Final answer:
The statement is true; an AC volts setting on a multimeter can be used to check AC signals from a speed sensor. Null measurements offer greater accuracy by balancing the circuit, although various factors can limit precision. Digital devices offer improved accuracy over galvanometers in null measurements.
Step-by-step explanation:
It is true that an AC volts setting on a multimeter might be used to check signals from a speed sensor. Speed sensors, particularly those used in automotive applications for measuring the speed of a vehicle's wheels or engine components, can output AC voltages. The multimeter's AC voltage setting is appropriate for measuring these varying signals. In contrast, null measurement techniques, though more accurate, involve balancing a circuit so no current flows through the measurement device. These can be limited by factors such as resistance in wires and connections, temperature variations, and the sensitivity of the measuring device. Using a digital device that is more sensitive than a galvanometer can improve the accuracy of null measurements, as it can detect smaller currents and brings the current closer to zero.