Yokogawa Adds Clamp-On 500 A and 200 A EV Test Sensors

Yokogawa Test & Measurement has announced two second-generation AC/DC split core current sensors, the CT500SA and CT200SA, covering the 500 A and 200 A ranges, which clamp directly onto conductors that cannot be cut to thread through a through-hole sensor and are designed for space-constrained environments such as EV test setups.

Yokogawa Test & Measurement has introduced two AC/DC split core current sensors, the CT500SA and the CT200SA, aimed squarely at a problem that anyone who has instrumented an electric vehicle powertrain knows well: the cable you need to measure is already terminated, already routed, and cannot be cut.

The two second-generation models cover the 500 A and 200 A ranges. Rather than requiring a conductor to be threaded through a fixed aperture, they open and clamp directly onto the cable. Yokogawa describes them as built for space-constrained environments such as EV test spaces, according to Charged EVs.

Why a split core matters on an EV test bench

Current sensors broadly divide into two families. A through-hole, or closed-core, sensor has a solid magnetic ring; the conductor must pass through the hole, which means either building the harness around the sensor or disconnecting and rethreading the cable. A split core sensor has a hinged core that opens, closes around the conductor and re-forms the magnetic loop. The measurement principle is the same. The installation is completely different.

On an EV development rig, that difference decides whether a measurement happens at all. Traction inverter phases, DC link busbars, battery pack outputs and onboard charger feeds are typically high-current, short-run and tightly packed. Disconnecting one to thread a sensor means breaking a safety-rated high-voltage connection, re-torquing terminals and re-validating the joint. In a thermal chamber or a shaker table setup, there may be no slack cable to work with in the first place.

Clamp-on sensing removes that step. An engineer can add a channel mid-campaign, move a measurement point after a first result looks odd, or instrument a vehicle-level test where the harness was never designed to be opened.

Where 500 A and 200 A sit in a powertrain

The two ranges Yokogawa has chosen map onto recognisable parts of an electrified drivetrain. The 500 A class covers the heavy end: battery pack discharge under hard acceleration, DC link current into a traction inverter, and the high-current DC paths that dominate a vehicle's efficiency map. The 200 A class fits auxiliary and mid-power circuits — onboard chargers, DC-DC converters feeding the low-voltage system, thermal management compressors and pumps, and smaller motor drives.

The AC/DC capability is the other half of the story. Efficiency work on an inverter requires measuring a DC input and a chopped AC output within the same test, on the same time base. A sensor that handles both, rather than an AC-only current transformer, keeps the setup coherent. DC-capable clamp sensors typically rely on Hall-effect or fluxgate elements inside the split core, which is what allows a reading at zero frequency where a plain transformer produces nothing.

Second generation, and what testers will want to see

Yokogawa has labelled these as second-generation models, which sets the comparison against its own earlier split core range rather than against a blank sheet. The specifications that will decide adoption are the usual ones for power analysis work: amplitude and phase accuracy across the frequency band, bandwidth relative to the switching frequencies of modern silicon carbide inverters, temperature drift, and how much of the rated range remains usable before the core saturates.

Phase accuracy deserves particular attention. In power measurement, an error of a fraction of a degree between the current and voltage channels translates directly into an error in measured power — and the effect grows as the power factor falls. Inverter efficiency campaigns often chase the last fraction of a percent, so a sensor's phase behaviour at high frequency matters more than its headline current rating.

Split core designs have historically traded a little accuracy for convenience, because the mating faces of a hinged core introduce a small air gap and the magnetic path is not perfectly uniform. Closing that gap in performance terms is what a second-generation product is generally for. Buyers evaluating the CT500SA and CT200SA against through-hole alternatives or competing clamp instrumentation should read the published accuracy class carefully rather than assume parity.

The test-equipment layer of the EV build-out

Instrumentation is the least visible part of the electrification supply chain and one of the more reliable ones. Every new battery chemistry, every inverter redesign, every charging architecture generates test demand before it generates a single unit of production volume. That work runs through power analysers, current sensors, thermal instrumentation and the software that ties them together — and it runs whether or not the underlying vehicle programme ultimately ships.

