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10.
CALCULATING TDS CONVERSION FACTOR
You can calibrate TDS using the value of the calibration standard solution
at a standard temperature such as 25 ºC. To determine the conductivity-
to-TDS conversion factor use the following formula:
Factor = Actual TDS ÷ Actual Conductivity @ 25 ºC
Actual TDS: Value from the solution bottle label or as a
standard made using high purity water and precisely weighed
salts.
ppm = milligram of salt(s) per liter of water = mg/L
ppt = gram of salt(s) per liter of water = g/L
Actual Conductivity: Value measured using a properly
calibrated Conductivity/Temperature meter.
Both the Actual TDS and the Actual Conductivity values must be in the
same magnitude of units. For example, if the TDS value is in ppm the
conductivity value must be in µS; if the TDS value is in ppt the conductivity
value must be in mS.
Check your factor by multiplying the conductivity reading by the factor in
the above formula. The result should be in TDS value.
When the TDS factor is set to 1.0, Conductivity = TDS.
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