TDS Meter

[Houndog]

I already have a pH meter, while looking for a EC/TDS meter I found COM-100 made by HM.

Does anyone have any experience with this meter/company?

Link to Meter

Link to Meter on ebay

Any comments would be appreciated.

Thanks, Jeff

 

[Roach]

Is this basically an electronic water hardness tester?

 

[Zapisto]

TDS mean Total Dissolv Solid ((NaCl standard) in PPM
EC mean electrical conductivity- in fact this mesurement give you water conductivity in microsiemens/cm

approximate sodium chloride TDS value = EC (in microSiemens/cm) x 1000 and divide by 2.

EC = PPM X 2 and divide by 1000.

exemple :
if EC is 1 :
1*1000/2= 500 ppm.

if ppm is 500:
500*2/1000= 1 EC

 

[Fred]

Zapisto,

I have a hardness meter as you described. I have wondered if there is a formula to convert TDS to GH, or if there are differences between the 2 measurements.

 

[Zapisto]

Zapisto,

I have a hardness meter as you described. I have wondered if there is a formula to convert TDS to GH, or if there are differences between the 2 measurements.

i never really look in this direction.
but my question is Why you will want to that ?
in my opinion the more important things for apisto is :
- TDS/EC
- PH
- Temp

and let me tell you as soon as my tank cycling i never test anything beside that time to time.
but probably yes i will check

 

[Houndog]

Finally getting around to breeding my checkerboards and want a bit more information than the pH. I am using an RO/DI unit, mixing the water with peat and using that for the setup (they like the water and the eggs are hatching).

The TDS should be useful if nothing more than monitoring my RO unit, but hopefully it will assist in providing/maintaining better water conditions (EC should be handy here also). Most of my fishkeeping has been done with freshwater, with the exception of using RO for my marine setup.

I found a local supplier and ordered one... hopefully I will find it useful.

Thanks, Jeff

 

[Fred]

Zapitso,

This is what I am thinking. I have an RO / DI unit. So for water changes, I use RO DI water with Equillibirum added to put minerals back in. I can test easily with the TDS meter, but all fish literature recommends harness in GH. I would be nice if I could test in TDS and know the hardness in GH. I guess it works out ok, because I now know how much to add, but that is why I would like to convert.

I am also not clear on PH buffering of this water. Ususally the PH is good, but if I do add anything to adjust PH, it doesn't take much with this type of water. Should I be adding both an acid and alkine buffers (in appropriate ratios) to make the ph more stable? I ask your forgiveness if this is a stupid question. I have never understood well how ph buffering works.

My strategy for this has been to ALWAYS adjust water in a holding tank, and make sure the ph is stable for several hours before doing the water change. It is amazing hold long ph can drift after adding an acid or alkaline buffer.

Looking forward to your feedback.

 

[Zapisto]

Zapitso,

This is what I am thinking. I have an RO / DI unit. So for water changes, I use RO DI water with Equillibirum added to put minerals back in. I can test easily with the TDS meter, but all fish literature recommends harness in GH. I would be nice if I could test in TDS and know the hardness in GH. I guess it works out ok, because I now know how much to add, but that is why I would like to convert.

There is no accurate conversion factor between the electrical conductivity of water (EC) and the hardness of water. Having said that, you can make a rough guess by assuming that the conductivity of the water is coming from only calcium carbonate (definitely a bad assumption) and that calcium carbonate and sodium chloride contribute identically to conductivity (probably a bad assumption). Then multiply the conductivity reading in micro siemens by .5 to convert to equivalent ppm of sodium chloride. Then multiply by 100/58 (molecular weight CaCO3/NaCl) to get equivalent ppm of Calcium Carbonate. Then divide by 17.9 to convert to German degrees hardness. Or, multiply the conductivity in microsiemens by .048 to get a rough guess of what the general hardness is.

The big thing I think is knowing what all the terms mean. Parts per million (ppm) and milligrams/liter (mg/l) are the same for our purposes.

