Liquid level sensor

• US 20040149032A1
• Filed: 01/31/2003
• Published: 08/05/2004
• Est. Priority Date: 01/31/2003
• Status: Abandoned Application

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Sell, Jeffrey A.
• Application Number:
  US10/356,074
• Publication Number:
  US 20040149032A1
• Time in Patent Office: Days
• US Class Current: 73/304C
• CPC Class Codes: G01F 23/263 by measuring variations in capacitance of capacitors
• CPC Class Codes: G01F 23/268 mounting arrangements of probes

Abstract

A capacitive liquid level sensor provides for a reliable and inexpensive means to measure fluid height. The capacitance measured at a sensor is interpreted by a control unit, which relays information regarding the liquid level to a display unit visible to the driver of the motor vehicle. In one embodiment, the sensor consists of two parallel electrode strips of a conductive material supported along their respective lengths by a substrate of an insulated material. The strips and the exposed side of the substrate are coated with a low conductivity porous material. The strips are connected to a control unit by a pair of electrical leads. When the sensor is immersed in a liquid, the control unit measures capacitance between the two strips and calculates the actual liquid height, based on the known dielectric constant of the liquid and the gas above it.

Claims

1. A liquid level sensor comprising:

an insulated substrate;

a pair of spaced apart electrically conductive electrodes supported by the insulated substrate; and

a layer of porous material overlying the pair of spaced apart electrically conductive electrodes.

2. The sensor of claim 1 wherein the spaced apart electrically conductive electrodes comprise parallel metallic electrodes.

3. The sensor of claim 1 wherein the spaced apart electrically conductive electrodes comprise non-parallel conductive electrodes.

4. The sensor of claim 1 wherein the layer of porous material comprises a porous oxide material.

5. The sensor of claim 4 wherein layer of porous material comprises a material selected from the group consisting of manganese oxide and aluminum oxide.

6. The sensor of claim 1 wherein the layer of porous material comprises Premair™

.

7. The sensor of claim 1 further comprising a contact to each of the pair of spaced apart electrically conductive electrodes, the contact configured for the attachment of an electrical lead.

8. A system for the measurement of liquid level in a motor vehicle, the system comprising:

a capacitive liquid level sensor immersed in a liquid the height of which is to be measured, the capacitive liquid level sensor comprising;

an electrically insulated substrate;

spaced apart electrically conductive electrodes supported by the electrically insulated substrate;

a porous material overlying the electrically conductive electrodes; and

a control unit electrically coupled to the electrically conductive electrodes.

9. The system of claim 8 wherein the control unit comprises a computing device configured to measure the capacitance between the electrically conductive electrodes.

10. The system of claim 9 wherein the control unit comprises a computing device configured to calculate the height of the liquid from the measured capacitance and to produce a signal corresponding to the calculated height.

11. The system of claim 10 further comprising a visual display device coupled to the control unit and configured to receive the signal and to produce a visual display responsive to the signal.

12. The system of claim 9 wherein the control unit comprises a computing device calibrated to measure capacitance between the electrically conductive electrodes immersed in a liquid characterized by a known dielectric constant.

13. The system of claim 8 wherein the spaced apart electrically conductive electrodes comprise copper leads and the porous material comprises a porous oxide material.

14. The system of claim 13 wherein the porous material comprises a material selected from the group consisting of manganese oxide and aluminum oxide.

15. A capacitive liquid level sensor comprising:

an electrically insulated substrate configured for orientation within and perpendicular to the surface of a liquid the height of which is to be measured;

two spaced-apart, rectangular, parallel metallic strips supported by the substrate, each of the strips configured with an electrical contact near an end thereof; and

a porous material overlying the metallic strips and portions of the insulated support member not covered by the metallic strips.

16. The sensor of claim 15 wherein the porous material comprises a material selected from the group consisting of manganese oxide and aluminum oxide.

17. A liquid level sensor comprising:

an insulated substrate;

a pair of spaced-apart electrodes supported by the insulated substrate, the spaced-apart electrodes comprising a porous conductive material; and

a contact area on each of the pair of spaced-apart, electrically conductive electrodes configured for the attachment thereto of an electrical lead.

18. A capacitive liquid level sensor comprising:

an insulated substrate;

a pair of spaced-apart comb-shaped conductive electrodes having interdigitated electrode teeth supported on the insulated substrate; and

a layer of porous material overlying the pair of spaced-apart comb-shaped electrodes.

19. A capacitive liquid level sensor comprising:

an insulated substrate;

a first electrically conductive electrode supported on the insulated substrate;

a non-porous capacitor dielectric overlying the first electrically conductive electrode; and

a porous conductive second electrode overlying the non-porous capacitor dielectric.