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Measurment of pH in Low Conductivity Water

Measuring pH between 0.056 and 10.0 Microsiemens /cm or resistivity between 18.2 and 10 megaohm-cm at 25°C.

Measuring pH of pure water.

The measurement of pure water pH can be one of the quickest indicators of process contamination in
the production or distribution of pure water. The presence of gaseous contaminants such as air or
carbon dioxide will shift the pH of the pure water, indicating air or gas intrusion into the process line.
The exhaustion of resin beds used to prepare or polish pure water can introduce contaminants that will
cause a shift in pH. These resin beds are typically cation and/or anion exchange resins in a hydronium
ion form (cation exchange) or hydroxide ion form (anion exchange).

While conductivity measurements will clearly indicate an ionic leakage, pH measurement changes can be diagnostic as to which resin is
exhausted. If the pH increases, the cation resin bed is becoming exhausted; if the pH decreases, the
anion resin bed is becoming exhausted.

Sentek have an answer-The P15 pH probe

P15A Probe
P15A Probe


The P15A is a glass combination electrode uses a special pH sensing glass. Some application such as pH in acid rain, rivers and lakes cause problems

for standard pH probes, but the P15A overcomes them, and is a lower cost option than other manufacture’s probes.

The P15A has a BNC connector and a cable length of 1 meter, shaft length is 120mm and stem diameter is 11.8mm

Reference: HgCl liquid filled single junction

Junction type: Annular Ceramic

Temperature range: 0-50°C

pH range: 0-11

Combination: Yes

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