Inline Thermal Mass Flow Meter with Flow Conditioning - QuadraTherm® 780i

QuadraTherm® 780i Inline Mass Flow Meter Offers Higher Performance

The QuadraTherm® 780i is the most accurate inline thermal mass flow meter for air/gas flow rate measurement on the market today, achieving gas mass flow rate accuracy never before possible, +/- 0.5% of reading above 50% of full scale. The QuadraTherm rivals accuracies of Coriolis technology for measuring gas mass flow rate with a breakthrough thermal dispersion technology achieving “percent of reading” accuracy.

Change Gas Mixtures in the Field-No Recalibration Needed

Each QuadraTherm thermal flow meter comes with on board qMix(tm) gas mixing software which allows you to create custom gas mixtures in the field to compensate for gas compositional changes-no costly recalibration needed. Perfect for managing changes in flare gas composition in the field for upstream oil & gas flare gas measuring applications and other applications in which gas composition fequently changes. Learn more.

Boiler MACT Certified

The QuadraTherm thermal mass flow meter is also ideal for compliance for Boiler MACT regulations for inlet fuel measurements for area source boilers (40 CFR 63, subpart JJJJJJ) and for major source boilers (40 CFR 63, subpart DDDDD).

  • Achieve the highest accuracy +/- 0.5% of reading
  • Eliminate drift with DrySense sensor
  • Reduce straight-run requirements with built-in flow conditioning
  • Needs only 1-diameter up and zero downstream diameters
  • Validate in the field for easy in-situ calibration
  • Backed by lifetime sensor warranty
  • Boiler MACT certified for area source boilers (40 CFR 63, subpart JJJJJJ) and for major source boilers (40 CFR 63, subpart DDDDD)
  • Part of Sierra's Big-3 iSeries family of flow meter technologies
QuadraTherm® 780i Inline Mass Flow Meter

QuadraTherm® 780i Inline Mass Flow Meter

Technical Details

Accuracy +/- 0.5% of Reading above 50% of full scale*
Repeatability +/- 0.15% of full scale
Pipe sizes 1.0" to 8.0" (1.3cm to 20.3cm)
Flow range 0 to 60,000 sfpm (305 smps)
Turndown 100:1
Measures All inert gases and all non-condensing clean gases
Flammable gases methane, propane, hydrogen, digester gas, natural gas
Corrosive gases Compatible with 316L stainless steel
Gas/ambient temperature -40°F (-40°C) to 392°F (200°C)
Response time three seconds to achieve 63% (one time constant) of final value
Power supply 100 to 240 VAC (0.4 Amps RMS at 230 VAC); 24 VDC +/- 10%, 1 Amp
Construction 316 stainless steel
Output signals RS-232, 4-20 mA flow, 4-20 mA temperature, 4-20 mA pressure (optional)
Alarm output (contact SPST/opto relays)
Pulse output User definable for totalized flow
Digital Communciations Foundation Fieldbus, HART, Modbus RTU, and Profibus DP
Hazardous-Area Location Enclosure (IP66)
  • cFMus–Explosion proof for Class I, Div I, Groups B,C,D
  • CE–European Conformity

*Verified by an independent NIST & NVLAP accredited lab

Product Information

Dry Sensor Offers True InSitu Calibration

QuadraTherm introduces a patented four-sensor thermal mass air flow meter design—three precision platinum temperature sensors and one patented DrySense mass velocity sensor backed by a lifetime warranty. This precision flow meter for air and gas measurement is available in the 640i air/gasflow meter insertion version and this 780i inline version.

The QuadraTherm

  • Introduces a patented four-sensor thermal mass air flow meter design—three precision platinum temperature sensors and one patented DrySense mass velocity sensor
  • Is backed by a lifetime warranty
  • Features built-in flow conditioning to drastically reduce upstream straight-run requirements, making the meter ideal for tight pipe configurations

Features Sierra’s proprietary Raptor OS™ operating system (formerly known as qTherm®)

QuadraTherm’s four sensor technology provides the critical inputs for Raptor's living, learning algorithm set and gas database to accurately manage changes in gas and pipe selection, gas temperature, gas pressure and outside temperature.

