Industry's Most Accurate Air / Gas Thermal Insertion Mass Flow Meters

QuadraTherm^® 640i

Achieve high accuracy +/- 0.75% of reading
Eliminate drift with patented DrySense™ sensor
Validate in the field for easy in-situ calibration
Use qMix software to easily change gas composition in the field and retain accuracy Download Flare Gas Mass Measuring Tech Note
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) Learn more >
Part of Sierra's Big-3 iSeries family of flow meter technologies Learn more >
Meet EPA rule 40 CFR 63 for flare gas measurement at ultra-low flows down sfps (0.03 smps) with QuadraTherm^® qMix RealTime Flare Measurement System (FMS)

Overview

The QuadraTherm® 640i is the most accurate insertion-probe thermal mass flow meter for air / gas mass flow rate measurement on the market today, achieving gas mass flow rate accuracy never before possible, +/- 0.75% of reading above 50% of full scale. The QuadraTherm 640i air / gas mass flow meter marks an accuracy breakthrough in thermal dispersion technology achieving extreme precision with "percent of reading" accuracy, which for the first time rivals accuracies of Coriolis technology for measuring mass air flow rate and other gases.

Each QuadraTherm thermal flow meter comes with onboard 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 frequently changes. Learn more. Sierra’s new breakthrough QuadraTherm® qMix RealTime Flare Measurement System (FMS) delivers real-time flare gas flow measurement to accurately measure flows down to 0.1 fps, meeting the full range of EPA regulations. Watch video.

Boiler MACT Certified

The QuadraTherm thermal mass 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). Learn More.

The QuadraTherm air mass flow meter features a patented four-sensor design—three precision platinum temperature sensors and one patented DrySense mass velocity sensor. This allows for precision air and gas flow measurement. Available in either an insertion version or inline version, this mass flow meter includes Sierra’s proprietary Raptor OS operating system.

QuadraTherm’s four-sensor technology provides the critical inputs for Raptor's living, learning algorithm set and gas database that accurately manages changes in gas and pipe selection, gas temperature, gas pressure and outside temperature. Also easily change gas composition in the field while retaining accuracy with qMix software.

Mass Air Flow Meter Operating Principle: Thermal dispersion technology provides direct mass air flow measurement featuring no pressure or temperature compensation needed; no moving parts; low pressure drop; and high turndown.

Product Benefits

Patented breakthrough "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 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)
Optimized (CH4) as well as N20, SF6, HFCs, PFCs and CO2, per the EPA mandate
Ideal for high-accuracy applications like custody transfer, wastewater treatment, hazardous areas, facilities management and general process control applications
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 and air mass flow rate, temperature and pressure
Total of four gases onboard; Capability to change gas (Dial-A-Gas®) in the field
Free qMix™ software to create custom gases or mixtures to compensate for compositional changes; upload mixtures to the unit in the field
Capability to change pipe size (Dial-A-Pipe®) in the field

Unique multi-gas flow totalizer and alarmsHigh flows up to 60,000 sfpm (305 smps)
Small-diameter, 3/4-inch (19.1 mm) sensor probe
Pipe/duct sizes up to 72" (2M)
Low and high pressure hot tap
An inline flow conditioned version is also available - Model 780i
Very low pressure drop
No moving parts
Free computer interface software
Connected to the most up-to-date gases in our proprietary Raptor Gas Library, update the instrument via the web
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) Learn More.
Meet EPA rule 40 CFR 63 for flare gas measurement at ultra-low flows down sfps (0.03 smps) with QuadraTherm qMix RealTime Flare Measurement System

Specifications

Accuracy: +/- 0.75% of reading above 50% of full scale*
Repeatability: +/- 0.15% of full scale
Flow range 0 to 60,000 sfpm (0 to 305 smps)
Turndown 100:1
Measure 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 Temperature: -40°F to 392°F (-40°C to 200°C)
Ambient temperature: -40°F to 140°F (-40°C to 60°C) / ATEX/IECEx Versions -4°F to 140°F (-20°C to 60°C)
1-inch (25.4 mm) diameter protective sensor shield option for improved sensor protection. Learn more.

