An electrode that has no response to the activity of hydrogen ions in the solution and has a known and constant electrode potential is called a reference electrode.
The main function of the reference electrode is to measure the electromotive force of the battery and the benchmark for calculating the electrode potential. (Note: the electrode measured by Bai is called the working electrode, and the electrode opposite to the working electrode is called the auxiliary electrode.)
Reference electrodes include mercurous sulfate electrode, calomel electrode and silver / silver chloride electrode. The most commonly used are calomel electrode and silver / silver chloride.
The function in the measuring battery is to provide and maintain a fixed reference potential. Therefore, the requirements for the reference electrode are that the potential is stable and important, the temperature coefficient is small, and the polarization potential is small when there is current. The commonly used reference electrode sold in the market is 232 reference electrode.