Digital eddy current proximity system: apparatus and method
First Claim
Patent Images
1. A method for measuring a gap between a proximity probe and a conductive target material, said method including the steps of:
- providing a network of components including a first electrical component, an extension cable component and a proximity probe component respectively serially connected, and locating the proximity probe adjacent a conductive target material;
driving a dynamic current through the serially connected electrical components for impressing a first analog voltage across the network and a second analog voltage across the serial connection of the extension cable component and the proximity probe component;
sampling and digitizing the first analog voltage impressed across said network to obtain a first digitized voltage value;
sampling and digitizing a second analog voltage impressed across the serial connection of the extension cable component and the proximity probe component to obtain a second digitized voltage value;
digitally convolving the first digitized voltage value and the second digitized voltage value into a first complex number and a second complex number respectively;
calculating a voltage ratio of the second complex number to a difference between the first complex number and the second complex number;
processing the voltage ratio into a gap value correlative to a gap between the proximity probe and the conductive target material.
3 Assignments
0 Petitions
Accused Products
Abstract
A digital eddy current proximity system including a digital impedance measuring device for digitally measuring the proximity probes impedance correlative to displacement motion and position of a metallic target object being monitored. The system further including a cable-length calibration method, an automatic material identification and calibration method, a material insensitive method, an inductive ratio method and advanced sensing characteristics.
87 Citations
14 Claims
-
1. A method for measuring a gap between a proximity probe and a conductive target material, said method including the steps of:
-
providing a network of components including a first electrical component, an extension cable component and a proximity probe component respectively serially connected, and locating the proximity probe adjacent a conductive target material;
driving a dynamic current through the serially connected electrical components for impressing a first analog voltage across the network and a second analog voltage across the serial connection of the extension cable component and the proximity probe component;
sampling and digitizing the first analog voltage impressed across said network to obtain a first digitized voltage value;
sampling and digitizing a second analog voltage impressed across the serial connection of the extension cable component and the proximity probe component to obtain a second digitized voltage value;
digitally convolving the first digitized voltage value and the second digitized voltage value into a first complex number and a second complex number respectively;
calculating a voltage ratio of the second complex number to a difference between the first complex number and the second complex number;
processing the voltage ratio into a gap value correlative to a gap between the proximity probe and the conductive target material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
where;
ZO is the measured open impedance of the extension cable, ZS is the measured short impedance of the extension cable, ZSM is the measured impedance of the load coupled to the extension cable in place of the proximity probe, Zstd is the known value of the load impedance, ZXM is the measured impedance of the probe coupled to the extension cable, Zprobe is the compensated complex electrical impedance of the proximity probe.
-
-
9. The method of claim 8 wherein said processing step further includes the step of processing the complex electrical impedance of the proximity probe into said gap value correlative to said gap between said proximity probe and said conductive target material.
-
10. The method of claim 9 further including the step of outputting a signal as a function of said gap value which is correlative to said gap between said proximity probe and said conductive target material.
-
11. The method of claim 8 wherein said processing step further includes the steps of normalizing the complex electrical impedance value of the probe into a normalized impedance value and processing the normalized impedance value into said gap value correlative to said gap between said proximity probe and said conductive target material.
-
12. The apparatus of claim 11 further including means for outputting a signal as a function of said gap value which is correlative to said gap between said proximity probe and said conductive target material.
-
13. The method of claim 1 further including the step of storing electrical parameters for a plurality of different proximity probes and extension cables and retrieving the electrical parameters of the proximity probe that is disposed adjacent the conductive target material and the electrical parameters of the extension cable coupled to that probe for use in the step of processing the voltage ratio into a gap value correlative to a gap between the proximity probe and the conductive target material.
-
14. The method of claim 1 further including the step of storing electrical parameters for a plurality of different target materials and retrieving the electrical parameters of the target material in which the proximity probe is disposed adjacent to and using the retrieved parameters in the step of processing the voltage ratio into a gap value correlative to a gap between the proximity probe and the conductive target material.
Specification