TDS Meter 442 or naci?

[Herrwibi]

Hi all,

For the last few months I've been using hm digital com 100 to test my tds in my caridina tank . I've been having a few issues with the tank lately and decided to investigate . All other parameters are within spec and I use ro water with gh+ .

I've looked more into my tds meter and realised I've been using naci 0.5 instead of 442 0.7 .

Am I right in saying it needs to be set to 442 0.7 for fresh water rather than naci as I think thats considered more for salt /brackish water testing ? If this is the case then my tds is high and need to dilute it. Any help would be great .

Thanks.

 

[_Maq_]

You'd better measure EC (electric conductivity). In fact, no tool can measure total dissolved solids.

 

[hypnogogia]

From the instruction manual:

Drinking Water (Filtered or Tap): ppm-442 or ppm-NaCl Filtration/Purification Systems: ppm-442 or ppm-NaCl Hydroponics/Gardening: Consult fertilizer or nutrient requirements Aquariums and Reef Tanks: ppm-NaCl or ppm-KCl
Colloidal Silver: ppm-NaCl or ppm442
Pools & Spas: ppm-NaCl
Car & Window Washing: ppm-442 or ppm-NaCl
Coffee: ppm-442 or ppm-NaCl

 

[Herrwibi]

From the instruction manual:

Drinking Water (Filtered or Tap): ppm-442 or ppm-NaCl Filtration/Purification Systems: ppm-442 or ppm-NaCl Hydroponics/Gardening: Consult fertilizer or nutrient requirements Aquariums and Reef Tanks: ppm-NaCl or ppm-KCl
Colloidal Silver: ppm-NaCl or ppm442
Pools & Spas: ppm-NaCl
Car & Window Washing: ppm-442 or ppm-NaCl
Coffee: ppm-442 or ppm-NaCl

KCl: Potassium Chloride is the international standard to calibrate instruments that measure
conductivity. The COM-100 is factory calibrated with a 1413 micro-seimens solution is the default
mode is EC-KCl.
442TM: Developed by the Myron L Company, 442TM simulates the properties of natural water
(rivers, lakes, wells, drinking water, etc.) with a combination of 40% Sodium Bicarbonate, 40%
Sodium Sulfate and 20% Chloride.
NaCl: Sodium Chloride is used in water where the predominate ions are NaCl, or whose
properties are similar to NaCl, such as seawater and brackish water.

Thank you for your reply. Above is also from the manual which is why I'm getting confused as I would say it refers more to 442 than naci . What would you suggest I set it to naci or 442 ?

 

[dw1305]

Hi all,

Am I right in saying it needs to be set to 442 0.7 for fresh water rather than naci

You'd better measure EC (electric conductivity). In fact, no tool can measure total dissolved solids.

As @_Maq_ says they are all <"conductivity meters"> and you normally use the "442" standard for freshwater (0.64 as a conversion factor from microS to ppm TDS). The reason is just that ions with higher valency (like SO4--) conduct more electricity than monovalent ions like Na+ and Cl-.

The "442" is just the ratio of salts used in the standard. they are 40% sodium sulphate (Na2SO4.nH2O), 40% sodium bicarbonate (NaHCO3-), 20% sodium chloride (NaCl)

Edit: I use the KCl calibration standard.

If you can get pure KCl it is 0.746g KCl in one litre to give 1411 microS. I keep the 0.1M KCl stock (7.46g in 1000cm3) in a stoppered bottle, but I only use the 1:10 diluted calibration solution once, and I use the whole large volume for calibration. The reason for this is that they aren't like pH buffers, any drips of lower conductivity water will dilute the standard and change the microS reading.

cheers Darrel

 

[Herrwibi]

Hi all,


As @_Maq_ says they are all <"conductivity meters"> and you normally use the "442" standard for freshwater (0.64 as a conversion factor from microS to ppm TDS). The reason is just that ions with higher valency (like SO4--) conduct more electricity than monovalent ions like Na+ and Cl-.

The "442" is just the ratio of salts used in the standard. they are 40% sodium sulphate (Na2SO4.nH2O), 40% sodium bicarbonate (NaHCO3-), 20% sodium chloride (NaCl)

Edit: I use the KCl calibration standard.


cheers Darrel

Thank you for your reply. Would you suggest 442 or KCI, unfortunately this is all new to me and I thought it was going to be straight forward .

 

[dw1305]

Hi all,

Thank you for your reply. Would you suggest 442 or KCI, unfortunately this is all new to me and I thought it was going to be straight forward .

It is pretty straight forward. I've never made up the "442" standard. I've always used KCl and the method above, and that is what I'd recommend. Conductivity meters really are <"plug and play">.

The differences, in terms of ions, are absolutely minute. As an example our tap water (about 17 dGH / 17 dKH) would be ~ 650 microS and water from the DI unit about 2 microS. Once you know that less than one gram of KCl in a litre of water raises the conductivity by ~1000 microS you know that the differences between calibration standards are only really relevant under experimental conditions.

...... If you can get pure KCl it is 0.746g KCl in one litre to give 1411 microS

Cheers Darrel

 

[dw1305]

Hi all,

For the last few months I've been using hm digital com 100 to test my tds in my caridina tank . I've been having a few issues with the tank lately and decided to investigate . All other parameters are within spec and I use ro water with gh+ .

I've looked more into my tds meter and realised I've been using naci 0.5 instead of 442 0.7 .

I should have said that I'd be surprised if it is a "TDS" issue.

cheers Darrel