Thermal Mass Measurement
Uses thermal sensing technology for compatible gas-flow measurement.
Flow Meters
Thermal Mass Flow Meter
Direct Mass Flow Measurement Using Thermal Sensing Technology
Direct Mass Flow Measurement Using Thermal Sensing
The FlowDo Thermal Mass Flow Meter uses thermal sensing technology to determine the mass flow of compatible gases. As gas moves across the sensing elements, it changes the transfer of heat from the heated sensor. The instrument processes this thermal response to determine the corresponding flow value.
MASS FLOW
Measurement
THERMAL
Technology
COMPATIBLE GASES
Primary Medium
NO ROTATING ROTOR
Moving Parts
Product Overview
Thermal Mass Flow Measurement for Industrial Gas Applications
Direct gas mass-flow determination based on heat-transfer response across precision thermal sensing elements.
The FlowDo Thermal Mass Flow Meter is designed to measure the mass flow of compatible process gases using thermal sensing technology.
The sensing assembly typically monitors how flowing gas affects heat transfer around the measurement elements. As gas flow changes, the thermal response of the sensing system also changes.
The instrument electronics process this response using the applicable calibration to determine the corresponding mass-flow value.
Because the measurement is based on thermal interaction with the gas rather than a rotating turbine, the technology can provide direct gas-flow measurement without requiring a mechanical rotor.
Technical Selection Notice: Correct product selection requires consideration of gas composition, flow range, pipe size, pressure, temperature, installation configuration, calibration conditions and required output.
Key Engineering Principles
- Direct mass-flow measurement based on gas heat-transfer dynamics
- No rotating mechanical turbine vanes or bearings in the gas stream
- Calibrated specifically to known process gas thermal characteristics
- Insertion probe and inline body options according to selected model
- Electronic signal conditioning translates thermal response into scalable output
- Digital display configurations provide local flow-rate and totalized volume
Instrumentation Capabilities
Key Features
Engineered for dependable, high-precision industrial gas flow measurement.
Direct Mass-Flow Response
The sensing system responds to heat transfer associated with flowing gas.
No Rotating Turbine
Measurement does not rely on a mechanical turbine rotor or moving bearing elements.
Continuous Flow Monitoring
Provides continuous flow information within the supported operating range.
Digital Indication
Applicable configurations provide local digital indication of rate and totalized flow.
Process Output
Supported transmitter configurations provide signals for remote monitoring and automation.
Industrial Construction
Built with robust wetted materials suited for industrial process environments.
Gas-Specific Configuration
Meter selection and calibration are matched to the intended gas/application.
Operational Advantages
Designed for Industrial Gas Flow Measurement
Engineered to deliver high measurement integrity across manufacturing and utility gas systems.
Direct Mass Flow Measurement
Designed to determine gas mass flow through thermal measurement without requiring external pressure/temperature compensation.
No Mechanical Rotor
No rotating turbine measurement element is required, eliminating mechanical rotor wear, bearing friction and moving-part failures.
Gas Measurement
Suitable for compatible gas-flow applications according to calibration and configuration.
Continuous Monitoring
Provides continuous process-flow information for operational oversight and efficiency tracking.
Automation Integration
Compatible outputs can integrate with industrial monitoring/control systems, PLCs and SCADA networks.
Low Pressure Impact
Minimal obstruction in the pipeline bore minimizes hydraulic pressure drops across the measuring point.
Technical Configuration
Product Specifications
Technical specifications vary according to selected FlowDo Thermal Mass Flow Meter model and application parameters.
Brand / Manufacturer
FlowDo Process Instruments
Product Name
FlowDo Thermal Mass Flow Meter
Primary Category
Flow Meters
Product Type
Industrial Thermal Mass Flow Meter
Measurement Technology
Thermal Mass Flow Measurement
Measured Parameter
Mass Flow / Standardized Volumetric Flow
Primary Medium
Compatible gases according to selected model
Gas Calibration
Application dependent (matched to process gas)
Sensor Principle
Thermal heat-transfer response
Sensor Architecture
According to selected configuration
Installation Style
Insertion / Inline (according to selected model)
Pipe Size
According to selected model and pipeline diameter
Flow Range / Velocity Range
According to selected configuration
Accuracy & Repeatability
According to selected model and application calibration
Turndown Ratio
According to selected model
Probe / Sensor Wetted Materials
According to selected configuration
Process Connection
According to selected model (flanged, threaded or hot-tap)
Process Operating Pressure
Model dependent
Process Temperature Range
Model dependent
Ambient Operating Temperature
Model dependent
Local Display
According to selected configuration
Analog Output
According to selected configuration
Digital Communication
According to selected configuration
Power Supply
According to selected model
Enclosure Protection
According to selected model
Primary Application
Industrial Gas Mass Flow Measurement
Engineering Notice: FlowDo manufactures and configures instruments for specific process criteria. Contact FlowDo technical sales to confirm exact specifications for your target gas, pressure, temperature, and pipe dimensions.
