The HP 8484A power sensor is used for measuring the average power supplied by an RF source to a 50-ohm load. The power sensor is highly sensitive, capable of measuring power levels as low as 0.1 nanowatt (nW). In use, the power sensor is connected to the RF source and to a compatible power meter. (Suitable meters are the HP 435B, 436A, 437B, and 438A power meters.) The power sensor places a 50-ohm load on the RF source, and the power meter indicates the power dissipated in this load. The power is determined from the RF voltage developed across the power sensor load, and is expressed in nW (or microW) and dBm.

The power sensor measures power levels from -70 dBm to -20 dBm (0.1 nW to 10 microW), at frequencies from 10 MHz to 18 GHz.