Measuring TDS ...

[diamond_discus]

I have a TDS meter (HM COM-100) which has 3 types of TDS measurement :
KCI, 442 and NaCI. Which reading should I use ? I am currently setting that to KCI reading

[Mr Wild]

mine is ppm, not sure of yours

[Ardan]

I think those three settings are for calibrating the meter for different uses

it states here
TDS meters are more accurate when calibrated at levels that are as close as possible to the sample being tested (such as for hydroponics, aquaculture, tinting and dying or brackish water). HM Digital sells NaCl calibration solution (http://www.tdsmeter.com/products/calibrationsolution.html) at 342 PPM and 1000 PPM. Calibration solutions at signifcantly higher levels are commercially available.

http://www.tdsmeter.com/calibration_maintenance.html

here are instructions on your meter. It states


1. Remove the cap.
2. Press the ‘ON/OFF’ button. The display will become active.
3. The default mode of the meter is for EC with a KCl temperature coefficient.

http://www.sensafe.com/PDF/COM100_Users_Guide.pdf
this is measuring in microsiemens not tds. It tells how to change it to tds (which is the total dissolved solids)
hth
Ardan

[diamond_discus]

I know how to switch between the EC and TDS mode.
My question is that for TDS mode, there are 3 ppm reading : KCI, 442 and NaCI

The 442 and NaCI are very high .. and the KCI ready seems to be closer to the ppm amount people are referring here.

BTW, I just read the manual more carefully and find the following:
442 is for natural water (rivers, lakes, wells, drinking water, etc)
NaCI is for seawater and brackish water
KCI is the international standard to calibrate instruments that measure conductivity.

Since I am measuring tap water and RO water, I assume I should be using the TDS-KCI mode ?

[wgtaylor]

Hey Larry, that's a great meter. :)

If you are like me, I get obsessive compulsive about water but if you read the information on these TDS meters it sort of states that the actual need for "exact" measurement is not too important. I have found the readings between KCI, 442 and NaCl are only different by a point or two. Most meters are measured in NaCl so I bought that calibration solution and use it to calibrate. If you wanted to get very accurate measurements than I would expect if you calibrated and used the 442TM you could get more accurate measurements but the difference would be only a couple points different.

I added some additional information below. Clean water is the most important element in keeping discus but it seems has less importantance other than keeping it soft and clean. Interesting stuff.
Source of information: http://www.tdsmeter.com/products/com100.html

Bill


KCl.
Potassium Chloride is the international standard to calibrate instruments that measure conductivity.
The COM-100 is factory calibrated with a 1413 microsiemens 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.

Measurements in EC (µS) do not have a conversion factor, but do require the correct setting for the proper temperature coefficient.

Other HM Digital products use the NaCl conversion factor.

Is pinpoint accuracy always necessary when testing for TDS or conductivity? Usually not.
TDS is primarily about range. For the majority of industries that require TDS testing, such as drinking water, aquaculture, hydroponics, etc.
it is more important for your TDS levels to be within a certain range. There are a few industries that do require a precise ppm level,
but that level is almost always zero. With the exception of colloidal silver, there is never a time in which someone needs an absolute precise level of TDS in their water.

Don’t you need the minerals in your drinking water?

Inorganic Minerals.
It is believed that mineral waters help furnish elements for body metabolism. However, there is scientific proof to suggest that most of these minerals are in an inorganic (dead) form.
While they may enter the circulation, they cannot be used in the physiological process of building the human cell.
With this in mind, we can see that mineral water may give "dead" or "inorganic" minerals to the body which cannot be properly assimilated.
These inorganic minerals only interfere with the delicate and complex biology of the body.

The body's need for minerals is largely met through foods, NOT DRINKING WATER." -The American Medical Journal.