Inside the meter, electromagnetic drive coils vibrate one or two measurement tubes at their resonant frequency. When fluid flows through the vibrating tube, the fluid at the inlet resists upward motion while fluid at the outlet resists downward motion, creating an opposing Coriolis torque that twists the tubes. Electromagnetic pick-off coils measure the microsecond time phase shift (Δt) between tube ends, which is directly proportional to true mass flow rate (m = Ks * Δt).

Industrial process pipes are typically sized for low velocities (1 to 2 m/s / 3 to 6 ft/s) to minimize pumping friction. If a Coriolis meter matches the line size, it operates in the bottom 10% to 15% of its measuring range. At this low turndown, the meter manufacturer Zero Stability (ZS) offset error dominates the reading, degrading calibration accuracy from ±0.1% to worse than ±2.0%. A properly sized meter is almost always 1 to 2 sizes smaller than the line.

Zero Stability is the maximum zero-point drift in kg/h or lb/h that can occur due to ambient temperature shifts, mechanical stress, or electronic noise when there is zero flow. At high flow rates, ZS represents a negligible fraction of the reading. However, as flow decreases, the relative zero error (ZS / Flow Rate * 100%) climbs hyperbolically, setting the practical minimum turndown ratio for custody transfer applications.

For clean liquids, the optimal velocity is 2.0 to 6.0 m/s (6.5 to 20 ft/s) with an upper limit of 8.0 m/s (26 ft/s) to prevent excessive pressure drop. For abrasive slurries or fluids with suspended particulates, velocity must be restricted to 1.5 to 3.0 m/s (5 to 10 ft/s) to prevent erosion of the thin-walled measurement tubes, which operate under high fatigue cycles.

Entrained gas bubbles create acoustic decoupling and severe energy damping in the vibrating fluid core. The drive amplifier must output maximum power (100% drive gain) to sustain oscillation. As liquid and gas accelerate at different rates inside the vibrating tube, the phase shift signal is severely distorted, resulting in false density readings and under-measurement of mass flow.