Flow Measurement Instruments
- Thermal Low Flow Liquid Meters
- Thermal Low Flow Gas Meters
- Thermal Duct Flow Meters for Air & Gas
- Low Flow Controller
- MaxExtractor Extraction Monitor
- Multi-Variable Process Meter
- Bidirectional Flow Meters
- RheoVac ® Multisensor Flow Monitors
- Custom Process Measurement
- Flow Switches
- Instruments for Hazardous Locations
- Electronics Options
Thermal Low Flow Gas Meters
Low flow gas flow meters are designed to measure the gas flow in pipelines at low flow rates. 
These low flow gas flow meters are employed in processes demanding high precision. Their compact design allows for seamless integration directly into gas pipelines. The Bionetics Corporation offers Rheotherm low-flow gas meters for measuring gas flow in small lines, typically 1″ or smaller, with flow rates from a few hundred standard cubic feet per minute (SCFM) down to 25 standard cubic centimeters per minute (SCCM). For flow measurement in larger pipes and ducts, you can consider our Duct Flow Meters.
These gas flow measurement instruments give a repeatable reading in mass or standard volume, without needing external temperature or pressure correction. With no mechanical parts, they are reliable and easy to maintain. We also provide low flow meters for gas measurement in hazardous environments, including intrinsically safe and NEMA 7 explosion-proof models. Please visit our Instruments for Hazardous Locations page to learn more about NEMA 7 explosion-proof models.
Our Rheotherm flow meters utilize the thermal mass flow measurement principle for precise gas measurement.
Exploring the Diverse Applications of Rheotherm Low Flow Gas Flow Meters
Our Rheotherm low flow gas flow meters are designed to measure the continuous flow of most gases, including corrosive and explosive gases. These thermal low flow gas flow meters measure everything from hydrogen to uranium hexafluoride. Here is a partial list of gas flow measurement instruments.
- Ammonia
- Argon
- Butane
- Carbon Dioxide
- Carbon Monoxide
- Chlorine Gas (Dry)
- Coal Gas
- Coke Gas
- Diesel Exhaust
- Digester Gas
- Ethane
- Ethanol Vapor
- Ethylene
- Flare Gas
- Flue Gas
- Fluorine Gas
- Fuel Gas
- HC Fuel Gas
- Helium
- Hydrocarbon Gas
- Methane
- Methanol Formaldehyde Vapor
- Natural Gas
- Oxygen
- Propane Vapor
- Propylene Gas
- Sulfur Dioxide
- Tungsten Hexafluoride (WF6)
We provide electropolished sensors for ultrahigh purity gases. The Bionetics Corporation has 50 years of experience in measuring complex fluids in challenging environments, making us a trusted leader in this field. Visit our applications section to explore the range of fluids measured using our inline gas flow meters.
Industries Served
Rheotherm low flow gas meters have been used in thousands of installations worldwide since 1978, which makes them an ideal monitoring tool across the following industries and more.
- Chemical and Petrochemical
- Aerospace
- Wastewater Treatment
- Natural Gas
- Oil and Gas Production
- Nuclear
- Pulp and Paper
For more information on industries and applications of gas flow measurement instruments, please visit our Industries Served page.
Installation Process Overview of Thermal Low Flow Gas Flow Meters
Installing Rheotherm low flow gas flow meters is quite straightforward and involves the following steps.
- Using standard tube fittings for Rheotherm inline gas flow meters. We offer them with optional flanges, sanitary fittings, and other configurations to meet your application requirements.
- Install inline flow meters for gas in any orientation, except vertical, with a downward flow direction.
- You may also consider installing models with integrated electronics, enhancing functionality and simplifying data collection. We also provide models with separate electronics enclosures that can be installed up to 200 feet from the inline low air flow sensor. This option is beneficial in restricted spaces where it is impractical to place the electronics in the same location as the sensor or in hazardous environments where the electronics can be placed in non-hazardous areas.
How Rheotherm Inline Gas Flow Meters can Measure Fluid Flow Accurately?
Our Rheotherm flow meters for gas measurement operate on the principle of thermal mass flow measurement. These low flow gas flow meters measure the thermal properties of the gas flowing through their body. The meter features a straight-through or looped flow tube, and two resistance temperature detectors (RTDs) mounted on the exterior tube wall. One RTD is heated while the other remains unheated, allowing the meter to measure the temperature differential between them. This differential generates the primary flow signal:
- At high flow rates, the temperature differential is low, as the flow effectively removes heat.
- At low flow rates, the differential is higher due to reduced heat removal.
This design guarantees that the gas only contacts the tube wall, eliminating the risk of mechanical wear or failure from moving parts.
The mass and volume flow of gases can be measured without temperature or pressure corrections. All these features and capabilities contribute to the accuracy and efficiency of our gas flow measurement instruments.
