QuadraTherm® 640i Air Mass Flow Meter

June 19, 2014

featured QuadraTherm 640iIndustry's Most Accurate Thermal Mass Flow Meters

The QuadraTherm® 640i marks a breakthrough in thermal dispersion technology for air mass flow meters. With the 640i, you can enjoy the many benefits of immersible thermal technology – wide turndown ratio, very low pressure drop, no moving parts, application flexibility and a direct gas mass flow rate measurement – while achieving extreme precision with "percent of reading" accuracy, which for the first time rivals accuracies of coriolis technology. The QuadraTherm air flow meter is ideal for custody transfer, wastewater treatment, hazardous areas, facilities management and general process control applications where high accuracy is critical. An inline flow conditioned version is also available.

The four sensor, QuadraTherm air mass flow meter features our no-drift DrySense velocity sensor and works with the qTherm algorithm set to achieve accuracy of +/- 0.75% of reading above 50% of full scale (Accuracy statement verified by an independent NIST and NVLAP accredited metrology laboratory). The qTherm is also the "brain" behind the flowmeter's capability to change gas (Dial-A-Gas) and pipe size (Dial-A-Pipe) in the field – adding to the meter's ease of use and flexibility. Connected to the most up-to-date gases in our proprietary qTherm Gas Library, it also updates the instrument via the web.  Instrument software also features a unique multi-gas flow totalizer.

A small-diameter, 3/4-in. (19.1 mm) probe insertion point means easy process installation. The air mass flow meters measure up to 60,000 sfpm (305 smps) and feature a 100:1 turndown. In addition, while the meter always measures mass flow rate and temperature, the addition of a pressure sensor to the sensor probe creates a fully multivariable version. The ability to change gases and pipe sizes in the field adds to the ease of use and flexibility of the instrument. Use the field calibration validation and meter diagnostics package to assure the meter is always operating at top performance.

Our digital communications solutions offer engineers and systems integrators,  full industrial system integration and networking capability with Sierra's thermal mass flow meters. Digital communications solutions include: Foundation FieldbusModbus RTUProfibus DP, and HART. This flexibility of communication features offers turnkey solutions for  integration of Sierra's thermal mass flow meters into any industrial automation system or applicatio


  • Accuracy: +/- 0.75% of Reading above 50% of FS*
  • Fluid: All inert gases, flamables and corrosives
  • Flow range 0-60,000 sfpm (305 smps)
  • 100:1 Turndown
  • Multivariable: Mass flow rate, temperature & pressure
  • Revolutionary QuadraTherm®four-sensor design
  • DrySense™ no-drift sensor with lifetime warranty

*Verified by an independent NIST & NVLAP accredited lab

  • qTherm™ living, learning “Brain” manages all inputs
  • Dial-A-Pipe™ : Change pipe size
  • Dial-A-Gas™ : Change gas type
  • qTherm Gas Library: 18 gases & mixtures (growing & improving)
  • ValidCal™ Diagnostics: Assure performance
  • Smart Interface Program: Computer interface software
  • Foundation Fieldbus, Profibus DP, HART (pending)
  • CE,cFMus, ATEX, IECEx approved



Copyright © 2022 North East Technical Services | Site: Bergey Creative Group