ELMETRON CX-401, Руководство пользователя

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The results are more accurate for homogeneous solutions (NaCl, KCl).
Concentration of salts mixture with unknown composition in most cases is
counted to NaCl. The usefulness of water for home or industry is usually
checked by determining TDS. In order to use the conductivity readout for
determining the TDS it is necessary to specify the W
TDS
coefficient, which
enables automatic conversion after having introduced it to the meter’s
memory. To determine the W
TDS
coefficient it is necessary to specify the
weight of dissolved substances. The laboratory method of determining the
dissolved solids content consists in taking a given volume of water,
evaporating the filtered sample, drying it to constant weight in temperature
103
÷
105
0
C, weighting and counting in volume ratio (mg/dm
3
). The received
weight is lower than total dry mass in water because apart from the dissolved
solids it contains also undissolved substances that are removed by filtering
before evaporating. It is possible to determine the approximate Total
Dissolved Solids content using the conductivity readout on the assumption
that the salt’s composition in the taken samples has not been changing
significantly.
17.1. Salinity measurement with conversion to NaCl or KCl
The measurement of salinity with conversion to NaCl or KCl content is made
in the following way:
-
choose the salinity measurement with conversion to NaCl or KCl content
according to the section 13.1;
- choose the unit (g/l or %);
- then act as during the conductivity measurement (chapter 16);
- after stabilisation check the reading.