This article is directed to measure hydrogen ion index (pH value) of a sample solution by measuring an electromotive force generated on a sensing film of a reference electrode (pH electrode). Parts of the design desired to be claimed is a reference electrode and a comparison electrode disposed in a tray where a sample is dropped. In this article, the comparison electrode can be mounted and demounted freely, and thus the solution measured can be added to a container in the tray.
The solid line part indicates a part desired to be claimed. In