This junction can become clogged by particulates in the
solution and can also facilitate poisoning by metal ions pres-
ent in the solution. If a clogged junction is suspected it is
best to soak the electrode in tap water to dissolve the mate-
rial and clear the junction. When not in use it is best to store
the electrode in either buffer 4.0 or buffer 7.0. Never store an
electrode in distilled or deionized water as this will cause
migration of the electrolyte solution from the electrode.
How long a pH electrode will last will depend on how it is
cared for and the solutions it is used to measure. Typically, a
gel-filled combination pH electrode will last six months to 1
year depending on the care and application.
How long an electrode will last is determined by how well the
probe is maintained and the pH application. The harsher the
system, the shorter the lifespan. For this reason it is always
a good idea to have a back-up electrode on hand to avoid
any system down time. Calibration is also an important part
of electrode maintenance. This assures not only that the
electrode is behaving properly but that the system is operat-
ing correctly.
pH Electrode
basics
pH Electrodes
8
www.milwaukeeinst.com
Model MA915B/2 - MA915B/3 MA920B/1 MA991B/1
Measuring Range 0 to 13 pH 0 to 12 pH 0 to 13 pH
Temperature Range -5 to 95°C 0 to 50°C (32 to 122°F) -5 to 100°C (23 to 212°F)
Shaft Material glass PVDF glass
Reference Electrolyte polymer Viscolene KCl 3.5M
Reference Junction ground glass open ceramic, single
Reference Type double, ground glass single, Ag/AgCl single, Ag/AgCl
Shape of membrane spheric conic spheric
Max pressure 3 bar 0.1 bar 0.1 bar
Connector Type BNC BNC BNC
Cable length 2 or 3 m coaxial, 1 m coaxial, 1 m
Shaft length 75 mm 75 mm più di 120 mm
Diameter 12 mm 6 mm 12 mm
Application industrial applications laboratory applications laboratory applications
12 mm
6 mm
75 mm
12 mm
120 mm
M
A
9
9
1
B
/1 =1 m
M
A
9
2
0
B
/1 =1 m
M
A
9
1
5
B
/2 =2 m
/3 =3 m
75 mm
Silver-Free
Electrolyte
Ceramic
Junction
Silver
Silver/Chloride
Reference
Wire
Double Junction
Electrode
Single Junction
Electrode
Outer
Ceramic
Junction
Electrolyte
Containing
Silver
Inner
Ceramic
Junction
Inner Tube
Housing the
Membrane
Sensing Wire
MA991B/1 (will be
replaced by SE120)
