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Consistent Thermal Flow Meter Measurement for Increased Accuracy and Profitability

With more than 40 years of experience developing and selling inline and insertion thermal flow meter technology, Sierra has established a large and successful installed base. Our immersible thermal gas mass flow meters were also deemed North America's #1 selling immersible thermal mass flow meter (2009 Flow Research, Yoder). We offer both inline and insertion thermal mass flow meters for heavy and light industrial applications. Our thermal flow meters range from our highest-performance QuadraTherm four-sensor technology to our more traditional, but also very accurate, two-sensor technology instruments.

Sierra’s immersible thermal gas mass flow meter technology offers customers rugged and reliable industrial gas and air mass flow measurement for small pipes, as well as very large ducts or stacks that have non-uniform velocity profiles, high turn-down requirements, dirty gas streams, wide temperature ranges, and fast velocity and temperature changes. With our new 640i QuadraTherm thermal flow meter, now you get extreme precision with percent of reading accuracy as part of the total QuadraTherm package.

All of our thermal gas flow meters feature the long-term stability of our patented no-drift DrySense swaged velocity sensor technology and are backed by a lifetime warranty. As the name implies, Sierra’s swaged velocity sensor is the only thermal sensor in the world that is truly “dry” using no organic or cement fillers that crack and shift causing drift over time. For specified heavy industrial products, we offer the following digital communications solutions: HART, Modbus RTU, and Profibus DP. View all of our digital communications solutions, offering turnkey results for industrial systems automation and control.


  • Fiberglass Manufacturing Requires Precise Gas Ratio Control
    Fiberglass insulation manufacturing is almost akin to making cotton candy!  A mixture of silica and other components are melted and passed through a spinning extruder, then rapidly cooled with compressed air. As older fiberglass manufacturing...
  • Multipoint Systems Measure Flare Gases
    To mitigate greenhouse gas emissions, many companies reuse their biogas for cogeneration, but the amount of biogas produced often exceeds the amount needed for cogeneration. In such cases, it is often not economical to purify, compress and store...
  • Conforming to GHG Reporting Rules
    In 2011, a new EPA rule (40 CFR Part 98) went into effect requiring a wide range of companies that emit Green House Gases (GHG) to submit annual reports to the EPA. These were primarily large facilities emitting 25,000 metric tons of carbon...
  • Helping China Deliver Cleaner Coal Power
    To keep pace with the electricity demands of its rapidly growing economy, China’s coal-fired power plant construction is booming. Conscious of their environmental impact, China has focused on building efficient, low polluting plants. One...
  • Producing Biogas from Solid Wastes
    Santa Cruz Wastewater Treatment Facility, located in Santa Cruz, California, generates the majority of its own electric power by using internal combustion engines that burn a mixture of methane gas produced by the sewage digestion process and...
  • Controlling Natural Gas Usage Costs
    A large American engine manufacturer required mass flow meters to measure natural gas usage in each of the eleven buildings on their campus. Natural gas is used to fire furnaces and other equipment. Because each facility is a separate profit center,...
  • Tuning Combustion Ratios in the Field
    For a major European gas manufacturer, the burner control systems in their power generators had long relied on three different technologies for natural gas mass flow measurement. These included a rotameter with integrated microprocessor to calculate...
  • Smart Compressed Air Measurement
    Air may be free, but compressed air certainly isn’t. Every day, leaks and inefficient compressors cost companies money and lead to more electricity usage. As air  compressors churn away 24/7, endlessly maintaining the air pressure in...
  • Air Usage Data Increases Company Profit
    A large American container company required mass flow meters on their air compressor lines to help evaluate the efficiency of blow mold machines in their plant. The manufacturer melts PET chips and extrudes them through blow mold machines to produce...
  • Boosting Gas Pipelines to Optimum Levels
    As gas pressure drops in the gas pipeline network, the transportation capacity is reduced. Compressor plants are used to boost gas pressure back up to optimum operating levels. Monitoring fuel gas to compressors is typically accomplished with an...
  • Flowmeter Choice Affects Efficiency in WWTP
    Wastewater treatment plant operators increasingly, in today's competitive climate, have to meet mandates to fine tune their plant's performance efficiency. One way to do this and save thousands of dollars is to choose the right ...

  • Exploring In-Situ Thermal Flow Meter Calibration Validation
    In-situ calibration validation is one of the great benefits of thermal mass flow technology. This video reviews in-situ calibration validation and details how the DrySense sensor stability found in Sierra thermal flow meters is the only way a...
