Which statement accurately describes a three-wire DC sensor?

• A. Has three conductors: power, ground, and signal.
• B. Has two conductors.
• C. Requires AC.
• D. Signals voltage rather than current.

Answer: (A)

A three-wire DC sensor is defined by having three separate conductors: one for power, one for ground, and one for the signal output. This third wire carries the sensor’s discrete output to the control circuit, allowing the sensor to drive the load directly while powered by DC. The other statements don’t fit: a two-wire sensor uses only two conductors; this type doesn’t require AC since it’s DC; and the signal on the output isn’t inherently limited to voltage—some three-wire sensors provide a current-type output depending on whether they are NPN or PNP and how the load is wired. The key point is the dedicated signal conductor alongside power and ground.