Owner manual
43
still produce an offset voltage, but using the same materials to connect
offsets to cancel.
The problem is, on the other side of the membrane is an unknown test
solution, not potassium chloride. The outside electrode, also called the
of a glass barrier to allow
Glass surface
Figure 33
KCl solution
Electrode wire
Electrode
wire
H
+
ions
Junction
Plug
of liquids through the plug material.
component pair. Migration does
occur, and this limits the lifetime of a
inside the reference junction or from
contamination. The junction may be
damaged if dried out because
insoluble crystals may form in a
layer, obstructing contact with test
4.
KCl solution
Figure 34
Junction plug
Platinum button
H
+
ions
Electrode wires
Glass
Glass
Surface
The sensor in the Ultrameter II
in an easily replaceable package.
The sensor body holds an oversize
solution supply for long life.
The reference junction “wick” is
porous to provide a very stable,
low permeable interface, and is
electrode. This construction
combines all the best features of
a.
The most common sensor problem will be a clogged junction because a
sensor was allowed to dry out. The symptom is a drift in the “zero” setting
II
unit of offset during calibration. At that point the junction is unreliable.
b. Sensitivity Problems
can diminish sensitivity and cause a long response time.