Thermo Fisher Scientific CyberScan pH 5000 - Manual (Page 137)

Instruction Manual CyberScan pH5500/ 5000
Reference electrodes typically consist of three elements: an internal
reference electrode, a filling solution, and a reference junction
through which the filling solution can “flow”, and provide electrical
contact with the sample and the internal reference electrode. The
most convenient internal reference electrodes are made from a metal
(such as silver or mercury) and its sparingly soluble salt (silver
chloride or mercurous chloride). The filling solution is most often a
concentrated solution of potassium chloride. Most problems with
reference electrodes are associated with the interrupted or blockage
of flow of the potassium chloride fills solution through the reference
junction.
The classic electrode pair separate pH indicating and reference half
cells, offer you unmatched versatility to match the needs of your
sample. This approach makes for the highest accuracy, as well as
low replacement costs, since usually only one of the pair is broken or
malfunctioning.
However, the pH reading indicating half-cell and the reference half-
cell can be merged into one electrode- a combination electrode.
Combination electrodes are quite popular for they offer distinct
advantages in convenience and compactness. Some combination
electrodes also incorporate a ATC probe into their body also,
providing temperature readout and compensation with meters
equipped with these features. Newer combination electrodes are
available in which the glass pH membrane sensor has been replaced
with a field effect transistor or FET. All CyberScan 5000 series meters
are capable of using this type of electrode by direct connection.
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