The DR359TX is an advanced, ion concentration meter which automatically calculates the relationship between two or more concentration standards and stores this in memory allowing unknowns to be read directly. Anion/cation recognition is automatic and up to 5 calibration points may be entered, enabling the user to cover a wide dynamic measurement range with just one calibration. The DR359TX also provides full pH facilities including automatic calibration and temperature compensation. The RS232 interface allows direct printing of results or full external computer control. The meter may be used with the complete range of combination and half-cell ISE's and pH electrodes readily available from EDT Instruments Ltd.