The commercial logic of a clamp-on sensor fits that pattern. It is not a component that goes into a car. It is a tool that shortens the loop between a design change and a validated number, which is where development cost actually accumulates. Test engineering budgets tend to reward anything that cuts rig downtime, because rig time is the scarce resource in a compressed vehicle programme.

Broader equity markets closed higher on the day the sensors were announced. The S&P 500 tracker (NYSEARCA: SPY) finished at $765.72, up 0.41%, against a previous close of $762.60 and a day range of $764.17 to $767.85. The Nasdaq 100 fund (NASDAQ: QQQ) closed at $713.44, up 0.35%, and the Dow tracker (NYSEARCA: DIA) closed at $532.22, up 0.89%. Those are last traded prices as of 20:00 GMT on 21 August 2026, with the market closed.

What to watch next

Three things will determine whether these sensors displace incumbent setups. First, the published bandwidth figure and whether it comfortably covers silicon carbide switching frequencies rather than sitting at the edge of them. Second, the physical envelope — jaw opening versus cable diameter, and body depth in a crowded engine bay or battery enclosure, since a sensor that clamps in theory but does not fit in practice solves nothing. Third, integration with existing power analyser inputs, because a sensor that requires a new mainframe is a much larger purchase than a sensor that plugs into hardware a lab already owns.

For laboratories running mixed fleets of test gear, the question is rarely whether a clamp-on sensor is convenient. It obviously is. The question is what accuracy it costs and whether that cost is acceptable for the measurement at hand — a screening run on a thermal loop tolerates more error than a certification-grade efficiency map. Yokogawa's detailed specification sheet, not the form factor, will settle that.

Key facts

• Products: Yokogawa CT500SA and CT200SA AC/DC split core current sensors
• Current ranges: 500 A (CT500SA) and 200 A (CT200SA); second-generation models
• Key capability: Clamp directly onto conductors that cannot be cut for a through-hole sensor
• Market close, 21 Aug 2026 20:00 GMT: SPY $765.72 (+0.41%), QQQ $713.44 (+0.35%), DIA $532.22 (+0.89%)

Frequently asked questions

What is a split core current sensor?

A split core current sensor has a hinged magnetic core that opens so it can be clamped around a live conductor, then closes to complete the magnetic loop. Unlike a through-hole sensor, it does not require the cable to be disconnected and threaded through a fixed aperture, which makes it far quicker to install on existing wiring.

What current ranges do the CT500SA and CT200SA cover?

Yokogawa's CT500SA covers the 500 A range and the CT200SA covers the 200 A range. Both are second-generation AC/DC split core models. The 500 A class suits heavy paths such as battery pack output and inverter DC link current, while the 200 A class fits onboard chargers, DC-DC converters and auxiliary drives.

Why does AC/DC capability matter in EV testing?

Inverter efficiency work requires measuring a DC input and a switched AC output in the same test on the same time base. A sensor that reads both, typically using a Hall-effect or fluxgate element, avoids mixing instrument types. A plain current transformer cannot read direct current at all, since it produces no output at zero frequency.

Do clamp-on sensors sacrifice accuracy versus through-hole types?

Historically yes, to a degree. The mating faces of a hinged core introduce a small air gap and a less uniform magnetic path, which can affect amplitude and phase accuracy. Closing that gap is generally the purpose of a second-generation design, so buyers should compare published accuracy classes rather than assume equivalence.

Why is phase accuracy important for power measurement?

Power is calculated from current and voltage together, so any timing offset between the two channels produces an error in the measured power figure. That error grows as the power factor falls. In inverter efficiency campaigns chasing fractions of a percent, phase behaviour at high frequency can matter more than the headline current rating.

Who typically buys this kind of instrumentation?

Automotive and supplier test laboratories, powertrain and inverter development teams, battery pack validation groups and charging equipment makers. Demand is driven by development programmes rather than production volumes, so test instrumentation orders often arrive well before a vehicle or component reaches manufacturing.

Sources

• Yokogawa’s new CT500SA and CT200SA current sensors clamp onto cables in tight EV test spaces — Charged EVs

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