We can provide these industrial gas flow meters with an optional 2 x 16 backlit LCD that shows mass/volume flow rate, temperature (°C or °F), and total accumulated flow stats. Our industrial gas flow meters feature a self-diagnostic feature that helps detect system problems, if any – from damaged sensors to corrupted data. These inline gas flow meters also produce appropriate status codes for users. Flow data can be extracted in both digital and analog formats.
How to Order Rheotherm’s Low Flow Gas Flow Meter?
You can contact our flow application specialists to configure a Rheotherm inline gas flow meter tailored to your application. Our flow application specialists will contact you when they receive your low flow gas meters RFQ. You can also download and complete the Flow Application Data Sheet and email it to us at sales-flow@bionetics.com.
For any product-related queries or assistance, please visit our Contact Us page for telephone, fax and email information.
Explore the key features of our inline flow meters for gas that make them an ideal choice for various gas flow measurement applications across industries.
- No moving parts
- Exclusive inline TU sensor
- Typical calibration ranges: 10:1 and options up to 200: 1 turndown
- Durable sensors, unaffected by over-ranging
- Advanced signal processing electronics
- Field adjustable; easy onsite calibration adjustments
- Maintenance-free
- Easy installation
- Choice of wetted materials
- Long-term reliability
We provide industrial gas flow meters in the following specifications.
| Standard | Options | |
| Temperature | Process: 0 – 140°F (-18 – 60°C) Environment: 0 – 120°F (-18 – 50°C) | -20 – 350°F (-30 – 175°C) |
| Pressure | 0 – 1,000 PSI | Up to 30,000 PSI |
| Calibration Ranges | 10:1 Turndown; | – Up to 200:1 turndown – Four calibration channels available (for multiple flow ranges or different fluids using the same sensor) |
| Calibration Accuracy | ± 1% of reading typical | |
| Response Time | 1 sec. ; 3 – 5 sec. typ. (63% of range); | Time constant/delay option |
| Repeatability | ± 0.5% of reading | |
| Standard | Options | |
| Line Sizes (flow range dependent) | Capillary; 1/16”; 1/8”; 3/16”; 1/4” 3/8”; 1/2”; 5/8”; 3/4”; 1” | Other sizes via fittings/adapters |
| Process Connection | Plain tube stubs suitable for compression fittings | – MNPT; – Tri-Clover (Sanitary); – SS Flange (1/2” – 2”): Most other fittings available |
| Wetted Material | 316 SS | – Hastelloy C-276®; – Monel®; – Alloy 20; – Titanium; – Tantalum; – Inconel |
| Display | 2 X16 backlit LCD with selectable display of: – Mass/volume flow rate – Temperature – Total accumulated flow | |
| Standard | Options | |
| Enclosure | Sensor: PVC Integrated Electronics: NEMA 4X Cast Aluminum Remote Electronics: NEMA 4 | Sensor: Stainless steel Remote electronics: – Stainless steel – NEMA 7 Explosion-proof |
| Hazardous Environment | Integrated electronics: FM-Approved for: – Class I, Div. 1, Groups B,C,D – Class I, Zone 1, IIB+H2 (US) – Class II, Div. 1, Groups E, F, G – Class III, Div. 1 Remote electronics: Same as above except addition of Group A using ISB | |
| Outputs | 4 – 20 mA (flow rate) or Serial Burst with Flow Rate, Totalizer, and Fluid Temperature | – 0 – 10 or 0 – 5 VDC; – Pulse (5 VDC open collector); – HART (4-20 mA); – SPDT relay; – 4 to 20 mA temp |
| Input Power | 24 VDC ±4V (200 mA; 300 mA w/display option) | 110/230 VAC ±10V |
The table below outlines the flow capacities of the Bionetics Corporation’s inline gas flow meters used for gas flow measurement.
Inline Sensor Flow Capacities for Gases
| TUBE SIZE | ||||||||||
| FLOW RATE LIMITS | C | 1/16 | 1/8 | 3/16 | 1/4 | 3/8 | 1/2 | 5/8 | 3/4 | 1 |
| Extended Maximum | 0.027 | 1.25 | 5 | 11 | 20 | 45 | 80 | 125 | 180 | 320 |
| Normal Maximum | 0.017 | 0.75 | 3 | 7 | 15 | 34 | 70 | 109 | 160 | 280 |
| Normal Minimum | 0.0017 | 0.02 | 0.1 | 0.2 | 0.4 | 0.9 | 1.6 | 2.5 | 3.6 | 6.4 |
| Extended Minimum | 0.0009 | 0.0017 | 0.05 | 0.1 | 0.2 | 0.5 | 0.8 | 1.2 | 2 | 3.2 |
| SCFM | ||||||||||
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