Capacitive electrical conductivity sensor integrated in a water meter

A method to determine a value of water conductivity, comprising:

• conducting a flow of water through a conduit and a capacitor assembly of a water meter, wherein a first electrode and a second electrode of the capacitor assembly are separated by a medium of the capacitor assembly, wherein the medium comprises at least part of the flow of water and at least part of the conduit used to conduct the flow of water;
• defining a model of the capacitor assembly, wherein the model comprises a circuit with a constant phase element (CPE) connected to a resistor Rb and a capacitor, wherein the resistor Rb and the capacitor are configured in parallel, and wherein the model has an initial calibration;
• applying inputs to the capacitor assembly over a range of frequencies, thereby using a plurality of inputs;
• measuring respective currents passing through the capacitor assembly at each input frequency, to obtain a plurality of measured outputs;
• deriving at least part of a complex admittance of the capacitor assembly based at least in part on the plurality of inputs and the plurality of measured outputs;
• identifying at least one parameter of the model based on at least part of the complex admittance, wherein the at least one parameter comprises a value of the resistor Rb;
• determining the value of water conductivity using the value of the resistor Rb and at least one value of the initial calibration of the model of the capacitor assembly;
• and
• reporting the value of water conductivity to a data-collecting device.

A water meter, comprising:

• a conduit to conduct a flow of water;
• an upstream transducer, attached to an upstream location in the conduit, to send a downstream-directed acoustic signal and to receive an upstream-directed acoustic signal;
• a downstream transducer, attached to a downstream location in the conduit, to send the upstream-directed acoustic signal and to receive the downstream-directed acoustic signal;
• and
• a processor to compare a first time-of-flight of the downstream-directed acoustic signal to a second time-of-flight of the upstream-directed acoustic signal and to determine a flowrate of the flow of water, wherein the processor additionally performs actions comprising:
• determining a value of at least part of a complex admittance of a capacitor assembly, wherein the flow of water forms at least part of a medium between a first electrode and a second electrode of the capacitor assembly;
• calculating an electrical conductivity of the flow of water using inputs comprising the value of at least part of the complex admittance of the capacitor assembly, wherein calculating the electrical conductivity of the flow of water comprises:
• mapping at least part of the complex admittance to a model of the capacitor assembly, wherein the model comprises a circuit with a constant phase element (CPE) connected to a first resistor Rb and a first capacitor Cb, wherein the first resistor Rb and the first capacitor Cb are configured in parallel, and wherein the model has an initial calibration comprising an inductor having value LC, a second capacitor having value CC, a second resistor having value RC, and a geometrical factor;
• and
• solving for a value of the first resistor Rb;
• wherein the inputs used to calculate the electrical conductivity of the flow of water additionally comprise the value of the first resistor Rb;
• measuring a flowrate of the flow of water passing through the water meter;
• and
• reporting information based at least in part on the electrical conductivity of the flow of water and the flowrate of the flow of water to a data-collecting device.

A water meter, comprising:

• a conduit to conduct a flow of water;
• an upstream transducer, attached to an upstream location in the conduit, to send a downstream-directed acoustic signal and to receive an upstream-directed acoustic signal;
• a downstream transducer, attached to a downstream location in the conduit, to send the upstream-directed acoustic signal and to receive the downstream-directed acoustic signal;
• a processor to compare a first time-of-flight of the downstream-directed acoustic signal to a second time-of-flight of the upstream-directed acoustic signal and to determine a flowrate of the flow of water, wherein calculating an electrical conductivity of the flow of water comprises:
• mapping at least part of a complex admittance of a capacitor assembly to the electrical conductivity of the flow of water using a lookup table, wherein the lookup table is based at least in part on a geometric factor that is based at least in part on a distance between a first electrode and a second electrode and a material from which a conduit, through which the flow of water is conducted, is made;
• measuring a flowrate of the flow of water passing through the water meter;
• and
• reporting information based at least in part on the electrical conductivity of the flow of water and the flowrate of the flow of water to a data-collecting device.

A method, comprising:

• determining an electrical conductivity of a flow of water passing through a water meter, wherein the determining comprises:
• determining a value of at least part of a complex admittance of a capacitor assembly, wherein the flow of water forms at least part of a medium between a first electrode and a second electrode of the capacitor assembly;
• and
• calculating the electrical conductivity of the flow of water using inputs comprising the value of at least part of the complex admittance of the capacitor assembly, wherein calculating the electrical conductivity of the flow of water comprises:
• mapping at least part of the complex admittance of the capacitor assembly to the electrical conductivity of the flow of water using a lookup table, wherein the lookup table is based at least in part on a geometric factor that is based at least in part on a distance between the first and second electrodes and a material from which a conduit, through which the flow of water is conducted, is made;
• measuring a flowrate of the flow of water passing through the water meter;
• and
• reporting information based at least in part on the electrical conductivity of the flow of water and the flowrate of the flow of water to a data-collecting device.