  • How Thermal Dispersion Mass Flow Meter Technology Works
    In this NEW video from Sierra, you’ll learn the operational principles of thermal dispersion mass flow technology. Industrial thermal mass flow meters, also known as thermal dispersion or immersible thermal mass flowmeters, comprise a family...
  • Flow Meter Recalibration and Repair Made Easy
    Learn about your Sierra Online Account and My Units Recalibration & Repair portal features you now have available to you. Travers Newell, associate project manager at Sierra Instruments, demonstrates how fast and easy it is to manage your mass...
  • Multi-Gas Flow Totalizer for QuadraTherm 640i/780i
    Sierra Instruments' Smart Interface Program (SIP) for QuadraTherm 640i/780i mass flow meters provides end-users with a powerful feature to totalize four unique gases independently. Learn how to set up and use this flow totalizer feature. Get the most...
  • How to Buy Industrial Flow Meters Online
    This Sierra Instruments video demonstrates how to easily order our in stock industrial mass flow meters online. We also show you all of the in stock mass flow meters and controllers available on Sierra's online store-all for 1 day delivery. The video...
  • Gas Flow Measurement - The Smart Way
    Sierra’s 780 mass flow meter with built-in flow conditioning provides precise flow measurement with the shortest piping requirements of any mass flow meter in the industry. One difficulty in measuring gas flow is that any change in the...
  • In-Situ Calibration
    Mid-to-large size facilities and campuses inevitably have hundreds of flow instruments to monitor, maintain, and repair. For a reliability engineer, ensuring that all instrumentation meets ISO 9000 or similar standards is a time-consuming...
  • Advances in Thermal Dispersion Mass Flow Meters - Part 1: Principle of Operation
    This paper by Sierra founder Dr. John G. Olin, describes an advanced microprocessor-based thermal dispersion mass flow meter that uses four temperature sensing elements in its flow sensor instead of the traditional two elements and has a dry velocity...
  • New Developments in Thermal Dispersion Mass Flow Meters
    This by Sierra founder, Dr. John G. Olin,paper describes a newly developed microprocessor-based thermal dispersion mass flow meter that uses four temperature sensing elements in its flow sensor instead of the traditional two elements...
  • In-The-Field Compensation for Changes in Natural Gas Composition
    The flow of natural gas in pipelines is often complicated by changes in the composition of the gas. The method described in this paper solves the problem of variable composition via a new four-temperature mass flow sensor. The new flow sensor feeds...
  • Advances in Thermal Dispersion Mass Flow Meters - Part 2: Installation and Flow Calibration
    Part 1 of this two-part series by Sierra founder, Dr. John G. Olin, describes the principle of operation of a new microprocessor-based thermal dispersion mass flow meter that uses four temperature sensing elements in its flow sensor and has a dry...
  • Introducing a New Paradigm for Thermal Dispersion Mass Flow
    Since the publication of the American Society of Mechanical Engineers (ASME) standard on thermal dispersion mass flowmeters in 2011, there have been major advancements in the technology. A review of that standard and a discussion of technology...
  • Sub-Metering of Natural Gas
    Traditionally, utility companies have used diaphragm meters to measure natural gas usage, which is then charged to customers on their monthly energy bill. Although diaphragm meters are a trusted billing mechanism by utility companies, they may not...
  • Flare Gas Mass Flow Metering
    As the drive towards energy independence in the United States continues at full speed, oil and gas companies are turning to hydraulic fracturing to increase production. Increasingly stringent state and national regulations for flare gas in particular...
  • QuadraTherm Sensor - Conquering the Problems
    Dr. Olin describes how all the problems that existed with Thermal Technology have been solved with the QuadraTherm sensor and qTherm algorithm set. The QuadraTherm sensor provides critical inputs to the qTherm algorithm to get highly accurate...
  • Relationship Between QuadraTherm Thermal Mass Flow Meter & Outside Temperature
    The secret to solving the first law of thermodynamics for thermal dispersion technology was revealed in the form of two revolutionary technologies—QuadraTherm® and qTherm® thermal mass flow meters, now both patented worldwide after...
  • Invention of the Perfect Thermal Sensor
    In early 2012, inventor Dr. Olin at his home in Carmel Valley, California, tells his thermal technology innovation story and how perfecting the immersible thermal sensor has been his life's work. He explains his key breakthrough discoveries in...
  • qTherm Living, Learning Math
    Dr.Olin explains how the gas library gets better over time through math factors from the qTherm algorithm set. With qTherm technology, we can tune the math and develop the calibration curves within the qTherm brain.
