# US 10,481,026 B2 · Piezoresistive pressure sensor provided with a calibration resistor of the offset

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- Number: US 10,481,026 B2
- Document ID: US10481026B2
- Status: Granted
- Kind: B2
- Application number: 15/665,584
- Filed: 2017-08-01
- Published: 2018-02-08
- Granted: 2019-11-19
- Earliest claimed: 2016-08-03
- Assignees: Kolektor Microtel S.P.A.
- Applicants: Kolektor Microtel S.P.A.
- Inventors: Roberto May; Erminio Maria Bersani; Paolo Pietro Suvighi
- Web page: https://patentgrep.com/patent/US10481026B2

## CPC

- G01L 9/0055: {bonded on a diaphragm}
- G01L 27/002: {Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination}
- G01L 27/005: {Apparatus for calibrating pressure sensors}
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)

## Abstract

The piezoresistive pressure sensor (1) comprises a rigid flat support (2), a flat flexible membrane (3) having a flat external face (4) exposed to a pressure of a fluid and a flat internal face (5) delimiting in cooperation with a flat internal face (7) of the support (2) a chamber (9) accommodating the deformation of the membrane (3), an electrical measuring circuit comprising a resistive Wheatstone bridge (10) applied on the flat internal face (5) of the membrane (3) for detecting the deformation of the membrane (3), and at least an electrical resistor (Rc) for calibrating the value of the output signal when the fluid is at a reference pressure, the calibration resistor (Rc) being applied on the flat internal face (5) of the membrane (3).

## Claims

### Claim 1

A piezoresistive pressure sensor (1) comprising:
a rigid flat support (2) having a flat internal support face (7),
a flat flexible membrane (3) having a flat external membrane face (4) exposed to a pressure of a fluid and a flat internal membrane face (5) delimiting, in cooperation with the flat internal support face (7), a chamber (9) accommodating a deformation of said flat flexible membrane (3),
an electrical measuring circuit comprising a resistive Wheatstone bridge (10) applied on the flat internal membrane face (5) for detecting the deformation of said flat flexible membrane (3), and
an electrical calibration resistor (Rc) for compensating an output signal value when said fluid is at a reference pressure,
wherein:
the calibration resistor (Rc) is applied on said flat internal membrane face (5);
the electrical measuring circuit comprises a bypass (19) of the calibration resistor (Rc);
the calibration resistor (Rc) is formed by a series of compartments (20) selectively excludable due to discrete variation of a calibration resistive value supplied;
for calibration, the bypass (10) is configured to include one or more laser cuts to exclude one or more compartments (20) of said calibration resistor (Rc); and
the one or more laser cuts of the bypass (10) occur at points between electrically conductive compartmentalization tracks (21), to exclude the one or more compartments (20), where a number of cuts are configured to vary, from sensor (1) to sensor (1), to individually quantify a value of a resistance added in series to each of both branches of the resistive Wheatstone bridge (10).

### Claim 2 (depends on 1)

The piezoresistive pressure sensor (1) according to claim 1, wherein the support (2) has a first pair of through-holes (11, 12) passing through a wall thickness thereof, clad in electrically conductive material (13, 14) and electrically connected to two supply terminals (V+, V−) of said resistive bridge (10), a second pair of through-holes (15, 16) coated with electrically-conductive material (17, 18) and electrically connected to two measuring terminals (0+, 0−) of an output signal of said resistive bridge (10) and on a flat external face (6) thereof a conditioning electronic device of said output signal electrically connected via a second pair of holes (15, 16) to said measuring circuit.

### Claim 3 (depends on 2)

The piezoresistive pressure sensor (1) according to claim 2, wherein the calibration resistor (Rc) is positioned in series or in parallel with said supply terminals (V+, V−) and with said measuring terminals (0+, 0−).

### Claim 4 (depends on 1)

The piezoresistive pressure sensor (1) according to claim 1, wherein the electrical measuring circuit and said calibration resistor (Rc) are coated by a dielectric passivation layer.

### Claim 5 (depends on 1)

The piezoresistive pressure sensor (1) according to claim 1, wherein the electrical measuring circuit and said calibration resistor (Rc) are screen-printed onto said flat internal membrane face (5).

### Claim 6 (depends on 1)

The piezoresistive pressure sensor (1) according to claim 1, wherein, for sharing said calibration resistor (Rc), the electrically conductive compartmentalization tracks (21) are provided, where the tracks (21) transversally intersect said calibration resistor (Rc) at a progressively growing distance from an end thereof and project transversally beyond said calibration resistor (Rc) up to intersecting said bypass (19).

### Claim 7 (depends on 1)

A calibrating method of the piezoresistive pressure sensor (1), according to claim 1, wherein calibration is carried out prior to a mechanical coupling between said support (2) and said membrane (3).