To understand how a weighted average meter measures alternating current, let's break down each option presented in the question:
Option A: It takes an average over a short period of time.
- This suggests that the meter measures the current at intervals and then computes an arithmetic average over those points. However, a weighted average meter is specifically designed to apply varying weights to different readings rather than taking a simple average.
Option B: It measures the current's ability to lift a small weight inside the meter.
- This implies a mechanical approach where the force generated by the current moves a small weight. This is not accurate for weighted average meters in electrical measurement, as they do not rely on mechanical movements of weights.
Option C: It reads the current at the test point and applies an averaging factor.
- Weighted average meters read the instantaneous current at specific test points and assign different weights to these readings before computing the average. This helps in accurately capturing fluctuating current values over time by considering more recent or significant changes more heavily.
Option D: It calculates the root mean square value of the current.
- The root mean square (RMS) value is a specific mathematical average particularly useful for assessing the power of AC currents. This method squares the current values, takes the arithmetic mean, and then the square root of the result, which is different from a weighted average.
From evaluating these options:
- Option C is correct. A weighted average meter works by reading the current at the test point and applying an averaging factor. This method ensures that more critical or recent current values are given more significance in the final average reading.
Thus, the correct answer is C. It reads the current at the test point and applies an averaging factor.
