digital PH meter ph Meter PH tester SmartSensor AS218 0.

 the preparation of the buffer solution1. PH4 buffer solution with accessories distribution of  powder in 250 ml distilled water, fully dissolved  dilution 30 minutes.2. PH6.86 buffer solution with accessories distribution  of powder in 250 ml distilled water, fully dissolved  dilution 30 minutes.3. PH9.18 buffer solution with accessories distribution  of powder in 250 ml distilled water, fully dissolved  dilution 30 minutes.