Method for detecting a differential pressure

• US 6,981,399 B1
• Filed: 09/25/2003
• Issued: 01/03/2006
• Est. Priority Date: 09/26/2002
• Status: Active Grant

• Current Assignee: Grundfos A/S (Poul Due Jensens Fond)
• Original Assignee: Grundfos A/S (Poul Due Jensens Fond)
• Inventors: Nybo, Peter Jungklas, Ilves, Lasse, Yli-Korpela, Heikki
• Primary Examiner(s): RAEVIS, ROBERT R
• Application Number:
  US10/670,953
• Time in Patent Office: 831 Days
• Field of Search: 73/15.7, 73/15.9, 73/16.2, 73/16.3, 73/16.9, 73/17.1, 73/17.3, 73/16.4, 73/16.6, 73/16.7, 417/38, 417/278
• US Class Current: 73/1.73
• CPC Class Codes: F04D 15/0218 the condition being a liquid level or a lack of liquid supply

Abstract

The invention relates to a method for detecting a differential pressure or for correcting a pressure value detected in the fluid on the basis of a pressure of a surrounding medium, wherein at a first point in time the pressure of the surrounding medium is detected and at a later, second point in time the pressure of the fluid is detected, and the pressure value detected in the fluid is corrected on the basis of the pressure of the surrounding medium. The invention furthermore relates to a pump system with a level sensor in which this method is applied, as well as to the use of a pressure sensor in such a pump system.

Claims

1. A method for correcting a pressure value in a level sensor of a submersible pump wherein there is provided a pressure sensor serving as said level sensor and at one point in time as a first pressure value the pressure of the surroundings is detected by said pressure sensor and at another point in time as a second pressure value the pressure of the fluid to be delivered by the pump is detected by said pressure sensor, and wherein said second pressure value is corrected on basis at said first pressure value by evaluating the pressure difference between the second and first pressure value.

2. The method according to claim 1, with which said pressure sensor for detecting the pressure of the surroundings at the one point in time is brought into a position above the surface of the fluid to be delivered.

3. The method according to claim 2, with which for determining the pressure of the surroundings the fluid level is lowered below the level (S₂) of said pressure sensor, and said pressure sensor detects the pressure of the surroundings for correcting the pressure value detected in the fluid at said other point in time.

4. The method according to claim 3, with which after reaching the level (S₂) of said pressure sensor the fluid level is lowered to a predefined value (S₁) below the level (S₂) of said pressure sensor.

5. The method according to claim 4, with which the fluid level after reaching the level (S₂) of said pressure sensor is further lowered for a period of time (t₁).

6. The method according to claim 5, with which the period of time is computed on the basis of the sinking speed (dh/dt) of the fluid level previously detected by the level sensor.

7. The method according to claim 4, with which the pump is switched off after reaching the level (S₂) of said pressure sensor after completion of the period of time (t₁) or on reaching a predefined fluid level (S₁) below the level (S₂).

8. The method according to claim 2, with which said pressure sensor for detecting the second pressure of the fluid to be delivered at the other point in time is brought into a position below the surface of the fluid to be delivered.

9. The method according to claim 1, with which the said pressure sensor for detecting the pressure of the fluid to be delivered at said other point in time is brought into a position below the surface of the fluid to be delivered.

10. The method according to claim 9, with which said pressure sensor for determining the pressure of the surroundings the fluid level is lowered below the level (S₂) of said pressure sensor and said pressure sensor detects the pressure of the surroundings for correcting the pressure value detected in the fluid.

11. The method according to claim 1, with which the detection of said pressure of the surroundings is only effected if the fluid level remains below the level (S₂) of said pressure sensor for a predefined period of time (t₂).

12. The method according to claim 11, with which the pump is started again if a detection of the pressure of the surroundings is not effected.

13. The method according to claim 1, with which a method step for evaluating the pressure of the surroundings is started if the fluid level begins to sink at a predefined minimum speed.

14. The method according to claim 1, with which a detection of the pressure of the surrounding medium is carried out at predefined, preferably regular points in time.

15. A submersible pump system with a fluid level sensor which comprises a pressure sensor for determining an absolute pressure, and control means which switches the pump on and/or off in dependence on the readings of the fluid level sensor, wherein the pump comprises a calibration means for correcting a second pressure value detected in a fluid on the basis of a first pressure value detected in the surroundings, wherein at one point in time said pressure sensor detects said first pressure value and at another point in time detects said second pressure value, and wherein said second pressure value is corrected on the basis of the first pressure value by evaluating the pressure difference between said second pressure value and said first pressure value.

16. The pump system according to claim 15, with which the fluid level sensor, the control means and the calibration means are an integral component of a pump unit.

17. The submersible pump system according to claim 15, with which said pressure sensor is arranged above the suction port of the pump.

18. The pump system according to claim 15, with which said pressure sensor is an absolute pressure sensor.

19. The use of a pressure sensor in a pump system according to claim 15, wherein said pressure sensor only has electrical connection conduits.