In this episode Shahriar repairs an Agilent EPM-441A (E4418A) Power Meter. The unit does not boot and displays “Loading firmware…”. After monitoring internal digital signals, the problem is traced to a faulty SRAM IC. After replacement, the unit completes the boot-up process.
Additionally, the principle operation of power sensors is reviewed including both thermocouple based, as well as diode rectifier based. The block diagram of a USB-based power sensor is examined along with a full teardown of a non-functional power sensor. The detector diode circuitry is examine under a microscope. Finally, the repaired unit is verified for calibration.