EDIT 24 Oct 2018 The schematic in this post contains an error. It will be reposted after receipt of the PCB and testing.
I am developing an inexpensive but reasonably accurate meter for measuring resistance in the milliohm range. The previous posts are listed in the related links at the bottom. In this post the design for the working prototype is expanded to include a second current source for measuring resistance up to 400 ohm and provision made for future auto-ranging. A new schematic and a PCB design are presented along with an update on meter options.