The HP 432A is an automatic, self-balancing power meter designed for use with temperature-compensated thermistor sensors. It provides high-accuracy RF and microwave power measurement by measuring the output voltage of the thermistor bridges and computing the corresponding power. By reducing thermoelectric error to a negligible level, the 432A maintains accuracy even on its most sensitive range, supporting measurement of microwave power as low as one microwatt when paired with a compatible thermistor mount.

A power meter is the instrument an RF engineer reaches for when they need to know exactly how much energy a signal is delivering — not its frequency content, not its waveform, but its absolute power level. Thermistor-based power meters work on a substitution principle: the RF energy heats a thermistor element, and the bridge circuit measures the DC power required to produce the same heating, yielding a direct and traceable power reading. The HP 432A serves this role across seven full-scale ranges spanning 10 µW to 10 mW, with the milliwatt scale also calibrated directly in dBm from -20 dBm to +10 dBm in 5 dB steps for the convenience of RF technicians who work in logarithmic units.

ValueTronics International has been a trusted source for legacy and current-production test and measurement equipment since 1992. All instruments are inspected and tested at our 20,000 sq ft secure warehouse at 1675 Cambridge Drive in Elgin, Illinois, where our technicians verify performance against published manufacturer specifications before shipment. For HP 432A power meters and the 478A, 8478B, and 486-series thermistor mounts that complete the measurement system, that in-house verification matters: these are precision instruments whose value depends on documented, traceable performance, and our process gives buyers a measurable starting point rather than an unverified description.

Brand Heritage

Hewlett-Packard's test and measurement business was spun off as Agilent Technologies in 1999, and the electronic measurement portion of Agilent became Keysight Technologies in 2014. Instruments carrying the HP brand — including the 432A power meter and its thermistor mount accessories — were manufactured during the original Hewlett-Packard era, and the underlying engineering lineage continues through Keysight today.

Compare Other Models in This Series

The HP 432A thermistor power meter is the central instrument in a measurement system that also includes a dedicated calibrator and a family of frequency-specific thermistor mounts. The 432A handles the bridge measurement and front-panel readout; the mounts provide the RF-to-DC thermistor sensing across different frequency bands and connector types; and the 8477A calibrator verifies the 432A's accuracy across all seven ranges. Selecting the right combination is a matter of matching the mount to the frequency range and connector interface of the application, then optionally adding the 8477A for in-house calibration capability.

Within the mount family, the 478A and 8478B are coaxial designs suited to general-purpose RF and microwave power measurement, while the 486A series uses waveguide flanges to cover specific microwave frequency bands extending to 40 GHz. Each model carries its own SWR specification across its operating range, documented on the datasheet.

Each pre-owned HP 432A, HP 8477A calibrator, and thermistor mount listed below is its own dedicated product page with condition-matched pricing and availability. Click through to the specific model that matches your frequency range and connector requirements.

The HP 432A itself is the bridge-and-readout instrument and does not change function based on which thermistor mount is connected — the mount selection determines the frequency coverage, connector interface, and maximum SWR of the complete measurement system.

The thermistor mounts differ on three dimensions documented in the datasheet: frequency range, connector type (coaxial versus waveguide band), and maximum SWR across the operating range. The 478A covers 10 MHz to 10 GHz with coaxial connection. The 8478B extends coaxial coverage to 18 GHz and is available with an APC-7 RF connector under Option 011. The 486A series uses waveguide flanges, with each model (X486A, P486A, K486A, R486A) covering a specific waveguide band from 8.20 GHz up through 40.0 GHz.

The HP 8477A calibrator is a separate companion instrument, not a mount — it is the verification accessory for the 432A itself and is used periodically to confirm the meter's accuracy, rather than as part of every measurement setup. See the comparison table that follows for the frequency range and maximum SWR specifications of each mount model.

Additional differences in specifications beyond the few shown above are not listed here — see each model's full specifications below.

Product Core & Specifications

About this used unit

• Warranty included
• Functional verification included
• Standard Calibration Upgrade Options: No Calibration Required, NIST Traceable, Z540.1 or ISO 17025 with Data, Z540.3 Guardbanding with Data.
• Note that unnecessary accessories may not be included (contact Test Architect to confirm).

Please review the Manufacturer's Data Sheet to verify published specifications. Feedback on this webpage is always welcome — please reach out to your Test Architect at any time for questions or concerns. Thank you, we truly appreciate you being our customer.