Final answer:
High-impedance meters measure electrical quantities without drawing significant current, thus not altering the circuit. Null measurements improve accuracy, achieving one part in 10^6.
Step-by-step explanation:
Understanding High-Impedance Meters and Measurement Techniques :
A high-impedance meter is a device designed to measure electrical quantities such as voltage or current without significantly affecting the circuit. The key to its design is its ability to make measurements without drawing a considerable amount of current, hence not altering the circuit's behavior. This is particularly important for ensuring the accuracy of the measurement. In contrast, standard voltmeters and ammeters can alter the circuit they are connected to, which can limit accuracy.