Current source modules are characterized by which statement?

• A. Current flows out of the field device
• B. Current flows into the field device
• C. No current flows in source modules
• D. It depends on the load

Answer: (B)

A current source module drives a fixed loop current into the field device. It supplies current into the loop, so the current enters the field device as the load in the circuit. In a 4-20 mA control loop, the transmitter (field device) modulates the loop current, but the source module provides that current, not the other way around. This is different from a current sink, which would pull current out of the field device. The option stating that current flows into the field device best describes how a current source module behaves, assuming the load is within the module’s compliance range.