When 10 ppm Matters: Compact Isolated Current Measurement Moves onto the Power PCB
What happens when the current sensor becomes the accuracy bottleneck?
A power converter can use fast switches, a carefully tuned control loop, and premium passive components, yet still deliver uncertain results if its current measurement drifts or bends away from linearity. That problem becomes especially visible in battery test systems, precision servo drives, laboratory power sources, and power analyzers. In these platforms, current feedback is not merely a protection signal. It is part of the measurement chain, the control reference, and often the evidence used to qualify another product.
A new compact isolated current transducer illustrates how that design tension is changing. The PCB-mount DP12IP series measures DC and AC current up to 18 A, specifies a maximum linearity error of 10 ppm, occupies a 32 mm form factor, and weighs 250 g. It can work with measurement resistors up to 100 ohms at full scale. Its combination of isolation, precision, and board-level integration targets equipment that cannot accommodate a large rack-mounted measurement assembly but still needs a highly stable feedback signal.
The event at the center: fluxgate precision in a smaller package
The important development is not simply another current rating. The device uses closed-loop compensated fluxgate technology, fixed-frequency excitation, and second-harmonic zero-flux detection. Together, these techniques seek to keep the magnetic core near a zero-flux operating point while an electronic compensation loop generates an output related to the primary current. This architecture can measure both DC and AC, provides galvanic isolation, and reduces the linearity and offset limitations that can constrain simpler magnetic sensing methods.
The 32 mm PCB-mount format is equally consequential. Precision magnetic transducers are often associated with substantial mechanical volume, external wiring, or instrumentation cabinets. A smaller component allows designers to place the sensing function closer to the power stage and potentially fit it into a 1U power supply. That shortens interconnects and simplifies assembly, but it also transfers more responsibility to PCB layout, thermal design, grounding, and magnetic-field management.
The stated application set includes magnet power supplies for particle accelerators, stable precision power supplies, precision servo drives, battery test benches, battery emulators, and power-measurement systems. These are demanding use cases because an error can accumulate over long test cycles, distort efficiency calculations, or cause a control system to regulate around the wrong reference.
Technical background: transducer, shunt, and control loop
A current transducer converts conductor current into a lower-level electrical signal that a controller, data converter, or instrument can process. A basic shunt resistor is attractive because it is direct, inexpensive, and potentially wide-bandwidth. The measured voltage follows Ohm’s law, but the shunt dissipates power, introduces insertion loss, and does not inherently isolate the measurement electronics from the high-voltage power domain. Its resistance and temperature coefficient also become part of the accuracy budget.
An isolated magnetic transducer addresses the domain-separation problem. In a compensated fluxgate design, excitation windings periodically drive the core, and harmonic content is used to detect residual flux. A feedback winding counters the field created by the measured current. Keeping flux near zero improves linearity and stability because the core is not used as a simple open-loop amplitude sensor. Fixed excitation also makes the sensing process more predictable, although excitation energy and switching artifacts still require careful filtering.
The allowance for measurement resistors up to 100 ohms at full scale gives system designers room to trade output level, dissipation, noise sensitivity, and interface requirements. That resistor is not a casual selection. Its tolerance, temperature coefficient, voltage coefficient, long-term drift, pulse behavior, and thermal gradients can all erode system accuracy. Kelvin connections may be needed where small parasitic resistances matter. The analog front end, ADC reference, connector resistance, and calibration method must be treated as one metrology chain rather than isolated catalog specifications.
Passive components surrounding the transducer also shape performance. Decoupling capacitors suppress supply noise; low-noise resistors set amplifier gain and filtering; inductors or ferrite beads may keep excitation or converter noise out of sensitive analog rails. ESR and ESL determine whether a capacitor remains effective at the disturbance frequency. An indiscriminately chosen ferrite bead can saturate or create an impedance peak with nearby capacitors, so EMI filtering should be validated across load and temperature instead of copied from a reference schematic.
Where the architecture can matter
Battery test benches and emulators need repeatable bidirectional current information across charge and discharge cycles. Stable sensing helps separate genuine cell behavior from fixture drift. In precision servo drives, cleaner current feedback can improve torque regulation and reveal small deviations in a motion profile. Accelerator magnet supplies demand stable current because magnet field consistency depends on it. Power analyzers and calibration-oriented supplies need a trustworthy signal to calculate loss, efficiency, and dynamic response.
The same engineering logic reaches data-center and AI power infrastructure even when a particular transducer is not designed into every server. High-power racks are moving toward denser conversion stages, tighter telemetry, and more detailed energy accounting. Accurate isolated measurement can be useful in development equipment, validation fixtures, rack-level supplies, battery-backup test systems, and manufacturing calibration. It can help engineers characterize transient loads without tying sensitive instrumentation directly to a noisy power domain.
For EV and industrial power electronics, SiC and GaN switching increase the challenge. Faster voltage edges and high common-mode transients can couple through parasitic capacitance into the sensing circuit. Precision at DC does not automatically guarantee clean behavior beside a fast inverter. Designers must examine common-mode immunity, frequency response, propagation behavior, shielding, conductor placement, and the distance from busbars, inductors, transformers, and switching nodes. Isolation is a system property, not merely a label on the sensor.
Engineering, procurement, and supply-chain implications
For engineers, the first lesson is to build an error budget before selecting a sensor. Maximum linearity error is only one term. Offset, gain error, temperature drift, hysteresis, noise, bandwidth, calibration interval, and long-term stability may dominate under different operating conditions. Thermal simulations should include the primary conductor, nearby shunt or burden resistor, copper losses, airflow, and heat from adjacent power semiconductors. A compact package is valuable only if the board preserves its precision.
Layout reviews should identify high-di/dt loops and external magnetic fields. The primary path must meet current-density and temperature-rise limits. Sensitive output and reference traces should avoid switch nodes and may require differential routing. Firmware should detect saturation or out-of-range behavior and retain traceable calibration coefficients.
For procurement teams, a sensor cannot be qualified by current rating alone. Useful comparison fields include isolation requirements, accuracy over temperature, linearity definition, output interface, auxiliary supply, package dimensions, approved calibration process, expected drift, and production test documentation. Second sourcing may require a board option because transducer footprints and interfaces are less standardized than commodity resistors. Buyers should coordinate an alternate strategy with engineering before a shortage occurs.
Conclusion: precision moves from the instrument rack to the board
The larger signal is architectural. High-accuracy isolated current measurement is moving closer to the power stage. That can reduce cabling and volume while enabling precise control and validation, but it concentrates measurement engineering on the PCB.
Design teams that benefit most will treat the transducer, resistors, analog front end, power passives, layout, thermal environment, calibration data, and sourcing plan as one system. A 10 ppm linearity claim is a useful starting point. The real competitive advantage comes from preserving enough of that performance after assembly, temperature cycling, EMI exposure, and years of operation.
Related Listed Companies to Watch
Directly Related Companies
| Company | Ticker | Market | Relation | Strength |
|---|---|---|---|---|
| Vishay | VSH | NYSE | Current-sense resistor and discrete-component supplier | High |
| Yageo | 2327 | TW | Chip-resistor and passive-component supplier | Medium |
| Walsin Technology | 2492 | TW | Chip-resistor and passive-component supplier | Medium |
Extended Supply-Chain Watch
| Company | Ticker | Market | Relation | Strength |
|---|---|---|---|---|
| Littelfuse | LFUS | NASDAQ | Circuit-protection and power-component supply-chain watch | Medium |
This section is for industry-chain reference only and does not constitute investment advice.