Patent law: What is the litmus test for 'inventive step' \'non obvious'?

Question

As I understand it the EPC (Europe) requires 'inventive step' and the USPTO require claims to be 'non obvious'. An electronic measurement was designed and tested. What are the questions that one should ask when determining:

1. How to identify the 'inventive step' of my invention?
2. How do I determine if the invention is 'obvious' (litmus test)

I have read the section below: said invention requires skills from electrical engineering, system engineering, computer science and industrial engineering.

35 U.S.C. 103 Conditions for patentability; non-obvious subject matter

A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.

Answer 1

In a rejection for obviousness, a USPTO examiner can't just say "it seems obvious to me". Assume the invention has three subcomponents interconnected and related in a certain way to accomplish a particular action. The examiner needs to find one or more references that call out each of those three elements. The "base" reference needs to be in a very closely related area but other references may not be as directly relevant. Then the examiner needs to argue that a person of ordinary skill in the area, given those three subcomponents and other teaching in the cited references, would come up with the invention.

An analogy with a litmus test is instructive; there is no litmus test, patent law is not remotely like science.