Thermal Sensing
Gas Flow Changes the Heat-Transfer Rate
How varying gas velocity directly influences thermal dissipation from the measurement elements.
LOW GAS FLOW VELOCITY
Lower Heat Removal
When gas velocity is low, fewer gas molecules pass the heated sensor per second. Heat dissipation into the gas stream is relatively small:
HEATED SENSOR → Lower Heat Removal → Lower Thermal Response
HIGHER GAS FLOW VELOCITY
Greater Heat Removal
As gas velocity increases across the sensing element, the rate of convective heat transfer increases significantly:
HEATED SENSOR → Greater Heat Removal → Higher Thermal Response
Sensor Architecture
A Thermal Measurement Pair
Differential thermal sensing combining process temperature compensation with active flow sensing.
Process Reference
Reference Sensor
Measures the actual process temperature of the passing gas. This measurement provides the dynamic temperature baseline required for accurate thermal comparison.
REFERENCE SENSOR ────► PROCESS TEMPERATURE
Active Element
Heated Sensor
Maintained at a controlled thermal condition above process temperature. Heat carried away by the passing gas represents the gas mass-flow rate.
HEATED SENSOR ────► THERMAL RESPONSE
REFERENCE + HEATED SENSOR RESPONSE + CALIBRATION ────► MASS FLOW
Thermal mass-flow instruments commonly use temperature-sensitive elements to establish process-gas temperature and thermal response. The exact sensing architecture depends on the selected FlowDo model.
Flow Fundamentals
Mass Flow and Volumetric Flow Are Different
Why direct mass measurement provides substantial engineering advantages in compressible gas systems.
PRIMARY PARAMETER
Mass Flow
Measures the actual quantity of mass passing through the system per unit time. Because mass is conserved regardless of pressure or temperature variations, mass flow directly quantifies the true substance flow.
Units: kg/h, kg/min, lb/h
VOLUMETRIC PARAMETER
Volumetric Flow
Measures the physical volume of fluid passing per unit time. For compressible gases, actual volume varies continuously with fluctuating process pressure and temperature.
Units: m³/h, L/min, CFM
Standardized Gas Flow Values (Nm³/h, Sm³/h)
Gas-flow instruments frequently standardize gas volumetric flow to common baselines such as Normal cubic meters per hour (Nm³/h) or Standard cubic meters per hour (Sm³/h). Direct thermal mass measurement allows seamless conversion to standardized volumetric rates without requiring separate external temperature and pressure transmitters when reference conditions are pre-defined.
Application Engineering
Gas Composition Affects Thermal Measurement
Different gases have different thermal properties. A Thermal Mass Flow Meter must therefore be selected and calibrated for the intended gas or gas mixture.
Specific heat capacity (Cp), thermal conductivity, and dynamic viscosity vary widely between gases. The sensor response is intrinsically linked to these specific thermodynamic attributes.
Calibration
Calibration Should Match the Application Gas
During instrument manufacturing, the transmitter electronics are programmed with characteristic conversion curves tailored to the designated gas calibration:
PROCESS GAS ──► CALIBRATION ──► THERMAL RESPONSE ──► MASS FLOW VALUE
Installation Configuration
Insertion and Inline Mounting Options
Mounting options designed to match pipeline sizing, pressure limits, and operational retrofitting constraints.
Large & Medium Pipes
Insertion Thermal Mass Flow Measurement
An insertion configuration positions the thermal sensing probe within the process pipe. Correct insertion depth and orientation are important for reliable measurement.
- Cost-effective installation on large-diameter headers and distribution lines
- Hot-tap options available on supported models without stopping process gas
- Compact mounting footprint with minimal line interruption
Small & Medium Lines
Inline Thermal Mass Flow Meter
Inline configurations incorporate the thermal sensing section within a dedicated meter body installed directly in the pipeline.
- Pre-calibrated flow profile inside dedicated measuring spool tube
- Ideal for smaller process lines, analytical sampling, and machinery skids
- Flanged or threaded process connections according to selected model
Correct Sensor Orientation Matters
The thermal sensing elements should be positioned according to the installation requirements of the selected FlowDo meter so that they are properly exposed to the process flow.
