Pearson-Anson effect

The Pearson-Anson effect, discovered by Stephen Oswald Pearson [Stephen Oswald Pearson,"Dictionary of Wireless Technical Terms" (London: Iliffe & Sons, 1926).] and Horatio Saint George Anson [Horatio Saint George Anson (1903-1924(?)). Son of Rear-Admiral Charles Eustace Anson, Superintendent of the Royal Navy’s Chatham Dockyard, and Maria Evelyn Ross. [Genealogical information: Marquis of Ruvigny and Raineval, "The Plantagenet Roll of the Blood Royal… The Anne of Exeter volume" (London: T.C. & E.C. Jack, 1907), page 92.] As a youth in the Royal Naval College, he developed an interest in research into radio. He subsequently joined Faraday House, the headquarters of the Institution of Electrical Engineers (now the Institution of Engineering and Technology), in London. There he discovered that the negative resistance of neon lamps could be exploited to create an oscillator. In 1924 he was appointed to the Research Department of the Royal Aircraft Establishment in Farnborough, England. He was immediately elected a fellow of the Physical Society of London. However, soon thereafter he died in a car accident. [See: Commander Frank W. Lipscomb, "The Wise Men of the Wires: The History of Faraday House" (London: Hutchinson, 1973), pages 96-97. ] ] , is the phenomenon of an intermittent electrical current through an electrical load exhibiting negative resistance (e.g., a neon lamp). In Pearson and Anson's original circuit, the load and a capacitor are connected in parallel and both are connected to a series circuit consisting of a high resistance and voltage source.

When a neon lamp serves as the load, the neon exhibits negative resistance. [Graph of current vs. voltage for a neon lamp: http://en.wikipedia.org/wiki/Neon_lamp . See also: http://www.answers.com/topic/negative-resistance-circuits?cat=technology .] That is, once the voltage across the lamp exceeds a critical value, the current through the lamp "increases" while the voltage across the lamp "decreases". In the Pearson-Anson circuit, this causes the capacitor to quickly discharge through the neon lamp as soon as the voltage across the capacitor has reached the lamp's critical voltage. The current through the resistor is too low to sustain conduction in the lamp, so, instead, the current recharges the capacitor until the cycle repeats. The circuit therefore exhibits a low-frequency oscillation, during which the lamp flashes each time it conducts.

References

* S. O. Pearson and H. St. G. Anson, " [http://www.iop.org/EJ/abstract/-search=11154593.1/1478-7814/34/1/435 Demonstration of Some Electrical Properties of Neon-filled Lamps] ", "Proceedings of the Physical Society of London", vol.34, no. 1 (December 1921), pp. 175-176 doi:10.1088/1478-7814/34/1/435
* S. O. Pearson and H. St. G. Anson, " [http://www.iop.org/EJ/abstract/1478-7814/34/1/341 The Neon Tube as a Means of Producing Intermittent Currents] ", "Proceedings of the Physical Society of London", vol. 34, no. 1 (December 1921), pp. 204-212 doi:10.1088/1478-7814/34/1/341

Footnotes