ERT vs ECT: Which Should You Choose?
A comparison and selection guide for Electrical Resistance Tomography (ERT) and Electrical Capacitance Tomography (ECT): measurement principle, suitable media, sensor form and typical applications — four dimensions to quickly judge which technology fits your process-monitoring needs.
Published: 20 May 2026 Related: Capacitance Tomography Resistance Tomography
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TL;DR
Medium is conductive (water-based, slurry, electrolyte) → choose ERT; Medium is non- or weakly conductive (gas, oil, organic solvent) → choose ECT.
Technology comparison
| Dimension | ECT (Capacitance Tomography) | ERT (Resistance Tomography) |
|---|---|---|
| Measured quantity | Inter-electrode capacitance (tied to permittivity contrast) | Inter-electrode resistance / conductance (tied to conductivity contrast) |
| Electrodes contact the medium? | No (electrodes on the outer wall) | Yes (electrodes immersed in the fluid) |
| Suitable continuous phase | Gas, or a liquid of low permittivity | Conductive liquid (water-based, electrolyte) |
| Typical dispersed-phase contrast | Gas-solid, gas-oil, low-water-cut gas-liquid | Oil-water, slurry, solid-liquid mixtures |
| Pipe-material requirement | Insulating wall needed (PVC, acrylic…) | Metal pipe acceptable (insulating liner required) |
| Pressure / temperature tolerance | Limited by electrode packaging; atmospheric to medium pressure | Limited by contact-electrode packaging and corrosive environment |
| Spatial resolution | Medium (typically 8-16 electrodes/plane) | Medium (typically 8-16 electrodes/plane) |
| Acquisition speed | Fast (100 fps order is common) | Medium-fast (electrode switching + safe-current limits) |
Quick scenario lookup
- Pneumatic conveying / fluidised bed (gas-solid) → ECT: clear permittivity contrast between gas and solid; non-contact mounting is convenient
- Gas-oil two-phase / low-water-cut oil-gas transport → ECT: sizeable gas-oil permittivity contrast, continuous phase is oil (low conductivity)
- In-tank mixing (water-based suspension) → ERT: continuous phase is conductive water; immersed electrodes give stable conductance measurement
- Slurry pipeline (high conductivity, solid-liquid) → ERT: slurry conductivity is high, ECT struggles; ERT uses direct conductance contrast
- Reactor stirring process (water-based) → ERT: conductive medium + need to observe mixing uniformity
- Oil-water separation process → ERT: large oil-water conductivity contrast; water cut and interface position can be obtained at once
Edge cases
- Metal phase / liquid metal present: neither ECT nor ERT is ideal — use EMT (Electromagnetic Tomography), which works by coil induction
- High-water-cut gas-liquid (e.g. wet steam): water’s permittivity lowers ECT contrast; if conductivity is also high, consider ERT or dual-modality ECT/ERT fusion
- Sealed metal pipe: ECT needs an insulating wall, so a metal pipe needs an insulating “window” spool; ERT can use contact electrodes and bypass this limit
- When unsure: run a bench trial first — validate on your medium once with our standard 12-electrode sensor, then decide on ECT, ERT or dual-modality
Next step
Read What Is Tomography for the underlying principle; or contact us directly with your medium, pipe size and measurement goal, and an engineer will recommend a concrete technical route.