  • Advanced Thermal Dispersion Mass Flowmeters
    Thermal dispersion (TD) mass flowmeters measure the mass flowrate of fluids (primarily gases) flowing through a closed conduit, such as a pipe. This article describes the operation and installation of TD mass flowmeters, and gives the reader...
  • Thermal Mass Flowmeters Fill the Bill in Precision Gas-Ratio Control Application
    Fiberglass insulation manufacturing is almost akin to making cotton candy. A mixture of silica and other components are melted and passed through a spinning extruder, then rapidly cooled with compressed air (see Figure). As older fiberglass...
  • The History & Evolution of Thermal Flowmeters
    Thermal flowmeters came onto the market in the mid-1970s, not long after Coriolis flowmeters. While the worldwide market for Coriolis flowmeters now exceeds $1 billion, the market for thermal flowmeters is under $150 million. Faced with such a wide...
  • A New Paradigm for Thermal Dispersion Mass Flow Meters
    Dr. John G. Olin, PhD, founder of Sierra Instruments, discusses the current ASME standard on thermal dispersion mass flow meters and recent technology advances in a his latest article, entitled “A New Paradigm for Thermal Dispersion Mass Flow...
  • Increase Efficiency and Production in WWTP with Flow Meters
    Wastewater treatment plant operators increasingly, in today's competitive climate, have to meet mandates to fine tune their plant's performance efficiency. One way to do this and save thousands of dollars is to choose the right  thermal mass...
  • Accounting for Stem Conduction
    A new article in IMT Fluid & Gas Journal discusses how Sierra’s thermal mass flow meters eliminate errors associated with traditional two-sensor mass flow meters. The result Coriolis level of accuracy, in a thermal meter.
  • The Quest for the Perfect Flow Meter
    Gases & Instrumentation had the opportunity to speak with Dr. John G. Olin, Founder and Chairman of the Board of Sierra Instruments about the evolution of thermal mass flow meters and his latest product in this...
  • Thermal Mass Flow Meters. What Does Half Percent Accuracy Really Mean?
    Sierra Instrument’s new QuadraTherm® 640i and 780i thermal mass flow meters promise to lift Thermal MFMs out of the commodity market.
  • Harnessing Biogas for Energy Savings
    For Santa Cruz Wastewater Treatment Facility (WWTF), dependability matters. Since 1989, this state-of-the-art WWTF, nestled in a shallow canyon in the coastal city of Santa Cruz...
  • A Market Prime for Boom
    Among the established flow measurement technologies, thermal flowmeters account for fewer units shipped than any other flow technology except for target meters. In perspective, thermal flowmeters, at a market size of under $100 million, represent...
  • In the Beginning
    Dr. John Olin, founder and chairman of Sierra Instruments, discusses the evolution of thermal mass flow measurement in this Q &A by Flow Control Magazine. 
  • Process Gas Mass Flow Controllers
    A mass flow controller (MFC) is used to control the flow of gases in a wide range of microelectronic processes. A well designed MFC maintains a constant flow within 1 percent of the full-scale flow, has a repeatabil­ity of 0.2 percent of full...
  • Industrial Thermal Mass Flowmeters
    Improved performance, enhanced user-interfaces and reduced cost-of-ownership have helped thermal mass flowmeters gain acceptance in the industrial process control market for gas flow measurements. Part I provides a comprehensive explanation of...
  • Choosing Flow Monitors for CEMS Applications
    As a result of the 1990 Clean Air Act Amendmentsl, electric power plants must reduce their emissions of sulfur dioxide and nitrous oxides—the primary causes of acid rain. The U.S. Environmental Protection Agency (EPA), in its...
  • Core Technology: Capillary & Immersible
    For gas mass flow measurement and control, Sierra offers the broadest selection of thermal mass flow measurement products on the market. This is because our thermal mass flow products incorporate two types of advanced thermal technologies, each...
  • Thermal Dispersion Mass Flow Meters
    Thermal dispersion mass flowmeters comprise a family of instruments for the measurement of the total mass flow rate of a fluid, primarily gases, flowing through closed conduits.  The operation of the thermal dispersion mass flowmeters is...
  • Power Industry Applications
    Precise, timely measurement of air, fuel, and gases is one way today's utilities can take action to protect themselves against rising costs and comply with increasingly stringent environmental requirements. Sierra thermal mass flow meters and control...
  • Chemical Industry Applications
    Today's chemical plants face escalating costs and tightening EPA control requirements. Sierra thermal mass flow meters provide the precise, useful data plants need. Thay can make a significant difference in all the following applicaitons.
