User's Manual

ManualsBrandsMilwaukee Instruments ManualsSonarMilwaukee Instruments Milwaukee Instruments SONAR MA917B/1

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

www.milwaukeeinst.com

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:

• 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.

• 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.

• 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

• 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.

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

/1 =1 m

8 mm

120 mm

Summary of content (6 pages)

PAGE 1
pH Electrodes pH Electrode basics 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.
PAGE 2
pH Electrodes pH Electrode basics The pH electrode, due to the nature of its construction, needs to be kept moist at all times. In order to operate properly, glass needs to be hydrated. Hydration is required for the ion exchange process to occur. If an electrode should become dry, it is best to place it in some tap water for a half hour to condition the glass. pH electrodes are like batteries; they run down with time and use. As an electrode ages, its glass changes resistance.
PAGE 3
pH Electrodes pH Electrode basics Single Junction Electrode Double Junction Electrode This junction can become clogged by particulates in the solution and can also facilitate poisoning by metal ions present in the solution. If a clogged junction is suspected it is best to soak the electrode in tap water to dissolve the material and clear the junction. When not in use it is best to store the electrode in either buffer 4.0 or buffer 7.0.
PAGE 4
pH Electrodes pH Electrode basics This means that the temperature is corrected to the value expected at 25 Deg C. Automatic temperature compensation requires input from a temperature sensor and constantly sends a compensated pH signal to the display. Automatic temperature compensation is useful for measuring pH in systems with wide variations in temperature.
PAGE 5
Electrodes Electrodes & Probes pH, ORP, Conductivity, Dissolved Oxygen Milwaukee has a wide assortment of pH, ORP, Conductivity and other specialty sensors 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 problem it is important to consider the following: electrode body, reference construction and junction.
PAGE 6
Electrodes Electrode Selection Guide pH, ORP, Conductivity, Dissolved Oxygen Milwaukee has a wide assortment of pH, ORP, Conductivity and other specialty sensors to meet all your specific requirements. Before selecting an electrode, please consult the table below.