Measurement of battery noise and resistor-current noise at subaudio frequencies

Using a low-noise low-frequency parametric convertor as a preamplifier, narrowband noise measurements have been carried out on wirewound resistors, two types of dry Leclanché batteries and two types of carbon resistor. Wire-wound resistors and one of the types of battery exhibited no measurable excess noise. An ordinary carbon resistor was found to produce 108 times its thermal noise at 3 c/s when passing 4A. The noise power produced by the second type of battery was linearly related to its current.