= John Bertrand Johnson
{c}
= J. B. Johnson
{c}
{synonym}
<John Bertrand Johnson> was an <electrical engineer> whose 1928 measurements established the thermal electrical fluctuations now called <Johnson-Nyquist noise>. He detected random <electric potential difference>[voltage] fluctuations in conductors through a vacuum-tube <amplifier> and a <thermocouple>, and related the measured effect to <temperature>, <electrical resistance> and the measurement system's <frequency response>.<Thermal Agitation of Electricity in Conductors by John Bertrand Johnson>[Publisher abstract, measured fluctuations and apparatus]{ref}
This reveals why the average <electric potential difference>[voltage] alone is not enough to characterize a fluctuating signal. Its <expected value> can vanish while its mean-square value is positive. The fluctuations become an experimentally measurable <noise> floor in sensitive electronics, and their <temperature> dependence connects circuit measurements with the <Boltzmann constant>.<Thermal Agitation of Electricity in Conductors by John Bertrand Johnson>[Abstract, determination of Boltzmann's constant and technical disturbance]{ref}
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