• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer
  • Subscribe
  • Advertise

Power Electronic Tips

Power Electronic News, Editorial, Video and Resources

  • Products
    • Power Supplies
    • AC-DC
    • DC-DC
    • Battery Management
    • Capacitors
    • Magnetics
    • MOSFETS
    • Power Management
    • RF Power
    • Resistors
    • Transformers
    • Transistors
  • Applications
    • 5G
    • AI
    • Automotive
    • EV Engineering
    • LED Lighting
    • Industrial
    • IoT
    • Wireless
  • Learn
    • eBooks / Tech Tips
    • EE Training Days
    • FAQ
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • Resources
    • Design Guide Library
    • Digital Issues
    • Engineering Diversity & Inclusion
    • LEAP Awards
    • Podcasts
    • White Papers
    • Design Fast
  • Video
    • EE Videos & Interviews
    • Teardown Videos
  • EE Forums
    • EDABoard.com
    • Electro-Tech-Online.com
  • Engineeering Training Days
  • Newsetter Subscription

Options for current sensing: part 2

August 22, 2017 By Bill Schweber

Part 1 of this FAQ discussed the issue of current measurement and four transducers that can measure current. The first two — shunt resistors and Hall-effect devices — can be used for AC or DC currents. We will now look at two other transducers — the Rogowski coil and the current transformer—which can be used only for AC but are nevertheless in widespread use.

Q: What is a Rogowski coil?

A: Named after the German physicist Walter Rogowski, the Rogowski Coil is an electrical device used for measuring alternating current (AC) including high-speed transients, pulsed currents, and or line-power sinusoidal currents. It uses a helical coil of wire, and the lead from one end returns through the center of the coil to the other end; thus, both terminals are at the same end of the coil. Next, the assembly is wrapped around the straight conductor whose current is to be measured, without need for a metal (iron) core, Figure 1.

Fig 1: The Rogowski coil may not be well known among engineers, but is widely used in applications where its unique characteristics make it a good fit. (Source: Electricalunits.com)

The voltage induced in the coil is proportional to the rate of change of current in the straight conductor, so the output of the Rogowski coil is usually connected to an analog integrator circuit to provide an output signal that is proportional to the current, or the integration function is implemented by a A/D converter and software.

Q: What are the major features of the Rogowski coil?

A: The coil has some interesting features:

  • It is best suited to high-current levels, on the order of tens of amps and higher;
  • It is coreless, so it can’t saturate;
  • It can measure current from about 1 Hz to tens of kHz due to its low inductance;
  • It is isolated from the current-carrying wire being sensed;
  • Because it is an “open” magnetic circuit, it is susceptible to external magnetic fields unless it is shielded;
  • It is low-cost;
  • It requires an integrator to provide a meaningful output.

Q: What about using a basic transformer?
A: The classic transformer is often used as a current-measuring transducer, and it is quite effective in the right applications. In practice, it is built as a toroidal configuration, with the wire to be sensed passing through the center of the transformer core and windings, Figure 2.

Fig 2: Among the oldest of electrical components, the transformer can be used as an effective current transducer when configured in a toroidal configuration. (Source: Vacuumschmelze GmbH)

The performance of the current-sense transformer is also determined by the specific magnetic material used for the core. Depending on the material, the design can tolerate a wider amount of DC component on the AC current; this DC component would normally saturate the core.

Q: What are some other specifics of the toroidal transformer as a current sensor?

A: The transformer has some well-known characteristics:

  • It is galvanically isolated;
  • It has moderate-to-high linearity and wide dynamic range but can saturate at the upper end of the range;
  • It is a closed magnetic circuit and so is immune to external magnetic fields; thus, shielding is not needed;
  • It is stable and reliable and can tolerate a wide range of temperatures;
  • It has low phase error, especially critical in power-line measurements;
  • It is easy to mount, install, use, and interface.

From Parts 1 and 2, we see that there are several viable options for the very important task of measuring AC and DC currents across a wide range of values and circumstances. As with most engineering alternatives, there are strong reasons to favor one solution over the others in a given situation, and there are also tradeoffs in performance, other technical attributes, and cost.

 

 

 

 

You may also like:

  • acienna
    Advanced current sensing for next-gen electronics

  • Options for current sensing: part 1

Filed Under: Battery Management, FAQ, Featured, Industry Experts, Power Management, Transformers Tagged With: basics, FAQ

Primary Sidebar

Featured Contributions

Robust design for Variable Frequency Drives and starters

Meeting demand for hidden wearables via Schottky rectifiers

The case for vehicle 48 V power systems

GaN reliability milestones break through the silicon ceiling

Developing power architecture to support autonomous transportation

More Featured Contributions

EE LEARNING CENTER

EE Learning Center

EE TECH TOOLBOX

“ee
Tech Toolbox: Internet of Things
Explore practical strategies for minimizing attack surfaces, managing memory efficiently, and securing firmware. Download now to ensure your IoT implementations remain secure, efficient, and future-ready.

EE ENGINEERING TRAINING DAYS

engineering
“power
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for EE professionals.
“bills

RSS Current EDABoard.com discussions

  • 10A fuse keeps blowing on an Okamoto Surface Grinding Machine Power supply
  • Will this TL084C based current clamp circuit work?
  • problem connecting to my xilinx device VIA global IP
  • How to determine the maximum PAD frequency ?
  • Help Creating .lib File for SCR in LTspice

RSS Current Electro-Tech-Online.com Discussions

  • AC Blower Motor Speed Control
  • how can we detect a stack overflow
  • RS485 bus: common ground wire needed or not?
  • Kawai KDP 80 Electronic Piano Dead
  • Good Eats

DesignFast

Component Selection Made Simple.

Try it Today
design fast globle

Footer

EE World Online Network

  • 5G Technology World
  • EE World Online
  • Engineers Garage
  • Analog IC Tips
  • Battery Power Tips
  • Connector Tips
  • DesignFast
  • EDA Board Forums
  • Electro Tech Online Forums
  • EV Engineering
  • Microcontroller Tips
  • Sensor Tips
  • Test and Measurement Tips

Power Electronic Tips

  • Subscribe to our newsletter
  • Advertise with us
  • Contact us
  • About us

Copyright © 2025 · WTWH Media LLC and its licensors. All rights reserved.
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media.

Privacy Policy