How to Measure Electrode Potential with a pH Meter
1. Turn on the power switch and the instrument enters pH measurement mode; Press the "Mode" button continuously (four times) to enter mV measurement mode for the instrument;
2. Clamp the ion selective electrode (or metal electrode) and the reference electrode on the electrode holder;
3. Clean the electrode head with distilled water, and then clean it once with the tested solution;
4. Insert the plug of the ion electrode into the measuring electrode socket;
5. Connect the reference electrode to the reference electrode interface at the back of the instrument;
6. Insert two types of electrodes into the tested solution, stir the solution evenly, and the electrode potential (mV value) of the ion selective electrode can be read on the display screen, and the ± polarity can also be automatically displayed.
7. If the measured signal exceeds the measurement (display) range of the instrument, or if the measuring end is open circuited, the display screen will show 1-- mV and trigger an overload alarm.
When measuring electrode potential using a metal electrode, use a Q9 plug with a clamp. Connect the Q9 plug to the measuring electrode socket and connect the clamp to the metal electrode wire; Alternatively, an electrode converter can be used, with one end of the electrode converter connected to the measuring electrode socket, and the metal electrode connected to the converter connector. Connect the reference electrode to the interface of the reference electrode.
Selection of pH meter electrodes
1. The glass shell is suitable for temperatures ranging from 0-150oC and is generally not corroded except by hydrofluoric acid solution, but it is prone to collision damage.
2. Polycarbonate shell is susceptible to corrosion in high alkaline solutions and some media, but resistant to collision and impact, suitable for temperatures<80oC. B. The selection of reference electrodes is generally based on Ag/AgCl reference electrodes, but general Ag/AgCl reference electrodes are prone to dissolution at high temperatures and have unstable potentials, while capillary structured Ag/AgCl reference electrodes have very stable reference potentials and are suitable for use under high temperature and long-term continuous testing conditions. C. The selection of liquid interface is the connecting component between the external reference solution and the measured solution, which requires stable and reproducible potential;
1. General liquid interface materials include fiber materials, ceramic cores, glass grinding ports, and other media. Fiber materials are generally used in plastic shell electrodes, and their solution leakage rate is fast and not easily blocked; 2. The glass grinding interface has a large contact area and leakage rate with the solution, making it suitable for the determination of weak ionic strength, high viscosity, turbid liquids or colloidal solutions.
3. Ceramic cores have good corrosion resistance, and the stability and reproducibility of the liquid interface potential are also good. They can be used in high-temperature media and are widely used as liquid interface materials; D. The commonly used socket for pH electrodes is BNC type (also known as Q9 type), and there are various other forms depending on the matching of the corresponding instrument.
