Hi Silver List,
"What multiplier do you use and how accurate do
you think your measurements are???"
I use 4 as the multiplier with TDS meters. Why?
To date no major reputable commerical manufacturer produces a meter to
specifically test for PPM levels for Colloidal Silver Suppensions. When I asked
(Hannah), "Not enough sales to justify manufacture, to small a market."
A TDS meter is designed to measure Total Dissolved Solids in soltion for
applications such as hydroponic gardening, testing tap water and Reverse
Osmosis water, industrial uses for contaminants.
The typical TDS meter measures from 0 ppm to 999 PPM and was not designed to
measure small measurements with an accuracy of less than 50% under 100 of PPM
TDS meters measure transconductance (opposite of resistance) in micro Siemens
and then use circuitry to convert this measurement into a PPM number (called a
Conversion Factor).
The Conversion Factor circuitry "translates" roughly 1 micro Siemen into 1ppm
at Part Per Million readings of 100 PPM or higher at 90% accuracy. At PPM
levels lower than 100 PPM the Conversion Factor translates 1 micro Siemen as
0.5 PPM, 50% of what is measured.
TDS meters were designed to measure dissolved solids conductivity and are
calibrated with Sodium Chloride (the "yellow" solution sold with these meters)
as a rough "Guesstimate." Salt is used as an average approximation of the
conductivity of the compounds and elements (and polutants) found in water.
(Potassium Chloride is the world standard for calibration, but then TDS meters
do not require scientific accuracy.)
Soldium Chloride or table salt has twice the conductivity of Silver. Or Silver
has 1/2 the conductivity of table Salt. So any measurement of Colloidal Silver
will be half of that for dissolved solids.
TDS meters round off their measurements downwards after conversion. 0 to 0.9
PPM will read as 000 PPM. Likewise, 1 to 1.9 PPM reads as 1 PPM, etc.
Let's use some numbers. Let's say I have finished a batch of CS and send half
of it to a lab that runs an Atomic Aborption Spectragraphy. The batch was made
with Lab & Tech distilled water (0 PPM). The test measurement is 10 ppm
I reach for my trusty TDS meter. The meter measures 90 % of the
transconductace (calibrated to Sodium Chloride which has twice transconductance
of CS) so 4.5 only is measured and the conversion factor has a 50% error
(under 100ppm readings) so 2.25, rounded down becomes 2 PPM.
I have a batch of 30 PPM CS. 15 X 90%= 13.5 microS measured multiplied by 50%
Conversion=6.75 rounded down to 6 ppm
If I have a reading of 3 PPM X 4= 12 PPM (3 times 2 (for Conversion Factor)
times 2 (Salt factor) equals 12 PPM)
This doesn't account for Commerical Distilled water which measures from 0 to 2
ppm (0 to 4 ppm if taking into account the Conversion Factor from circuitry).
The DW will measure as 0 ppm at levels as high as 1.9 ppm (actual).
That is why I use the number 4 as a multiplier when using a TDS meter to
measure CS batches.
How accurate do I think these measures are with TDS meters?
Not very accurate, but better than nothing, or shelling out $400 USD everytime
I make CS to get an accurate reading.
Regards,
Steve Foss
If you are using Sodium Chloride or Sodium bicarbonate as an electrolyte this
muddies the water (and the measurement) further.
>Question for the group: What multiplier do you use and how accurate do
you think your measurements are???
Just make sure the TDS meter probe is not contaminated when measuring,
make sure there are no bubbles on the probe tips and do not try to
measure moving water (keep TDS meter still in water).
- Steve
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Hi Steve. How does one use a TDS meter? Thanks. Faith G.