Set the Correct Insertion Depth
The sensing element must be positioned correctly within the pipe's flow profile. Required insertion depth depends on meter design, pipe size and installation arrangement.
Stable Flow Conditions Support Reliable Measurement
Flow disturbances caused by elbows, valves, reducers, pumps and other components can affect the velocity profile. Follow the upstream/downstream installation requirements specified for the selected FlowDo Thermal Mass Flow Meter.
Meter Sizing
Pipe Size Is an Important Selection Parameter
Core process factors that determine the mechanical and electronic sizing of thermal mass meters.
Pipe Size
For insertion Thermal Mass Flow Meters, pipe dimensions are required to convert the measured velocity/mass-flow response into the applicable process-flow value according to the instrument configuration.
Verify Operating Pressure
The selected sensor, probe assembly and process connection must be suitable for the process operating/design pressure. Pressure can also influence actual volumetric gas flow and gas density.
Process Temperature Affects Meter Selection
The sensing probe and electronics must be suitable for the actual gas temperature and ambient operating conditions: Process Gas Temperature + Ambient Temperature → Select Correct Meter Configuration.
Select the Meter Around the Actual Operating Range
Provide minimum, normal and maximum expected flow when selecting the meter. This helps ensure the application remains within the selected instrument's supported measurement range.
Energy & Utilities
Monitor Compressed-Air Consumption
Industrial gas applications benefiting from dedicated thermal mass flow monitoring.
Monitoring compressed-air consumption and distribution provides essential visibility into industrial plant operating costs and pneumatic system efficiency.
Direct thermal mass measurement in main compressor headers, distribution risers, and machine feed lines delivers continuous flow and totalized consumption figures. Flow data can support compressed-air leak and consumption analysis.
Compressor Header → Air Distribution → Thermal Mass Meter → Local Display / SCADA / IoT
Compatible Gas Applications
- Compressed Air: Header efficiency, sub-metering, and usage audits
- Nitrogen: Inert gas blanketing, purge lines, and gas consumption tracking
- Utility & Aeration Air: Wastewater aeration basins and industrial blowers
- Process Gases: Compatible clean manufacturing process streams
Renewable Gas
Thermal Mass Flow Measurement for Biogas
Biogas composition can vary, and thermal properties depend on the gas mixture. Product selection should therefore consider the expected composition (CH4, CO2), moisture, contaminants, pressure, temperature and flow range.
Fluid Suitability
Process Gas Suitability Considerations
Evaluating process gas conditions, moisture, and composition stability prior to instrument selection.
Consider Moisture and Condensation
Liquid droplets or condensation contacting a thermal sensing element can alter heat-transfer behavior and may affect measurement depending on the sensor design: Dry/suitable gas supports stable measurement, while condensation requires application review.
Changing Gas Composition Can Change the Measurement Response
If the process-gas composition changes significantly from the calibration basis, measurement performance may be affected because the thermodynamic properties deviate from the programmed conversion table.
Clean Process Gases Supported
Thermal mass meters perform reliably with non-condensing, particulate-free compatible gases. Applications with heavy coatings, sticky particulates or wet vapor streams require review by FlowDo application engineers.
Technology Comparison
Comparing Thermal Mass Flow with Other Technologies
Selecting the optimal measurement principle for your industrial fluid, pipe, and accuracy requirements.
Thermal Mass Flow Meter
- Principle
- Convective heat-transfer rate.
- Measured Medium
- Typically compatible gases.
- Rotating Parts
- No mechanical rotor or vanes.
- Key Consideration
- Gas composition and matching calibration.
Turbine Flow Meter
- Principle
- Fluid velocity drives rotor rotation.
- Measured Medium
- Compatible clean liquids.
- Rotating Parts
- Yes (mechanical rotor & bearings).
- Key Consideration
- Fluid cleanliness and bearing friction.
Vortex Flow Meter
- Principle
- Kármán vortex street shedding frequency.
- Measured Medium
- Compatible liquids, gases, steam.
- Rotating Parts
- No (stationary bluff body).
- Key Consideration
- Minimum velocity threshold & vibration.
Ultrasonic Flow Meter
- Principle
- Sound-wave transit-time difference (Δt).
- Measured Medium
- Acoustically transmissive liquids.
- Rotating Parts
- No (clamp-on or inline transducers).
- Key Consideration
- Acoustic coupling & pipe fill condition.
Thermal Mass or Turbine Flow Meter?
