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Created on 2025.03.04

Technical Comparative Analysis of Velocity Water Meters and Positive Displacement Water Meters

Technical comparison and analysis between velocity water meter and volumetric water meter

Technical Comparative Analysis of Velocity Water Meters and Positive Displacement Water Meters

1. Basic principles and structure

1.1 Velocity Water Meter

Working principle: Based on the principle of fluid dynamics, the flow rate is calculated by measuring the water flow velocity. When the water flows through the metering chamber, the impeller/turbine is driven to rotate, and the speed is proportional to the flow velocity.
Typical structure:
  • Single jet type: water flow single channel impact impeller (accuracy ± 2%)
  • Multi-jet type: water flows in multiple channels to evenly drive the impeller (accuracy ±1.5%)
  • Turbine type: Axial water flow drives high-precision turbine (accuracy ±1%)
  • Woltman type: large-diameter horizontal/vertical turbine structure (DN50-DN500)
Working Principle: Based on hydrodynamics, calculating flow by measuring water velocity. Water flow drives impeller/turbine rotation in metering chamber, with rotational speed proportional to flow velocity.
Typical Structures:
  • Single-jet type: Single-channel flow impacts impeller (Accuracy ±2%)
  • Multi-jet type: Multi-channel flow evenly drives impeller (Accuracy ±1.5%)
  • Turbine type: Axial flow drives high-precision turbine (Accuracy ±1%)
  • Woltman type: Large-diameter horizontal/vertical turbine (DN50-DN500)

1.2 Positive Displacement Water Meter

Working principle: Adopt mechanical isolation measurement method to achieve cumulative measurement by accurately measuring a fixed volume of fluid space.
Typical structure:
  • Piston type: reciprocating piston separates the metering chamber (accuracy ±0.5%)
  • Rotary piston type: the elliptical piston and the inner wall of the metering chamber form a crescent cavity
  • Nutating disk type: the nutating motion of the disk in the conical cavity
  • Dual rotor type: two 8-shaped rotors rotate in opposite directions (industrial standard)
Working Principle: Using mechanical isolation method, achieving cumulative measurement by precisely metering fixed-volume fluid spaces.
Typical Structures:
  • Piston type: Reciprocating piston divides metering chamber (Accuracy ±0.5%)
  • Rotary piston type: Oval piston forming crescent chambers with inner wall
  • Nutating disc type: Disc nutates in conical chamber
  • Twin-rotor type: Two figure-8 rotors counter-rotating (Industrial grade)

2. Performance Characteristics Comparison

2.1 Advantages of velocity water meters

  1. Pressure loss characteristics: Streamlined structure brings 0.03-0.1MPa low pressure loss
  2. Range ratio: up to Q3/Q1=100:1 (electronic type up to 250:1)
  3. Economical: Manufacturing cost is 30-50% lower than volumetric type
  4. Large flow adaptability: DN500 caliber maximum flow rate can reach 3000m³/h
Advantages:
  1. Pressure loss: Streamlined structure with 0.03-0.1MPa low pressure drop
  2. Turndown ratio: Up to Q3/Q1=100:1 (250:1 for electronic types)
  3. Cost-effectiveness: 30-50% lower manufacturing cost
  4. High-flow capacity: Max 3000m³/h for DN500 models

2.2 Advantages of volumetric water meters

  1. Measuring accuracy: up to 0.5 level accuracy in the range of Q2-Q4
  2. Starting flow: can detect a small flow of 0.5L/h
  3. Fluid compatibility: can measure high viscosity liquids (up to 100cSt)
  4. Anti-interference: Not affected by pipeline vibration and electromagnetic interference
Advantages:
  1. Accuracy: Class 0.5 accuracy in Q2-Q4 range
  2. Start-up flow: Detect minimum 0.5L/h flow
  3. Fluid compatibility: Measure high-viscosity liquids (up to 100cSt)
  4. Anti-interference: Immune to pipeline vibration and EMI

3. Key Technical Differences

Comparison Dimensions
Velocity water meter
Volumetric water meter
Measuring principle
Flow rate-volume conversion
Direct volume measurement
Moving Parts
Impeller/turbine single shaft rotation
Piston/rotor compound motion
Accuracy curve
Stable accuracy in high flow rate area
Full range linear accuracy
Water quality requirements
Particles > 100 μm need to be filtered
Particles > 50 μm need to be filtered
Maintenance cycle
5-8 years (mechanical)
3-5 years (lubrication maintenance required)
Temperature adaptability
-30℃~+90℃
-10℃~+60℃
Key Technical Differences:
Aspect
Velocity Meter
Positive Displacement
Principle
Velocity-volume conversion
Direct volume measurement
Moving parts
Single-axis impeller
Complex piston/rotor motion
Accuracy curve
Stable at high flow
Linear full-range accuracy
Water quality
Filter＞100μm particles
Filter＞50μm particles
Maintenance
5-8 years (mechanical)
3-5 years (lubrication)
Temperature
-30℃~+90℃
-10℃~+60℃

IV. Application scenario recommendations

4.1 Typical applications of velocity water meters

  1. Municipal water supply network: DN40-DN500 main pipeline monitoring
  2. Industrial circulating water: power plant cooling water system (flow rate > 100m³/h)
  3. Agricultural irrigation: sprinkler/drip irrigation system (sand content <5kg/m³)
  4. Building water supply: high-rise building zone metering (rectifier required)
Typical Applications:
  1. Municipal water supply networks (DN40-DN500)
  2. Industrial circulation systems (＞100m³/h)
  3. Agricultural irrigation (sand content＜5kg/m³)
  4. Building water supply (with flow conditioner)

4.2 Typical applications of volumetric water meters

  1. Household metering: 1.5-level accuracy cold water meter (Q3=2.5m³/h)
  2. Commercial complex: air conditioning refrigerant water metering (viscosity 1-10cSt)
  3. Food and pharmaceutical industry: CIP cleaning system (sanitary certification required)
  4. Prepayment system: IoT smart water meter (pulse signal output)
Typical Applications:
  1. Residential metering (Class 1.5, Q3=2.5m³/h)
  2. Commercial HVAC systems (1-10cSt viscosity)
  3. Food/pharmaceutical CIP systems (sanitary grade)
  4. Prepayment IoT smart meters (pulse output)

5. Technology Development Trends

  1. Composite design: combined metering of velocity and volume (such as Badger Meter's HYBRID technology)
  2. Non-magnetic sensing: optical encoding or inductive signal acquisition (to solve the problem of magnet demagnetization)
  3. Self-powered technology: turbine power generation + supercapacitor energy storage (EN 1434 standard certification)
  4. Digital Twin: Built-in traffic self-diagnosis algorithm (ISO 4064:2017 standard)
Development Trends:
  1. Hybrid design: Combined velocity+displacement (e.g. Badger Meter HYBRID)
  2. Non-magnetic sensing: Optical/inductive signal acquisition
  3. Self-powering: Turbine generation + supercapacitor (EN 1434)
  4. Digital twin: Embedded flow diagnostics (ISO 4064:2017)
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