JJF 1575-2016 "Outline for Type Evaluation of Laboratory pH (acidity) Meters" is applicable to the type evaluation of laboratory pH (acidity) meters with classification code 46080500. The standard describes in detail the working principle and composition structure of laboratory pH Meters, mainly through the measurement of pH value of aqueous solutions by potentiometry. The instrument is composed of pH meter unit and electrode unit, wherein the meter unit includes Impedance converter, amplifier, function regulator and display, etc.; The electrode unit includes indicator electrode and reference electrode. Common electrode types include Glass electrode, Hydrogen electrode, hydroquinone electrode, etc. The standard also describes the use of pH composite electrodes to facilitate experimental operation. Measurement principle is based on the comparison method. After calibrating with standard buffer solution, the pH value of the tested solution is measured. The standard refers to the laboratory pH Meter and related standard documents to ensure the accuracy and Reliability of the evaluation process. It is suitable for the needs of accurate measurement and calibrating of solution acid alkalinity in scientific research laboratories and industrial production.