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Liquid Nitrogen Sensor

IP.com Disclosure Number: IPCOM000095071D
Original Publication Date: 1965-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Moruzzi, VL: AUTHOR

Abstract

To provide automatic refilling of an experimental liquid nitrogen Dewar flask 14, thermomagnetic switch 15 is placed at a predetermined level inside the flask. The switch 15 housing is ordinarily under the level of liquid nitrogen 9. Sensor switch 15 comprises a leaf spring with open contacts 16, when submerged in liquid nitrogen, and button 17 of EuO on the same contact leaf.

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Liquid Nitrogen Sensor

To provide automatic refilling of an experimental liquid nitrogen Dewar flask 14, thermomagnetic switch 15 is placed at a predetermined level inside the flask. The switch 15 housing is ordinarily under the level of liquid nitrogen 9. Sensor switch 15 comprises a leaf spring with open contacts 16, when submerged in liquid nitrogen, and button 17 of EuO on the same contact leaf.

Use is made of the fact that EuO becomes ferromagnetic at a temperature slightly above that of liquid nitrogen. It is not ferromagnetic at room temperature or when above cryogenic temperatures. Liquid nitrogen under pressure in source 10 is transmitted through pipe 1 1 as controlled by refill control solenoid 12. This connects via circuit 13 to switch 15 submerged in liquid nitrogen 9 in Dewar 14. As long as sensor 15 is at the low temperature of the liquid, contacts 16 are open. Power source PS is disconnected from solenoid 12 which holds the valve closed to shut off the supply. When the sinking level of nitrogen 9 in Dewar 14 exposes sensor 15, its temperature rises.

EuO button 17 loses its ferromagnetic quality and separates from permanent magnet button 18 opposing it on an associated contact support structure. This serves to allow contacts 16 to close and activate solenoid 12. Thus, the valve is opened to provide passage from Dewar 10 for refilling Dewar 14 to the level of sensor 15. Liquid nitrogen 9 now causes EuO button 17 to again become ferromagnetic. In that...