Myron L TH1 - Manual (Page 33)

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1. If NaCl compensation is used, an instrument would report 1035
µS compensated, which corresponds to 510 ppm NaCl.
2. If 442 compensation is used, an instrument would report 1024
µS compensated, which corresponds to 713 ppm 442.
The difference in values is 40%.
In spite of such large error, some users will continue to take data in
the NaCl mode because their previous data gathering and process
monitoring was done with an older NaCl referenced device.
Selecting the correct Solution Type on the TechPro II will allow the user
to attain true TDS readings that correspond to evaporated weight.
XIX. TEMPERATURE COMPENSATION (Tempco)
and TDS DERIVATION (TPH1 & TP1)
When taking conductivity measurements, the Solution Selection
determines the characteristic assumed as the instrument reports what a
measured conductivity would be if it were at 25°C. The characteristic is
represented by the tempco, expressed in %/°C. If a solution of 100 µS
at 25°C increases to 122 µS at 35°C, then a 22% increase has occurred
over this change of 10°C. The solution is then said to have a tempco of
2.2 %/°C.
Tempco always varies among solutions because it is dependent on their
individual ionization activity, temperature and concentration. This is why
the TechPro II features mathematically generated models for known salt
characteristics that also vary with concentration and temperature.
XX. pH MEASUREMENT (TPH1 & TH1)
A. pH as an Indicator (TPH1 & TH1)
pH is the measurement of Acidity or Alkalinity of an aqueous solution. It
is also stated as the Hydrogen Ion activity of a solution. pH measures the
effective, not the total, acidity of a solution.