The Keysight 478A Coaxial Thermistor Mount (formerly Agilent Technologies) is designed for use with the Keysight Model 431 and 432 Power Meters to measure microwave power from 1 μW to 10 mW. Design of the mount minimizes adverse effects from enviromental temperature changes during measurement. For increased measurement accuracy, Effective Efficiency and Calibration Factor are measured for each mount, and at selected frequencies across the operating range; the results are marked on the label of the instrument.
The 478A can be used over the 10-HMz to 10-GHz frequeny range. Throughout the range, the mount terminates the coaxial input in a 50 ohm impedance, and has a SWR of not more than 1.75 without external tuning. Keysight 478A Coaxial Thermistor Mount instruments were previously manufactured by Agilent Technologies.