  • Petroleum Industry Applications
    The measurement and control of gas flows in prodcution, refinery, and R&D operations has a direct effect on efficiency, costs, safety, and environmental standards. Sierra mass flow meters and controllers provide direct, fast-response measurements...
  • Pulp & Paper Industry Applications
    Rising cost and tighter emission control requirements have created a need for information that is more useful and precise. Sierra thermal mass flow meters fill this need and support cost-effective mill management in a number of applications.
  • Evolution of Thermal Mass Flow Meters
    John Olin, founder and CEO of Sierra Instruments, Inc., in Monterey, California, provides a historical perspective on the development of thermal mass flow. Thermo-Systems, Inc. (TSI) began in its founder’s basement in 1959, with a cooled-film...
  • QuadraTherm® 640i/780i Air Flow Meters Now With Full Suite of Global Agency Approvals-cFMus, ATEX and IECEx
    MONTEREY, CA — July 10, 2014 —Sierra Instruments, a leading global mass flow meter manufacturer, is pleased to announce its evolutionary QuadraTherm® 640i/780i air flow meters haves received global approvals for the...
  • New Animated Video Shows Principle of Operation of Thermal Mass Flow Meters
    MONTEREY, CA — April 24, 2014 — Sierra Instruments, a leading global mass flow instrument manufacturer, announces the release of their new video entitled, “Principle of Operation: Thermal Mass Flow Meter,” which shows how...
  • Sierra Instruments Announces New Digital Communication Protocol Web Resources
    MONTEREY, CA — June 3, 2013 —Sierra Instruments today announces its new digital protocol communication website functionality, making it easy for customers to get information about Sierra’s full suite of digital communications....
  • Sierra's QuadraTherm® 640i/780i Wins Industry Award
    MONTEREY, CA — March 25, 2013 — Sierra Instruments is pleased to announce that their new product, the QuadraTherm® 640i/780i flow meter is the Gold Winner for  Gases and Instrumentation’s 2013 Golden Gas Awards for...
  • Sierra Announces Never Before Possible Accuracy For Thermal Dispersion Technology
    Monterey, CA — November 1, 2012 — Sierra Instruments today introduces their new QuadraTherm® 640i / 780i Thermal Mass Flow Meter Series, marking a disruptive breakthrough in thermal dispersion technology. With its sensor design...
  • Sierra Increases Online Store Product Line
    Monterey, CA — May 25, 2012 —With the addition of the BoilerTrak™ 620S and FastFlo™ 620S industrial thermal mass flow meters to their online store, Sierra Instruments, a global leader in mass flow instrumentation, offers the...
  • New Chlorine Measurement Breakthrough
    Monterey, CA — November 15, 2011 — Sierra Instrument’s new Chlorine-Trak™ 760S Thermal Mass Flow Meter was specifically designed to perform as an accurate and cost-effective mass flow measurement solution for chlorine...
  • New Clean Energy Guide From Sierra
    Monterey, CA — January 17, 2011 —Sierra Instruments, a leading global mass flow instrument manufacturer, announces the publication of its new free 40-page Sierra Clean Energy Guide in printed format. The guide offers engineers, scientist,...
  • New Lifetime Warranty Policy for Sensors
    MONTEREY, CA — January 25, 2010 —Sierra Instruments has announced that it will offer lifetime warranty coverage for the Dry-Sense™ sensors in all Sierra Immersible Mass Flow Meters. Sierra has incorporated their proprietary...
  • New Flowmeters for GHG Reporting
    MONTEREY, CA — December 10, 2009 — This week, Sierra Instruments introduced a line of mass flow meters Certified by Sierra for Green House Gas (GHG) reporting. All Sierra GHG meters now conform to the new EPA rule (40 CFR Part 98), which...
  • Sierra a Pivotal Role in Biogas Production
    MONTEREY, CA – November 25, 2009 – In the conversion of solid wastes to high-efficiency fuel, digestion plays a critical first step in producing raw biogas.  For Santa Cruz Wastewater Treatment Facility, Sierra’s Immersible...
  • Sierra Shows AirTrak 628S At Testing Expo
    Lansing, MI – October 23, 2009 – Sierra Instruments’ Emissions Systems Division will show their Air-Trak™ Model 628S Engine Air Intake Mass Flow Meter at the Automotive Testing Expo in Novi, Michigan on October 27-29,...
