# A set-up for measurement of low frequency conductance fluctuation (noise) using digital signal processing techniques

Ghosh, Arindam and Kar, Swastik and Bid, Aveek and Raychaudhuri, AK (2004) A set-up for measurement of low frequency conductance fluctuation (noise) using digital signal processing techniques. [Preprint]

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We describe a set up for measurements of low frequency (1 mHz < f < 20 Hz) conductance fluctuations in a solid conductor. The set-up uses a five probe a.c. measurement technique and extensive digital signal processing to reach a noise floor down to $Sv(f){\leq} 10^{-20} V^2Hz^{-1}.$ The set up also allows measurement of noise using an a.c. in presence of a superimposed direct current. This feature is desirable in studies of electromigration damage or in systems that show non-linear conductivity. In addition, we describe a scheme which allows us to obtain the probability density function of the conductance fluctuation after subtracting the extraneous noise contributions (background) from the observed noise. The set-up has been used for conductance fluctuation measurement in the temperature range 1.5 K < T < 500 K in the presence of magnetic fields. We present some representative data obtained by this system.