air flow meters, SteelMass 640

SteelMass 640S Flow Meter

Insertion,Totalizing Meter Application

Accurate monitoring of peak, low flow and total gas mass flow rates is a critical part of many industrial process control systems. If you need a portable analog or digital air flow meter that easily inserts into industrial ducts and pipes (up to 72 inches), choose Sierra Instruments SteelMass® 640S.

Sierra, a leader among global flow measurement and control equipment manufacturers and suppliers, recommends its SteelMass air volume flow meter for compressed air flow, aeration basin air flow, combustion air flow, natural gas fuel flow, custody transfer and stack gas emissions flow monitoring.  All of our thermal instruments feature our proprietary DrySense™ Sensor Technology backed by a Lifetime Limited Warranty.

Customize Your SteelMass 640S

SteelMass 640S can be customized for your air velocity and intake applications with:

  • Larger probe lengths.
  • High temperature option (750 degrees F).
  • Self-cleaning purge option for dirty flow environments.
  • Wide range of process connections (including hot tap).
  • Multipoint flow averaging arrays for very large ducts, complete with a self-contained human-machine interface (HMI) panel for touch-screen field programming and system operation.

SteelMass inline air flow meters also feature Sierra's unique Smart Electronics Package for field rangeability, flow-range adjustment and validation and diagnostics. With very low pressure drops and wide turndowns, these products are hazardous-area approved by CSA and CRN (Canada); FM (USA); ATEX, CE and PED (EU); GOST R (Russian Federation); and Chinese Pattern Approval (China). Meter accuracy is +/- 1% of reading, plus +/-0.5% of full scale with repeatability of +/- 0.2% of full scale.

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 Fieldbus, HART, Modbus RTU, and Profibus DP. This flexibility of communication features offers turnkey solutions for integration of Sierra's thermal mass flow meters into any industrial automation system or application. 

SteelMass 640S are GHG Certified

As a certified greenhouse gas (GHG) air flow meter, the SteelMass:

  • Meets all requirements defined by the EPA (40 CFR Part 98).
  • Is optimized for highly accurate and repeatable mass flow meters for methane (CH4) as well as N20, SF6, HFCs, PFCs and CO2, per the EPA mandate.

SteelMass is also a popular choice for landfill gas (LFG) measurement applications. LFG – a very humid, dirty gas that leaves the landfill at low pressure (20 - 40 mBarg) and about 40-60°C (100°F) – makes differential pressure (dP) devices like orifice plates unsuitable, while variable flows require a large turndown. Sierra’s 640S Insertion Mass is ideal for LFG, as it offers 100:1 turndown, has no moving parts and generates nominal pressure drop across the immersible sensor probe.

View our complete line of air and gas flow meters or learn more about selecting gas mass flow products. Contact us for additional information or get live help.

A global leader in flow measurement and control for over 35 years, Sierra instruments designs and manufactures high performance air flow instrumentation for gas, liquid and steam applications commonly found in the semiconductor, environmental, scientific research, petrochemical, energy, aerospace, and general manufacturing industries. With over 150 offices in 50 countries, Sierra is uniquely positioned to provide their innovative meters and flow products with lifetime support for the leading companies of today and the growth enterprises of tomorrow.

Smart Interface Program
Click to download a zipped Smart Interface Program (Note extended download time required)

Unique Product Features
• 316SS construction
• Range of process connections (including hot tap)
• Field Validation/Configuration
+/- 1% of reading plus +/-0.5% of full scale
• Very large installed base
• Removable probe for recalibration and service
• Meters all process gases
• 3/4” diameter insertion probe
Digital communications solutions include: Foundation Fieldbus, HART, Modbus RTU, and Profibus DP.

View Application Slide Show

Product Related Documents & Downloads


  File Title Version Release Date
  SteelMass 640S Instruction Manual L 09/04/2015
  640S/780S ATEX Instruction Manual C.1 11/07/2014
  S-Series Pulse Output Information Sheet B 05/08/2013
  S-Series Smart Interface Software User Manual B 08/01/1999


  File Title Version Release Date
  SteelMass 640S Technical Datasheet I 09/04/2015
  600/700 Series Application Datasheet V5 10/17/2014


  File Title Version Release Date
  600/700 Series Product Software SIP134 04/16/2013

Digital Communications - HART(2)

  File Title Version Release Date
  600/700 Series HART Instruction Manual V1 05/02/2013
  600/700 Series HART Quick Install Guide V1 05/02/2013

Digital Communications - Profibus DP(5)

