The maximum permissible error (MPE) standards for mechanical water meters are classified based on international/regional technical specifications (e.g., ISO 4064, OIML R49) and meter accuracy classes, with divisions primarily depending on flow rate ranges and meter types (volumetric or turbine-type).
The classification of maximum permissible error (MPE) for mechanical water meters adheres to globally recognized standards such as ISO 4064 (International Organization for Standardization) and OIML R49 (International Organization of Legal Metrology). The core classification principles are as follows:
- Accuracy Class Definition: Mechanical water meters are categorized into accuracy classes (e.g., Class 1, Class 2 per ISO 4064-1) based on their measurement performance. Each class specifies mandatory MPE limits across distinct flow rate intervals.
- Flow Rate Interval Division: The operating flow range of a water meter is divided into two key intervals: the “low flow rate range” (from the minimum flow rate Q₃ to the transitional flow rate Q₂) and the “high flow rate range” (from Q₂ to the overload flow rate Q₄).
- MPE Limit Specification: For Class 1 meters, the MPE is ±5% within the low flow range and ±2% within the high flow range. For Class 2 meters, the MPE is ±3% in the low flow range and ±2% in the high flow range. These limits ensure consistent measurement reliability across actual usage scenarios.
- Special Requirements for Small-Diameter Meters: For domestic small-diameter mechanical water meters (e.g., nominal diameter ≤15 mm), additional provisions may apply to the “minimum flow rate (Q₃)” error to ensure accurate measurement of low-flow or dripping conditions.
All classifications are designed to align with practical water consumption patterns, balancing measurement precision with operational feasibility for legal metrology and commercial use.
Post time: Nov-18-2025