Self-heated liquid level sensor

• US 7,181,965 B2
• Filed: 12/20/2004
• Issued: 02/27/2007
• Est. Priority Date: 12/20/2004
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kearney, Daniel J., Zoodsma, Randy J.
• Primary Examiner(s): Gutierrez; Diego
• Assistant Examiner(s): Maslova; Oxana
• Application Number:
  US11/017,604
• Publication Number:
  US 20060133448A1
• Time in Patent Office: 799 Days
• Field of Search: 374/54, 374/4, 340/603, 340/618, 340/612, 340/622, 732/95, 732/04
• US Class Current: 73/295
• 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;

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;

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

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

4. 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.

5. The liquid level sensor of claim 4 wherein:

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