In a 4-20 mA control loop, what does a higher loop current generally indicate about the process variable?

In a 4-20 mA control loop, what does a higher loop current generally indicate about the process variable?

• A. A higher process variable value
• B. A lower process variable value
• C. No change in the process variable
• D. The loop is in standby

Answer: (A)

In a 4-20 mA loop, the current acts as the signal that represents the measured process variable. The transmitter converts the PV into a current that flows through the loop, with a direct, linear mapping: 4 mA corresponds to the lower end of the PV range and 20 mA to the upper end. As the process variable increases, the transmitter increases the loop current accordingly. This means a higher loop current is an indication that the process variable is higher. (Note: some systems can be configured differently, but the standard setup uses direct proportionality.)

In a 4-20 mA loop, the current acts as the signal that represents the measured process variable. The transmitter converts the PV into a current that flows through the loop, with a direct, linear mapping: 4 mA corresponds to the lower end of the PV range and 20 mA to the upper end. As the process variable increases, the transmitter increases the loop current accordingly. This means a higher loop current is an indication that the process variable is higher. (Note: some systems can be configured differently, but the standard setup uses direct proportionality.)