally Posted by DonW
Id get seperate meters. com100 tds and pinpoint ph and if desired pinpoint salinity.

Don

Quote:
Originally Posted by Scooterman
http://www.tdsmeter.com/products/com100.html

I got my HM Com-100 EC/TDS/Temp Combo Meter in as well as some TDS 342 ppm Calibration Solution as you and Don recommended.

Calibrating the unit looks self-explanatory as the manual handles that well. My questions is how do you use it to test your RO water? I noticed that there are 3- EC modes and 3- TDS modes. I'm assuming that I will be using the TDS setting first of all but which mode (KCl, 442, or NaCl)? Is there anything that I should know before I begin using it besides making sure there are no air bubbles trapped on the electrodes but swirling? Also, are there any other uses for aquarium testing that you use it besides testing the quality of your RO water?

FYI: I was able to pickup the Com-100 meter new for $49.99 shipped and two 3 oz. bottles of 342 ppm solution for $15 shipped. My Pinpoint pH monitor should be coming in today. I was able to pick it up for $81 shipped.

Thanks,
Dennis

I thought this would be a good place to post these questions so we can the proper answers.

 

[Boomer]

Scoot

That was me that recommended the HM-COM-100

It has 3 scales and 3 ranges

Scales

1. 442 ppm TDS. To be used for FW for the most accurtate readings to include tap, RO, RO/DI

2. NaCl ppm TDS. What most TDS meters are set to.

3. KaCl ppm TDS. Do not bother with this scale

4. µS or mS This is a true conbducivity reading. It is this reading that is converted to 1,2 and 3 to TDS in ppm as 442 , NaCl or KCl.

Ranges

[FONT=Verdana, Arial, Helvetica, sans-serif]Low = 0-99: 0.1 µS/or ppm [/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Med = 100-999: 1 µS or ppm [/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]High= 1000-9990 10 µS orppm[/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]. [/FONT]

TDS 342 ppm

Set meter to Med range and cal the meter to read 342 ppm NaCl (scale) TDS. Then switch the meter to the Low range and select the 442 scale. This is for for post RO and post DI 0-100 ppm. For tap water use the 442 scale and Mid range, 100-999 ppm.

Note: The 342 ppm is fine for tap water, lakes and stream water. For a more accurate readings for RO, RO/DI you should look for a cal solution of around 10 - 25 ppm.

You can get them here if you want

This one WD-00653-16 Conductivity standard solution, 84 µS

OK, that 84 µS. Do not worry. Set meter to Low range in µS scale and cal to meter to read 84 µS. Then leave in Low range but switch to 442 TDS ppm scale. The meter will convert the 84 µS in 442 ppm TDS automatically. The meter will now read "ture" (442) FW TDS in ppm from 0-100 ppm.

To get it back to tap water use your 342ppm and recal for a more accurate reading or leave as is, this is close enough for tap in most cases, otherwise you will be cal'ing it again in the 84 µS. Just switch the scale to the 100-999 Range ppm 442 scale to test tap water. When done testing tap water just swtich back to the Low 442 range 0 -100 ppm.

http://www.4oakton.com/proddetail.asp?parent=144&prod=227&value=detail

This will help you understand things

What is TDS?
http://www.reefkeeping.com/issues/2004-04/rhf/feature/index.htm

Look at Table 2. This will explain the Scales. Think of the scales as meaning the same only they differ just like C = F = K temps differ by conversion or cm = in. by converison.

 

[Scooterman]

:idea: I knew we would get a better answer than I would have also for the record I wanted to have a reference, so Thanks Boomer!:shock:

 

[Boomer]

Scoot

I missed this cal solution. This is really the best for RO/DI. It = about 15 ppm 442 TDS. That 84 µS is about 50 ppm 442 TDS

WD-00653-23 Conductivity standard solution, 23 µS

Cal the same as I gave for the 84 µS only meter to read 23 µS

 

[Scooterman]

http://www.4oakton.com/proddetail.asp?parent=144&prod=227&value=detail

$8.99, cheap!
So this 23 uS solution is all that is needed to test RO/DI output right, we cal. to it as in post for the 83Us & should be good to go!

 

[DonW]

http://www.4oakton.com/proddetail.asp?parent=144&prod=227&value=detail

$8.99, cheap!
So this 23 uS solution is all that is needed to test RO/DI output right, we cal. to it as in post for the 83Us & should be good to go!

Cool I figured it out µ = alt 230 I'm easily amused.

Don

 

[Boomer]

Yup the alt keys work nice