# US 5,929,635 A · Digital oscillator and supply circuit for an eddy current probe

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- Number: US 5,929,635 A
- Document ID: US5929635A
- Status: Granted
- Kind: A
- Application number: 08/930,178
- Filed: 1997-10-20
- Granted: 1999-07-27
- Earliest claimed: 1995-06-20
- Assignees: Intercontrole
- Inventors: Edouard De Ledinghen
- Web page: https://patentgrep.com/patent/US5929635A

## CPC

- G01N 27/9046: {by analysing electrical signals}
- G06F 1/0335: {the phase increment itself being a composed function of two or more variables, e.g. frequency and phase}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

The present invention relates to a digital oscillator comprising an oscillator (40), a counter (41), a memory (42), a digital-analog converter (43) and a low-pass filter (44). The memory is able to directly store a complex signal, rendering the use of a real time calculating unit unnecessary.

## Claims

### Claim 1

Supply circuit of an eddy current probe, comprising two digital oscillators generating two synchronized signals, one used for injection and the other for balancing, the two digital oscillators coupled to the same quartz oscillator, each digital oscillator comprising a counter connected to the quartz oscillator, a memory coupled to the counter which stores a complex signal, a digital-analog converter coupled to the memory and a low-pass filter coupled to the converter, the synchronized injection signal being input into a first amplifier which functions to provide voltage control and make it possible to sample at its output an absolute measurement voltage corresponding to eddy currents, the output of said first amplifier being connected to an input of a second amplifier which functions to provide a supply voltage to the eddy current probe, the synchronized balancing signal being connected to said input of said second amplifier.

### Claim 2 (depends on 1)

Circuit according to claim 1, characterized in that said output of said first amplifier is sampled so as to detect said absolute measurement voltage corresponding to said eddy currents.

### Claim 3 (depends on 1)

Circuit according to claim 1, characterized in that the sampling of said absolute measurement voltage corresponding to said eddy currents and the supplying of the probe are performed separately.