Appendix B - Amprobe WT-60 User Manual

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APPENDIX B: CALCULATING TDS CONVERSION FACTORS
The meter can be calibrated using TDS calibration standard solutions. The
calibration standard only needs to give the TDS value at a standard temperature
such as 25°C. To determine the Conductivity-to-TDS conversion factor use the
following formula:
Factor = Actual TDS ÷ Actual Conductivity @ 25°C
Definitions:
Actual TDS: Value from the solution bottle label or as a standard you make
using high purity water and precisely weighed salts.
Actual Conductivity: Value measured using a properly calibration Conductivity
/TDS/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 in is ppm,
the conductivity value must be in μS; if the TDS value is in ppt, the conductivity
value must be in mS. Check this number by multiplying the conductivity reading
by the factor in the above formula and the result is the TDS in ppm.
APPENDIX C: TEMPERATURE EFFECT
Conductivity measurements are temperature dependent, if the temperature
increases, conductivity increases. For example the conductivity measured in
a 0.01M KCl solution at 20°C is 1.273 mS/cm whereas, at 25°C, it is 1.409 mS/
cm. The concept of reference temperature (Normalization temperature)
was introduced to allow the comparison of conductivity results obtained at
different temperature. The reference temperature is usually 20°C or 25°C.
The conductivity meter measures the actual conductivity and temperature and
then converts it to the reference temperature using a temperature correction
function and displays the conductivity at the reference temperature.
It is mandatory to always associate the temperature together with a
conductivity result. If no temperature correction is applied, the conductivity
is the value taken at measurement temperature. The WT-20 use linear
temperature correction.
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