Schematic symbol preferences are very personal, but it is important to make them understandable. How do your drawings compare to this engineer's guidelines?

Scope Symbols are included to depict mathematical functions, graphs, process equipment, instruments, and electrical equipment. The symbols are suitable for use in dynamic displays, as on cathode-ray ...

Next to the master diagram, make a column of any rules that cannot be integrated into the diagram. However you want to express those rules, keep your symbols easy and consistent.