The chloride ISE is a solid state sensor that measures free chloride ions in ground water, boiler water, drinking water, and many other applications including in concrete materials testing. This chloride ISE is available as either a single half-cell or combination design with a reference cell. The ISE is a convenient way to measure chloride. The chloride ISE used with the mulitparameter meter does not use ISA. The activity coefficient is based on typical surface water conductivity values.