JP7156969B2 - Pressure sensor driving method - Google Patents

Description

The present invention relates to a pressure sensor driving method .

Conventionally, as a device for detecting atmospheric pressure fluctuations in the outside air, it has a sealed cavity (sealed cavity), and the pressure difference generated between the cavity and the outside air is detected by a pressure receiving part, or gas flows into and out of the cavity. A pressure sensor is known in which a permeable hole is provided and a pressure receiving portion is arranged above the permeable hole to detect atmospheric pressure fluctuations in the outside air (see, for example, Patent Document 1).

JP-A-4-208827

In the case of a pressure sensor with a sealed cavity, when dropped or hit, the pressure receiving part is subject to sudden pressure fluctuations and is easily damaged. In particular, a high-sensitivity type pressure sensor has a large displacement of the pressure-receiving portion, so the pressure-receiving portion is more likely to be damaged.
In addition, in the case of a pressure sensor in which the pressure receiving part is arranged above the transmission hole, if the transmission hole is small, there are problems similar to those of the sealed cavity. Since they arrive at the same time, it becomes difficult for the pressure-receiving portion to be displaced, and high-sensitivity pressure fluctuation detection cannot be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of driving a pressure sensor that is not damaged even when a sudden change in atmospheric pressure occurs and that enables highly sensitive measurement.

In order to solve the above problems, a pressure sensor according to one aspect of the present invention includes a pressure receiving portion that is displaced by receiving an air pressure difference between the inside of a cavity and the outside air, and a displacement detection that detects and outputs the displacement of the pressure receiving portion. and a portion, wherein the cavity comprises a sealable cavity opening.

The cavity is mounted on one side of a substrate having a through hole penetrating in the thickness direction, and the pressure receiving portion is composed of a cantilever arranged so as to cover the through hole. The inside of the cavity and the outside air may communicate with each other through a gap formed between the edge of the hole and the through hole.

The cavity opening may comprise a lid that can be opened and closed.

The cavity opening may be composed of an openable and closable slide plate.

The sealing of the cavity opening may be irreversible.

The sealing of the cavity opening may be the release of a sealed adhesive.

A pressure sensor driving method according to an aspect of the present invention includes a pressure receiving portion that is displaced by receiving an air pressure difference between the inside of a cavity and the outside air, and a displacement detection portion that detects and outputs the displacement of the pressure receiving portion. A sensor driving method, wherein the cavity comprises a sealable cavity opening, the cavity opening is open when the pressure sensor is not driven, and the cavity is opened when the pressure sensor is driven. The opening is sealed.

The cavity opening is composed of a lid that can be opened and closed, and when the pressure sensor is not driven, the lid is opened to open the cavity opening, and when the pressure sensor is driven, the lid is closed. The cavity opening may be sealed.

The cavity opening is composed of a slide plate that can be opened and closed. When the pressure sensor is not driven, the slide plate is moved to open the cavity opening, and when the pressure sensor is driven, the slide is used. A plate may be moved to seal the cavity opening.

A sealed adhesive is disposed near the cavity opening, and the sealed adhesive is released to seal the cavity opening prior to driving the pressure sensor. good too.

A pressure sensor carrying method according to one aspect of the present invention includes a pressure receiving portion that is displaced by receiving a pressure difference between the inside of a cavity and the outside air, and a displacement detection portion that detects and outputs the displacement of the pressure receiving portion. A method of transporting a sensor, wherein the cavity comprises a sealable cavity opening and the pressure sensor is transported with the cavity opening open.

