FP640 flame photometer (Potassium, Sodium) technical parameter Stability: Continuous injection of standard solution, with a relative maximum change of ≤ 3% in instrument readings within 15 seconds Measure once per minute for a total of 6 measurements, with a relative maximum change in instrument readings of ≤ 15% Repeatability ≤ 3% Linear error K: ≤ 0.005mol/L; Na：≤0.03mmol/L； Detection limit K: ≤ 0.004mmol/L; Na:≤0.008mmol/L；