The standard "JB/T 9456-1999 Mechanical ventilated wet and dry meters, technical conditions" specifies the technical requirements and performance indicators of mechanical ventilated wet and dry meters. The standard is applicable to equipment measuring Humidity and temperature in the environment, ensuring its accuracy and Reliability in industrial and scientific research applications. The standard covers the design, manufacture, calibrating and testing methods of equipment, and guides the technical specifications to be followed in the production and use process to meet the needs of different application scenarios.