Rogowski Coils vs. Coaxial Shunts: A Comparison

1. Specifications

The most prominent specification is bandwidth; the coaxial shunt has an ultra-high bandwidth unlike conventional probes: 400/1200/2000MHz,

It is highly suitable for measurements requiring high frequency, such as new-material semiconductor devices. A Rogowski coil generally reaches 30MHz,Longer coils have lower bandwidth,

The highest closed-loop coil can achieve 50/100MHz.From bandwidth alone, the coaxial shunt is indeed much better than the Rogowski coil; let us look at other aspects.

2. Installation method

The main feature of the Rogowski coil is ease of use: the coil is plugged and unplugged, with no need to open the circuit for installation.

Rogowski coils are available in different thicknesses and lengths, suitable for measurement on various large, medium, small, and micro devices. Thick coils with 8.5mm diameter can be made 1 m or even longer,

They can measure large and medium-sized equipment; thin coils are 4.5/3/1.7mm or even 1mm, especially suitable for pins of MOS transistors in semiconductor power devices,

No need to open the circuit or damage the conductor, and they can be used even in tight corners.

Installation of the coaxial shunt requires insertion into the circuit; it is essentially a precision resistor, and in-line wiring applications are generally less common,

At present, its main application is mounting on PCB test boards; in addition to the upfront test-board design and package size, it also imposes relatively high requirements on installation conditions and skill.

Poor installation introduces more stray inductance and has a certain impact on measurement data.

Left image: SDN soldering; right image: nut mounting

3. Accuracy

The overall accuracy of the Rogowski coil is ±2%, some series are ±1%, and under optimal calibrated conditions the accuracy at the coil center can reach up to ±0.2%.

The accuracy of the coaxial shunt is 0.2%; in terms of accuracy, the coaxial shunt is superior.

4. Selection, ranges, and overload

Considering only the current specification, Rogowski coils are subdivided into 13 ranges, from 30A to 300KA; custom ranges are also available if these are insufficient,According to your peak current magnitude

Select a range model; the more suitable the range, the higher the accuracy. There is no magnetic saturation limit, and transient currents pose no overload risk, but long durations are not acceptable.

A coaxial shunt does not need to be selected according to current magnitude; it has no range divisions. Its main specification follows one rule: do not exceed the Joule heating specified in the specifications!

Refer to the formula [Joule = current squared * resistance * pulse width time]; if exceeded, it will burn out.

Burning one costs around 4,000; the trial-and-error cost is somewhat high

V. Isolation

Obviously, a Rogowski coil is completely isolated.

A very common and important problem in double-pulse testing is that many people do not know that this shunt is not isolated; the shunt housing and

the oscilloscope share a common ground, forming a loop that generates a negative current; if the gate probe does not use differential isolation, it can damage the shunt and even the oscilloscope.

We have also published relevant experiments on this specific principle:Negative current problem in double-pulse experiments on GaN devices。

VI. Price and lead time

The tax-included unit price of an entry-level Rogowski coil configuration is just over 10,000; higher ones range from 20,000 to 40,000.

Conventional coaxial shunt models are generally around 4K; higher-power ones also exceed 10,000.

From this perspective, the coaxial shunt still offers quite high cost-effectiveness.

Regarding lead time, because coaxial shunts are now widely used in semiconductors and other industries, Probemart has kept regular stock of some conventional coaxial shunt models,

such as the full SDN/SSDN-414 series, in stock domestically and responding very quickly to users' needs; non-stock models generally have a lead time of 4-6 weeks at the fastest.

Because Rogowski coils are segmented by current range, coil thickness, and length, IWATSU alone has more than 100 models,

We can only stock some common models based on the market and experience; non-standard models generally have a lead time of 2-3 months.

By now you should have a clear understanding. So which one should you choose, the Rogowski coil or the coaxial shunt? There is no perfect standard answer,

Choose according to your own test requirements, depending on which parameter you weigh more heavily, or factors such as the installation conditions of the test environment.

If I follow my product-promotion logic and suggest buying both: using the two at the same time causes no interference, and they can corroborate each other, so it is also a good choice!

Below is the PK summary comparison table: