The selection of large-diameter ultrasonic water meters directly impacts measurement accuracy, operational convenience, and service life. It requires comprehensive evaluation based on actual operating conditions, with core considerations summarised across five key dimensions:

I. Precise Flow Range Matching

Flow parameters form the core prerequisite for selection. Three key indicators must first be established: the typical flow rate, minimum flow rate (Q1), and maximum flow rate (Q3) within the actual water usage scenario. The primary advantage of large-diameter ultrasonic water meters lies in their wide range ratio. The standard range ratio (Q3/Q1) typically ranges from 100 to 500. When selecting a model, it is advisable to prioritise those with a range ratio ≥250. This ensures no data loss at low flow rates and prevents exceeding the measurement range at high flow rates, thereby achieving precise measurement across all operating conditions.

Example: For a typical flow rate of 50m³/h and a maximum peak flow of 500m³/h, select a model with Q1 ≤ 50m³/h and Q3 ≥ 500m³/h, while ensuring the range ratio meets requirements.

II. Accuracy Class for Application Scenarios

Accuracy class must align closely with the usage scenario to avoid ‘over-specification’ or ‘insufficient accuracy’:

- For routine monitoring or internal accounting, Class 2 accuracy fully meets requirements and offers better value for money;

- For trade settlement, water bill collection, or other scenarios demanding stringent measurement accuracy, Class 1 products must be selected.

Special note: Accuracy class must align with the selected flow range. If actual flow consistently falls below Q1 or exceeds Q3, measurement accuracy will significantly deteriorate. This issue should be mitigated by adjusting the flow range or optimising operating conditions.

III. Installation and Environmental Compatibility

1. Pipeline Compatibility

Two core requirements must be verified prior to installation: Firstly, the pipe's internal diameter must precisely match the water meter's nominal bore to prevent flow turbulence caused by mismatched diameters. Secondly, straight pipe run requirements must be met, typically necessitating a 10-times pipe diameter (10D) straight section upstream and a 5-times pipe diameter (5D) straight section downstream (where D is the pipe diameter). Where space constraints exist, consult the manufacturer in advance to select specialised models compatible with shorter straight pipe runs.

2. Water Quality and Environmental Compatibility

- Water Quality Compatibility: Where the medium contains contaminants such as silt, sand, or suspended impurities, select meter models with strong interference resistance. Prioritise products with a protection rating of ≥IP68 to prevent metering failure due to water quality erosion.

- Temperature Compatibility: Standard models suffice for ambient temperatures (0–30°C). For high-temperature (>30°C) or low-temperature (<0°C) environments, select specialised water meters with high-heat resistance or low-temperature freeze protection to prevent damage to internal components.

IV. Aligning Communication and Functional Requirements

1. Communication Method Selection

From an operational efficiency perspective, prioritise water meters with NB-IoT or 4G wireless communication. These enable remote meter reading, real-time data uploads, and abnormal flow alerts, significantly reducing manual inspection costs. Where network coverage is unavailable at the installation site, wired communication (RS485) models may be selected for integration with local data acquisition terminals.

2. Value-Added Function Selection

Select value-added functions according to management requirements to avoid redundancy:

- Prepaid management scenarios: Opt for valve control functionality to enable automatic shut-off for unpaid bills and remote valve reopening upon payment;

- Multi-system integration scenarios: Select data pass-through capability with strong compatibility to ensure seamless integration with existing water management platforms;

- Complex operational scenarios: Add pressure monitoring and flow curve recording functions to assist in pipeline network performance analysis.

V. Ensuring Brand and Quality Compliance

Large-diameter water meters are subject to mandatory verification as measuring instruments. When selecting models, two core qualifications must be verified: Firstly, the product must possess a Measuring Instrument Type Approval Certificate (CPA), ensuring compliance with national standards such as the ‘Cold Water Meter’ (GB/T 778-2021). Secondly, prioritise brands with strong market reputation and comprehensive after-sales service. Refer to application cases from large-scale water projects within the industry, focusing particularly on the product's long-term stability and fault response efficiency.