Agilent / Keysight N8485A Thermocouple Power Sensors 10 MHz to 26.5 GHz

The Keysight N8485A is a thermocouple power sensor engineered for precise RF and microwave power measurements across 10 MHz to 26.5 GHz. Delivering <1% power linearity and dynamic range from -35 dBm to +20 dBm, this sensor combines high accuracy with repeatability for demanding test environments. An onboard EEPROM automatically stores and downloads calibration factors, linearity corrections, and temperature compensation data - eliminating manual entry and streamlining measurement workflows.

Technical Specifications

• Frequency: 10 MHz to 26.5 GHz (33 GHz with Option 033)


• Dynamic Range: -35 dBm to +20 dBm


• Average Power Measurement: -30 dBm to +20 dBm


• Dual-range power capability for enhanced sensitivity Accuracy & Performance


• Power Linearity: <1%


• Temperature Compensation: 0 to 55 °C (re-zero recommended above ±5 °C variation for measurements below -25 dBm)


• Impedance: 50 Ohms


• NIST-traceable calibration Damage Levels & Limits


• Average Power: +25 dBm maximum


• Peak Power: 15 W / 2 µs


• Maximum Energy Per Pulse: 30 W·µs Physical & Interface


• Connector: 3.5 mm (m)


• Dimensions: 60 mm length × 20 mm diameter


• Includes 3.5 mm (f) to Type-N (m) calibration adapter

Key Features

• EEPROM calibration storage eliminates manual factor entry and reduces setup errors


• Built-in temperature compensation maintains accuracy across operating range


• Low SWR minimizes mismatch uncertainty


• Excellent repeatability and linearity for stable, reliable measurements


• Compact 60 mm probe design

Typical Applications

• RF and microwave power measurement in laboratory and field environments


• Power linearity and dynamic range testing


• Calibration and verification of RF systems


• Temperature-compensated power analysis

Compatibility & Integration The N8485A interfaces with Keysight power meters including EPM, EPM-P, and P-Series families. Compatibility may require firmware upgrade. The sensor's standard 3.5 mm connector and included calibration adapter support direct integration into existing test setups.