By definition, 1 dGH = 10 ppm CaO. Or, 1 German degrees general hardness is obtained by dissolving 10 milligrams of calcium oxide into 1 liter of water. Or, 1 dGH equals 7.1 ppm Ca++ (calcium ion). Or, 1 dGH equals 17.9 ppm CaCO3 (calcium carbonate). The last conversion is sometimes stated as ppm Ca++ as CaCO3.

By definition, 1 dKH = 10.7 ppm CO3--. This one is not straight forward, because the carbonate ion CO3-- only exists while dissolved in water (and other solvents). So immediately you need conversion factors. Dissolving 17.9 mg CaCO3 in to 1 liter of water will raise the dKH by 1 degree. Or, 1 dKH = 21.8 ppm HCO3-.

Fundamentally, hardness is supposed to mean how much calcium carbonate is dissolved in the water. When this is actually true, then the GH and the KH are the same, and then dividing the total dissolved solids (TDS) in ppm by 17.9 would give you the GH and KH in degrees hardness. It is never that simple!! There are many more dissolved substances in our tap water than calcium carbonate, and there is no easy way that I know of to measure TDS. Conductivity is easy to measure, and is created by TDS, the more stuff dissolved in the water, the higher the conductivity.

A conductivity meter measures the how easily electricity passes through the water and is usually reported in microsiemens/cm. The problem is the conversion factor used to calibrated to read in ppm. As far as I know, sodium chloride (NaCl) is used. The meter is calibrated by dissolving a known amount of NaCl into a known amount of distilled water at a known temperature. Based on previous experiments, you know the conductivity, and you know the ppm by dividing the weight of salt added by the volume of water. All ions make water conductive. Knowing the conductivity of the water does not tell you what ions are making the water conductive, it only tells you how much of the calibration salt would make the water that conductive. It turns out, as others have said, that .5 ppm of NaCl will raise the conductivity by 1 microsiemen/cm.

General hardness and carbonate hardness test kits add to the confusion. They measure more than Ca++ and CO3--, respectively. The GH test kits measure magnesium and calcium. The KH test kits measure alkalinity. Alkalinity is a measure of how much the pH drops when an acid is added. High levels of alkalinity mean the pH does not drop as much when an acid is added. The thing is that the carbonate ion is not the only one that can contribute to alkalinity, so again you're measuring the presence of other substances.

Conductivity meters, GH test kits, and KH test kits are all very, very valuable tools. You just need to know their limitations. Conductivity meters will give you a very good look at how much stuff is dissolved in the water. It just can't tell you how much of what. Soft water fish don't like much of anything dissolved in the water, so the conductivity meter is a really good tool to use that will tell you if you've departed from low TDS conditions. GH test kits measure both magnesium and calcium, IMHO no big deal really. KH kits measure alkalinity, again IMHO no big deal really.

Hope this helps!

here an example (due to the conversion factor problem):
for pinpoint conductivity meter.

33 microSiemens = 17.9ppm
33microSiemens = 1dH (German ° hardness)
1dH = 17.9ppm

Important : i would say this conversion is acurate only with Pinpoint conductivity meter

I am also not clear on PH buffering of this water. Ususally the PH is good, but if I do add anything to adjust PH, it doesn't take much with this type of water. Should I be adding both an acid and alkine buffers (in appropriate ratios) to make the ph more stable? I ask your forgiveness if this is a stupid question. I have never understood well how ph buffering works.

My strategy for this has been to ALWAYS adjust water in a holding tank, and make sure the ph is stable for several hours before doing the water change. It is amazing hold long ph can drift after adding an acid or alkaline buffer.

Looking forward to your feedback.

i did not understand what is your question clearly

 

[Fatts]

Zapisto,
Excelent responce. I read his question and was trying to think of a way to explain it. But you did a better job than even my LFS when I was trying to figure all this out.