Analytical and measuring apparatus and instruments; analytical and measuring machines and instruments for water quality or solution; water quality meters or testers; pH meters and testers; ORP (oxidation reduction potential) meters and testers; ion meters and testers; conductivity meters and testers; resistivity meters and testers; salt meters and testers; TDS (total dissolved solids) meters and testers; electrodes for water quality or solution analysis; glass electrodes for water quality or solution analysis; pH electrodes for water quality or solution analysis; ion selective electrodes for water quality or solution analysis; sensors used for water quality or solution analysis; transmitters used for water quality or solution analysis; assemblies used for water quality or solution analysis; accessories used for water quality or solution analysis; electrode holders