초록 ▼

A capacitive liquid level indicator having a capacitive sensor array superposed on each side of a dielectric substrate, wherein the sensor signal detection electronics are located immediately adjacent each capacitive sensor. These provisions result in high sensitivity of detection of submergence in

A capacitive liquid level indicator having a capacitive sensor array superposed on each side of a dielectric substrate, wherein the sensor signal detection electronics are located immediately adjacent each capacitive sensor. These provisions result in high sensitivity of detection of submergence in the liquid, as well as essentially eliminating parasitic electric fields. The preferred capacitive sensors are interdigitated capacitors, and the preferred sensor signal detection circuit is an RC bridge and a comparator, wherein the comparator senses a voltage difference in the RC bridge between a sensor resistor and sensor capacitor of a first leg thereof and a reference resistor and reference capacitor of a second leg thereof. It is preferred for the capacitive liquid level indicator to be coated with a low dielectric conformal coating to thereby insulate the electronic components (inclusive of the capacitive sensors) thereof with respect to the liquid into which it is submerged. The sensitivity of the capacitive liquid level sensor according to the present invention is extremely high; as a result, a reference capacitive sensor is obviated, and there are no false indications of liquid due to any film of the liquid clinging to an exposed portion of the capacitive liquid level sensor.

대표청구항 ▼

[ What is claimed is:] [1.] A capacitive liquid level indicator comprising:a dielectric substrate having a first side and an opposite second side;a dual capacitive sensor array comprising a first capacitive sensor array located at said first side of said substrate and a second capacitive sensor arra

[ What is claimed is:] [1.] A capacitive liquid level indicator comprising:a dielectric substrate having a first side and an opposite second side;a dual capacitive sensor array comprising a first capacitive sensor array located at said first side of said substrate and a second capacitive sensor array located at said second side of said substrate, said first and second capacitive sensor arrays comprising a plurality of capacitive sensor pairs; andelectronic means for sensing capacitance of said dual capacitive sensor array in response to fluids contacting said dual capacitive sensor array;wherein said electronic means comprises:oscillator means for providing an oscillating voltage; andsensor signal detection circuit means connected with said oscillator means and each said capacitive sensor pair for providing an electronic signal responsive to the capacitance of each respective capacitive sensor pair;wherein said sensor signal detection circuit means comprises a sensor signal detection circuit for each said capacitive sensor pair comprising:an RC bridge comprising:a first leg comprising a sensor resistor and a respective capacitive sensor pair; andsecond leg comprising a reference resistor and a reference capacitor;a first connection to said first leg located between said sensor resistor and said respective capacitive sensor pair;a second connection to said second leg located between said reference resistor and said reference capacitor; andcomparator means connected with said first and second connections for switching between an on state and an off state responsive to voltage differences between said first and second connections.