Thermal mass meters measure gas mass flow without moving parts, whereas turbine meters determine liquid velocity using mechanical rotor rotation.
View Turbine Flow Meter →Thermal Mass or Vortex Flow Meter?
Thermal mass meters specialize in direct gas mass flow, while vortex meters measure volumetric flow across steam, gas, and liquid using stationary bluff bodies.
View Vortex Flow Meter →Thermal Mass or Ultrasonic Flow Meter?
Thermal mass meters monitor heat transfer in gas streams; ultrasonic meters monitor acoustic sound waves across filled liquid pipes.
View Ultrasonic Flow Meter →Thermal Mass or Electromagnetic Flow Meter?
Thermal mass meters measure compatible gases with no conductivity requirement; electromagnetic meters require electrically conductive liquids.
View Electromagnetic Flow Meter →| Measurement Attribute | Thermal Mass Flow Meter (This Product) | Electromagnetic Flow Meter | Turbine Flow Meter | Vortex Flow Meter | Ultrasonic Flow Meter |
|---|---|---|---|---|---|
| Measurement Principle | Thermal convective heat transfer | Electromagnetic induction | Flow-driven rotor rotation | Vortex shedding (Kármán street) | Sound waves (transit time) |
| Primary Measured Medium | Compatible industrial gases | Conductive liquids | Clean low-viscosity liquids | Steam, gas, liquid | Acoustic clean liquids |
| Primary Measurement Output | Direct Mass Flow (kg/h, Nm³/h) | Volumetric Flow (m³/h, L/min) | Volumetric Flow (m³/h, L/min) | Volumetric / Mass Flow | Volumetric Flow (m³/h, L/min) |
| Moving Mechanical Parts | No moving parts | No moving parts | Yes (rotor & bearings) | No moving parts | No moving parts |
| Conductivity Required? | No conductivity required | Yes (≥ 5 μS/cm) | No conductivity required | No conductivity required | No conductivity required |
| Mounting Configuration | Insertion probe or inline spool | Inline flanged / wafer | Inline flanged / threaded | Inline flanged / wafer | Clamp-on or inline spool |
| Added Pipeline Pressure Drop | Negligible to very low | Zero (unobstructed bore) | Low to moderate across rotor | Low to moderate across bluff body | Zero for clamp-on |
| Primary Selection Focus | Gas composition, pipe size, flow range | Fluid conductivity, liner compatibility | Fluid cleanliness, viscosity | Minimum velocity threshold, vibration | Acoustic transmission, wall thickness |
Selection depends on process medium, pipe conditions, flow range, pressure, temperature, installation access and required measurement performance.
System Integration
From Gas Flow to Process Monitoring
Converting sensor heat-transfer responses into plant control signals, PLC inputs, and remote cloud dashboards.
FlowDo Thermal Mass Flow Meter
Precision Convective Heat Transfer in Pipeline Gas Stream
↓
Differential Thermal Sensing & Linearization
Reference Sensor (T_gas) + Heated Sensor (T_heat) • Factory Gas Calibration
↓
Transmitter Electronics & Outputs
Local Digital Display • Scaled Mass Flow (kg/h, Nm³/h) • 4–20 mA / Pulse / RS485 Modbus
↓
Local Process Indicator / Totalizer
FlowDo FDI-96 Digital Flow Indicator / Sub-metering Panel
PLC / Plant SCADA
Combustion Air Control, Compressor Skids & Burner Management
↓
FlowDo IoT Cloud & Telemetry
Live web dashboards, compressed-air leak analysis, historical audits & automated alarms
Product Configuration
Configure the Thermal Mass Flow Meter for Your Gas Application
Provide key pipeline and gas parameters to identify a suitable FlowDo Thermal Mass Flow Meter configuration.
Gas Type
Specify the exact process gas to be measured (e.g., Compressed Air, Nitrogen, Biogas, or specified process gas).
Gas Composition
Indicate whether the gas is pure or a multi-component mixture with expected percentage breakdown.
Pipe Size
Provide pipeline internal/external diameter, pipe schedule, and material specification.
Minimum Flow
Minimum expected process gas flow rate during low-demand or baseline periods.
Normal Flow
Nominal operating gas flow rate under typical continuous operational conditions.
Maximum Flow
Maximum anticipated peak gas demand or upset-condition capacity.
Flow Units
Required engineering rate and totalizer units (e.g., Nm³/h, kg/h, Sm³/h, or SCFM).
Process Pressure
Normal operating pipeline pressure and maximum design pressure rating.
Process Temperature
Normal and maximum gas temperature inside the pipeline stream.
