Which circuit is responsible for producing the time base line used in distance measurements?

• A. Marker circuit
• B. Sweep circuit
• C. Pulser
• D. Receiver

Answer: (B)

In ultrasonic testing, distance is determined by how long it takes for a pulse to travel to a reflector and back, so the display must have a consistent time axis to map that elapsed time to distance. The sweep circuit provides that time base—the horizontal timing signal that drives the display so echoes appear at positions corresponding to their time of flight. By using the known speed of sound in the material, you translate the time base into a distance scale on the screen. The pulser starts the event by sending the initial pulse, the receiver handles the echo signals, and a marker circuit may place reference marks, but none of these establish the primary time axis. Therefore, the circuit that produces the time base line used in distance measurements is the sweep circuit.