Bubble level meter and related method

• US 6,799,457 B2
• Filed: 04/06/2004
• Issued: 10/05/2004
• Est. Priority Date: 03/08/2001
• Status: Active Grant

• Current Assignee: Hydro-Quebec (Province of Québec)
• Original Assignee: Hydro-Quebec (Province of Québec)
• Inventors: Bouchard, Claude
• Primary Examiner(s): Kwok, Helen
• Assistant Examiner(s): FRANK, RODNEY T
• Application Number:
  US10/471,096
• Publication Number:
  US 20040149031A1
• Time in Patent Office: 182 Days
• Field of Search: 733/01, 732/98, 732/90.R
• US Class Current: 73/301
• CPC Class Codes: G01F 23/168 with electric indicating or recording
• CPC Class Codes: G01F 23/808 containing circuits handling parameters other than liquid level
• CPC Class Codes: G01F 25/20 of apparatus for measuring liquid level

Abstract

The invention concerns bubble level meter having a pneumatic tube connected to a gas generator and to a pressure sensor. A deflecting valve is interposed along the pneumatic tube, for deflecting the air outlet at a predetermined height from the usual lower outlet of the tube. A control circuit controls the deflecting valve and the gas generator based on predetermined set values, processes the pressure measurements obtained from the pressure sensor, checks the calibration of the sensor on the basis of the measurements and the differences in height between the tube outlet, and generates level data based on the processed pressure measurements and a calibrating coefficient. Another valve interposed between the sensor and the tube and monitored by the circuit control, enables to take into account the possible drift of the sensor.

Claims

1. A bubble level meter, comprising:

a pneumatic tube submersible in part and having opposite lower and upper openings;

a gas generator connected to the upper opening of the pneumatic tube;

a pressure sensor connected to the upper opening of the pneumatic tube in order to measure a pressure in the pneumatic tube;

a deflection valve interposed along the pneumatic tube above and at a predetermined distance from the lower opening, the deflection valve having a port for communication with an external liquid milieu in which a submerged portion of the pneumatic tube is located, and closed and open positions wherein the upper opening of the pneumatic tube communicates respectively with the lower opening of the pneumatic tube and the port of the deflection valve; and

a control circuit connected to the gas generator, the pressure sensor and the deflection valve, the control circuit being configured for;

processing pressure measurements obtained from the pressure sensor;

controlling the deflection valve and the gas generator as a function of preset settings;

verifying a calibration coefficient of the pressure sensor as a function of the pressure measurements obtained from the pressure sensor when the deflection valve is alternately in closed position and in open position, and as a function of the distance between the lower opening of the pneumatic tube and the port of the deflection valve; and

generating level data as a function of the processed pressure measurements and the calibration coefficient.

2. The level meter according to claim 1, further comprising:

an additional deflection valve interposed between the pressure sensor and the upper opening of the pneumatic tube, the additional deflection valve being connected to the control circuit and having a port for communication with an external atmospheric milieu in which an emerged portion of the pneumatic tube is located, and closed and open positions wherein the pressure sensor communicates respectively with the upper opening of the pneumatic tube and the port of the additional deflection valve;

and wherein the control circuit is further configured for;

controlling the additional deflection valve as a function of the preset settings; and

verifying an offset factor of the pressure sensor as a function of the pressure measurements obtained from the pressure sensor when the additional deflection valve is alternately in closed position and in open position, the level data generated by the control circuit being also as a function of the offset factor.

3. The level meter according to claim 2, wherein the control circuit comprises a memory for storing the level data.

4. The level meter according to claim 3, wherein the preset settings are stored in the memory.

5. The level meter according to claim 2, wherein the deflection valves comprise bi-directional solenoid valves under control of the control circuit.

6. The level meter according to claim 2, wherein the pneumatic tube is provided with a protective tube surrounding the pneumatic tube over a length of the pneumatic tube.

7. The level meter according to claim 2, further comprising an enclosure in which the gas generator, the pressure sensor and the control circuit are mounted, the enclosure having a lower opening receiving an upper end of the pneumatic tube comprising the upper opening, and a lateral opening receiving a tube connecting the port of the additional deflection valve with the external atmospheric milieu.

8. The level meter according to claim 1, wherein the control circuit has:

a normal measurement mode wherein the control circuit sets the deflection valve in closed position and the gas generator in operation for opposing a hydric pressure in the pneumatic tube until obtaining a balanced pressure at the lower opening of the pneumatic tube, and takes a pressure measurement from the pressure sensor when the balanced pressure is reached; and

a verification mode wherein the control circuit sets the deflection valve along the pneumatic tube in open position for a preset duration, takes a pressure measurement from the pressure sensor at the opening of the deflection valve, and determines the calibration coefficient as a function of the pressure measurement.

