Edge detector
AssigneeNorth American Manufacturing Company
InventorDennis Keith Mull
Life of this patent
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Abstract
A capacitance measuring circuit having a sensor electrode and a reference electrode that are spaced apart so that a material can be positioned between the two electrodes. A first polarity and a second polarity voltage source are used to charge the sensor electrode and a switch controller controls the charging and discharging of a capacitor by the sensor electrode. The charge on the capacitor after being charged and at least partially discharged by the sensor electrode represents the capacitance between the sensor electrode and the reference electrode. The charge on the capacitor is used to measure the position of the material relative to the sensor and reference electrode. The measuring circuit also has a system parasitic controller to measure and adjust for system parasitic capacitance in the measuring circuit.
Claims87
A capacitance measuring circuit comprising:
- a) a sensor electrode and a reference electrode, said sensor electrode and said reference electrode being spaced apart so that at least one edge of a material can be at least partially positioned between said sensor electrode and said reference electrode;
- b) a first polarity and a second polarity voltage source;
- and
- c) a switch controller to electrically ground said reference electrode and to electrically connect said sensor electrode to a capacitor after said first polarity voltage source has been applied to said sensor electrode, and to electrically connect together said capacitor and said sensor electrode after said second polarity voltage source has been applied to said reference electrode and said sensor electrode.
A method of measuring the capacitance of a circuit comprising the steps of:
- a) providing a material;
- b) providing a sensor electrode and a reference electrode spaced apart from one another;
- c) positioning at least one edge of said material at least partially between said sensor electrode and said reference electrode;
- d) providing a capacitor to represent the capacitance between said sensor electrode and said reference electrode;
- e) charging said capacitor by connecting said sensor electrode to said capacitor after a reference voltage has been applied to said sensor electrode while said reference electrode is grounded;
- and
- f) at least partially discharging said capacitor by connecting said sensor electrode to said capacitor after an opposite polarity reference voltage has been applied to said sensor electrode when said sensor electrode and said reference electrode have substantially the same potential.
Dependencies are inferred from the claim text.