Converting between voltage units
Converts electrical potential between microvolts, millivolts, volts, kilovolts, and megavolts. Useful for electronics work where sensor readings are often in millivolts or microvolts, while household and industrial power specifications are usually in volts or kilovolts.
Why sensor readings use such tiny voltage units
Many sensors (temperature probes, strain gauges, microphones) produce a very small electrical change in response to whatever they're measuring - representing that signal in volts would mean working with long strings of decimal zeros, so millivolts or microvolts give a more precise and far more readable scale for values that small.
Why household and industrial specifications sit at the opposite end of the scale
Mains power and industrial equipment operate at voltages large enough that volts and kilovolts are the natural, readable unit - the same underlying unit system just scaled differently depending on whether you're describing a sensor's tiny output signal or the power actually running through a wall outlet or an industrial line.
Why this matters when comparing a datasheet to a power spec side by side
Electronics work often means reading a sensor's millivolt-scale datasheet in the same session as a device's volt-or-kilovolt-scale power requirements - converting both into one common unit makes it easy to sanity-check that a sensor's expected input range and a power supply's actual output are compatible before wiring anything together.