# US 11,946,740 B2 · Coating thickness measurement instrument

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- Number: US 11,946,740 B2
- Document ID: US11946740B2
- Status: Granted
- Kind: B2
- Application number: 17/528,792
- Filed: 2021-11-17
- Published: 2022-05-26
- Granted: 2024-04-02
- Earliest claimed: 2020-11-20
- Assignees: Elcometer Limited
- Applicants: Elcometer Limited
- Inventors: Philip Anthony May; Simon Trevena Coulton; Alan James Dodd; Maria Isabel Jimenez-Lopez
- Web page: https://patentgrep.com/patent/US11946740B2

## CPC

- G01B 7/105: {for measuring thickness of coating}
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS

## Abstract

A coating thickness measuring instrument comprising: a magnetic induction probe comprising at least one drive coil and at least one pick-up coil; a driver for driving an alternating current in the or each drive coil; and a detector for detecting the output of the or each pick-up coil; and a processor configured to: apply a transfer function to the detector output to produce an output which corresponds to a measured coating thickness; and, scale both the drive current and detector output simultaneously in response to the output. The scaling may be changed in a step-wise manner. The scaling applied to the drive current may be inversely proportional to the scaling applied to the detector output. The scaling may be defined by a first and second scaling factor, stored as a pair. The instrument may store two or more pairs of scaling factors and select a pair in response to the measured coating thickness.

## Claims

### Claim 1

A coating thickness measuring instrument comprising:
a magnetic induction probe comprising at least one drive coil and at least one pick-up coil;
a driver for driving an alternating drive current in the or each drive coil and comprising a first modulator configured to scale the drive current in the or each drive coil according to a first scaling factor;
a detector for detecting an output of the or each pick-up coil;
a second modulator configured to scale an output of the detector according to a second scaling factor; and
a processor configured to: apply a transfer function to an output of the second modulator to produce an instrument output corresponding to a measured coating thickness; and change both the first and second scaling factors simultaneously based on the instrument output.

### Claim 2 (depends on 1)

An instrument as claimed in claim 1 wherein the processor is further configured to store the first and second scaling factors as a pair.

### Claim 3 (depends on 2)

An instrument as claimed in claim 2 wherein the processor is further configured to store two or more pairs of scaling factors, and select a pair of scaling factors according to the instrument output.

### Claim 4 (depends on 3)

An instrument as claimed in claim 3 wherein the processor is configured to associate each pair of scaling factors to a corresponding range of the instrument output, and select a pair of scaling factors when the instrument output is within the pair's associated range.

### Claim 5 (depends on 1)

An instrument as claimed in claim 1 wherein the transfer function depends on the applied scaling factors.

### Claim 6

A method of measuring coating thickness using a coating thickness probe comprising at least one drive coil and at least one pick-up coil, the method comprising the steps of:
driving an alternating drive current in the or each drive coil;
scaling the alternating drive current in the or each drive coil according to a first scaling factor using a first modulator;
detecting a signal output by the or each pick-up coil using a detector;
scaling an output of the detector according to a second scaling factor using a second modulator;
applying a transfer function to an output of the second modulator to determine an instrument output corresponding to a measured coating thickness; and
changing both the first and second scaling factors simultaneously based on the instrument output.

### Claim 7 (depends on 6)

A method as claimed in claim 6 wherein method includes the step of changing the first and second scaling factors in a step-wise manner.

### Claim 8 (depends on 6)

A method as claimed in claim 6 wherein the scaling applied to the detected output of the or each pick-up coil counters the scaling applied to the drive current.

### Claim 9 (depends on 8)

A method as claimed in claim 8 wherein the step of scaling comprises an increase in the drive current and a decrease in the detected output of the or each pick-up coil, or a decrease in the drive current and an increase in the detected output of the or each pick-up coil.

### Claim 10 (depends on 6)

A method as claimed in claim 6 wherein the step of determining the measured coating thickness comprises reading a look-up table relating the instrument output to the measured coating thickness.

### Claim 11 (depends on 6)

A method as claimed in claim 6 including the step of storing two or more pairs of scaling factors, wherein each pair of scaling factors comprises a first and second scaling factor.

### Claim 12 (depends on 11)

A method as claimed in claim 11 including the step of storing a relation between each pair of scaling factors and a range of the instrument output.

### Claim 13 (depends on 11)

A method as claimed in claim 11 including the step of selecting a pair of scaling factors with reference to the instrument output.

### Claim 14 (depends on 13)

A method as claimed in claim 13 including the step of repeating the method if the instrument output indicates a different pair of scaling factors should be selected.

### Claim 15 (depends on 6)

A method as claimed in claim 6 wherein the step of applying the transfer function includes determining a normalised output and using the normalised output in place of the instrument output.

### Claim 16 (depends on 6)

A method as claimed in claim 6 wherein the transfer function is
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where T(x) is the transfer function with output Vout(x)=T(x)Vin, Vd(x) is the detected output of the or each pick-up coil, Gi and G2 are the first and second scaling factors, and Vin, f3 and Vose are constants, Vin is a voltage set point used to control the alternating drive current, Vose is an amplitude of the alternating drive current and Vout(x) is the instrument output used to determine the measured coating thickness.

### Claim 17

A coating thickness measuring instrument comprising:
a magnetic induction probe comprising at least one drive coil and at least one pick-up coil;
a driver for driving an alternating drive current in the or each drive coil;
a detector for detecting an output of the or each pick-up coil; and
a processor configured to: apply a transfer function to a detector output to produce an instrument output corresponding to a measured coating thickness;
and scale both the alternating drive current and the detector output simultaneously in response to the instrument output,
wherein the transfer function is
T
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where T(x) is the transfer function with output Vout(x)=T(x)Vin, Vd(x) is the detected output of the or each pick-up coil, G1 and G2 are first and second scaling factors which define the scaling applied to the alternating drive current and detector output respectively, and Vin, f3 and Voseare constants, Vin is a voltage set point used to control the alternating drive current, Vose is an amplitude of the alternating drive current and Vout(x) is the instrument output used to determine the measured coating thickness.