Keysight (Agilent) N8487S Balance Thermocouple Power Sensor, DC to 50 GHz

The Keysight N8487S is a balance thermocouple power sensor engineered for precision RF power measurements from DC to 50 GHz. Built on dual thermopile power detectors integrated on a single chip, this sensor employs RF to DC thermoelectric substitution measurement for high accuracy and metrological traceability. It is a measurement standard in microcalorimeter-based primary systems and as a secondary or reference standard across demanding applications.

Technical Specifications

• Frequency Range: DC to 50 GHz


• Power Measurement Range: −35 dBm to +20 dBm


• Measurement Method: RF to DC thermoelectric substitution


• Sensitivity (RF Connector at 25 °C): 1080 mV/W


• Reflection Coefficient Magnitude: <0.2 across operating frequency range (50 Ω reference)


• Load Resistance (Coaxial Connector): 50.9 Ω typical


• DC Heater Resistance: 50.1 Ω


• Thermocouple Resistance (Dual, RF and DC): 17.1 Ω


• SWR (Typical): 1.05 DC–2 GHz | 1.09 above 2–12.4 GHz | 1.11 above 12.4–18 GHz


• Maximum Input RF Power (CW): 316 mW (+25 dBm at 50 Ω)


• Power Linearity: <0.55% (−1 to +15 dBm) | <0.80% (+15 to +30 dBm)


• Zero Set: <25 nW


• Zero Drift: <10 nW


• Measurement Noise: <80 nW


• Calibration Factor Uncertainty: ±1.10% at 14.0 GHz (25 ± 3 °C) | ±2.60% at 30.0 GHz (0–+55 °C)

Key Features

• Dual thermopile architecture for stability across temperature and time


• EEPROM stores calibration factors, eliminating manual entry


• 2.4 mm male connector interface


• Wide impedance compatibility from 50 Ω to 2 kΩ DC resistance range

Typical Applications

• Primary measurement standards in microcalorimeter-based systems


• Secondary and reference standards in RF power characterization


• Broadband power measurement from DC through millimeter-wave frequencies

Compatibility & Integration Backward compatible with Agilent P-Series, EPM-P Series, and EPM Series power meters. Supports SCPI codes compatible with 8480 Series (Option CFT) and E-Series sensors.