Achieving Accurate and Reliable Low Level Electrical Measurements

Summary form only for tutorial. This tutorial offers the participants the skills to identify low level measurements and to relate an electrically measured quantity to the physical property of interest. At the conclusion of the tutorial, participants will be able to identify and explain fundamental limitations and non-idealities of basic electrical measurements, as well as the techniques to address them. In pursuit of this goal, the tutorial will include a discussion of the Johnson Noise equation as a primary method of determining the finite limit of voltage and current measurements. The presenter will provide an overview of common sources of error in test environments. Participants will understand how to negate offset voltages and avoid the effects of temperature fluctuations when making low voltage measurements. The tutorial describes the use of current reversal techniques in low resistance measurements to compensate for thermoelectric voltage errors. The presentation will also consider techniques for making successful low current and high impedance measurements. As an introduction, participants will learn about common measurement mistakes, including contamination and the use of improper cables, and their impact on test results. The presenter will show how guarding and shielding are effective in reducing leakage currents due to imperfect insulators and in eliminating interference from radio frequency, electromagnetic, and electrostatic sources. The tutorial will present an example of how these methods are combined to yield femtoamp-level current measurements. To link the theoretical with the practical, throughout the tutorial, the presenter will show how real instrumentation differs from ideal.