US 6,586,949 B1Granted

Volume charge density measuring system

OwnerJohn S. Sargent, Frank T. Sargentinventors

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Abstract

A capacitive sensor includes one or more chambers through which a material can flow. Two conductors are located to partially surround the flow chamber so that the material flows between the conductors. Where more than one chamber is used, additional conductors are provided. A measurement circuit connected to the conductors provides an output corresponding to a difference between test and reference frequencies. A display indicates the measured capacitance as a continuous-scale, proportional representation or a binary representation. The sensor system can measure volume charge density of a fluid or parameters responsive to changes in volume charge density, such as flow velocity.

Claims20

Dependent claims

A sensor for testing a material sample, comprising:

a housing having an electrically conductive shield;
at least one chamber disposed within the housing for containing the material sample, the at least one chamber formed from an electrically non-conductive material and having at least one inlet and at least one outlet for allowing movement of the material sample through the at least one chamber;
at least two electrical conductors corresponding to and disposed on opposite sides of the at least one chamber;
a measurement circuit within the housing coupled to the at least two electrical conductors for producing a measurement signal having a frequency responsive to a capacitance defined by the at least two electrical conductors and the material sample between the at least two electrical conductors, the measurement circuit comprising:
an oscillator circuit coupled to a first electrical conductor of the at least two electrical conductors;
and
a circuit ground potential coupled to a second electrical conductor of the at least two electrical conductors;
and
at least one of a first electrically-conductive extension and a second electrically-conductive extension, wherein
the first electrically-conductive extension is positioned adjacent the at least one inlet, the first electrically-conductive extension having a first end for contacting the material sample in the at least one chamber, and a second end for connecting to a around potential, the first electrically-conductive extension conducting charges within the material sample to the ground potential;
and wherein
the second electrically-conductive extension is positioned adjacent the at least one outlet, the second electrically-conductive extension having a first end for contacting the material sample in the at least one chamber, and a second end for connecting to the ground potential, the second electrically-conductive extension conducting the charges within the material sample to the ground potential.

9 more elements

A sensor for measuring a volume charge density of a fluid, the sensor comprising:

a conductive housing for providing a shield against outside electric fields;
at least one chamber inside of the conductive housing and held by a support structure, the at least one chamber formed from an electrically non-conductive material and providing a flow channel for the fluid;
at least two conductive plates placed on opposite sides of the at least one chamber and held by the support structure;
a measurement circuit coupled to the at least two conductive plates for producing a measurement signal having a frequency responsive to a capacitance defined by the at least two conductive plates and the fluid contained in the flow channel of the at least one chamber, the measurement circuit comprising:
excitation circuitry coupled to a first conductive plate of the at least two conductive plates;
and
a circuit ground coupled to a second conductive plate of the at least two conductive plates;
an inlet end piece connected to a first end of the at least one chamber for receiving the fluid into the flow channel;
an outlet end piece connected to a second end of the at least one chamber for discharging the fluid from the flow channel;
and
at least one electrically-conductive extension connected to one of the inlet end piece and the outlet end piece, the at least one electrically-conductive extension having a first end for contacting the fluid in the at least one chamber, and a second end for connecting to a ground potential, the at least one electrically-conductive extension conducting a charge within the fluid to the around potential.

8 more elements

A sensor for testing a fluid, the sensor comprising:

a conductive housing for providing a shield against outside electric fields;
at least one chamber inside of the conductive housing and held by a support structure, the at least one chamber formed from an electrically non-conductive material and providing a flow channel for the fluid;
at least two conductive plates placed on opposite sides of the at least one chamber and held by the support structure;
a measurement circuit coupled to the at least two conductive plates for producing a measurement signal having a frequency responsive to a capacitance defined by the at least two conductive plates and the fluid contained in the flow channel of the at least one chamber;
an inlet end piece connected to a first end of the at least one chamber for receiving the fluid into the flow channel, and an outlet end piece connected to a second end of the at least one chamber for discharging the fluid from the flow channel, each of the inlet end piece and the outlet end piece comprising:
an exterior surface;
an interior surface in contact with the fluid in the flow channel;
a bore extending from the exterior surface to the interior surface;
and
an electrically-conductive button for placement in the bore, the electrically-conductive button having a first end for contacting the fluid in the flow channel, and a second end for connection to a ground potential, the electrically-conductive button conducting a charge within the fluid to the ground potential;
and
a thermistor disposed within a hollow interior of the electrically-conductive button of at least one of the inlet end piece and the outlet end piece, the thermistor having a lower end adjacent the first end of the electrically conductive button and an upper end comprising connecting wires, wherein the upper end of the thermistor is connected to the measurement circuit for providing a signal representative of a temperature of the fluid.

9 more elements

Dependencies are inferred from the claim text.

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Abstract

A sensor for testing a material sample, comprising:

a housing having an electrically conductive shield;
at least one chamber disposed within the housing for containing the material sample, the at least one chamber formed from an electrically non-conductive material and having at least one inlet and at least one outlet for allowing movement of the material sample through the at least one chamber;
at least two electrical conductors corresponding to and disposed on opposite sides of the at least one chamber;
a measurement circuit within the housing coupled to the at least two electrical conductors for producing a measurement signal having a frequency responsive to a capacitance defined by the at least two electrical conductors and the material sample between the at least two electrical conductors, the measurement circuit comprising:
an oscillator circuit coupled to a first electrical conductor of the at least two electrical conductors;
and
a circuit ground potential coupled to a second electrical conductor of the at least two electrical conductors;
and
at least one of a first electrically-conductive extension and a second electrically-conductive extension, wherein
the first electrically-conductive extension is positioned adjacent the at least one inlet, the first electrically-conductive extension having a first end for contacting the material sample in the at least one chamber, and a second end for connecting to a around potential, the first electrically-conductive extension conducting charges within the material sample to the ground potential;
and wherein
the second electrically-conductive extension is positioned adjacent the at least one outlet, the second electrically-conductive extension having a first end for contacting the material sample in the at least one chamber, and a second end for connecting to the ground potential, the second electrically-conductive extension conducting the charges within the material sample to the ground potential.

9 more elements