Hall-effect fine resolution liquid level indicator

• US 6,481,278 B1
• Filed: 02/06/2001
• Issued: 11/19/2002
• Est. Priority Date: 02/06/2001
• Status: Expired due to Fees

• Current Assignee: Predator Systems, Inc. (Curtiss-Wright Corporation)
• Original Assignee: Predator Systems, Inc. (Curtiss-Wright Corporation)
• Inventors: Blum, Alvin Seymour, Yowell, Gordon, Samuelson, Duane, Kaylor, Stephen
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): WILSON, KATINA M
• Application Number:
  US09/776,877
• Time in Patent Office: 651 Days
• Field of Search: 733/08, 733/13, 733/14, 73D/IG.3, 340/624, 340/618, 340/623, 338/33, 338/32.H, 200/84.C
• US Class Current: 73/313
• CPC Class Codes: G01F 23/74 for sensing changes in level only at discrete points
• CPC Class Codes: H01H 36/02 actuated by movement of a float carrying a magnet

Abstract

A liquid level indicator apparatus provides direct readout of liquid level at high resolution using an array of vertically disposed Hall-effect magnetic switches. To overcome the limit to closer spacing of the switches imposed by their vertical dimension, they a disposed side by side horizontally and vertically by a distance less than the vertical dimension of each switch. They are mounted on a flat flexible substrate and then bent around into a hollow cylinder or prism shape. A floating magnet of annular shape surrounds the cylinder, or a magnet corresponding to the cylindrical or prismatic shape floats inside the surrounding circuit board. Several circuits are shown for displaying a liquid level readout resulting from the actuation of the switches by the magnet.

Claims

1. In a liquid level measuring apparatus having a plurality of spaced-apart Hall-effect switches vertically arranged for positioning in a liquid for sequential actuation by a floating magnet, with electronic means for indicating liquid level based on switch actuation by the magnet, the improvement comprising:

a) a plurality of Hall-effect switches, each switch having a single magnetic sensor, a maximum vertical dimension A, and a maximum horizontal dimension B;

b) each switch having a center point positioned vertically by a first distance less than A from the center points of the immediately adjacent upper and lower switches;

c) each switch having a center point positioned horizontally by a second distance at least as great as B from the center points of the immediately adjacent upper and lower switches; and

d) a permanent magnet constructed to float in the liquid to be measured and to actuate the switches uniformly in turn as the liquid level rises.

2. The apparatus according to claim 1, in which the Hall-effect switches are supported upon a common base, said base being non-planar so as to enable the magnet to energize each of the switches in turn with substantially equal magnet force.

3. The apparatus according to claim 2, in which the base is arranged substantially cylindrically, and the magnet is configured to provide a corresponding magnetic field.

4. The apparatus according to claim 2, in which the base is arranged in the form of an elongate prism with a plurality of equal sides, and the magnet is configured to provide a corresponding magnetic field.

5. The apparatus according to claim 2, in which the base is first assembled in substantially planar configuration and then bent into a cylindrical configuration.

6. The apparatus according to claim 2, in which the base is first assembled in substantially planar configuration and then bent into a prismatic configuration.

7. The apparatus according to claim 2, further comprising:

a) a constant current DC power source;

b) a string of uniform resistors connected in series with the constant current power source at one end and ground at the other end;

c) the switches arranged to selectively apply ground between each pair of resistors as each switch is actuated by the magnet; and

d) display means connected to the power source for displaying the voltage applied by the power source in liquid level readable format.

8. The apparatus according to claim 2, further comprising:

a) a DC power source;

b) a first string of resistors connected in series with the power source through a first dropping resistor at one end and ground at the other end;

c) the switches arranged to selectively apply ground between each pair of resistors as each switch is actuated by the magnet;

d) a second string of resistors connected in series with the power source through a second dropping resistor, identical to the first dropping resistor, at one end and ground at the other end, the first and second strings being composed of uniform resistors;

e) a ratio circuit having;

i) a first input connected to the first string at its connection to the first dropping resistor;

ii) a second input connected to the second string at its connection to the second dropping resistor; and

iii) an output that is a ratio of the first and second inputs; and

f) display means connected to the output for displaying the ratio output in liquid level readable format.

9. In a liquid level measuring apparatus having a plurality of spaced-apart Hall-effect switches vertically arranged for positioning in a liquid for sequential actuation by a floating magnet, with electronic means for indicating liquid level based on switch actuation by the magnet, the improvement comprising:

a) a plurality of Hall-effect switches, each switch having a single magnetic sensor, a maximum vertical dimension A, and a maximum horizontal dimension B;

b) each switch having a center point positioned vertically by a first distance less than A from the center points of the immediately adjacent upper and lower switches;

c) each switch having a center point positioned horizontally by a second distance at least as great as B from the center points of the immediately adjacent upper and lower switches;

d) a permanent magnet constructed to float in the liquid to be measured and to actuate the switches uniformly in turn as the liquid level rises;

e) the Hall-effect switches being supported upon a common base said base being non-planar so as to enable the magnet to energize each of the switches in turn with substantially equal magnet force;

f) a constant current DC power source;

g) a string of uniform resistors connected in series with the constant current power source at one end and ground at the other end;

h) the switches arranged to selectively apply ground between each pair of resistors as each switch is actuated by the magnet; and

i) display means connected to the power source for displaying the voltage applied by the power source in liquid level readable format.

10. The apparatus according to claim 9, in which the base is arranged substantially cylindrically, and the magnet is configured to provide a corresponding magnetic field.

11. The apparatus according to claim 9, in which the base is arranged in the form of an elongate prism with a plurality of equal sides, and the magnet is configured to provide a corresponding magnetic field.

12. In a liquid level measuring apparatus having a plurality of spaced-apart Hall-effect switches vertically arranged for positioning in a liquid for sequential actuation by a floating magnet, with electronic means for indicating liquid level based on switch actuation by the magnet, the improvement comprising:

a) a plurality of Hall-effect switches, each switch having a maximum vertical dimension A, and a maximum horizontal dimension B;

b) each switch having a center point positioned vertically by a first distance less than A from the center points of the immediately adjacent upper and lower switches;

c) each switch having a center point positioned horizontally by a second distance at least as great as B from the center points of the immediately adjacent upper and lower switches;

d) a permanent magnet constructed to float in the liquid to be measured and to actuate the switches uniformly in turn as the liquid level rises;

e) the Hall-effect switches being supported upon a common base, said base being non-planar so as to enable the magnet to energize each of the switches in turn with substantially equal magnet force;

f) a DC power source;

g) a first string of resistors connected in series with the power source through a first dropping resistor at one end and ground at the other end;

h) the switches arranged to selectively apply ground between each pair of resistors as each switch is actuated by the magnet;

i) a second string of resistors connected in series with the power source through a second dropping resistor, identical to the first dropping resistor, at one end and ground at the other end, the first and second strings being composed of uniform resistors;

j) a ratio circuit having;

A) a first input connected to the first string at its connection to the first dropping resistor;

B) a second input connected to the second string at its connection to the second dropping resistor; and

C) an output that is a ratio of the first and second inputs; and

k) display means connected to the output for displaying the ratio output in liquid level readable format.

13. The apparatus according to claim 12, in which the base is arranged substantially cylindrically, and the magnet is configured to provide a corresponding magnetic field.

14. The apparatus according to claim 12, in which the base is arranged in the form of an elongate prism with a plurality of equal sides, and the magnet is configured to provide a corresponding magnetic field.