VWR International sympHony, User Manual

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53
sympHony
™
Meter User Guide
The conductivity of a solution with a specific electrolyte concentration changes with
temperature and this relationship is described by the temperature coefficient of the
solution. The meter has a default temperature coefficient of 2.1 percent change in
conductivity per ˚C, which is representative of many aqueous samples.
Solution (25 °C to 50 °C) Temperature Coefficient (% / °C)
Ultra Pure Water 4.55
Salt (NaCl) 2.12
5% NaOH 1.72
Dilute Ammonia 1.88
10% HCl 1.32
5% Sulfuric Acid 0.96
98% Sulfuric Acid 2.84
Sugar Syrup 5.64
Total Dissolved Solids (TDS)
The sympHony conductivity meters measure TDS as the total amount of dissolved
inorganics in a solution. The dissolved inorganics carry a current that is measured
by the conductivity probe. Since there is a direct relationship between conductivity
and TDS, conductivity readings are used to estimate the presence of inorganics.
The user must enter a TDS factor between 0.01 and 10 mg/L in the setup menu.
The standard method of determining TDS involves evaporating a sample to dryness
at 180 ˚C and weighing the residue. The TDS factor is calculated by taking the
residue weight and dividing it by the sample conductivity. Subsequent conductivity
readings are multiplied by the TDS factor to determine the TDS value of the sample.
Automatic Calibration
The sympHony conductivity meters are capable of automatically recognizing
100 µS/cm, 1413 µS/cm and 12.9 mS/cm conductivity standards when the nominal
cell constant of the conductivity probe is entered in the setup menu. For the meter
to recognize the conductivity standard, the entered cell constant must be accurate
within a factor of 3. For example, if the actual cell constant is 1.0 cm
-1 , entering a
nominal cell constant in the range of 0.3 cm
-1
to 3.0 cm
-1
would allow the meter to
identify the conductivity standard and perform the automatic calibration.
Special Meter Setup Menu Features