Arrangement for measuring the level of liquified gases

• US 5,293,896 A
• Filed: 11/28/1990
• Issued: 03/15/1994
• Est. Priority Date: 12/11/1989
• Status: Expired due to Term

• Current Assignee: INFICON GmbH (Inficon Holding AG)
• Original Assignee: Balzers Aktiengesellschaft (OC Oerlikon Corporation AG)
• Inventors: Lobel, Gerd, Gleichmann, Luder
• Primary Examiner(s): Walton, George L.
• Application Number:
  US07/619,230
• Time in Patent Office: 1,203 Days
• Field of Search: 137/392, 137/558, 62/49.1, 62/49.2, 73/295, 73/304 R, 257/87, 257/90, 257/102, 313/498, 313/499, 340/619, 340/620, 116/109, 116/202, 116/216, 116/227
• US Class Current: 137/392
• CPC Class Codes: F17C 13/021 having the height as the parameter
• CPC Class Codes: F17C 2221/014 Nitrogen
• CPC Class Codes: F17C 2223/0161 cryogenic, e.g. LNG, GNL, PLNG
• CPC Class Codes: F17C 2227/0302 by heating
• CPC Class Codes: F17C 2227/0374 in the liquid
• CPC Class Codes: F17C 2250/036 using alarms
• CPC Class Codes: F17C 2250/0408 Level of content in the vessel
• CPC Class Codes: F17C 2250/0447 Composition; Humidity
• CPC Class Codes: F17C 2250/0491 Parameters measured at or inside the vessel
• CPC Class Codes: F17C 2250/061 Level of content in the vessel
• CPC Class Codes: G01F 23/22 by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water involving the use of floats G01F23/30
• CPC Class Codes: G01F 23/246 thermal devices
• CPC Class Codes: G05D 9/12 characterised by the use of electric means
• CPC Class Codes: H01L 33/305 characterised by the doping materials
• CPC Class Codes: Y10T 137/7306 Electrical characteristic sensing
• CPC Class Codes: Y10T 137/8342 Liquid level responsive indicator, recorder or alarm

Abstract

A semiconductor sensor detects the existence of liquified gases by immersion or approaching the liquid. A high signal amplitude of the sensor permits a simple signal evaluation of high reliability. The sensor permits the realization of filling level measuring devices or level control devices for liquified gases.

Claims

1. An arrangement in combination with cryogenic liquified gas for indicating when the cryogenic liquified gas reaches a predetermined level within a container comprising:

at least one light emitting diode acting as a coil-free sensing element and having a pn structure on one of a GaP and a GaAsP base which is doped with nitrogen so that, because said at least one diode is doped with nitrogen, it has a characteristic such the temperatures below -50°

C. as the cryogenic liquified gas approaches the diode, causes non-linearity of a forward voltage for the nitrogen doped diode, said at least one diode being placed adjacent the predetermined level so that when the level of the liquified gas is rising and approaches the diode, said diode is exposed to a changing low temperature due to the rising liquified gas to generate an indication signal which is characteristic for said diode;

a control logic unit connected to said diode for receiving and acting upon the indication signal which is dependent on the temperature of said diode, said indication signal always being a forward voltage change greater than 1 Volt and the voltage change increasing continuously in a non-linear manner as temperature decreases continuously downwardly from -50°

C., the relationship between forward voltage and dropping temperature being a non-linear relationship with continuously increasing slope for temperatures below -50°

C.

2. An arrangement according to claim 1 including at least one additional diode having an additional pn structure on a said one of a GaP and GaAsP base, the additional pn structure being doped with nitrogen, the first mentioned and additional diodes being positioned at different predetermined levels for measuring the level of liquified gas in at least two steps corresponding to the levels of the first mentioned and additional diodes.

3. An arrangement in combination with cryogenic liquified gas for indicating when the cryogenic liquified gas reaches a predetermined level within a container comprising:

at least one light emitting diode acting as a coil-free sensing element and having a pn structure on one of a GaP and a GaAsP base which is doped with nitrogen so that, because said at least one diode is doped with nitrogen, it has a characteristic such the temperatures below minus 50°

C. as the cryogenic liquified gas approaches the diode, causes non-linearity of a forward voltage for the nitrogen doped diode, said at least one diode being placed adjacent to predetermined level so that when the level of the liquified gas is rising and approaches the diode, said diode is exposed to a changing low temperature due to the rising liquified gas to the rising liquified gas to generate an indicational light signal which is characteristic for said diode, said diode being a light emitting diode; and

a control logic unit connected to said diode for receiving and acting upon the indication light signal which is dependant on the temperature of said diode, said control logic unit including means for detecting a spectral change of light being emitted by said diode when the cryogenic liquified gas approaches the diode, the at least one diode having a forward voltage change that increases continuously in a non-linear manner as temperature increases continuously downwardly from -50°

C., the relationship between the forward voltage and the dropping temperature being a non-linear relationship with continuously increasing slope for temperatures below -50°

C.

4. An arrangement according to claim 3 wherein the evaluation unit comprises at least one photo receiver which is tuned to a spectral emission characteristic of the light emitting diode.

5. An arrangement according to claim 4 including at least one optical filter between the photo receiver and the light emitting diode for tuning light from the light emitting diode.

6. An arrangement according to claim 5 including, in combination, a container containing said predetermined level, and wherein the diode is light emitting, the photoreceiver and the filter are built as a single compact unit placed within the container and exposed to the rising level of liquified gas.

7. An arrangement according to claim 3 including at least one additional diode having an additional pn structure on a said one of a GaP and GaAsP base, the additional pn structure being doped with nitrogen, the first mentioned and additional diodes being positioned at different predetermined levels for measuring the level of liquified gas in at least two steps corresponding to the levels of the first mentioned and additional diodes.

8. An arrangement according to claim 3 wherein the evaluation unit includes refilling control means which respond to a signal from the diode for refilling a level of liquified gas.