Ionode IJ pH V5.1 - Manual (Page 7)

Ionode IJ Instruction Manual 7
4.2. Electrode Characteristics
4.2.1. Construction
A pH electrode consists of two electrochemical
half-cells usually co-axially combined into a
single housing called a “combination electrode”
to form an electrical circuit. The sensing half-
cell comprises a pH sensitive glass membrane
attached to a sealed insulating tube containing
a solution of fixed pH in contact with a silver-
silver chloride element. A voltage proportional
to pH is measured between the sensing half-
cell and a reference half-cell which ideally
maintains a stable potential independent of the
sample.
V
Figure 6
Sample
Internal Filling
Solution
Primary Reference
Electrolyte
Sleeve Electrolyte
(renewable)
Porous Wick
Primary Reference
pH Membrane
Ground Surface
Intermediate
Junction (secondary
reference
electrolyte)
Ag/AgCl Elements
pH Meter