Published 6 July 2026 at 07:24
An electrician’s current measurement in high-voltage and high-current power systems is limited by the physical form of the instrument. A standard clamp meter has fixed metal jaws that open around a conductor — this works perfectly on a 16 mm² cable in a residential installation, but it works poorly or not at all in industrial high-current installations where busbars can be 100×10 mm flat steel or where cables are arranged in tightly packed bundles. At 3000 A, a completely different sensor technology is required: the flexible Rogowski coil.
What the Chauvin Arnoux MA3018 Is
3000A True RMS AC Flexible Clamp Meter (MA3018) is a digital multimeter-style clamp meter where the fixed metal jaw has been replaced by a 45.7 cm (18 inch) flexible Rogowski coil with a 7.5 mm outer diameter. The clamp meter:
- Measures alternating current from milli-amperes to 3000 A in three ranges.
- Uses a True-RMS algorithm for accurate measurement of distorted and non-sinusoidal waveforms.
- Features a backlit LCD display for reading in dark electrical cabinets.
- Displays warnings when the measured value is out of range and when battery level is low.
- Turns off automatically (with the option to disable).
- Powered by two AAA batteries.
Basic specifications:
- AC Current Range: 3 ranges up to 3000 A
- Sensor Type: Rogowski coil (flexible)
- Coil Length: 45.7 cm (18 inches)
- Cable Diameter: 7.5 mm
- Waveform Type: True-RMS for non-sinusoidal current
- Display: Backlit LCD
- Battery: 2× AAA (included)
- Protection Class: CAT-rated for industrial use
Why a Rogowski Coil Instead of a Fixed Jaw
A traditional clamp meter operates with two metal jaws that form a ferromagnetic circuit around a current-carrying conductor. When the jaws close, the magnetic flux from the conductor’s current flows through the metal of the jaws, and a sensor measures the flux. This works well for cables that fit within the jaw opening, but it has four physical limitations:
- The opening size is fixed: A 30-40 mm jaw does not fit around a 60 mm busbar. A 55 mm jaw does not fit around a 100 mm busbar.
- The jaw shape is straight: Cables bent at sharp angles (around a corner of an electrical cabinet) are difficult to access.
- The jaw takes up space: In a tightly packed electrical cabinet, there may be no room to open a 100 mm jaw around a busbar.
- The jaw requires releasing the current: In many cases, the operator must lift a conductor from its normal position to open the jaw around it.
A Rogowski coil is an air-core coil in the form of a flexible hose. The hose is manually wrapped around the conductor and connected at the ends (like a necklace). There is no ferromagnetic core — the measurement is based on Faraday’s law of induction, where the change in current in the conductor induces a voltage in the coil. The advantages:
- No fixed opening: The 45 cm coil can be wrapped around anything from a 6 mm² cable to a 100 mm busbar.
- Flexible design: The hose can be twisted around corners, through tight spaces, and around bent cables.
- No need for mechanical opening: The hose simply needs to be wrapped and connected.
- No saturation: Without an iron core, the coil can measure currents up to 3000 A without saturating (unlike iron-core sensors which saturate at high currents).
Why True-RMS Is Critical for Modern Installations
A standard average-RMS sensor assumes that the current is a pure sine wave at 50 Hz. This holds true for traditional loads such as incandescent lamps, motors without frequency converters, and pure resistive loads. But it does NOT hold true for:
- Frequency Converters (VFD/frequency inverters): Output chopped current in PWM form with high harmonic content.
- UPS Systems: Also generate modified sine waves.
- Lighting with switching power supplies: LED drivers and electronic ballasts for fluorescent lighting draw pulsed current.
- Electronics-loaded electrical cabinets: Servers, computer equipment, and battery chargers.
The average-RMS sensor underestimates the actual heat generation (which is proportional to the root mean square value of the current) by 10-30% with distorted waveforms. This can lead to cable sizing appearing correct on paper while the cable actually overheats in practice.
The True-RMS algorithm samples the waveform at a high frequency and calculates the true root mean square value — providing an accurate value regardless of the waveform shape.
Where the Rogowski Solution Makes a Real Difference
Industrial electrical cabinets with busbars: Motor controls with 500-3000 A collection busbars are impossible to measure with fixed jaws. The Rogowski coil is wrapped around the bar.
Solar cell installations: Inverters have powerful AC outputs (up to 100 A per phase). The Rogowski coil measures actual output power without having to stop the converter.
Wind power installations: Turbine generators produce current at varying frequencies before being converted. A Rogowski coil can measure even at low frequencies (unlike jaw sensors with iron cores which have frequency limitations).
Data centers and server rooms: Rack PDU circuit monitoring where cables are bundled and there is no space for fixed jaws.
Hospital installations: Backup generator systems and UPS where every second of downtime is dangerous — the Rogowski coil can be installed without cutting off the power.
Ships and offshore platforms: Tight engine rooms with powerful propulsion motors where access to a busbar can be very limited.
Traction power (railway, tram): High currents in convertible form, often with significant harmonic content from frequency inverters.
Aluminum and steel works: Electrolysis cells and arc furnaces with thousands of amperes of DC current. (Note: MA3018 measures AC; for DC, a Hall-effect model is required.)
Cable thermography verification: When a thermal camera shows a hot spot on a cable, current measurement is needed to confirm the cause. The Rogowski coil can be quickly wrapped around the cable without stopping work.
Testing short-circuit currents and overloads: During short-circuit tests, the Rogowski coil can measure transient currents where jaw sensors would saturate.
Handling and Practical Considerations
The Rogowski coil is physically more sensitive than a jaw sensor. Practical tips:
- Bending radius: Avoid bending the coil tighter than a ~30 mm radius — this can damage the inner coil.
- Symmetry: The conductor should be centered in the coil for optimal accuracy. Asymmetry results in 1-2% measurement error.
- External magnetic fields: Place the coil at least 10 cm away from other current-carrying conductors to avoid induction errors.
- Frequency range: Optimal at 50-60 Hz. At very low frequencies (below 5 Hz), accuracy decreases.
- Low-current measurement: At currents below 5-10 A, accuracy is worse than for a dedicated low-current meter with an iron core.
What You Get for Your Money
Chauvin Arnoux MA3018 3000 A True-RMS AC flexible clamp meter, 45.7 cm (18″) Rogowski coil with 7.5 mm cable diameter, 3 measurement ranges up to 3000 A, True-RMS algorithm for non-sinusoidal current, backlit LCD display, warning for out-of-range and low battery, automatic shutdown, complete with 2× AAA batteries.
3,138 SEK is the instrument investment. Compared to a fixed-jaw 1000 A clamp meter (2,000-4,000 SEK, limited to a 55 mm jaw opening), the MA3018 offers a three-times higher measurement range and access to busbars and tightly packed installations that a jaw can never reach. Compared to factory-installed current transformers (5,000-15,000 SEK per phase plus installation time), the MA3018 is a portable solution that can be used in any installation without installation work.
Read more: 3000A True RMS AC flexible clamp meter MA3018 in the shop →