According to the pressure sensor, the method for driving the pressure sensor, and the method for transporting the pressure sensor according to each aspect of the present invention, there is no need to detect fluctuations in the outside air pressure during transportation, and there is a possibility that the outside air pressure may suddenly fluctuate due to dropping or the like. In some cases, by keeping the cavity opening open, the pressure sensor will not be damaged even if a sudden change in atmospheric pressure occurs.
In addition, when driving, that is, when detecting fluctuations in the outside air pressure, by closing the cavity opening, even if the fluctuations in the outside air pressure are minute, a differential pressure can be generated between the air pressure inside the cavity and high sensitivity. Detection becomes possible.
In other words, it is possible to provide a pressure sensor, a pressure sensor driving method, and a pressure sensor transporting method which are not damaged even when a sudden change in atmospheric pressure occurs and which can perform highly sensitive measurements.

1 is a cross-sectional view of a pressure sensor according to a first embodiment of the invention; FIG. 1 is a cross-sectional view of a pressure sensor according to a first embodiment of the invention; FIG. 1 is a block diagram of a sensor module of a pressure sensor according to an embodiment of the invention; FIG. FIG. 5 is a graph showing barometric pressure variation and displacement of a pressure sensor when the cavity opening is closed; FIG. FIG. 5 is a graph showing barometric pressure variation and displacement of a pressure sensor when the cavity opening is closed; FIG. FIG. 5 is a graph showing barometric pressure variation and displacement when the cavity opening is open; FIG. FIG. 5 is a cross-sectional view of a pressure sensor according to a second embodiment of the invention; FIG. 5 is a cross-sectional view of a pressure sensor according to a second embodiment of the invention; FIG. 5 is a cross-sectional view of a pressure sensor according to a third embodiment of the invention; FIG. 5 is a cross-sectional view of a pressure sensor according to a third embodiment of the invention;

Hereinafter, a pressure sensor, a pressure sensor driving method, and a pressure sensor carrying method according to embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, the configuration of the pressure sensor according to the first embodiment of the present invention will be described. 1 and 2 are sectional views of a pressure sensor 1 (differential pressure sensor, sensor module) according to this embodiment. The pressure sensor 1 includes a sensor substrate 2 and a cavity housing 3 (cavity) mounted on the upper surface of the sensor substrate 2 . The cavity housing 3 is formed, for example, in the shape of a quadrangular (cubic) bottomed box.

The sensor board 2 is, for example, a circuit board. An SOI substrate 10 and a pressure receiving portion 6 are mounted on the upper surface of the sensor substrate 2 inside the box-shaped cavity housing 3 (cavity interior 5 ). A through hole 30 is formed through the sensor substrate 2 in the thickness direction, and the cavity interior 5 and the outside air 4 communicate with each other through the through hole 30 .

Note that, in a plan view of the sensor substrate 2, one of the two directions orthogonal to each other is referred to as the front-rear direction L1, and the other direction is referred to as the left-right direction L2. The sensor substrate 2 is formed in a rectangular shape in a plan view such that the length along the front-rear direction L1 is longer than the length along the left-right direction L2. However, the shape of the sensor substrate 2 is not limited to this case, and may be changed as appropriate.

The pressure receiving portion 6 is displaced by receiving the pressure difference between the outside air 4 and the inside of the cavity housing 3 (inside the cavity) 5 . In the example shown in FIG. 1 , the pressure receiving portion 6 is composed of a cantilever that bends and deforms according to pressure fluctuations of the outside air 4 . In this specification, the outside air means gas outside the cavity housing 3 , that is, gas outside the pressure sensor 1 .

The cantilever 6 is formed of a semiconductor substrate bonded to the upper surface of the sensor substrate 2 while being superimposed thereon. The example of FIG. 1 shows an SOI substrate 10 as a semiconductor substrate in which a silicon support layer 12, an insulating layer 13 such as a silicon oxide film, and a silicon active layer 14 are arranged in this order from below. The cantilever 6 is therefore formed by the SOI substrate 10 .

However, the cantilever 6 is not limited to being formed by the SOI substrate 10 . The silicon support layer 12 is maintained at a constant potential (for example, the silicon support layer 12 is connected to the ground of the sensor substrate 2 or the like) to suppress variations in the potential difference in the thickness direction of the SOI substrate 10 . is preferred.

