Which of the following controls the voltage supplied to the vertical deflection plates of the CRT in an A scan UT setup?

• A. Sweep generator
• B. Pulser
• C. Amplifier circuit
• D. Clock timer

Answer: (C)

In an A-scan UT display, the vertical axis shows the amplitude of the received echoes, while the horizontal axis maps time after emission. The voltage that actually drives the CRT’s vertical deflection plates comes from the amplified received signal. The amplifier circuit conditions and boosts the weak ultrasonic echoes from the receiver so they fall within the CRT’s vertical range, making peak heights correspond to flaw indications or back-wall reflections. The sweep generator, not the vertical deflection, controls the horizontal time base, while the pulser triggers the pulse and the clock timer handles timing aspects of the sweep. So, the amplifier circuit is the element that controls the vertical deflection.