Capacitance sensing systems and methods

1 . An apparatus for measuring capacitance of a load, the apparatus comprising:

a first node;

a second node;

a DC power source arranged between the first node and the second node, the DC power source is configured to apply a DC voltage onto a conduction path;

a signal injection component coupled to the conduction path and configured to inject a time varying signal on to the conduction path;

a time varying signal source configured to provide the time varying signal to the signal injection component via galvanic isolation;

a current monitor configured to measure current in the conduction path; and

a capacitance module coupled to the current monitor, the capacitance module configured to determine a capacitance based upon the measured current.

2 . The apparatus of claim 1 , wherein the capacitance module is configured to determine the capacitance by processing a digital signal representation of the measured current.

3 . The apparatus of claim 1 , wherein the capacitance module is configured to provide capacitance data via galvanic isolation.

4 . The apparatus of claim 1 , wherein the time varying signal source is an AC signal source.

5 . The apparatus of claim 1 , wherein the signal injection component comprises a secondary of a transformer that is arranged in the conduction path and the time varying signal source is coupled to a primary of the transformer.

6 . The apparatus of claim 1 , wherein a time varying signal source comprises a digital synthesizer to produce a digital representation of the time varying signal and a digital-to-analog converter to convert the digital representation to the time varying signal wherein the digital synthesizer and the digital-to-analog converter receive power and control signals via galvanically-isolating coupling.

7 . The apparatus of claim 1 , wherein the DC power source is a switch mode power supply.

8 . The apparatus of claim 1 , wherein the time varying signal source includes a linear amplifier.

9 . The apparatus of claim 1 , wherein the current monitor comprises one or more of a flux gate sensor, a resistive shunt sensor, a hall effect sensor, or a current mirror circuit.

10 . The apparatus of claim 1 , wherein the current monitor includes one or more of a peak to peak detector, root-mean-square detector, or a synchronous detector to measure AC current in the conduction path.

11 . An apparatus for measuring capacitance of a load, the apparatus comprising:

a ground connector configured to couple to ground;

an output connector configured to couple to the load;

a floating time-varying signal source configured to inject a time-varying voltage signal onto a conduction path between the ground connector and the output connector;

a DC power source configured to apply a DC offset to the time-varying voltage signal, the DC power source and the floating time-varying signal source are arranged in series on the conduction path between the ground connector and the output connector, and the floating time-varying signal source is coupled between the DC power source and the output connector;

a current monitor configured to measure time-varying current in the conduction path; and

a capacitance module configured to determine the capacitance based upon at least one of the time-varying current and a frequency of the time-varying voltage signal.

12 . The apparatus of claim 11 , wherein the floating time-varying signal source comprises a transformer, wherein a primary of the transformer is coupled to a signal source and a secondary of the transformer is in series with the conduction path.

13 . A method for determining capacitance of a load, the method comprising:

applying a DC voltage with DC power source to a load via a conduction path;

applying a time-varying voltage signal along a portion of the conduction path between the DC power source and the load with a floating time-varying signal source;

measuring a time-varying current that is provided to the load; and

determining the capacitance of the load based upon the time-varying current.

14 . The method of claim 13 comprising:

displaying capacitance information.

15 . The method of claim 13 , wherein the DC power source comprises a switch-mode power supply.

16 . The method of claim 13 comprising:

galvanically isolating the floating time-varying signal source from ground.

17 . The method of claim 13 comprising:

applying the time-varying voltage signal to the conduction path via a secondary of a transformer.

18 . The method of claim 13 comprising:

applying the time-varying voltage signal to the conduction path via a digital to analog converter.