Moreover, the SOI substrate 10 is formed in a rectangular shape in a plan view such that the length along the front-rear direction L1 is longer than the length along the left-right direction L2, similarly to the sensor substrate 2 . In the silicon support layer 12 and the insulating layer 13, similarly to the sensor substrate 2, a through hole 30 is formed through the silicon support layer 12 and the insulating layer 13 in the thickness direction.

The cantilever 6 has a plate shape extending in one direction from a base end (left side in the drawing) to a tip end (right side in the drawing), and is flexurally deformed according to the pressure difference between the cavity interior 5 and the outside air 4 . The cantilever 6 has a cantilever structure in which the base end portion is supported by a cantilever, the base end portion is connected to the semiconductor substrate, and the tip portion is a free end. are placed in

A gap 20 is formed along the outer peripheral edge of the cantilever 6 between the outer peripheral edge of the cantilever 6 and the edge of the through hole 30 . Through-holes 30 in sensor substrate 2 , silicon support layer 12 and insulating layer 13 communicate with cavity interior 5 located above cantilever 6 through gap 20 . Thereby, the cavity interior 5 and the outside air 4 communicate with each other through the gap 20 and the through hole 30 .

A portion of the cantilever 6 on the proximal end side is a piezoresistive portion (resistive element), and serves as a displacement detection resistor 6a (displacement detection portion) whose electrical resistance changes according to the amount of deflection (displacement) of the cantilever 6. Function. The piezoresistive section is formed of a doped layer (impurity semiconductor layer). This doped layer is formed by doping a dopant (impurity) such as phosphorus by various methods such as ion implantation and diffusion.

An external electrode 15 made of a conductive material (for example, Au (gold) or the like) having an electrical resistance lower than that of the doped layer is formed on the base end of the cantilever 6 . This external electrode 15 functions as an end of the displacement detection resistor 6a.

FIG. 3 is a block diagram of the sensor module according to this embodiment. The sensor module is composed of an analog section 50 and a microcomputer 60 . The analog section 50 is composed of a bridge circuit 55 , an amplifier 56 and a filter 57 . The bridge circuit 55 is composed of a displacement detection resistor 6a, a reference resistor 52, a variable resistor 53, and a fixed resistor .

The displacement detection resistor 6a has a first end connected to the voltage Vcc supply line and a second end connected to the node N1. The reference resistor 52 has a first end connected to the node N1 and a second end connected to the power supply GND. The variable resistor 53 has a first end connected to the voltage Vcc supply line and a second end connected to the node N2. The fixed resistor 54 has a first end connected to the node N2 and a second end connected to the power supply GND.

The displacement detection resistor 6 a is configured inside the pressure sensor 1 , and the variable resistor 53 and the fixed resistor 54 are external resistors provided outside the pressure sensor 1 . The reference resistor 52 is, for example, a resistor formed so as to have the same temperature characteristics as the displacement detection resistor 6a. may be

The amplifier 56 has an inverting input terminal (- terminal) connected to the node N1 and a non-inverting input terminal (+ terminal) connected to the node N2. Amplifier 56 amplifies the potential difference between nodes N1 and N2 and outputs it as an output signal. It should be noted that this potential difference is a value corresponding to a change in the resistance value of the displacement detection resistor 6a (piezoresistive portion), that is, a value based on the displacement of the cantilever. The output signal is filtered in filter 57 and propagated to microcomputer 60 .

The microcomputer 60 is composed of an A/D converter 61 and a pressure calculator 62 . The output signal propagated from the analog section 50 is digitally converted in the A/D conversion section 61 and propagated to the pressure calculation section 62 . The pressure calculator 62 performs software processing such as temperature correction on the output signal, and outputs the processing result as a pressure value.

