I wanted to know how Energy msr collect data? Where are the sensors located and how the power information is translated into energy counter?
For servers, "Energy Efficient Servers: Blueprints for Data Center Optimization" is a good source. The ebook is available free of charge at Springer.
For a reference implementation on accessing the power counters, checkout PCM on github.
I want to endorse Thomas' recommendation about the "Energy Efficient Servers" ebook. I did a search for "RAPL" in the PDF file and found a lot of details in those sections that I did not realize that Intel had made public. This includes specific documentation about the use of power models vs power measurement in different processors, which seems quite pertinent to the original question....