A thermal mass flowmeter measures gas flow by detecting the heat transfer between a heated sensor and the flowing gas — directly yielding mass flow rate without requiring separate pressure or temperature inputs for compensation. This makes it simpler, more reliable, and more accurate than inferential methods that calculate mass flow from separate measurements.

The TMS Series Thermal Mass Flowmeter uses a patented dual-sensor arrangement: one heated sensor and one reference sensor. The difference in temperature between the two sensors is a direct measure of the mass flow rate of gas passing through. Available in insertion and in-line configurations, it covers pipe sizes from 10 mm to 6,000 mm — making it suitable for everything from small process lines to large industrial ducts and stacks.

What can it measure?

The TMS Series Thermal Mass Flowmeter measures:

• Mass flow rate — directly, with no pressure or temperature compensation required
• Standard or normal volumetric flow rate
• Media temperature
• Accumulated total flow
• Bi-directional flow (forward and reverse)

Typical Applications

The TMS Series is designed for single or mixed gases with lubricating or non-lubricating properties. It is widely used across the following industries and applications:

• Biogas measurement — landfill gas, anaerobic digestion, and biomethane
• Compressed air — plant air systems, leak detection, and energy auditing
• Natural gas and methane — distribution, custody transfer support, and consumption monitoring
• Power generation — combustion air, flue gas, and cooling gas measurement
• Chemical and petrochemical — process gas monitoring and flow control
• Steel and metals manufacturing — blast furnace gas, nitrogen purging, and inert gas blanket monitoring
• Pulp, paper, and waste — process gas flows and emissions monitoring
• Food and beverage — CO₂, nitrogen, and other process gases
• Large ducts and stacks — HVAC, ventilation, and environmental monitoring

Note: Acetylene and other explosive gases are not approved for use with this flowmeter.

Key Advantages

• Measures mass flow directly — no pressure or temperature compensation required, unlike differential pressure or vortex meters
• High accuracy: ±1% of reading; ±0.5% of full scale (with USA NIST-traceable calibration)
• Wide turndown ratio of 100:1 — highly sensitive to very low flow rates
• Extremely wide pipe size range: 10 mm to 6,000 mm (½” to 240″) — covers both small process lines and large industrial stacks
• Fast response time: 1 second (0.2 s time constant) — ideal for dynamic processes
• Bi-directional flow measurement capability
• No moving parts — minimal maintenance and long service life
• Wide temperature range: –40°C to +100°C standard; up to +510°C for high-temperature processes
• Available in AISI 316 stainless steel, Hastelloy C, and Titanium — suitable for corrosive and aggressive gases
• Certified for hazardous areas: Intrinsically safe (Ex ia IIC T5) and Flameproof (Ex d IIC T4)
• IP65 and NEMA 4X protection rating
• All calibrations traceable to USA National Institute of Standards and Technology (NIST)

All TMS flow sensors are calibrated against a gas flow primary standard and are traceable to the USA National Institute of Standards and Technology (NIST) and other international standards. Where the specific gas is not available for calibration, a NIST-traceable air calibration is performed with accurate corrections applied for the thermal properties of the target gas.

The TMS Series Thermal Mass Flowmeter is sized based on pipe diameter, gas type, and expected flow velocity range. Both insertion and in-line configurations are available.

Click here to contact our specialists for assistance with sizing and selection for your application.