Capacitive sensor for measuring the level of a substance in a tank
A capacitive sensor for measuring the level of a substance in a tank is provided, which has a motherboard with a plurality of layers ( 1 a, 1 b, 1 c, 1 d, 1 e ), wherein each layer ( 1 a, 1 b, 1 c, 1 d, 1 e ) has one or more plates with components, such as measuring electrodes ( 2 ), microcontroller ( 3 ), and tracks ( 4 ) for connecting the measuring electrodes ( 2 ) to the microcontroller ( 3 ), wherein the capacitive sensor has a first layer ( 1 a ) which in turn has a plate having a plurality of linearly distributed measuring electrodes ( 2 ), wherein all the tracks ( 4 ) for connecting the measuring electrodes ( 2 ) to the microcontroller ( 3 ) has the same shape and length, and are surrounded by at least one guard plate ( 8 ) and optionally at least one shielding plate ( 7 ), both made of a conductive material.
1 . A capacitive sensor for measuring a level of a substance in a tank, comprising:
a motherboard with a plurality of layers including one or more areas of components comprising measuring electrodes, an electronic signal conditioning circuit, and tracks for connecting the measuring electrodes to the electronic signal conditioning circuit,
a first layer of the plurality of layers comprising an area including the measuring electrodes, wherein the measuring electrodes are linearly distributed and the tracks for connecting the measuring electrodes to the electronic signal conditioning circuit:
each comprise the same shape and length, and;
are surrounded by a guard plate and at least one shielding plate, each of the guard plate and the at least one shielding plate made of a conductive material, the guard plate being configured to be subjected to a guard voltage substantially equal to a measuring voltage of the measuring electrodes to prevent coupling between the tracks that may influence a capacitance measured by each of the measuring electrodes, and the at least one shielding plate being connected to ground for the electromagnetic shielding of the tracks, and
wherein the plurality of layers further comprise a second layer comprising a shielding plate of the at least one shielding plate, a third layer comprising the tracks for connecting the measuring electrodes to the electronic signal conditioning circuit, and a fourth layer comprising the guard plate, wherein the first layer and the second layer are outer layers of the motherboard, and wherein the third layer is arranged between the second layer and the fourth layer.
2 . The capacitive sensor according to claim 1 , wherein, wherein each track is inserted into a corresponding elongated window made on the guard plate.
3 . The capacitive sensor according to claim 1 , wherein a ground electrode is arranged between every two measuring electrodes, wherein all the ground electrodes are connected to one and the same electric potential.
4 . The capacitive sensor according to claim 3 , wherein the ground electrodes are connected to ground.
5 . The capacitive sensor according to claim 1 , wherein the electronic signal conditioning circuit is configured to measure the capacitance of the each of the measuring electrodes at the measuring voltage by connecting all the measuring electrodes to one and the same voltage.
6 . The capacitive sensor according to claim 3 , wherein the electronic signal conditioning circuit is configured to measure the capacitance between the each of the measuring electrodes and the ground electrodes.
7 . The capacitive sensor according to claim 1 , wherein in addition to the first layer, the capacitive sensor comprises an additional layer having an additional plurality of measuring electrodes, wherein the first layer and the additional layer are outer layers of the motherboard.
8 . The capacitive sensor according to claim 1 , wherein the electronic signal conditioning circuit is arranged in an area located in the first layer adjacent to an area comprising the measuring electrodes.
9 . The capacitive sensor according to claim 8 , wherein the fourth layer comprises a shielding plate of the at least one shielding plate for the electronic signal conditioning circuit, wherein said shielding plate for the electronic signal conditioning circuit is at an electric potential different from the guard plate.
10 . The capacitive sensor according to claim 1 , wherein the electronic signal conditioning circuit is arranged in an area located in the second layer attached to a second shielding plate of the at least one shielding plate arranged in said area.
11 . The capacitive sensor according to claim 10 , wherein the first layer comprises a further shielding plate of the at least one shielding plate for the electronic signal conditioning circuit, wherein said shielding plate for the electronic signal conditioning circuit is arranged adjacent to the area comprising the measuring electrodes.
12 . The capacitive sensor according to claim 10 , wherein the third layer comprises a third shielding plate of the at least one shielding plate for the electronic signal conditioning circuit, wherein said third shielding plate for the electronic signal conditioning circuit is connected to ground.
13 . The capacitive sensor according to claim 1 , wherein the measuring electrodes are linearly distributed in a length direction of the motherboard and the tracks extend in the length direction, each of the measuring electrodes being connected by a corresponding one of the tracks to the electronic signal conditioning circuit.
14 . The capacitive sensor according to claim 1 , wherein the measuring electrodes and the tracks are configured to each be connected to the measuring voltage.
15 . A capacitive sensor for measuring a level of a substance in a tank, comprising:
a motherboard with a plurality of layers including one or more areas of components comprising measuring electrodes, an electronic signal conditioning circuit, and tracks for connecting the measuring electrodes to the electronic signal conditioning circuit, a first layer of the plurality of layers comprising an area including the measuring electrodes, wherein the measuring electrodes are linearly distributed and the tracks for connecting the measuring electrodes to the electronic signal conditioning circuit:
each comprise the same shape and length, and;
are surrounded by a guard plate and at least one shielding plate, each of the guard plate and the at least one shielding plate made of a conductive material, the guard plate being configured to be subjected to a guard voltage substantially equal to a measuring voltage of the measuring electrodes to prevent coupling between the tracks that may influence a capacitance measured by each of the measuring electrodes, and the at least one shielding plate being connected to ground for the electromagnetic shielding of the tracks, and
wherein the plurality of layers further comprise a second layer comprising a shielding plate of the at least one shielding plate and a third layer comprising the guard plate as well as the tracks for connecting the measuring electrodes to the electronic signal conditioning circuit, wherein each track is inserted into a corresponding elongated window made on the guard plate, wherein the first layer and the second layer are outer layers of the motherboard, and wherein the third layer is arranged between the first layer and the second layer.
16 . A capacitive sensor for measuring a level of a substance in a tank, comprising:
a motherboard with a plurality of layers including one or more areas of components comprising measuring electrodes, an electronic signal conditioning circuit, and tracks for connecting the measuring electrodes to the electronic signal conditioning circuit,
a first layer of the plurality of layers comprising an area including the measuring electrodes, wherein the measuring electrodes are linearly distributed and the tracks for connecting the measuring electrodes to the electronic signal conditioning circuit:
each comprise the same shape and length, and;
are surrounded by a guard plate and at least one shielding plate, each of the guard plate and the at least one shielding plate made of a conductive material, the guard plate being configured to be subjected to a guard voltage substantially equal to a measuring voltage of the measuring electrodes to prevent coupling between the tracks that may influence a capacitance measured by each of the measuring electrodes, and the at least one shielding plate being connected to ground for the electromagnetic shielding of the tracks, and
wherein the electronic signal conditioning circuit is configured to measure the capacitance of the each of the measuring electrodes at the measuring voltage by connecting all the measuring electrodes to one and the same voltage.