Fine resolution liquid level detector

• US 4,589,282 A
• Filed: 08/20/1984
• Issued: 05/20/1986
• Est. Priority Date: 03/29/1982
• Status: Expired due to Fees

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Sprague Electric Company
• Inventors: Dumery, Stefaan D.
• Primary Examiner(s): Frankfort, Charles
• Assistant Examiner(s): Will, Thomas B.
• Application Number:
  US06/642,459
• Time in Patent Office: 638 Days
• Field of Search: 73/308, 73/313, 73/DIG. 3, 73/DIG. 5, 324/204, 340/620, 340/624, 340/625, 200/84 C
• US Class Current: 73/313
• CPC Class Codes: G01F 23/72 using magnetically actuated indicating means
• CPC Class Codes: Y10S 73/03 Hall effect

Abstract

A large number of equally spaced Hall-sensors form a column. They are mounted in a tube with a closed bottom. Each sensor is a packaged integrated circuit with a Hall-cell connected to a Schmitt Trigger circuit. An annular float being fitted slidably about the tube carries a compound magnet that generates a pattern of regularly spaced apart magnetic field regions each having the same dimensions and each capable of switching an immediately adjacent Hall-sensor. The Hall-sensors are energized sequentially and one at one time. By counting the number of Hall-sensors scanned, from the beginning end of the column to the first Hall-sensor that is switched, a rough measure of the liquid level is obtained. The magnetic field regions are spaced apart by a distance that is not equal to the Hall-sensor spacing so that the pattern of Hall-sensor output voltages provides a unique vernier measure of the liquid level that is appropriately added to the afore-said rough measure.

Claims

1. A fine resolutrion liquid level detector comprising:

(a) a column of uniformly spaced Hall-sensors, each of said Hall-sensors being capable of producing at an output thereof one type of electrical signal when in a magnetic field of one polarity and being capable of producing at said output another type electrical signal when in another polarity of magnetic field;

(b) a compound megnet assembly for producing at said column a fixed pattern of spaced apart magnetic field regions of said one polarity, there being only a number n of said regions, each of said regions having a uniform center to center spacing b as measured along the axis of said column, b being greater than a and ##EQU5## wherein a is said uniform spacing of said Hall-sensors;

(c) means for holding said column vertically in a liquid;

(d) means for guiding said compound magnet assembly along and at a substantially fixed distance from said Hall-sensors column; and

(e) means for keeping said compound magnet assembly at the surface of said liquid.

2. The liquid level detector of claim 1 wherein the span m of each of said field regions measured along said column axis is related to said number of field regions n by ##EQU6##