  • Sierra Introduces New MultiTrak 670S
    MONTEREY, CA – July 15, 2009 –Sierra is proud to announce the release of its new Multi-Trak™ Model 670S Multi-Point Mass Flow Meter System. The new Multi-Trak™ Model 670S is an advanced state-of-the-art instrument for...
  • 640S Receives Russian Certification
    MONTEREY, CA – April 2, 2009 -- Sierra’s Steel-Trak™ Model 640S Thermal Mass Flow Meters have recently received both the  GOST R Certificate of Conformity (1Exd IIC T6…T2 ) for use in hazardous areas and the Pattern...
  • Sierra Instruments Receives CRN Approval
    MONTEREY, CA – March 13, 2009 -- Sierra Instruments is pleased to announce that all of its Scientific & Industrial Thermal Mass products now have CRN (Canadian Registration Number) approval. The successful qualification of Sierra’s...
  • 640S Flow Meter With Self-Cleaning Port
    MONTEREY, CA – February 27, 2009 –Sierra’s industry-leading Steel-Mass™ Model 640S Immersible Thermal Mass Flow Meter is now available with a new self-cleaning purge port field proven to remove even the toughest caked-on dust...
  • Sierra Releases High Temperature 640S
    MONTEREY, CA – February 17, 2008 –Sierra’s industry-leading Steel-Trak™ Model 640S Immersible Thermal Mass Flow Meter is now available in a high-temperature design capable of trouble-free operation in process temperatures up...
  • Sierra Introduces New AirTrak 628S
    MONTEREY, CA – October 17, 2008 –Sierra Instruments’ Emissions Systems Division will show their Air-Trak™ Model 628S  Air Intake Mass Flow Meter at the Automotive Testing Expo in Novi, Michigan on October 22-24,...
  • New Online Flowmeter Selections Tools
    MONTEREY, CA – April 30, 2008-- Sierra is proud to announce Flow Meter Selection Tools designed to help visitors research and identify the best Sierra flow meter for their gas, liquid, or steam application quickly and efficiently. Visitors can...
  • New Online Flow Application Resource
    Monterey, CA – January 17, 2008-- The Sierra Chronicles™ is a unique online resource that features real-life examples of how mass flow technology improves customer productivity and efficiency, saves money, and increases customer...
  • QuadraTherm┬« 640i Air Mass Flow Meter
    Worlds most accurate insertion thermal meter. Accuracy: +/- 0.75% of reading; 3/4-inch (19.1 mm) insertion probe up to 72-inch (2m) long, multivariable outputs, flow ranges up to 60,000 sfpm (305 smps). Agency approvals: CE, cFMus, ATEX, IECEx.
  • SteelMass 640S
    Traditional thermal insertion meter; Accuracy: ± 1.0% of reading +0.5% of full scale; Mass flow measurement workhorse in heavy industrial applications; Flow range is up to 20,000 sfpm (102 smps).
  • BoilerTrak 620S BT
    Optimized for boiler and heater effeciency applications; Product accuracy is ± 1% of full scale and the flow range is 80 to 1600 scfm (natural gas) with standard accuracy.
  • FastFlo 620S Mass Flowmeter
    Very fast 200 msec time-response; Product accuracy is ± 1% of full scale with flow range is up to 20,000 sfpm (102 smps) on air.
  • QuadraTherm┬« 780i Inline Mass Flow Meter
    Worlds most accurate inline thermal meter; Accuracy: +/- 0.5% of reading; inline version with built-in flow conditioning; multivariable outputs, flow ranges up to 60,000 sfpm (305 smps). Agency approvals: CE, cFMus, ATEX, IECEx.
  • FlatTrak 780S
    Traditional thermal inline meter; Accuracy: ± 1.0% of reading +0.5% full scale; Built-in flow conditioning; Flow range is up to 20,000 sfpm (102 smps).
  • FlatTrak 780S-UHP
    Bulk gas delivery in ultra-clean processes; 316L electropolished tubing 7-10 Ra or 20-25 Ra interior finishes.
  • MultiTrak 670S
    Measure mass flow rates in very large ducts or stacks; non-uniform velocity profiles, high turn-down requirements, dirty gas streams, wide temperature ranges and fast velocity and temperature changes.
  • ChlorineTrak 760S Mass Flow Meter
    Cost-effective mass-flow measurement solution for chlorine injection processes; Flow range is up to 300 scfm chlorine in a 4” Kynar® flow body; No need for expensive hastalloy materials.

* Online sales purchases only. Limited time end-of-year inventory reduction. Use code Holiday20 to apply discount. Offer expires December 22, 2014 5 p.m. PST.