Yamato Scientific WG221S Water Purifiers - Manual (Page 36)

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Run Menu
Indication of Water Quality
Measurement of Electric conductivity
The water quality examiner in the operation panel shows the electric conductivity at the exit of ion-
exchange resin cartridge and of distilled water condenser. Use the indication as the standard for
exchanging ion-exchange resin cartridge. When you read the indication, be sure that the part of electrode
is in the full of water; that is in the flowing of Ion-exchanged water. Besides that the part of electrode is not
in the water, the indication is not correct for the influence of bubbles in the following case.
1. At the beginning of running or during the unit stopped
2. Just after exchanging pre-treatment cartridge or ion-exchange resin cartridge
3. Just after the beginning of distillation of water
Electric conductivity
●Electric conductivity shows how much electricity can pass. As water contains more electrolyte or
impurity, more electricity can pass through and the value of conductivity gets larger. On the contrary, the
value gets smaller as water contains less electrolyte.
●That means water is more pure as the conductivity is smaller.
However, the value of conductivity shows containment of electrolyte only but does not indicate any
containment of non-electrolyte such as organic, colloid, dissolved gas and microorganism. Therefore,
conductivity is just one of indicators to shows water purity.
●Resistivity is to indicate the same property as the electric conductivity shows. Resistivity is reciprocal to
electric conductivity. The larger resistivity indicates higher purity.
●To calculate the resistivity from the electric conductivity;
R= Resistivity ρ=Electric conductivity
R［Ω･m］ R［Ω･m］ R［Ω･m］ R［Ω･m］
1 11 1
S SS S m］ m］ m］ m］
=
ρ
[ /
or
R［×10 R［×10 R［×10 R［×10 Ω･m］ Ω･m］ Ω･m］ Ω･m］
1 11 1
Ч10 Ч10 Ч10 Ч10 S SS S m］ m］ m］ m］
４ ４ ４ ４
−４ −４ −４ −４
=
ρ
[ /
Pure water theoretically has the following value.
R=18.3×10
4 Ω･m (18.3MΩ･cm) 25℃
(The resistivity is displayed by the integral number within 18 to 1 ×10 4 Ω･m. Note there is no decimal
number indication.)
ρ=0.055 ×10 -4 S/m (0.055 ・/cm) 25 ℃
Quality of ion-exchanged/distilled water
●Ion-exchanged water and distilled water have the following properties respectively. Select either water
according to your requirement.
It is ideal to use distilled water just after you collect. If you do not use the water soon, drain the distilled
water tank. When you keep distilled water in the tank for a while, drain the tank and store new distilled
water in the tank to use.
(1) Ion-exchanged water
Since almost all electrolyte are removed from ion-exchanged water, you can get water with the
lowest electric conductivity. But it is impossible to remove non-electrolytic impurity. Purity is a little
low with a new resin or at the re-start of flow after operation stops.
(2) Distilled water
The mode can remove averagely electrolyte and non-electrolyte except ammonia and other
substances with low boiling point.
However, water absorbs carbonic acid gas from air and creates carbonic gas during its production
process (in condensation and storage).
Accordingly, water quality is worse than ion-exchanged water and becomes weak acid (pH5 to 6)
with its electric conductivity about 1 to 2×10
-4 S/m 25 ℃ (1 to 2.5・/cm).