# US 2022/0163315 A1 · Coating thickness measurement instrument

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- Number: US 2022/0163315 A1
- Document ID: US20220163315A1
- Status: Published application
- Kind: A1
- Application number: 17/528,792
- Filed: 2021-11-17
- Published: 2022-05-26
- 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/US20220163315A1

## 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 current in the or each drive coil;
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 instrument output corresponding to a measured coating thickness; and scale both the drive current and detector output simultaneously in response to the instrument output.

### Claim 2 (depends on 1)

An instrument as claimed in claim 1 wherein the processor is configured to scale the drive current and detector output according to a first scaling factor and a second scaling factor respectively.

### Claim 3 (depends on 2)

An instrument as claimed in claim 2 wherein the processor is further configured to store the first and second scaling factors as a pair.

### Claim 4 (depends on 3)

An instrument as claimed in claim 3 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 5 (depends on 4)

An instrument as claimed in claim 4 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 6 (depends on 2)

An instrument as claimed in claim 2 wherein the transfer function depends on the applied scaling factors.

### Claim 7

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 current in the or each drive coil; detecting a signal output by the or each pick-up coil; applying a transfer function to the detected signal to determine an instrument output corresponding to a measured coating thickness; and scaling both the drive current and the detected output of the or each pick-up coil simultaneously in response to the instrument output.

### Claim 8 (depends on 7)

A method as claimed in claim 7 wherein method includes the step of changing the scaling applied in a step-wise manner.

### Claim 9 (depends on 7)

A method as claimed in claim 7 wherein the scaling applied to the detected output of the or each pick-up coil counters the scaling applied to the drive current.

### Claim 10 (depends on 9)

A method as claimed in claim 9 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 11 (depends on 7)

A method as claimed in claim 7 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 12 (depends on 7)

A method as claimed in claim 7 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 corresponding to the scaling applied to the drive current and detected output of the or each pick-up coil respectively.

### Claim 13 (depends on 12)

A method as claimed in claim 12 including the step of storing a relation between each pair of scaling factors and a range of the instrument output.

### Claim 14 (depends on 12)

A method as claimed in claim 12 including the step of selecting a pair of scaling factors with reference to the instrument output.

### Claim 15 (depends on 14)

A method as claimed in claim 14 including the step of repeating the method if the instrument output indicates a different pair of scaling factors should be selected.

### Claim 16 (depends on 7)

A method as claimed in claim 7 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 17 (depends on 7)

A method as claimed in claim 7 wherein the transfer function is
T
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=
(
1
G
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1
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G
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2
·
V
d
⁡
(
x
)
V
o
⁢
s
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)
(
1
+
β
G
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1
⁢
G
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2
·
V
d
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(
x
)
V
o
⁢
s
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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 pick-up coil, G1 and G2 are first and second scaling factors which define the scaling applied to the drive current and the detected output respectively, and Vin, β and Vosc are constants.