What are the verification procedures for ultrasonic water meters?

(1) Preparation Stage:

Sample meter pre-treatment: Clean the flow channel and remove air bubbles (ultrasonic water meters are sensitive to air bubbles); power on and preheat for 30 minutes to stabilize the electronic components.

Equipment calibration: The standard device uses the static mass/volume method (accuracy ≤ 0.2 grade), such as a standard set of metal measuring instruments; environmental control: water temperature (15~25℃), humidity (30~85%RH).

(2) Appearance and Structure Inspection and Compliance Verification:

Nameplate information (model, caliber, manufacturer, metering license mark);

Sensor installation angle (±0.5° tolerance);

Interface dimensions (DN15~DN400 comply with GB/T 778 standard).

Disqualifying defects: Cracks in the casing, transducer detachment, or damaged display screen → Directly judged as unqualified.

(3) Sealing Test Method:

Maintain pressure at 1.6 times the nominal pressure (PN1.6MPa meters require pressurization to 2.56MPa) for 2 minutes;

Acceptance criteria: Pressure drop ≤ 0.005MPa, no leakage or structural deformation.

(4) Static Metering Performance Test: Zero-point drift detection:

Close the valve and record the flow reading in the empty pipe state;

Allowable deviation: ≤ 1/3 of the error limit corresponding to the minimum flow rate (Q1).

Static current test: Current in sleep mode ≤ 10μA (to prevent excessive battery consumption).

(5) Dynamic Flow Rate Verification

Testing is performed on the flow rate standard device at 7 characteristic flow rate points:

Special Test Items:

Sound Velocity Verification: Inject water at different temperatures (5℃/50℃) and compare the calculated sound velocity with the measured value;

Bidirectional Flow Test: Reverse the pipe flow direction, the error change should be ≤0.5%.

(6) Electronic Characteristics and Function Verification: Signal Integrity:

Simulate strong electromagnetic interference (30V/m field strength), the error deviation should be ≤0.5%;

Communication Protocol Test: For water meters supporting MODBUS/M-Bus and other protocols, the data frame accuracy needs to be verified (≥99.9%);

Fault Diagnosis: Artificially create disconnections and air bubble blockages, and check whether the alarm code output is correct.

(7) Safety and Environmental Adaptability: IP Protection Rating:

IP68 water meters are immersed in 1 meter of water for 2 hours, with no water ingress;

Temperature Cycling: -25℃ (freezing for 4 hours) → +60℃ (baking for 4 hours) for 5 cycles, without degradation of metering performance.

(8) Data Verification and Conclusion Determination: Data Processing:

Outliers are removed (Grubbs' criterion), and the expanded uncertainty is calculated (k=2); Issuance of Certificates: Qualified: Issued with a green mandatory inspection mark + "Verification Certificate" (validity period ≤ 6 years); Unqualified: Issued with a "Notice of Non-conformity," listing the defects.

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