*Verified by an independent NIST & NVLAP accredited lab

View All Specs

Response time is 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
316 stainless steel construction
Output signals: RS-232, 4 to 20 mA flow, 4 to 20 mA temperature, 4 to 20 mA pressure (optional)
Alarm output (contact SPST/opto relays)
User definable pulse output for totalized flow
Digital communications: HART and Modbus RTU
Hazardous-Area Location Enclosure (IP66)
Approvals:
- cFMus–Explosion proof for Class I, Div I, Groups B,C,D
- ATEX
- IECEx
- GOST R
- Chinese Pattern
- CE–European Conformity

Documents & Downloads

	File Title	Version	Release Date
Datasheets(2)
	QuadraTherm 640i/780i Series Application Datasheet	V8	06/09/2015
	QuadraTherm 640i /780i Series Technical Datasheet	V36	04/19/2024
Manuals(7)
	File Title	Version	Release Date
	QuadraTherm 640i/780i ATEX/IECEx Manual	F	09/15/2021
	qMix Gas Mixing Feature Instruction Manual (German Translation)	German, V1	08/09/2017
	QuadraTherm Série 640i/780i Mode d'emploi (French Translation)	French, V4	12/04/2015
	QudaraTherm 640i/780i Bedienungsanleitung (German Translation)	German, V10	12/04/2015
	qMix Gas Mixing Feature Instruction Manual	V7	05/10/2023
	640i/780i Flow Totalizer Instruction Manual	V.3	06/26/2019
	QuadraTherm 640i/780i Series Instruction Manual	V17	04/19/2024
Guides(2)
	File Title	Version	Release Date
	QuadraTherm 640i/780i Series Quick Installation Guide	V6	04/30/2020
	QuadraTherm 640i/780i qMix Quick Install Guide	P/N 47-0559 V3	01/04/2023
Software(2)
	File Title	Version	Release Date
	640i/780i Flow Totalizer Instruction Manual	V.1	09/24/2013
	QuadraTherm 640i/780i Series Product Software (SIP)	v1.3.12	01/14/2020
Digital Communications - Flow Meter Digicom - Modbus RTU(3)
	File Title	Version	Release Date
	QuadraTherm 640i/780i Modbus Manual	V3	12/07/2022
	QuadraTherm 640i/780i Modbus Quick Install Guide	P/N: 47-0503	12/03/2013
	KepserverEx 4.0 Software for Use With MODBUS	4.0	05/29/2014
Digital Communications - HART(4)
	File Title	Version	Release Date
	QuadraTherm 640i/780i HART	V1	07/25/2014
	QuadraTherm 640i/780i HART Quick Install Guide	PN: 47-0520	12/01/2015
	QuadraTherm 640i/780i DD Files (Field Communicator)	00A5A57F0101	07/21/2014
	QuadraTherm 640i/780i DD Files (PC Programs)	0000a5	07/21/2014
Certificates(16)
	File Title	Version	Release Date
	QuadraTherm 640i/780i ATEX Certificate	3.21.24	04/19/2024
	QuadraTherm 640i/780i cFMus Certificate of Conformity (Canada)	3.20.24	04/19/2024
	QuadraTherm 640i/780i cFMus Certificate of Conformity (USA)	3.20.24	04/19/2024
	QuadraTherm 640i/780i Series CE Declaration of Conformity	3.0	12/06/2017
	ARRA Certificate of Conformity	11/3/17	11/03/2017
	Gost Approval EX Explosive Certificate	1.0	06/23/2014
	Gost Approvals Thermal Mass Flow Meters	1.0	06/23/2014
	CRN Approvals Alberta	2019-2029	02/20/2024
	RoHS 3, REACH, and WEEE Compliance	2.0	09/20/2021
	CRN Approval	2.0	09/20/2019
	CRN Approval Quebec	2.0	09/20/2019
	CRN Approval British Columbia	2.0	09/20/2019
	CRN Approval Ontario	2.0	09/20/2019
	CRN Approval Saskatchewan	2.0	09/19/2019
	CRN Approval Manitoba	2.0	09/20/2019
	ISO 9001:2015	2024	05/14/2024
Additional Documentation(9)
	File Title	Version	Release Date
	Big-3 Overview Brochure	V1	06/29/2017
	Flow Energy Field Guide	V1	05/25/2018
	Boiler MACT Information Guide	2.0	06/09/2016
	Full Line Catalog - German Version	V1	08/07/2017
	Sierra Clean Energy Guide	V1	01/28/2011
	Service Brochure	2.0	04/06/2015
	Terms and Conditions	1.0	11/01/2010
	Warranty Statement	2.0	04/01/2015
	Full Line Product Offering	V4	08/03/2023