In this embodiment, part of the cavity housing 3 serves as the cavity opening 7 . In the example of FIGS. 1 and 2, the cavity opening 7 is composed of a lid that can be opened and closed, and schematically shows how the lid can be opened to one side via a hinge 7a. 1 shows a state in which the cavity opening 7 is closed, and FIG. 2 shows a state in which the cavity opening 7 is open. When the cavity opening 7 is closed as shown in FIG. 1, the air pressure 24 of the outside air 4 and the air pressure 25 inside the cavity 5 can have different values. On the other hand, when the cavity opening 7 is open as shown in FIG. 2, the atmospheric pressure of the outside air 4 and the atmospheric pressure inside the cavity 5 through the opening 40 are always the same value.

FIG. 4(a) is a graph showing atmospheric pressure fluctuations 25 inside the cavity 5 when atmospheric pressure fluctuations 24 occur in the outside air 4 when the cavity opening 7 is closed as shown in FIG. 4(b) is a graph showing the displacement 26 of the pressure receiving portion 6 at this time. The horizontal axis of the graph is time (sec), and the vertical axis of the graph is pressure value (Pa) in FIG. 4(a) and length (μm) in FIG. 4(b).

When atmospheric pressure fluctuation occurs in the outside air 4 at a certain timing, the atmospheric pressure 24 of the outside air 4 changes at once, and the atmospheric pressure 25 inside the cavity 5 changes with a delay, as shown in FIG. 4(a). After a while, the atmospheric pressure 24 of the outside air 4 and the atmospheric pressure 25 of the inside of the cavity 5 become the same pressure value. The displacement 26 of the pressure receiving portion 6 changes according to the difference between the atmospheric pressure 24 of the outside air 4 and the atmospheric pressure 25 inside the cavity 5 . Therefore, as shown in FIG. 4(b), the displacement 26 of the pressure receiving portion 6 temporarily increases, but converges to 0 after a while.

In this embodiment, the pressure receiving portion 6 is an extremely thin Si cantilever, and since even a slight differential pressure causes a large displacement, it is a highly sensitive pressure sensor. In this specification, a highly sensitive pressure sensor means a sensitive pressure sensor capable of detecting a pressure change of 1 Pa, for example.

FIG. 5(a) shows atmospheric pressure fluctuation 34 of outside air 4 when the pressure sensor is dropped or brought into strong contact with some object when the cavity opening 7 is closed as shown in FIG. 5(b) is a graph showing the displacement 36 of the pressure receiving portion 6. FIG. The horizontal axis of the graph is time (sec), and the vertical axis of the graph is pressure value (KPa) in FIG. 5(a) and length (μm) in FIG. 5(b).

At this time, the air pressure 34 of the outside air 4 increases instantaneously, but the value is much larger than that in FIG. For example, as shown in the graph of FIG. 5(a), the atmospheric pressure fluctuation 34 of the outside air 4 is several KPa, which is several thousand times the atmospheric pressure fluctuation 24 of the outside air 4 shown in the graph of FIG. 4(a). On the other hand, the atmospheric pressure fluctuation 35 inside the cavity 5 cannot catch up with the atmospheric pressure fluctuation 34 of the outside air 4 because the inflow speed of the air is slow. As shown in the graph of FIG. 5(a), the air pressure variation 35 inside the cavity 5 is substantially flat. As a result, as shown in FIG. 5(b), the displacement 36 of the pressure receiving portion 6 becomes extremely large, and the pressure sensor is damaged.

FIG. 6(a) shows atmospheric pressure fluctuation 44 of outside air 4 and atmospheric pressure fluctuation 44 when the pressure sensor is dropped or is brought into strong contact with some object when the cavity opening 7 is open as shown in FIG. 6(b) is a graph showing the displacement 46 of the pressure receiving portion 6. FIG. The horizontal axis of the graph is time (sec), and the vertical axis of the graph is pressure value (KPa) in FIG. 6(a) and length (μm) in FIG. 6(b).

