US 7,114,391 B2 · Liquid level detection apparatus

Abstract

There is provided a liquid level detection apparatus for detecting the level of a liquid, including a pair of first electrodes, a pair of second electrodes arranged at a different height to that of the first electrodes, a pair of electrode leads having respective ends connected with the first electrodes and sandwiching therebetween the second electrodes, a grounding unit that changes, between a current-carrying state and an open state, a second electrode current bypass from the second electrodes to a ground line, a first electrode capacitance measurement unit that measures a first electrode capacitance between the first electrodes, with the second electrode current bypass set in the current-carrying state to establish a connection from the second electrodes to the ground line, and a level determination unit that determines the liquid level based on the first electrode capacitance between the first electrodes and a second electrode capacitance between the second electrodes.

Claims17

Dependent claims

An apparatus for detecting the level of a liquid, comprising:

a pair of first electrodes at least partly immersed in the liquid;
a pair of second electrodes arranged at a different height to that of the first electrodes and at least partly immersed in the liquid;
a pair of electrode leads having respective ends connected with the first electrodes and sandwiching therebetween the second electrodes;
a grounding unit that changes, between a current-carrying state and an open state, a second electrode current bypass from the second electrodes to a ground line;
a first electrode capacitance measurement unit that measures a first electrode capacitance between the first electrodes, with the second electrode current bypass set in the current-carrying state to establish a connection from the second electrodes to the ground line;
and
a level determination unit that determines the liquid level based on the first electrode capacitance between the first electrodes and a second electrode capacitance between the second electrodes.

4 more elements

An apparatus for detecting the level of a liquid in a container, comprising:

a sensor mounted onto the container, the sensor including a pair of first electrodes immersed in the liquid to develop a first electrode capacitance, a pair of second electrodes vertically aligned to the first electrodes and immersed in the liquid to develop a second electrode capacitance, a pair of first electrode leads connected with the respective first electrodes and sandwiching therebetween the second electrodes and a pair of second electrode leads connected with the respective second electrodes;
and
a detection circuit module electrically connected with the first and second electrodes through the electrode leads, the circuit module including a grounding circuit for establishing and breaking a connection from the second electrodes to a ground line and a microcomputer configured to control the grounding circuit so as to connect the second electrodes with the ground line at the time of measurement of the first electrode capacitance, control the grounding circuit so as to insulate the second electrodes from the ground line at the time of measurement of the second electrode capacitance and determine the liquid level based on the first and second electrode capacitances.

Dependencies are inferred from the claim text.

Liquid level detection apparatus

Life of this patent

Liquid level detection apparatus

Life of this patent

Abstract

Claims17