The Calcium Ion-Selective Electrode (ISE) can be used to measure the concentration of Calcium (Ca2+) in aqueous samples. Specifications: Range: 1 to 40,000 mg/L or ppm; Accuracy: ±10% of full scalre (calibrated 10 to 1000 mg/L); pH Range: 3 to 10; Interfering Ions: Pb2+, Hg2+, Sr2+, Cu2+, Ni2+; Electrode Resistance: 1 to 4 MΩ; Electrode Slope (log voltage vs. concentration): +28 mV/decade; Temperature range (can be placed in): 0 to 50°C (no temperature compensation); Minimum immersion: 1.1 inch; Electrode Length: 155 mm; Body Diameter: 12 mm; Cap Diameter: 16 mm; Cable Length: 100 cm.