What type of meter uses a bandstop filter for testing purposes?

The correct choice refers to a SINAD meter, which is specifically designed to measure the Signal-to-Noise and Distortion ratio in a communication signal. This type of meter incorporates a bandstop filter to eliminate specific unwanted frequencies from the signal being tested, allowing for an accurate assessment of the desired signal's quality. By filtering out noise and distortion that may interfere with the measurement, the SINAD meter enables precise calculations of the ratio, providing insights into the clarity and integrity of signals in communication systems.

In contrast, a digital voltmeter measures voltage without needing to filter out specific bands of frequency; it simply provides a reading of electrical potential difference. An efficient multimeter serves multiple purposes, including voltage, current, and resistance measurements, but does not specifically utilize a bandstop filter for testing. A noise reduction meter may aim to minimize background noise but is not defined by the same operational standards as a SINAD meter, particularly regarding the use of a bandstop filter for assessing signal quality.