Introduction One of the first principals learned as an engineering student is the “observer effect” which states that simply observing a situation or phenomenon necessarily changes that phenomenon. This is often the result of instruments that, by necessity, alter the state of what they measure in some manner. Accurate high-voltage measurement is a clear example of the validity of this theory. The accuracy of the resulting measurements is affected by three important elements: environmental factors, errors that are introduced by the measurement probe, and the intrinsic accuracy and performance of the measuring instrument. This article will address each of [...]