Little Bee

An affordable, high performance current & magnetic field probe

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The behavior of an electronic device is determined by both voltages and currents. Measuring voltages with an oscilloscope is easy, but current probes are expensive enough to be out of reach for many people. Little Bee is an affordable and high performance current probe and magnetic field probe that will allow you to debug and analyze electronic devices more effectively.

Little Bee is based on an Anisotropic Magneto-Resistive (AMR) magnetic sensor, which gives it performance comparable to current probes based on fluxgate magnetometers and those with hybrid approaches that couple AC current transformers with DC hall effect sensors. But it offers that level of performance at a much lower cost.

Current probes are especially important for power electronics, where they are needed to measure power converter input and output currents and switching waveforms. Every electronics device has some form of power supply but the high cost of current probes and other test equipment prevents many people from investigating these power supplies or designing their own. Today, power electronics is of rising importance due to its relevance in electric vehicles, alternative energy, and high efficiency power supplies. We hope to make the world of power electronics accessible to more people by delivering a much needed piece of test equipment at a low price.

Magnetic Field Sensing

Little Bee can be used as a sensitive magnetic field (B Field) probe. Unlike normal current probes, field probes allow for the non-intrusive measurement of current flowing through PCB traces and inductors by measuring the magnetic fields they generate. While non-intrusive current sensing does not measure an exact current amplitude, it does allow you to verify circuit waveforms quickly and identify faults and shorts circuits.

Below is a photograph of a sample application in which we use Little Bee to measure the stray magnetic field of a PCB-mount DC/DC converter, providing a waveform proportional to the inductor current.

(Click to Expand)

Current Sensing

With the included flux concentrator attachment, Little Bee functions as a traditional current probe and can provide isolated measurements of the current in a wire. It can measure currents over a wide bandwidth: from DC to the MHz range. Below is a photograph of a sample application in which we use Little Bee to measure the input current to an AC-powered switch-mode power supply.

(Click to Expand)

Open Source

It is important that the open source community have access to high-quality tools. It was a desire to make a once prohibitively expensive technology accessible to a wider audience that inspired us to produce Little Bee. In line with these goals, the final product will be open source and OSHWA certified.


  • Adjustable bandwidth (10 MHz and 1 MHz)
  • SMA Output Connector
  • Connects to any standard 1 MΩ impedance oscilloscope input
  • Powdered by a single AA battery (4 hour battery life)
  • Automatic offset adjustment

Typical Electrical Performance

Current sensing

  • Bandwidth: DC - 10 MHz
  • Sensitivity: 0.25 Volts/Amp
  • Max Current: +/- 5 A
  • Noise
    • 25 mA p-p at 10 MHz bandwidth
    • 10 mA p-p at 1 MHz bandwidth
  • DC Accuracy: +/- 15%
  • Insertion Impedance: 100 nH in parallel with 70 Ohms

Magnetic Field Sensing

  • Bandwidth: DC - 10 MHz
  • Sensitivity: 0.2 Volts/Gauss
  • Max Field: +/- 6 Gauss
  • Noise
    • 32 mG p-p at 10 MHz bandwidth
    • 13 mG p-p at 1 MHz bandwidth

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