Digital liquid-level sensor having at least one tunneling magnetoresistance switch

Patent metadata

Field	Value
Publication number	US-11035716-B2
Application number	US-201414763431-A
Country	US
Kind code	B2
Filing date	Jan 24, 2014
Priority date	Jan 25, 2013
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

A digital liquid-level sensor comprises a non-magnetic conduit, a floater provided outside the non-magnetic conduit and capable of axially moving along the non-magnetic conduit, and a permanent magnet fixed on the floater. The non-magnetic conduit further comprises a switch unit and an encoding unit. The switch unit comprises at least one tunneling magnetoresistance switch which is turned on or turned off under the effect of the magnetic field produced by the permanent magnet; and the encoding unit comprises at least one encoder, of which an input end receives an on/off signal from the tunneling magnetoresistance switch and outputs a digital signal indicating the position of the floater. The digital liquid-level sensor is of a small size; has low cost, low power consumption, high reliability, high sensitivity, high solution, long service life, and a good anti-interference capability; and can directly output the digital signal.

First claim

The invention claimed is:

1. A digital liquid-level sensor for placement within a container for fluid to measure a level of the fluid and output a digital signal representing the level of the fluid, the digital liquid-level sensor having low current consumption during operation, the digital liquid-level sensor comprising a structure configured to be placed in fluid within the fluid in the container, the structure comprising:
a nonmagnetic tube configured to be rigidly fixed in place in the container for the fluid, and one or more printed circuit boards sealed within the nonmagnetic tube;
a float configured to float in the fluid near and outside of the nonmagnetic tube, such that the float is able to move through a plurality of positions along the side of the nonmagnetic tube in the axial direction as the level of the fluid changes;
a permanent magnet fixed to the float, wherein the permanent magnet is configured to produce a magnetic field within the nonmagnetic tube;
a plurality of tunneling magnetoresistance switches on the one or more printed circuit boards sealed within the nonmagnetic tube, wherein the permanent magnet and each of the one or more of the tunneling magnetoresistance switches are configured to cooperate to trigger one or more of the tunneling magnetoresistance switches near the permanent magnet, wherein each of the plurality of tunneling magnetoresistance switches is characterized by a low current consumption of less than 10 microamps thereby providing the digital liquid-level sensor with the low current consumption during operation;
an encoding unit including at least one encoder on the one or more printed circuit boards sealed within the nonmagnetic tube, wherein the at least one encoder is operably connected to the plurality of tunneling magnetoresistance switches to generate a unique digital signal for each of the plurality of positions of the float;
a power supply terminal on the one or more printed circuit boards sealed within the nonmagnetic tube for connection to a power supply line; and
a data bus operably connected to an output of the at least one encoder and configured for use in outputting the unique digital signal representing the level of the fluid from the digital liquid-level sensor,
wherein the digital liquid-level sensor is configured to be placed in the container, measure the level of the fluid by sensing a position of the permanent magnet fixed to the float using the plurality of tunneling magnetoresistance switches and output digital signals from the plurality of tunneling magnetoresistance switches, using the encoding unit to convert the digital signals output from the plurality of tunneling magnetoresistance switches into the unique digital signal on the data bus for each of the plurality of positions of the float.

2. The digital liquid-level sensor of claim 1 , wherein the nonmagnetic tube has an axial length of 10 to 12000 mm and an outer diameter of 12 to 40 mm.

3. The digital liquid-level sensor of claim 1 , wherein the float has a width of 10 to 200 mm and a height of 10 to 200 mm.

4. The digital liquid-level sensor of claim 1 , wherein the magnetization direction of the permanent magnets is parallel to the axial direction of the nonmagnetic tube, the tunneling magnetoresistance switches are omnipolar or unipolar tunneling magnetoresistance switches, and the sensitive direction of the tunneling magnetoresistance switches is parallel to the axial direction of the nonmagnetic tube.

5. The digital liquid-level sensor of claim 1 , wherein the magnetization direction of the permanent magnets is perpendicular to the axial direction of the nonmagnetic tube, the tunneling magnetoresistance switches are omnipolar, bipolar, or unipolar tunneling magnetoresistance switches, and the sensitive direction of the tunneling magnetoresistance switches is perpendicular to the axial direction of the nonmagnetic tube.

6. The digital liquid-level sensor of claim 1 , wherein the float is coaxially disposed around the nonmagnetic tube, and the inner diameter of the float is greater than the outer diameter of the nonmagnetic tube.

7. The digital liquid-level sensor of claim 1 , wherein the tunneling magnetoresistance switches are disposed at equal intervals on the printed circuit board.

8. The digital liquid-level sensor of claim 1 , wherein the encoders are priority encoders.

9. The digital liquid-level sensor of claim 8 , wherein the encoders have 2 N input terminals and N output terminals, where N is an integer.

10. The digital liquid-level sensor of claim 8 , wherein the position of the float is represented using a set of numbers 0 , 1 , . . . , 2 N -1, where N is an integer, and the numbers are linearly proportional to the height of the liquid's surface.

11. The digital liquid-level sensor of claim 1 , wherein the encoder is implemented as an ASIC or programmable logic device including an FPGA or a CPLD in order to minimize the number of components on the printed circuit board.

12. The digital liquid-level sensor of claim 1 , wherein the number of tunneling magnetoresistance switches is 2 N , the data bus is at least N bits wide, and N is an integer.

13. The digital liquid-level sensor of claim 1 , wherein an output terminal of each of the tunneling magnetoresistance switches is connected to an input terminal of the encoders.

14. The digital liquid-level sensor of claim 1 , wherein the encoders have an output interface electrically connected to the corresponding terminals in the data bus.

15. The digital liquid-level sensor of claim 1 , wherein the printed circuit board is a flexible printed circuit board.

16. The digital liquid-level sensor of claim 1 , wherein the encoders and the tunneling magnetoresistance switches are small rigid printed circuit boards that are interconnected by a flexible printed circuit board.

17. A digital liquid-level sensor with low current-consumption for placement within a container for fluid, comprising:
a nonmagnetic tube configured to be rigidly fixed in place in the fluid, and one or more printed circuit boards sealed within the nonmagnetic tube;
a float configured to move through a plurality of positions along a side of the nonmagnetic tube;
a permanent magnet fixed to the float;
the nonmagnetic tube containing a magnetic switching unit on the one or more printed circuit boards sealed within the nonmagnetic tube, the magnetic switching unit comprising tunneling magnetoresistance switches, each of the tunneling magnetoresistance switches configured to consume less than 10 μA and to be closed or opened by a magnetic field produced by the permanent magnet, and containing an encoding unit on the one or more printed circuit boards sealed within the nonmagnetic tube, including at least one priority encoder operably connected to each of the tunneling magnetoresistance switches and configured output from the digital liquid-level sensor a unique digital signal representing one of the plurality of positions; and
a power supply terminal on the one or more printed circuit boards sealed within the nonmagnetic tube for connection to a power supply line, and an internal voltage regulator to provide temperature compensation,
wherein the tunneling magnetoresistance switches that each consume less than 10 μA enable the digital liquid-level sensor to have the low-current consumption through the power supply line during operation, and
wherein the digital liquid-level sensor is configured to be placed in the container, measure the level of the fluid by sensing a position of the permanent magnet fixed to the float using the plurality of

Assignees

• Multidimension Technology Co Ltd

Inventors

• Deak James Geza
• Xue Songsheng

Classifications

• G01F23/74 Primary

  for sensing changes in level only at discrete points · CPC title

• G01F23/72

  using magnetically actuated indicating means · CPC title

• G01F23/62 Primary

  using magnetically actuated indicating means · CPC title