Why Do We Use 4-20mA Instead Of 0 20mA Current Signal?
Why Do We Use 4-20mA Instead Of 0 20mA Current Signal? The 4 mA is used as “range zero”. If the range zero were truly zero mA, then there would be no current, and therefore no power to drive the field instrument. Field instrument would require 3 or 4 wire devices. Additional wiring costs come