Ambient Temperature
Environmental ambient temperature range at the transmitter installation location.
Installation Style
Select between Insertion probe mounting or Inline spool-body configuration.
Process Connection
Flanged, threaded, or hot-tap valve connection matching piping standards.
Output Signal
Required control signal (e.g., 4–20 mA analog, pulse, or frequency).
Digital Communication
Industrial bus protocol if digital networking is required (e.g., RS485 Modbus RTU or HART).
Local Display
Integrated transmitter digital display for rate and totalized volume indication.
Totalizer Requirement
Specify whether integrated forward totalization or batch volume is required.
Portfolio
Related Flow Measurement Products
Explore complementary FlowDo industrial flow and process instrumentation.
Vortex Flow Meter
Industrial vortex flow meter using vortex-shedding technology for compatible steam, gas, and liquid process-flow applications.
View details & specs →
Ultrasonic Flow Meter
Industrial ultrasonic flow meter for non-intrusive and inline transit-time pipeline flow measurement.
View details & specs →
Turbine Flow Meter
High-precision rotor rotation flow meter for clean, low-viscosity liquid measurement and batching.
View details & specs →
Electromagnetic Flow Meter
Full-bore electromagnetic induction flow meter for conductive liquids, water, wastewater, and slurries.
View details & specs →Frequently Asked Questions
Thermal Mass Flow Meter FAQs
Technical guidance and answers for common industrial gas mass-flow questions.
What is a Thermal Mass Flow Meter?
A Thermal Mass Flow Meter measures the mass flow of compatible gases by monitoring heat-transfer behavior around thermal sensing elements.
How does a Thermal Mass Flow Meter work?
Gas flowing across the sensing element changes the rate of heat transfer. The transmitter processes this thermal response using the applicable calibration to determine mass flow.
Does it have a rotating turbine?
No. Thermal mass-flow measurement does not require a rotating turbine measurement element.
What does mass flow mean?
Mass flow represents the amount of mass passing through the system per unit time.
Is mass flow the same as volumetric flow?
No. Mass flow measures mass per unit time, while volumetric flow measures volume per unit time.
Why does gas type matter?
Different gases have different thermal properties, so the meter's calibration and configuration should correspond to the intended process gas.
Can it measure compressed air?
Compressed-air measurement should only be advertised where confirmed for the selected FlowDo configuration.
Can it measure biogas?
Biogas applications require review of gas composition, moisture, contaminants, pressure, temperature and flow range.
Can it measure oxygen?
Oxygen service requires appropriate materials, cleanliness and product suitability. It should only be advertised when the selected FlowDo meter is specifically approved/configured for the application.
Does pressure affect thermal mass flow measurement?
Process pressure should be included during meter selection. Actual volumetric gas properties vary with pressure, while the thermal mass-flow measurement architecture is based on gas thermal response and calibration.
Does temperature matter?
Yes. Both process-gas and ambient temperature must remain within the limits of the selected meter.
Does gas composition affect accuracy?
Yes. Significant changes in gas composition can alter thermal properties and affect measurement response.
Can it measure wet gas?
Wet-gas or condensation conditions require application review because liquid droplets can affect the thermal sensor.
What is an insertion Thermal Mass Flow Meter?
An insertion meter places the sensing probe into the process pipe to measure gas-flow conditions.
What is an inline Thermal Mass Flow Meter?
An inline configuration integrates the sensing section into a dedicated meter body installed in the pipeline.
Can it provide 4–20 mA?
4–20 mA should only be shown where the selected FlowDo configuration confirms it.
Does it support Modbus?
Modbus or other digital communication should only be advertised where confirmed.
Can it connect to PLC or SCADA?
Yes, where the selected meter's output/interface is compatible with the automation system.
Can it connect to FlowDo IoT Cloud?
FlowDo IoT integration should only be shown where a compatible telemetry/interface architecture is available.
How do I select the correct Thermal Mass Flow Meter?
Provide gas type/composition, pipe size, minimum/normal/maximum flow, pressure, temperature, installation type and required output.
Need Help Selecting a Thermal Mass Flow Meter?
Configure the Right Thermal Mass Flow Meter for Your Gas Application
Share your gas type, gas composition, pipe size, minimum/normal/maximum flow, pressure, temperature, installation requirement and required output with FlowDo to identify a suitable Thermal Mass Flow Meter configuration.
For faster selection, provide: Gas Type • Gas Composition • Pipe Size • Minimum Flow • Normal Flow • Maximum Flow • Process Pressure • Process Temperature • Installation Type • Process Connection • Required Output