9. The level meter according to claim 2, wherein the control circuit has:

a normal measurement mode wherein the control circuit sets the deflection valves in closed position and the gas generator in operation for opposing a hydric pressure inside the pneumatic tube until obtaining a balanced pressure at the lower opening of the pneumatic tube, and takes a pressure measurement from the pressure sensor when the balanced pressure is reached;

a first verification mode wherein the control circuit sets the deflection valve along the pneumatic tube in open position for a preset duration, takes a pressure measurement from the pressure sensor at the opening of the deflection valve, and determines the calibration coefficient as a function of the pressure measurement; and

a second verification mode wherein the control circuit sets the additional deflection valve between the upper opening of the pneumatic tube and the pressure sensor in open position for a preset duration, takes a pressure measurement from the pressure sensor at the opening of the additional deflection valve, and determines the offset factor as a function of the pressure measurement.

10. The level meter according to claim 9, wherein, in the first verification mode, the control circuit ensures that the additional deflection valve between the upper opening of the pneumatic tube and the pressure sensor is in closed position before the opening of the deflection valve along the pneumatic tube, and in the second verification mode, the control circuit ensures that the deflection valve along the pneumatic tube is in closed position before the opening of the additional deflection valve between the upper opening of the pneumatic tube and the pressure sensor.

11. The level meter according to claim 2, wherein the control circuit is provided with a display.

12. The level meter according to claim 1, further comprising a supplementary deflection valve interposed along the pneumatic tube between the lower opening of the pneumatic tube and the deflection valve already in place, the supplementary deflection valve having a port for communication with the external liquid milieu, and closed and open positions wherein the upper opening of the pneumatic tube communicates respectively with the lower opening of the pneumatic tube and the port of the deflection valve, the control circuit being configured for operating the deflection valves independently.

13. A method for improving pressure measurements in a bubble level meter comprising a pneumatic tube submersible in part having opposite lower and upper openings, a gas generator connected to the upper opening of the pneumatic tube, a pressure sensor connected to the upper opening of the pneumatic tube, and a control circuit connected to the gas generator and the pressure sensor and configured for processing measurements obtained from the pressure sensor and generating level data as a function of the processed measurements, the method comprising:

interposing a deflection valve along the pneumatic tube above and at a predetermined distance from the lower opening, the deflection valve having a port for communication with an external liquid milieu in which a submerged portion of the pneumatic tube is located, and closed and open positions wherein the upper opening of the pneumatic tube communicates respectively with the lower opening of the pneumatic tube and the port of the deflection valve;

connecting the deflection valve to the control circuit; and

configuring the control circuit for;

controlling the deflection valve as a function of preset settings;

verifying a calibration coefficient of the pressure sensor as a function of pressure measurements obtained from the pressure sensor when the deflection valve is alternately in closed position and in open position, and as a function of the distance between the lower opening of the pneumatic tube and the port of the deflection valve; and

generating the level data as a function of the calibration coefficient.

14. The method according to claim 13, further comprising:

interposing an additional deflection valve between the pressure sensor and the upper opening of the pneumatic tube, the additional deflection valve having a port for communication with an external atmospheric milieu in which an emerged portion of the pneumatic tube is located, and closed and open positions wherein the pressure sensor communicates respectively with the upper opening of the pneumatic tube and the port of the additional deflection valve;

connecting the additional deflection valve to the control circuit; and

configuring the control circuit for;

controlling the additional deflection valve as a function of the preset settings;

verifying an offset factor of the pressure sensor as a function of the pressure measurements obtained from the pressure sensor when the additional deflection valve is alternately in closed position and in open position; and

generating the level data as a function of the offset factor.

15. The method according to claim 14, further comprising:

storing the level data in a memory of the control circuit.

16. The method according to claim 14, wherein the control circuit performs a level measurement by proceeding successively by:

a setting of the additional deflection valve between the pressure sensor and the upper opening of the pneumatic tube into open position when the deflection valve along the pneumatic tube is in closed position;

a determination of the offset factor of the pressure sensor as a function of a measurement obtained from the pressure sensor;

a setting of the additional deflection valve between the pressure sensor and the upper opening of the pneumatic tube in closed position;

a setting into operation of the gas generator for opposing a liquid pressure in the pneumatic tube until obtaining a balanced pressure at the lower opening of the pneumatic tube;

a processing of a first measurement obtained from the pressure sensor corresponding to a reading of pressure at the lower opening of the pneumatic tube;

a setting of the deflection valve along the pneumatic tube in open position;

a processing of a second measurement obtained from the pressure sensor corresponding to a reading of pressure at the port of the deflection valve along the pneumatic tube;

a setting of the deflection valve along the pneumatic tube back in closed position,

a determination of the calibration coefficient as a function of a difference between the first and second measurements; and

a generation of the level data based on the pressure measurements as a function of the calibration coefficient and of the offset factor.