Agilent/Keysight N2781B

The Keysight N2781B is a hybrid AC/DC current probe engineered for precision current measurements across power supplies, motor drives, and electronic circuit characterization. Combining Hall-effect and AC current transformer technology, it delivers accurate measurements from 20 mA to 150 Arms continuous, with pulse capability to 300 A. The probe spans DC to 10 MHz bandwidth with 35 ns rise time, enabling capture of both steady-state and transient events.

A split-core design allows non-invasive clamping onto conductors up to 20 mm diameter without circuit interruption. Output sensitivity is 10 mV/A, and amplitude accuracy reaches ±1.0% of reading ±100 mA. Built-in demagnetize and zero adjustment functions correct residual magnetism and temperature drift, while overload protection safeguards against excessive current.

The 2 m cable terminates in a high-impedance BNC connector rated CAT II 600 V, with maximum power dissipation of 5.5 VA at rated current.

Technical Specifications

• Bandwidth: DC to 10 MHz


• Maximum Continuous Current: 150 Arms


• Maximum Pulse Current: 300 A


• Minimum Measurable Current: 20 mA


• Amplitude Accuracy: ±1.0% of reading ±100 mA


• Rise Time: 35 ns or less


• Output Voltage: 10 mV/A (100:1)


• Maximum Rated Voltage: 600 V CAT II


• Maximum Rated Power: 5.5 VA


• Conductor Diameter: 20 mm


• Output Impedance: 7 Ω


• Cable Length: 2 m

Key Features

• Hybrid Hall-effect and AC current transformer technology


• Split-core construction for non-invasive clamp-on attachment


• Low noise and insertion loss with high signal-to-noise ratio


• Demagnetize function removes residual core magnetism


• Zero adjustment compensates for voltage offset and temperature drift


• Built-in overload protection


• AC/DC input coupling

Typical Applications

• Power supply characterization


• Motor drive analysis


• Transient current event capture


• Low-current precision measurement


• Fast-switching circuit diagnostics

Compatibility & Integration Connects to any oscilloscope with 1 MΩ high-impedance BNC input, including Keysight InfiniiVision and Infiniium series. For 50 Ω oscilloscopes, use the E2697A adapter or N5449A high-impedance probe adapter. Requires external Keysight N2779A 3-channel power supply; up to three N278xB probes operate from a single supply unit.