These voltages arise when different parts of a circuit are at different temperatures and when conductors made of dissimilar materials join together. ![]() ![]() Thermoelectric voltages (or thermoelectric EMFs) are the most common sources of errors in low-voltage measurements. However, when measuring low-level voltages in the micro- and nanovolt range, sources of noise and thus error need to be accounted for and minimized. WHEN MAKING traditional voltage measurements using a digital multimeter (DMM) one didn’t have to consider error or noise sources because the measured voltages were relatively high. So it can be useful to review the main difficulties that arise when working with circuitry handling signals that would have been in the noise levels of most electronics fielded just a few decades ago. Measurements at these extremely low levels are subject to error sources that engineers usually ignore when working with more traditional logic and IC technologies. This trend has put a new emphasis on accuracy in measurements of nano- and picoamp currents and micro- and nanovolt voltages. For example, ultra-low-voltage digital designs in CMOS now operate with minimum supply voltages in the 200-mV range. Signal levels in state-of-the-art electronics have become diminishingly small. Here are the biggest culprits and surefire ways to avoid them. Subtle difficulties can plague tests involving low voltages.
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