Used for determining nitrate ion activity or concentration in aqueous solutions. Plastic membrane half-cell is unbreakable. Measures from 1.0 to 7 x 10-6 M (14,000 to 0.1 ppm) as N. Operating temperature range from 0 to 40°C. Has a gelled PVC membrane. The membrane, reference solution and ion exchanger are fitted into a screw-on replaceable electrode module. BNC connector.