When sourcing a sodium meter, you must prioritize measurement range (typically 0 to 19,900 ppm) and resolution (0.01 mg/L). Ensure the device features Automatic Temperature Compensation (ATC), as sodium ion activity is highly sensitive to temperature fluctuations. For industrial or laboratory use, look for a 3-point or 5-point calibration capability to ensure linearity across a wide concentration spectrum. Additionally, verify the electrode type; high-quality glass-sensitive membranes or PVC ion-selective electrodes (ISE) are preferred for longevity and precision.