At this time, the pressure value 44 of the outside air 4 that has fluctuated in pressure becomes a large value, but since the cavity opening 7 is open, the pressure 45 inside the cavity 5 is always the same as the pressure 44 of the outside air 4 . Therefore, as shown in FIG. 6A, the atmospheric pressure fluctuation 45 inside the cavity 5 overlaps the atmospheric pressure fluctuation 44 of the outside air 4 . As a result, as shown in FIG. 6B, the displacement 46 of the pressure receiving portion 6 does not fluctuate at all, and the pressure sensor is not damaged.

As described above, in this embodiment, the cavity housing 3 is provided with the sealable cavity opening 7 constituted by an openable/closable lid. When the pressure sensor 1 is not driven, the pressure inside the cavity 5 and the pressure of the outside air 4 can be equalized through the opening 40 by opening the cavity opening 7, that is, by opening the lid. Therefore, the displacement 46 of the pressure receiving portion 6 does not fluctuate at all, and damage to the pressure sensor 1 can be prevented.

When the pressure sensor 1 is driven, the air pressure 24 of the outside air 4 and the air pressure 25 inside the cavity 5 can have different values by sealing the cavity opening 7, ie closing the lid. Therefore, the pressure value can be obtained based on the resistance value change (displacement of the pressure receiving portion 6) of the displacement detection resistor 6a (piezoresistive portion).

(Second embodiment)
Next, the configuration of the pressure sensor according to the second embodiment of the invention will be described. 7 and 8 are sectional views of the pressure sensor 51 (differential pressure sensor, sensor module) according to this embodiment. The difference from the pressure sensor 1 of the first embodiment is that in the pressure sensor 51 of this embodiment, part of the cavity housing 53 is a cavity opening 57 made up of a slide plate. The slide plate has a structure that can be opened and closed by sliding horizontally with respect to the cavity housing 53 . Other than that, this embodiment is the same as the first embodiment, so the description is omitted.

7 shows a state in which the cavity opening 57 is closed, and FIG. 8 shows a state in which the cavity opening 57 is opened by sliding (moving) the slide plate in the horizontal direction. When the cavity opening 57 is closed as shown in FIG. 7, the air pressure of the outside air 4 and the air pressure inside the cavity 5 can have different values. On the other hand, when the cavity opening 57 is open as shown in FIG. 8, the atmospheric pressure of the outside air 4 and the atmospheric pressure inside the cavity 5 through the opening 40 are always the same value.

Thus, in the present embodiment, the cavity housing 53 includes a sealable cavity opening 57 which is composed of an openable and closable slide plate. When the pressure sensor 51 is not driven, the pressure inside the cavity 5 and the pressure of the outside air 4 can be made the same by moving the slide plate to open the cavity opening 57 . Therefore, the displacement of the pressure receiving portion 6 does not fluctuate at all, and damage to the pressure sensor 51 can be prevented.

When driving the pressure sensor 51, by moving the slide plate to seal the cavity opening 57, the air pressure of the outside air 4 and the air pressure inside the cavity 5 can have different values. Therefore, the pressure value can be obtained based on the resistance value change (displacement of the pressure receiving portion 6) of the displacement detection resistor 6a (piezoresistive portion). As described above, the present embodiment has the same effect as the first embodiment, and can reduce the size of the pressure sensor as a whole because only a part of the cavity housing 53 slides.

(Third Embodiment)
Next, the structure of the pressure sensor according to the third embodiment of the invention will be described. 9 and 10 are sectional views of the pressure sensor 61 (differential pressure sensor, sensor module) according to this embodiment. The difference from the pressure sensor 1 of the first embodiment is that in the pressure sensor 61 of the present embodiment, part of the cavity housing 63 is the cavity opening 67, and near the opening 40 of the cavity opening 67, The difference is that a bag 68 in which an adhesive 69 is sealed is arranged. Other than that, this embodiment is the same as the first embodiment, so the description is omitted.

