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Operating principle
A pH
(potential of Hydrogen)
probe measures the hydrogen ion activity in a liquid.
At the tip of a pH probe is a glass membrane. This glass membrane permits hydrogen
ions from the liquid being measured to defuse into the outer layer of the glass, while
larger ions remain in the solution. The difference in the concentration of hydrogen ions
(outside the probe vs. inside the probe) creates a VERY small current. This current is
proportional to the concentration of hydrogen ions in the liquid being measured.
Base: pH > 7
Neutral: pH = 7
Acid: pH < 7
Junction
Reference wire
Silver chloride
Silver wire
KCL reference solution
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