Patent US3755801A successfully refreshed from Google Patents.
US3755801A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Detecting helium liquid level
Assignee: United States Department of the Army
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Filing: 1972-01-12
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Granted: 1973-08-28
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Expires: 1992-01-12
Abstract
Abstract A constant current is fed through a pair of silicon diodes whose voltage varies with the heat sinking capability of its surrounding. These diodes are positioned at the top level of the liquid helium and the voltage across the diodes are compared by two comparators. One comparator lights a signal light whenever one or more diode is in the liquid helium, and the other comparator lights the signal light only when both diodes are in the liquid.
Inventors
- 👤 W Milo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 08:00
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/24; G01F23/246; G01F23/247
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
224 words
An indicating device comprising a constant current source; at least one diode connected to said constant current source so as to be supplied thereby; first comparator means connected to said constant current source and said diode; a first indicating means having an input whereby it can be turned on or off; said comparator means having a voltage value at its output sufficient to turn on said indicating means when saiD constant current source is over a predetermined voltage value; means connecting the comparator''s output to the input of said indicating means; a second diode connected to be supplied with constant current by said constant current source; a second comparator; a second indicating means; said diodes being subjectable to first and second ambient surroundings; said first ambient surrounding having a poor heat sink capacity as compared to the heat sink capacity of the second ambient surrounding; both comparator means turning said first and second indicating means to an on condition when both diodes are in said second ambient surrounding; both said comparator means turning said indicator means to an off condition when both said diodes are in said first ambient surroundings; and one of said comparator means turning said indicating means to an on condition while the other comparator means turns its indicator to an off condition when said diodes are in different ambient surroundings.
Claim 2
Dependent Claim
224 words
An indicating device comprising a constant current source; at least one diode connected to said constant current source so as to be supplied thereby; first comparator means connected to said constant current source and said diode; a first indicating means having an input whereby it can be turned on or off; said comparator means having a voltage value at its output sufficient to turn on said indicating means when saiD constant current source is over a predetermined voltage value; means connecting the comparator''s output to the input of said indicating means; a second diode connected to be supplied with constant current by said constant current source; a second comparator; a second indicating means; said diodes being subjectable to first and second ambient surroundings; said first ambient surrounding having a poor heat sink capacity as compared to the heat sink capacity of the second ambient surrounding; both comparator means turning said first and second indicating means to an on condition when both diodes are in said second ambient surrounding; both said comparator means turning said indicator means to an off condition when both said diodes are in said first ambient surroundings; and one of said comparator means turning said indicating means to an on condition while the other comparator means turns its indicator to an off condition when said diodes are in different ambient surroundings.
Claim 3
Dependent Claim
101 words
An indicating device as set forth in claim 1 wherein said first ambient surrounding is gaseous helium and said second surrounding is liquid helium; each of said indicating means comprising an indicating lamp connected in series with a transistor and a voltage source; the input for the indicator means being the input to the transistor; each of said comparator means having an amplifier with an output connected to the input of said transistors; first and second variable reference voltage connected individually to one input of different amplifiers; and the other inputs of said amplifiers being connected to said constant voltage source.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-27 | 1977-02-26 | 1977-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-27 | 1981-02-26 | 1981-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-27 | 1985-02-26 | 1985-08-28 | $7700.00 | Window Closed / Lapsed |