  File Title Version Release Date
  600/700 Series Profibus DP Instruction Manual V1 05/02/2013
  600/700 Profibus DP Quick Install Guide V1 05/02/2013
  600/700 Series Profibus DP Bit Map Files 1.0 05/02/2013
  600/700 Series Profibus DP GSD Files 1.0 05/02/2013
  KepserverEx 4.0 Software for Use With Profibus DP P 4.0 05/29/2014

Digital Communications - Foundation Fieldbus(4)

  File Title Version Release Date
  600/700 Series Foundation Fieldbus Instruction Manual V1.1 12/04/2013
  600/700 Series Foundation Fieldbus Quick Install Guide P/N: 47-0505 12/04/2013
  600/700 Series Foundation Fieldbus Bit Map Files 1.0 12/03/2013
  Fieldbus Device Description Files 3.0 02/20/2015

Digital Communications - Modbus RTU(3)

  File Title Version Release Date
  600/700 Series Modbus Instruction Manual V1.1 05/06/2013
  600/700 Series Modbus Quick Install Guide PN: 47-0493-B 07/19/2014
  KepserverEx 4.0 Software for Use With MODBUS 4.0 05/29/2014


  File Title Version Release Date
  640S/780S CE Declaration of Conformity 3.0 12/23/2013
  640S/780S Series ATEX Certificate V3 01/10/2014
  600/700 Series CE Declaration of Conformity 1.0 12/23/2013
  Sierra FM Approvals 1.0 12/28/2012
  China Patter Approval Certificate 01/28/2014
  Gost Approval EX Explosive Certificate 1.0 06/23/2014
  Gost Approvals Thermal Mass Flow Meters 1.0 06/23/2014
  CRN Approval 1.0 11/20/2008
  ISO 9001:2008 1.0 01/22/2013
  CRN Approval 0F09333.26 Quebec 1.0 04/09/2009
  CRN Approval 0F09333.25 Ontario 1.0 12/29/2008
  CRN Approval 0F09333.24 Manitoba 1.0 11/20/2008
  CRN Approval 0F09333.23 Saskatchewan 1.0 09/09/2009
  CRN Approval 0F09333.2 Alberta 1.0 12/21/2010
  CRN Approval 0F09333.21 British Columbia 1.0 12/29/2008
  ARRA Certificate of Conformity 8/5/14 08/06/2014


  File Title Version Release Date
  Sierra Clean Energy Guide V1 01/28/2011
  Terms and Conditions 1.0 11/01/2010
  Service Brochure 2.0 04/06/2015
  Warranty Statement 2.0 04/01/2015
  Full Line Product Offering V3_10.15 10/04/2015
Sensor Design The Key Advantaga in Thermal Mass Flow meter Perfomance
March, 2007 - Instrument Design & Technology
Industrial Thermal Mass Flow Meters Pt.1 / Pt.2
June, 1999 -
Measurement & Control
Air Compressor Supply Inc.:
Putting a Price Tag on Compressed Air Waste 

The Sierra Chronicles show how Sierra has provided mass flow solutions to our customers' flow challenges for the last 4 decades.  Our commitment  to increasing customer productivity and efficiency has always been and will always be, the common thread.
Foundation Fieldbus

Foundation Fieldbus

Foundation Fieldbus technology is the world's leading digital protocol for process automation. It provides end users with the "Freedom to Choose" best-in-class, interoperable control products from their suppliers of choice, and the "Power to Integrate" control systems, subsystems and devices across the plant enterprise.


Sierra supports HART digital communication protocol for flexible integration of our mass flow meters and controllers into any automation or control system. The HART (Highway Addressable Remote Transducer) Protocol is the global standard for sending and receiving digital information across analog wires between smart devices and control or monitoring system.
Modbus RTU

Modbus RTU

Sierra supports Modbus RTU digital communication protocol for flexible integration of our mass flow meters and controllers into any automation or control system. Modbus Protocol is a messaging structure developed by Modicon in 1979. It is used to establish master-slave/client-server communication between intelligent devices.
Profibus DP

Profibus DP

Sierra supports Profibus DP digital communications protocol for flexible integration of our mass flow meters and controllers into any automation or control system. PROFIBUS is the fieldbus-based automation standard of PROFIBUS & PROFINET International (PI).
Report Bug
Sending Report...
Send Feedback Report


Reproducibility (Did you try to reproduce the issue?)


Summarize the problem but be specific enough that it can be recreated.

Note: Page, browser, and OS are automatically saved