Milwaukee Instruments SONAR MA917B/1 Benutzerhandbuch
pH electrodes are constructed from a special composition
glass which senses the hydrogen ion concentration. This
glass is typically composed of alkali metal ions. The alkali
metal ions of the glass and the hydrogen ions in solution
undergo an ion exchange reaction, generating a potential
difference. In a combination pH electrode, the most widely
used variety, there are actually two electrodes in one body.
One portion is called the measuring electrode, the other the
reference electrode. The potential generated at the junction
site of the measuring portion is due to the free hydrogen
ions present in solution.
The potential of the reference portion is produced by the
internal element in contact with the reference fill solution.
This potential is always constant. In summary, the measur-
ing electrode delivers a varying voltage and the reference
electrode delivers a constant voltage to the meter. The volt-
age signal produced by the pH electrode is a very small,
high impedance signal. The input impedance requires that it
be interfaced only with equipment with high impedance cir-
cuits.
pH Electrode
basics
pH Electrodes
6
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Milwaukee has a wide assortment of pH and ORP elec-
trodes to meet all your specific requirements. Finding
the right electrode for a specific application is a very
important task and in order to solve this selection prob-
lem it is important to consider the following:
trodes to meet all your specific requirements. Finding
the right electrode for a specific application is a very
important task and in order to solve this selection prob-
lem it is important to consider the following:
• Glass body electrode versus Epoxy (plastic)
body electrode: Glass body electrodes stand
higher temperatures (typically 100°C against 80°C
for plastic) and are more resistant to corrosive
chemicals and solvents. They are easier to clean
and are available in different shapes depending on
the application. On the other hand plastic body
electrodes are more rugged and the glass bulb is
better protected.
higher temperatures (typically 100°C against 80°C
for plastic) and are more resistant to corrosive
chemicals and solvents. They are easier to clean
and are available in different shapes depending on
the application. On the other hand plastic body
electrodes are more rugged and the glass bulb is
better protected.
• Gel filled electrodes versus refillable electrodes:
refillable electrodes last longer since electrolyte
can be changed for repeated usage. The
response is faster due to a greater outflow of elec-
trolyte into the sample and therefore less likely to
clog. Gel filled electrodes require less mainte-
nance and resist to higher pressure.
can be changed for repeated usage. The
response is faster due to a greater outflow of elec-
trolyte into the sample and therefore less likely to
clog. Gel filled electrodes require less mainte-
nance and resist to higher pressure.
• Double reference junction versus Single junc-
tion reference: Double junction reference elec-
trodes have a longer live and protects the sample
measured from silver contamination from the elec-
trolyte. The Silver wire is more protected and
therefore gets less contaminated. The single junc-
tion electrodes normally costs less and are ideal
for general purpose applications
trodes have a longer live and protects the sample
measured from silver contamination from the elec-
trolyte. The Silver wire is more protected and
therefore gets less contaminated. The single junc-
tion electrodes normally costs less and are ideal
for general purpose applications
• Conic shaped versus Sphere shaped: The
conic-shaped electrode is easier to clean and to
maintain (ideal for applications such as dairy). Has
a more rugged tip and therefore ideal for penetra-
tion. The sphere-shaped has a faster response
time due to the larger surface area on the bulb.
maintain (ideal for applications such as dairy). Has
a more rugged tip and therefore ideal for penetra-
tion. The sphere-shaped has a faster response
time due to the larger surface area on the bulb.
Model
MA919B/1
MA924B/1
Measuring Range
0 to 13 pH
±2000 mV
Temperature Range
-5 to 80 °C
-5 to 80 °C
Shaft material
glass
glass
Reference Electrolyte
KCL 3.5M
KCL 3.5M
Reference Type
double Ag/AgCl
double Ag/AgCl
Reference Junction
open open
Shape of membrane
spheric
Platinum ring
Max. Pressure
0,1 bar
0,1 bar
Connector type
BNC
BNC
Cable length
coaxial 1 meter
coaxial 1 meter
Shaft length
120 mm
120 mm
Diameter
8 mm
8 mm
Application
food laboratory
food laboratory
8 mm
M
A924
B /1 =1 m
M
A919
B /1 =1 m
8 mm
120 mm
120 mm