Measurement of physical constants using noise

Abstract

Measuring physical constants by examining suitable types of noise has a long history. In this experiment, in contrast to previous works, the computer does much of the data gathering and processing. Once an undergraduate student understands the elements of the theory of thermal and shot noise, a little bit about Windows commands that interface with the SoundBlaster, and something of the filter design using MATLAB, the student will be able to design the apparatus and implement the measurements described in this article. Using well-known formulas for thermal and shot noise, we designed experiments for measuring two physical constants: the Boltzmann constant and the charge on the electron. We were able to perform the experiments in a particularly simple fashion by making use of widely available computer-based measurement and processing tools. In particular, the measurement of the Boltzmann constant only required one operational amplifier and three resistors. Our measurements achieved reasonable accuracies, considering the nature of the instruments with which we performed the measurements. The experiments are well suited to use in a laboratory setting, and they allow one to see some of the connections between random noise, physics and signal processing.