David L. Jones Discussing the µCurrent Device
Jones has assembled and tested devices that sell in the US for about $60 from adafruit.com . David graciously made the design open-source and the schematic , PCB assembly , and component overlay are available at http://www.alternatezone.com . Jones also did an article on the uCurrent in the April 2009 issue of Silicon Chip Magazine and posted it on the web. It explains the problem, how it is solved, and the operation and use of the µCurrent.
You have to love the open-source access and the detail provided. Not only can you make the device but you also get the documentation and a detailed explanation thrown in.
Engineers can follow David Jones who blogs on engineering topics on the mentioned sites. His posts are excellent, informative (unedited and sometimes lengthy), and he has quite a bit of energy. I remember David taking Microchip to task on a blog entry for going backward on their PICkit3 design, the replacement of the PICkit2 programmer. His input had an effect on the changeover and the Microchip engineers and management created a humorous video retort.
The µCurrent is a needed accessory for measuring current accurately with your current DMM while not affecting the operation of the circuit.