Why is it not necessary to measure the unregulated DC voltage on a line extender with a switching mode power supply (SMPS)?

Measuring the unregulated DC voltage on a line extender with a switching mode power supply (SMPS) is typically unnecessary because SMPS technology inherently provides wider DC voltage regulation. An SMPS is designed to convert power efficiently from an AC supply while maintaining a consistent output voltage across a range of input voltages and load conditions. This means that the output voltage remains stable even with fluctuations in input voltage or varying load requirements.

This ability to regulate voltage effectively reduces the need for direct measurement of unregulated DC voltage, as the SMPS is already engineered to ensure a reliable voltage output. Thus, for a line extender using an SMPS, one can trust that the voltage levels will fall within acceptable limits without needing to frequently measure unregulated DC voltage levels, making it less critical to perform these measurements.

In contrast, the other options do not accurately reflect the operational characteristics of an SMPS and its application in line extenders. For example, while measuring might be risky or potentially damaging, this is not the primary reason that measuring the unregulated DC voltage is unnecessary. The efficiency of an SMPS or the effects of measuring it do not relate directly to the importance of measuring unregulated DC voltage.