pH Meter

Glass-electrode voltmeter reading hydrogen-ion activity, born from a request to grade lemon juice.

Core Principles & Analysis

• Arnold Beckman built the first commercial pH meter in 1934 for a California citrus lab.
• The glass electrode develops about 59 mV per pH unit at room temperature, per the Nernst equation.
• Meters drift and must be calibrated against standard buffer solutions before use.

Specifications & Metrics

• MEASURES: H⁺ activity (pH)