Self-heated liquid level sensor

• US 20060133448A1
• Filed: 12/20/2004
• Published: 06/22/2006
• Est. Priority Date: 12/20/2004
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kearney, Daniel J., Zoodsma, Randy J.
• Granted Patent: US 7,181,965 B2
• Time in Patent Office: Days
• US Class Current: 374/45
• CPC Class Codes: G01F 23/247 for discrete levels
• CPC Class Codes: G01F 23/248 Constructional details; Mounting of probes

Abstract

A liquid level sensor comprising a thermistor probe and a power source connected to the thermistor probe to heat the thermistor probe. A cover encases the thermistor probe and includes openings allowing liquid to enter and exit an interior of the cover and contact the thermistor probe. A detector detects a liquid level in response to a voltage at the thermistor probe.

Claims

1. A liquid level sensor comprising:

a thermistor probe;

a power source connected to the thermistor probe to heat the thermistor probe;

a cover encasing the thermistor probe, the cover including openings allowing liquid to enter and exit an interior of the cover and contact the thermistor probe;

a detector detecting a liquid level in response to a voltage at the thermistor probe.

2. The liquid level sensor of claim 1 wherein:

the cover is frusto conical.

3. The liquid level sensor of claim 1 wherein:

the cover includes a circular rib formed on an interior surface of the cover, the rib extending toward a longitudinal axis of the cover.

4. The liquid level sensor of claim 3 wherein:

the rib includes an opening for allowing liquid to pass through the rib.

5. The liquid level sensor of claim 1 wherein:

the cover has a bottom sidewall having a pitch to drain liquid from the cover.

6. The liquid level sensor of claim 5 wherein:

the pitch is greater than a maximum tilt of a tank in which the liquid level sensor is mounted.

7. The liquid level sensor of claim 1 wherein:

further comprising an analog-to-digital converter generating a digital value from the thermistor voltage and providing the digital value to the detector.

8. The liquid level sensor of claim 7 wherein:

the detector includes a look-up table to output a temperature based on the digital value.