Why is accuracy limited on the scale of an analog wattmeter?

The correct choice highlights that accuracy on the scale of an analog wattmeter is often limited because the upper third of the meter is calibrated to provide more precise readings. Analog wattmeters typically have a non-linear scale, which means that the sensitivity and accuracy can vary throughout the scale. In fact, many analog meters are designed such that they yield the most accurate readings in the higher range, often within the upper third of the scale. This is due to the inherent characteristics of the measurement elements within the meter, which tend to provide better resolution at higher signal levels.

This increased accuracy at the top end of the scale is important because it allows users to better interpret measurements that approach maximum capacity. In contrast, readings taken in the lower portions of the scale may not be as reliable due to potential parallax errors or other inaccuracies inherent in analog devices. Therefore, understanding that the upper range provides the best accuracy is essential for anyone operating or interpreting the results from an analog wattmeter.