Both Coriolis and thermal mass flowmeters output mass flow directly, sidestepping the temperature and pressure compensation that a volumetric meter paired with a density device would need [S1][S3].
Coriolis achieves ±0.05% to ±0.1% typical accuracy on both liquids and gases by detecting the phase shift between two points on an oscillating tube, and it also returns density and temperature from the same instrument [S4][S8]. Thermal mass meters are typically limited to clean gases and trade accuracy for a much lower installed cost, with performance dependent on the specific heat, thermal conductivity, and density of the gas [S2][S3][S6].
Measuring principles: phase shift vs heat dissipation
A Coriolis flowmeter forces the process fluid through one or more curved or straight tubes driven at the natural frequency by a central actuator coil; the mass flow produces a proportional phase shift between inlet-side and outlet-side velocity sensors, while the tube's resonant frequency independently tracks fluid density [S4]. Endress+Hauser notes this delivers "real" mass flow independent of the fluid's physical properties, which is why it dominates fiscal metering in oil and gas and batching in food and pharma [S1].
A thermal mass flowmeter injects a controlled amount of heat into the flowstream and infers mass flow from the cooling effect on a heated RTD; the controller either holds a constant temperature differential between two sensors and varies current, or holds current constant and watches the temperature drop widen with flow [S2][S5]. This heat-transfer approach is fundamentally dependent on gas composition, so it needs a known, consistent gas to stay within spec [S2][S9].
Accuracy, turndown, and fluid coverage
Coriolis accuracy is commonly quoted at ±0.05% to ±0.1% of rate, with turndown ratios on the order of 100:1 and the ability to handle liquids, slurries, multi-phase mixtures, and gases from a few g/h up to thousands of t/h [S8]. Because the same sensor pair resolves mass flow, density, and temperature simultaneously, one Coriolis line can replace a volumetric meter plus densitometer plus thermometer in custody-transfer skids [S1][S4].
Thermal mass meters generally fall in the ±1% to ±3% range, with turndown often between 10:1 and 50:1 depending on the manufacturer, and the published accuracy only holds when the calibrated gas matches the flowing gas [S2][S3]. Liquids are not a practical target: the heat absorption capacity of liquids saturates the sensor and the measurement resolution collapses [S2]. The thermal mass flowmeter article in the encyclopedia covers the calibration drift you should expect when gas composition shifts.
Cost, installation, and pressure drop
Installed cost is the clearest line between the two technologies: a Coriolis meter at 1–2 inch line sizes can run several times the price of a comparable thermal mass meter, and the higher price reflects the precision-machined sensor tubes, the drive and pickoff coils, and the more sophisticated transmitter [S3][S8]. A Coriolis tube also imposes a higher permanent pressure drop than an in-line thermal probe because the flow path is restricted and the flow must change direction through the curved or bent tube geometry [S1].
Thermal mass meters are available as small inline probes and as insertion-style sensors for large ducts, which keeps installation cost low and eliminates the need to break the pipe for many retrofits [S3][S5]. The trade-off is that any change in the gas's specific heat or thermal conductivity, including entrained moisture or particulate, will bias the reading unless the meter is re-calibrated for the new composition [S2][S9].
Application fit: which fluid, which duty
Pick Coriolis when the fluid is a liquid, slurry, or two-phase mixture, when you need density and temperature in addition to mass flow, when the duty is fiscal/custody transfer, pharmaceutical dosing, or food batching, or when the process sees wide swings in viscosity, temperature, or entrained air [S1][S4][S10]. Endress+Hauser and Bronkhorst both list Coriolis as the default choice for batch control where the label has to match the actual mass dispensed [S1][S4].
Pick thermal mass when the working fluid is a clean, dry, known-composition gas: compressed air, natural gas, nitrogen, flare gas, biogas, flue gas, or fuel-air ratio trim on burners and steam generators [S2][S5][S6]. The coriolis flowmeter reference entry makes the same point from the opposite direction: thermal wins on gas-only, low-pressure services where absolute accuracy is less critical than repeatability. For higher-pressure gas custody transfer, a Coriolis again becomes the default despite the cost premium [S1][S8].
Decision matrix: criteria by criteria
On accuracy, Coriolis is roughly an order of magnitude better at ±0.05–0.1% versus thermal's typical ±1–3% [S8][S2]. On fluids served, Coriolis covers liquids, gases, and slurries while thermal is essentially gas-only [S2][S4]. On turndown, Coriolis typically reaches 100:1 while thermal is in the 10:1 to 50:1 band, and on density and temperature outputs Coriolis delivers both as native variables while thermal reports only mass flow [S4][S8]. On installed cost thermal wins, often by a factor of several, and on pressure drop thermal probes and insertion designs also beat a bent Coriolis tube [S1][S3][S5]. On composition sensitivity thermal loses, because any change in specific heat or thermal conductivity shifts the calibration; Coriolis is largely immune to that class of error because it measures mass inertia directly [S2][S9].
Failure modes and operating limits
Coriolis meters are sensitive to two-phase flows, entrained air in liquids, and to vibration on the pipe run, all of which can disturb the tube oscillation and bias the density reading; published work also documents the limits when the meter is operated near its upper flow ceiling where pressure drop and wear become real [S10]. Mounting orientation and support are not optional, and the meter should be installed with the manufacturer's recommended upstream and downstream straight runs and pipe bracing.
Thermal meters are sensitive to moisture, oil aerosol, and particulate fouling on the RTD, and to any change in the gas's specific heat ratio, all of which are common in field air lines and dirty flare gas; thermal dispersion sensors also have a maximum gas velocity above which the heat-transfer relationship is no longer linear [S2][S5][S6]. For broader context on flow measurement trade-offs, the encyclopedia entry walks through where Coriolis and thermal sit relative to vortex, ultrasonic, and magnetic technologies.
Sourcing, standards, and the 2026 selection snapshot
As of 2026 the published OEM and integrator guidance has not changed the basic fit-for-purpose picture: Coriolis is the only direct mass flow technology that routinely supports custody transfer for both liquids and gases, while thermal remains the go-to for clean-gas service where repeatability and low installed cost matter more than absolute accuracy [S7][S8]. The current IQS Directory and Patsnap comparisons keep recommending both technologies for "direct, highly accurate measurement in complex or variable conditions," which in practice means Coriolis for the complex side and thermal for the cleaner, gas-only side [S7][S8].
Track two signals over the next buying cycle: whether new low-flow Coriolis offerings from Bronkhorst and Endress+Hauser compress the price gap on the 1–6 mm tube sizes used in gas dosing, and whether thermal mass meters with on-board gas-property compensation (composition + temperature + pressure in one head) can tighten the ±1–3% spec into sub-1% territory [S4][S6]. Until either moves, the rule of thumb in the flow meter reference still holds: Coriolis when you need certainty, thermal when you need a clean, cheap gas number.
Background reading: Deformed Rebar vs Plain Round Bar: Geometry, Bond, Grade.