Dry-Wet Reference Leg; Level Instrument

I remember somebody discussed about wet & dry leg for level instrument few years ago. I searched in google and wikipedia and found very difficult explanation to get it. Finally I found very simple explanation about wet & dry reference leg application to measure a liquid level where gas or vapor existing on the top …

4-20 mA; A Myth

Honestly it's very difficult to find books or references which explain clearly why analog signal 4-20 mA is used on electric signal transmission. I remember I saw somebody gave his opinion in a mailing list but I forget already what he told exactly and unfortunately I lose the email by now. Sometimes I think 4-20 …