A pressure transmitter operates on a standard 4-20mA loop. What is the primary advantage of using a "live zero" (4mA) instead of 0-20mA?
Answers
AIt saves power by drawing less current
BIt prevents the transmitter from freezing in cold weather
CIt allows the loop to carry voice communications
DIt allows the control system to detect a broken wire (0mA) as a fault, distinguishing it from a zero reading
Correct answer: D — It allows the control system to detect a broken wire (0mA) as a fault, distinguishing it from a zero reading
With 4-20mA, 4mA represents 0% of the scale. If the wire breaks, current drops to 0mA, instantly alerting the system to a loop failure (dead zero).
MIFOTRA exam practicealigned to CompTIA (General IT) / BICSI·1 mark·Easy