Quick answer: A fluxgate device measures magnetic field, not current. To make a current probe you must convert field to current through a known geometry and a calibrated transfer function, and neither of those comes from the sensor datasheet. A datasheet rating is a device characteristic, not measured performance of a finished probe.
What the device provides
The Texas Instruments DRV425 datasheet is the concrete reference available here. It describes an integrated single-axis fluxgate sensor with an internal compensation coil that provides an analog output proportional to sensed magnetic field, and it lists a magnetic sensing range of plus or minus 2 mT with bandwidth up to 47 kHz. Those are device characteristics.
It is worth being precise about what that means. The plus-or-minus 2 mT figure is a magnetic field range, not a current rating, and 47 kHz is a device bandwidth, not a promise that a finished probe measures current to 47 kHz. If your sensor’s part number is not confirmed from its own documentation, treat a related device as an illustration rather than a match.
Device characteristic versus system requirement
| Documented device property | What it does not establish |
|---|---|
| Plus-or-minus 2 mT magnetic sensing range | The current range of a probe built around it |
| Up to 47 kHz bandwidth | End-to-end system bandwidth after analog stages |
| Internal compensation coil | Conductor geometry and external-field rejection |
| Analog output proportional to field | A calibrated current transfer function |
For adjacent instrumentation references, see the Arduino oscilloscope guide and the auto-ranging ohmmeter guide.
An ordered evaluation process
- Confirm the actual sensor part number. Do not assume a specific device without documentation; a related part is not a confirmed match.
- Separate field sensing from current measurement. The device senses field; current depends on geometry and a transfer function you must establish.
- Read range and bandwidth as device specs. Treat plus-or-minus 2 mT and up to 47 kHz as characteristics, then state your own probe’s measured band separately.
- Account for external-field rejection. Geometry and shielding affect what the probe reads; these are system design questions, not datasheet answers.
- Address rated isolation independently. A sensor datasheet is not proof of whole-module isolation or a CAT rating.
- State the measurement bands plainly. Publishing a band you can defend is more useful than implying a sensitivity you have not verified.
Reader questions
Is the plus-or-minus 2 mT range also my current range?
No. It is a magnetic sensing range. The current you can measure depends on conductor geometry and the transfer function you establish, which the datasheet does not supply.
Does 47 kHz bandwidth mean the probe measures 47 kHz currents?
No. That figure is a device bandwidth characteristic, not measured performance of a complete DIY probe.
Is the probe based on the DRV425?
Only if your sensor documentation says so. A related device is not a confirmed identification, and inferring the part from a similar project would be an unverified jump.
Can I use such a probe on mains wiring?
Not from this guide. There is no CAT rating or isolation claim here, and datasheet characteristics are not proof of module isolation. Keep the discussion to low-energy calibration and evaluation.
Documentation
Note: no probe was built, calibrated or tested. The specific sensor part number is not confirmed here, and microamp sensitivity, 20 kHz bandwidth, complete probe insulation and a measured transfer function are not established. No CAT rating or mains isolation is implied.
