Combination capacitive proximity sensor and ultrasonic sensor for material level monitoring

• US 7,610,805 B2
• Filed: 01/24/2006
• Issued: 11/03/2009
• Est. Priority Date: 01/25/2005
• Status: Expired due to Fees

• Current Assignee: The GSI Group Inc
• Original Assignee: The GSI Group Inc
• Inventors: Crider, Brett
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Devito, Alex
• Application Number:
  US11/883,110
• Publication Number:
  US 20080148845A1
• Time in Patent Office: 1,379 Days
• Field of Search: 340/621, 733/04.C, 732/91, 324/323, 324/335
• US Class Current: 73/304.00C
• CPC Class Codes: G01F 23/265 for discrete levels
• CPC Class Codes: G01F 23/2962 Measuring transit time of reflected waves

Abstract

A material level detection sensor (10) having a continuous ultrasonic sensor (12) and a capacitive proximity sensor (13). The capacitive proximity sensor detects the material only when the material is at or within the dead zone (15) of the ultrasonic sensor, at which point it switches the ultrasonic sensor off. The ultrasonic sensor transmits a level detection output signal until it is turned off by the capacitive proximity sensor. The capacitive proximity sensor transmits a level detection output signal only when it detects the material, and it will switch the ultrasonic sensor on when it does not detect the material. The material level detection sensor transmits only a single level detection output signal at any given time, providing an accurate and reliable estimate of material level. The device is particularly useful for measuring inventory and consumption of particulate solids and powders in bins or silos (11).

Claims

1. A device (10) for sensing the level of material (16) in a container (11), comprising:

a) a continuous ultrasonic sensor (12); and

b) a capacitive proximity sensor (13);

c) wherein said capacitive proximity sensor is positioned to detect the material only at a level proximate or within the limit of a dead zone (15) of said ultrasonic sensor and said ultrasonic sensor provides a level detection signal only when said capacitive proximity sensor does not detect the material.

2. The device of claim 1 wherein said capacitive proximity sensor provides a level detection signal only when said capacitive proximity sensor detects the material.

3. The device of claim 1 further comprising a switch (34) that is activated when said capacitive proximity sensor detects the material, said switch preventing said ultrasonic sensor from providing a level detection signal when said switch is activated.

4. The device of claim 1 wherein said capacitive proximity sensor has a rod (14) to detect the material only at a level proximate or within the limit of the dead zone of said ultrasonic sensor.

5. The device of claim 1 wherein said device produces a single level detection signal.

6. The device of claim 1 wherein the material is non-liquid.

7. The device of claim 1 wherein the material is liquid.

8. A device (10) for sensing the level of material (16) in a container (11), comprising:

a) a continuous ultrasonic sensor (12) and a capacitive proximity sensor (13);

b) wherein said capacitive proximity sensor has a rod (14) to detect the material only at a level proximate or within the limit of a dead zone (15) of said ultrasonic sensor;

c) wherein said ultrasonic sensor provides a level detection signal only when said capacitive proximity sensor does not detect the material;

d) wherein said capacitive proximity sensor provides a level detection signal only when said capacitive proximity sensor detects the material;

e) a switch (34) that is activated when said capacitive proximity sensor detects the material, said switch preventing said ultrasonic sensor from providing a level detection signal when said switch is activated; and

f) wherein said device produces a single level detection signal.

9. A method (30) for sensing the level of material (16) in a container (11), comprising the steps of:

a) detecting said material level continuously with a first sensor (12) until said material level reaches a dead zone (15) of said first sensor, said first sensor providing a level detection signal;

b) detecting when said material level reaches said dead zone with a second sensor (13); and

c) switching off the level detection signal of said first sensor when said second sensor detects said material level reaches said dead zone.

10. The method of claim 9, further comprising the step of providing a level detection signal from said second sensor only when said second sensor detects said material.

11. The method of claim 9, further comprising the step of producing a single level detection signal.

12. The method of claim 9 wherein said material is non-liquid.

13. The method of claim 9 wherein said material is liquid.

14. The method of claim 9 wherein said first sensor is a continuous ultrasonic sensor and said second sensor is a capacitive proximity sensor.

15. A method (30) for sensing the level of material (16) in a container (11), comprising the steps of:

a) detecting said material level continuously with a continuous ultrasonic sensor (12) until said material level reaches a dead zone (15) of said ultrasonic sensor, said ultrasonic sensor providing a level detection signal;

b) detecting when said material level reaches said dead zone with a capacitive proximity sensor (13);

c) switching off the level detection signal of said ultrasonic sensor when said capacitive proximity sensor detects said material level reaching said dead zone;

d) providing a level detection signal from said capacitive proximity sensor only when said capacitive proximity sensor detects said material; and

e) producing a single level detection signal from said device.