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In time: A pH electrode is the sensitive part of an instrument. Simply put, pH is measured by the difference in electrical potential between the measuring electrode (or half measuring cell) and the reference electrode (or half reference cell). This potential difference (mV) is converted to the proportional pH value.
Most Digimed pH electrodes are combinated electrodes. This means that both the measuring half-cell and the reference half-cell are built into a single body. If you need it, Digimed also manufactures the measurement and reference electrodes separately.
Body
Most of the electrodes manufactured have a glass body. Because it is an inert material, it is used in most applications. Other materials, such as polyacetal and kynar, can be used if glass is not the most suitable for the sample.
It is worth mentioning that for solids and semisolids such as meat and cheese, the electrode can have a stainless steel or polyacetal coating.
Type of electrolyte
Electrolytes are the solutions present inside the electrode body and allow the connection (salt bridge) between the two half-cells to be created, generating the ionic mobility required for the measurement.
The sensors with a recharge hole have the characteristic of being self-cleaning, as the electrolyte flows through the junction.
On the other hand, sensors with gel-like polymers do not have a recharge hole, and are "shielded". The big advantage is that they do not need electrolyte replacement, and are widely used in processes and portable meters.
Junction
When there is contact between the reference electrolyte and the sample through the junction, the measurement takes place. Any obstruction in the junction can cause errors in the reading. Therefore the type of junction is directly related to the type of sample that will be analyzed.
The best known junction is ceramic because it integrates easily with the glass and is porous enough to allow the electrolyte to pass through.
Polytetrafluoroethylene (PTFE) can also be used because it is hydrophobic and has excellent chemical resistance. Widely used in samples with presence of oils and greases.
Bulb
There are different bulb shapes to meet the needs of samples with different characteristics.
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Spherical: The classic round shape that aims to have the largest possible contact area with the sample. Known for its versatility and large number of applications. |
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Conch: This shape was developed to reduce the contact area of the bulb with the sample. This is particularly positive for samples that have a large amount of particulate material, which can mechanically damage the bulb. |
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Conical: With a perforated shape, the bulb enters semisolids easily. Together with the stainless steel knife, it can even be used in solids. Applications are mainly in meat packing plants and dairy products. |
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Flat: Developed for direct contact on the surface. Applications in paper, leather and pharmaceutical industries. |
Connector
There is a very wide variety of connectors that can depend on the application. As a rule, the most common are the BNC, DIN, Pin, Banana and Fork models. We manufacture the electrodes according to the connector you need.
As you can see, choosing an electrode requires a lot of attention to the process you take care of, especially the physical-chemical composition and condition of the sample.
Remember that this guide is just a quick reference about our pH sensors. Every application is always unique and empirical to your process. Please refer to the instruction manual or contact us for more information, procedures, and suggestions for new possibilities.
Please contact our experts!
Whatsapp: +55 11 96477-0708
E-mail: support@digimed.ind.br