pH meter composite electrode structure
An electrode that combines a pH glass electrode and a reference electrode is called a pH composite electrode. If the shell is made of plastic, it is called a plastic shell pH composite electrode. Those with a glass shell are called glass pH composite electrodes. The biggest advantage of composite electrodes is that they are combined into one and are easy to use. The structure of the pH composite electrode mainly consists of an electrode bulb, a glass support rod, an internal reference electrode, an internal reference solution, a shell, an external reference electrode, an external reference solution, a liquid junction, an electrode cap, an electrode lead, a socket, etc.
1. Electrode bulb: It is melt-blown from lithium glass with hydrogen function. It is spherical in shape, with a film thickness of about 0.1~0.2mm and a resistance value of 250 megohms (25℃).
2. Glass support tube: It is a glass tube that supports the electrode bulb. It is made of lead glass with excellent electrical insulation. Its expansion coefficient should be consistent with the electrode bulb glass.
3. Internal reference electrode: It is a silver/silver chloride electrode. Its main function is to draw out the electrode potential. It is required that its potential is stable and its temperature coefficient is small.
4. Internal reference solution: The internal reference solution with a zero potential of 7pH is a mixed solution of neutral phosphate and potassium chloride. The glass electrode and the reference electrode form a battery to establish the pH value of the zero potential, which mainly depends on the internal reference solution. pH value and chloride ion concentration.
5. Electrode plastic shell: The electrode plastic shell is a shell that supports the glass electrode and the liquid junction and holds the external reference solution. It is molded by PPS.
6. External reference electrode: It is a silver/silver chloride electrode. Its function is to provide and maintain a fixed reference potential. It requires stable potential, good reproducibility, and small temperature coefficient.
7. External reference solution: 3.3mol/L potassium chloride gel electrolyte, which is not easy to lose and does not need to be added.
8. Sand core liquid junction: The liquid junction is the connecting component that connects the external reference solution and the measured solution, and requires stable penetration.
9. Electrode wire: It is a low-noise metal shielded wire. The inner core is connected to the internal reference electrode, and the shielding layer is connected to the external reference electrode.
