Gypsum blocks, cast around two concentric, stainless steel electrodes.
The gypsum blocks are manufactured under controlled conditions to obtain a maximum degree of uniformity and fast response to soil moisture changes.
The GB-1 measures 22mm (7/8”) dia. x 29mm (1 1/8”) in height.
It is the most widely used sensing unit, easy to install and especially suited for extensive sampling of soil at various depths.