Electrode integrity checking
First Claim
1. A method of obtaining an in situ measure of impedance between potential sensing electrodes of a meter having a high input impedance, the method comprising applying a substantially linear voltage ramp waveform to a capacitor coupled to one of the electrodes to generate a substantially constant current, and deriving a measure of impedance by comparing a potential developed across the electrodes while the constant current is flowing to a potential developed across the electrodes when no current, or a different current, is flowing.
1 Assignment
0 Petitions
Accused Products
Abstract
Impedance between potential sensing electrodes of a high impedance meter is measured by applying a ramp waveform through a capacitor coupled to one of the electrodes to generate a substantially constant current, a measure of impedance being obtained by comparing this to the potential developed across the electrodes when a different current is flowing.
-
Citations
24 Claims
- 1. A method of obtaining an in situ measure of impedance between potential sensing electrodes of a meter having a high input impedance, the method comprising applying a substantially linear voltage ramp waveform to a capacitor coupled to one of the electrodes to generate a substantially constant current, and deriving a measure of impedance by comparing a potential developed across the electrodes while the constant current is flowing to a potential developed across the electrodes when no current, or a different current, is flowing.
- 10. Sensing apparatus for a meter arranged to derive a measure of a physical property from a measure of potential across sensing electrodes, the sensing circuit comprising a potential measuring circuit having a high input impedance and inputs arranged for connection to the electrodes and means for obtaining a measure of the impedance between the electrodes comprising a capacitor coupled between one of said inputs and means for generating a substantially linear ramp voltage so that the ramp voltage generates a substantially constant current through the electrodes, the means for obtaining a measure of impedance being arranged to derive said measure based on the difference in potential across the electrodes when the substantially constant current is supplied and when no current, or a different value of current is supplied.
- 21. A method of obtaining measurements of flow of a fluid and electrode impedance in an electromagnetic flowmeter having field generating coils and potential sensing electrodes, the method comprising applying a substantially linear voltage ramp waveform to a capacitor coupled to one of the flowmeter sensing electrodes to generate a substantially constant current, deriving a measure of impedance by comparing the potential developed across the electrodes while said constant current is flowing to the potential developed across the electrodes when no current, or a different current, is flowing, and deriving a measure of flow from the potential developed across the electrodes when no current is flowing, or based on a plurality of values of potential measured at a plurality of different values of said substantially constant current.
Specification