Subsonic meters have long been used to provide quality flow measurements of both gases and liquids. Flow Systems designs, manufactures and integrates subsonic VenturisASME Flow Nozzle and orifice meters for use in many applications. The mass flow through an subsonic meter is proportional to the square root of the product of density and the metering differential pressure. Thus these devices can service a range of mass flow rates at a constant density. This is an attractive feature in low-pressure systems.

Sonic Nozzles

Subsonic meters can be customized to accommodate a wide variety of design options including:

Advantages of Sonic Nozzles
  • Sizing
  • Bi-Directional Venturis
  • Cavitating Venturis
  • Line Size
  • End Connections
  • Material of Construction
  • Venturi Divergent Options
  • Meter Tubes

Subsonic meters create a restriction in the flow, which causes static pressure to be reduced as fluid velocity is increased. If the fluid state, area restriction, and differential pressure are known, the flow can be calculated accurately. These devices have different performance characteristics, the most significant being the overall pressure loss.

Advantages of Subsonic Meters
  • Internationally Recognized Flow Meters
  • Variable Flow
  • Long Term Accuracy
  • Good to Excellent Repeatability
  • No Moving Parts
Common Subsonic Meter Applications
  • Calibration of Flowmeters
  • PTC Applications
  • Flow Metering
  • Calibration of Turbine Engine Component Passages
  • Calibration of Automotive Component Passages
  • Measurement of Automotive Induction Air
  • Automotive Emissions Testing
  • Compressor or Pump Discharge Capacity Tests
  • Valve CV Tests
  • Flow Limiting both Choking and Cavitation
  • Over Speed Protection of Gas Flowmeters
Subsonic Meters Manufactured by Flow Systems

Flow Systems designs and manufactures subsonic VenturisASME Flow Nozzle, and orifice meters in accordance with both ASME and ISO standards. The geometry is such that the gas is accelerated along the circular arc converging section and then is expanded in a conical diverging section, which is designed for pressure recovery.

Subsonic Meter FormulaFlow Systems designs and manufactures subsonic meters in accordance with both ASME and ISO standards.

Without calibration, ASME predictions for flow rate accuracy are at best ±1.5% of reading. Flow calibrations traceable to NIST in conjunction with standard instrumentation packages allow for ±0.77% or ±0.50% of reading accuracy levels.

Calibration of subsonic meters installed in actual piping networks that contain fittings and valves gives extended confidence to flow measurements, especially when design constraints prevent less than optimal installations.

Multiple Element Arrays

Multiple subsonic meters can be fixtured between a common inlet and outlet plenum. This will increase rangeability and minimize installation requirements.

Flowrate Calculation Software

In addition to manufacturing subsonic meters, Flow Systems offers subsonic meter flowrate calculation software.