Combination capacitive proximity sensor and ultrasonic sensor for material level monitoring

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.

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.

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.