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Thermal Gas Mass Flowmeter Technology

Flow Rate of DP FlowmeterFlow Rate of Fox Flowmeter  

Thermal Gas Mass Flowmeter Technology

All thermal Gas Mass Flow Meters from Fox utilize the thermal sensing principle, a proven, accurate direct mass flow measurement technology. This technology performs at high levels of accuracy for a wide variety of gases.

Theory of Operation in Gas Flow Measurement Technology

Fox Thermal Flow Meters use a constant temperature differential (constant Δ T) technology to measure mass flow rate of air and gases. Fox Models FT2A and FT3 are equipped with the PowerPro™ Sensor while the Model FT1 has the DDC-Sensor™. Both thermal mass flow sensors consist of two Resistance Temperature Detectors (RTD’s). The sensor elements are constructed of a reference grade platinum wire wound around ceramic mandrels that are inserted into stainless steel tubes.
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For specific information on the features available on the Fox Models:  

DDC-Sensor™ Technology Description
The Fox DDC-Sensor™ is a new state of the art sensor technology used in the Fox Model FT1 Thermal Gas Flow Meter. The DDC-Sensor™, a Direct Digitally Controlled sensor, is unlike other thermal flow sensors available on the market. Instead of using traditional analog circuitry, the DDC-Sensor™ is interfaced directly to the FT1 microprocessor for more speed and programmability. The DDC-Sensor™ accurately responds to changes in process variables (gas flow rate, pressure, and temperature) which are used by the microprocessor to determine mass flow rate, totalized flow, and temperature.

Fox’s DDC-Sensor™ provides a technology platform for calculating accurate gas correlations. The FT1 correlation algorithms allow the meter to be calibrated on a single gas in the factory while providing the user the ability to select other gases in the Gas-SelectX® gas menu. Fox’s Model FT1 with its DDC-Sensor™ and state-of-the-art correlation algorithms provide an accurate, multi-gas-capable thermal gas flow meter.

Learn More about the FT1 Flow Meter
The PowerPro™ Sensor: A High-Powered Technology

Compared to a typical Differential Pressure type flowmeter, the PowerPro™ sensor offers better low flow or low end sensitivity and exceptional accuracy at high velocities.

The PowerPro™ Sensor operates at twice the power level than competitor sensors to achieve a higher sensitivity to flow; even at very low flow rates. A wider measurement range - 50 to 60,000 SFPM – and a fast response time (0.9 seconds) make the flowmeters that use the PowerPro™ Sensor able to measure accurately for a long list of industries and applications.

The PowerPro™ Sensor uses a bridge-type connection to interface with the flowmeter’s microprocessor. Fox flowmeters were the first flowmeter on the market to carry on-board microprocessors. Fox has been leading the market with technological advancements like onboard communication protocol options, as well.

Learn More about the FT2A Flow Meter      Learn More about the FT3 Flow Meter
Benefits of Using Thermal Gas Mass Flow Over Other Technologies
Fox Models FT2A and FT3 use the Fox PowerPro™ sensor* and the Model FT1 uses the DDC-Sensor™ to measure mass flow rate. All Fox meters share these benefits:
  • Direct mass flow measurement of air and gases in standard volumetric units (ie SCFM or NM3/H) or mass units (ie lbs/m or kg/h)
  • No additional pressure or temperature compensation required
  • Exceptionally broad measurement range: up to 1000:1 (100:1 typical)
  • Standard linear 4 to 20 mA output proportional to mass flow rate
  • Low pressure drop
  • No moving parts
  • Insertion (all Fox models) and inline (FT2A & FT3 only) configurations
  • Microprocessor based, field rangeable electronics
  • Proprietary DDC-Sensor™ and Power Pro™ Sensor
  • Measures flow rate and flow total
*standard and high gas temperature range sensors are available.

There are many benefits of thermal gas mass flow meters over other flow measurement technologies. Thermal Mass Flow Meters have no moving parts or orifices which eliminate the need to replace bearings and prevent undetected shifts in accuracy. They also don’t require temperature or pressure compensation and provide excellent accuracy and repeatability over a wide range of flow rates. They calculate mass flow, rather than volume, and are one of the few technologies that can measure flow in large pipes. They are easy to install and come in both insertion and inline styles. Furthermore, Fox Thermal Instruments offers a wide variety of communication options and NIST-traceable “actual condition” calibrations to suit almost any application. The thermal mass flow meter is cost effective and accurate making it an excellent choice for a wide variety of gas flow applications.

Learn More about the FT2A Flow Meter
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