Loop Check

What did google say?

Most places consider a loop check a process to ensure circuit continuity by simulating an input and checking to see that the input appears at the 'far' end and that the logic associated with the loop (control action, alarm, output to final control element) is executed in a reasonable form. But it really depends on how the site defines "loop check".

You can read an overview (8 pages) of loop checks in ISA's paper, "Introduction to Loop Checking", here,

http://www.isa.org/Template.cfm?Section=Find_Books1&template=Ecommerce/FileDisplay.cfm&ProductID=7580&file=Peview.pdf

There's a 141 page book, Loop Checking, A Technician's Guide by Harley M. Jeffrey, published by ISA.