Accuracy Never Before Possible

From Sierra’s beginning over 40 years ago, Founder Dr. John G. Olin was driven by the vision of supplying industrial customers with the world’s most accurate thermal air mass flow meter. He knew it was a “sensor” game. The development of an industrialized metal-sheathed sensor in the early ’80s was Sierra’s first big step, but Dr. Olin, a driven innovator who saw thermal mass flow as his life’s work, knew this was only the beginning. Many successful innovations followed, but in 1999 Sierra experienced a major breakthrough with the introduction of its patented, no-drift DrySense™ thermal mass velocity sensor. Sierra engineers now recognized they were on the cusp of realizing Dr. Olin’s vision.

Realizing the Vision

Thermal technology, by its very nature, uses the physics of heat transfer and conservation of energy in a closed system to measure mass flow rate. This means that for thermal air mass flow meters to achieve greatest accuracy, they must solve the First Law of Thermodynamics (Heat Energy In = Heat Energy Out) for each data point. As you can imagine, solving the First Law in a flow instrument was no easy task. By Dr. Olin’s own accounting, it took decades of his and the Sierra engineering team’s “hard-nosed dedication to excellence,” years of testing and his stack of yellow note pads over five feet high—j jammed with his handwritten equations and designs—to finally yield the secret in the form of QuadraTherm and Raptor OS, now both patented worldwide.

Product Benefits

  • Patented breakthrough QuadraTherm "Quad" 4-Sensor thermal sensor technology
  • Patented zero drift DrySense™ velocity sensor
  • Lifetime warranty on sensor
  • "Percent of reading" accuracy, which for the first time rivals accuracies of Coriolis technology
  • Sierra's state-of-the-art ISO 9000 closed-loop calibration facility matches each application for best accuracy
  • Greenhouse Gas (GHG) certified to meet EPA (40 CFR Part 98)
  • Ideal for high accuracy applications like custody transfer, wastewater treatment, hazardous areas, facilities management and general process control applications
  • Built-in flow conditioning elements drastically reduce upstream straight-run requirements
  • Features our proprietary Raptor OS operating system (formerly known as qTherm)
  • ValidCal™ Diagnostics: Field calibration validation and meter diagnostics to assure operating performance.
  • Multivariable outputs - gas mass flow rate, temperature and pressure
  • Total of four gases onboard; capability to change gas (Dial-A-Gas) in the field
  • Capability to change pipe size (Dial-A-Pipe®) in the field
  • Unique multi-gas flow totalizer and alarms
  • High flows up to 60,000 scfm (305 smps)
  • Range of process connections
  • Very low pressure drop
  • No moving parts
  • Free computer interface software
  • Free Raptor software to create custom gases or mixtures to compensate for compositional changes; upload mixtures to the unit in the field  
  • Connected to the most up-to-date gases in our proprietary Raptor Gas Library, update the instrument via the web
  • An insertion version for pipes/ducts up to 72 inches (2 m) available - Model 640i
  • Large LCD display and pushbutton interface, remote enclosure mounting available
  • Multi-language display interface: English, German, Chinese, Spanish, Dutch
  • Certified for Boiler MACT measurement meeting EPA regulations for area source boilers (40 CFR 63, subpart JJJJJJ) and for major source boilers (40 CFR 63, subpart DDDDD)

Operating Principle

The principles of operation in thermal mass flow technology and how thermal dispersion mass flow meter technology works.

Thermal dispersion technology provides direct mass flow measurement featuring: no pressure or temperature compensation needed; no moving parts; low pressure drop; and high turndown.

Sierra’s unique QuadraTherm™ sensor probe is responsible for the unsurpassed accuracy, ruggedness, and reliability of Sierra industrial flow meters. The immersible sensor consists of four sensing elements–a velocity sensor, a temperature sensor, and two stem conduction sensors that measure heat lost to the outside.

When power is applied to the flow meter, the transducer electronics heats the velocity sensor to a constant temperature differential above the gas temperature and measures the cooling effect of the gas flow. The electrical power required to maintain a constant temperature differential is directly proportional to the gas mass flow rate. The two stem conduction sensors ensure that any heat lost is due to this cooling effect, and not due to conduction to the outside.

The velocity sensor is a reference-grade platinum resistance temperature detector (RTD). The platinum RTD wire is wound on a rugged ceramic mandrel for strength and stability. The temperature sensor is clad in 316 stainless steel. The velocity sensor is clad in a Pt/Ir Alloy.