PowerMon

PowerMon is a device that can be inserted between a computer power supply and the computer's main board to measure power usage at each of the DC power rails supplying the board. The device measures voltage and current on eight DC rails, reporting measurements at a rate of up to 1024 Hz per channel up to 3072 Hz aggregate, and fits in a standard 3.5" hard drive bay.

PowerMon has been used to resolve and highlight variations in power consumption and energy efficiency during individual sub-processes of software applications at the subsystem level.  The parts cost is about $150 each, in small batches. (Assembled cost ~$250, in quantities of 50.)

Related publications:
D. Bedard, M. Lim, R. Fowler, and A. Porterfield, \ldblquote PowerMon: Fine-Grained and Integrated Power Monitoring for Commodity Computer Systems,\rdblquote  Southeastcon, 2010. IEEE, pp start-finish, March 18-21, 2010.

The entire design is licensed under the Renci Open Source License v1.0 (see ./license), meaning, essentially, that you can use it in any otherwise legal project, as long as you provide attribution.

Directory tree:

+-application/    A sample application in C
| +-pm_app.c
+-assembly/       BOM, centroid, drawings, instructions
+-firmware/       Device firmware
| +-bootloader/
| +-system/
|   +-adm1191.c
|   +-adm1191.h
|   +-config.c
|   +-config.h
|   +-powermon.c
|   +-timer2.c
|   +-timer2.h
|   +-usart.c
|   +-usart.h
+-gerber/         Production drawings for printed circuit boards
+-pcb/            Board layout, in Eagle PCB, PDF formats
+-schematic/      Schematic, in Eagle PCB, PDF formats
+-README          This file.
+-license         The RENCI Open Source License v1.0