1. Principle of Operation: The fundamental principle involves the mathematical integration of the input signal over a fixed time interval. For a periodic input signal $v(t)$, the instrument effectively calculates:
$$V_{avg} = \frac{1}{T} \int_{0}^{T} v(t) \, dt$$
2. Noise Immunity: The primary advantage of the integrating technique is its inherent ability to reject superimposed noise, especially power line interference. Because the average of a complete cycle of AC interference is zero, the integration process "washes out" these fluctuations, leaving only the
true average value of the DC signal.
3. Comparison with other types:
• RMS value: Measured by true RMS meters, which involve squaring, averaging, and then taking the square root.
• Peak value: Measured by peak detectors or peak-responding voltmeters.
• Precision: This is a performance characteristic (degree of reproducibility) rather than a physical quantity to be measured.
Therefore, because the device integrates the signal over time, it naturally outputs the true average value of the input.