FIG. 9 shows a state in which the cavity opening 67 is fixed to the cavity housing 63 with an adhesive 69, and FIG. is fixed in the vicinity of the opening 40 of the . When the cavity opening 67 is closed as shown in FIG. 9, the air pressure 24 of the outside air 4 and the air pressure 25 inside the cavity 5 can be different values. On the other hand, when the cavity opening 67 is open as shown in FIG. 10, the atmospheric pressure of the outside air 4 and the atmospheric pressure inside the cavity 5 through the opening 40 are always the same value.

Thus, in this embodiment, the cavity housing 63 has a cavity opening 67 that can be sealed by releasing the sealed adhesive. Before the pressure sensor 61 is driven, the pressure inside the cavity 5 and the pressure of the outside air 4 can be made the same via the opening 40 of the cavity opening 67 . Therefore, the displacement of the pressure receiving portion 6 does not fluctuate at all, and damage to the pressure sensor 61 can be prevented.

When the pressure sensor 61 is driven, the opening 40 is filled by breaking the sealed bag 68 and releasing the adhesive 69 to seal the cavity opening 67, so that the atmospheric pressure of the outside air 4 and the cavity The air pressure inside 5 can be different values. Therefore, the pressure value can be obtained based on the resistance value change (displacement of the pressure receiving portion 6) of the displacement detection resistor 6a (piezoresistive portion). Further, the cavity opening 67 is fixed to the cavity housing 63, so that strong fixation is possible. The ideal timing for closing the cavity opening 67 is preferably immediately before the pressure sensor is driven. In this embodiment, unlike the first and second embodiments, the sealing of the cavity opening 67 is irreversible and cannot be reopened once closed.

In the above description of the embodiment, the case where the pressure receiving portion is a cantilever has been described, but the present invention is not limited to this, and can also be applied when the pressure receiving portion is not a cantilever. For example, when the present invention is applied to a pressure sensor that uses the air pressure inside the cavity in a vacuum state, the opening of the cavity is sealed when the pressure sensor is driven, and the air pressure inside the cavity is further reduced to a vacuum. It can function as a sensor. Also, the illustrated cavity opening is a schematic diagram and does not strictly show the structure. Any structure may be used as long as it realizes the function described above as the cavity opening.

As described above, when the pressure sensor is being transported (including during manufacturing), there is no need to function as a pressure sensor, that is, there is no need to detect changes in the outside air pressure. However, there is a risk that the pressure sensor may be damaged due to a sudden change in the external air pressure due to a drop of the pressure sensor or the like. According to the pressure sensor and the pressure sensor driving method according to each aspect of the present invention, when the pressure sensor is not used as a pressure sensor, such as during transportation, the opening of the cavity is kept open. The pressure inside and outside air can be the same. As a result, the displacement of the pressure receiving portion does not fluctuate at all, and damage to the pressure sensor can be prevented.

Also, when driving as a pressure sensor, that is, when detecting fluctuations in the outside air pressure, by closing the cavity opening, even if the fluctuations in the outside air pressure are minute, a pressure difference from the pressure inside the cavity can be generated. , highly sensitive detection becomes possible. That is, it is possible to provide a pressure sensor and a method for driving the pressure sensor which are not damaged even when a sudden change in atmospheric pressure occurs and which can perform highly sensitive measurements.

In this specification, directional terms such as front-back, left-right, up-down, and horizontal are used to describe embodiments of the present invention. Accordingly, these terms used to describe the specification of the present invention should be interpreted relative to the device of the present invention.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments and their modifications. Configuration additions, omissions, substitutions, and other changes are possible without departing from the scope of the present invention. Moreover, the present invention is not limited by the foregoing description, but only by the scope of the appended claims.

1, 51, 61 pressure sensor (differential pressure sensor, sensor module)
2 sensor substrate 3, 53, 63 cavity housing (cavity)
4 outside air 5 cavity interior 6 pressure receiving part (cantilever)
6a displacement detection resistor (displacement detection part, piezoresistive part)
7, 57, 67 cavity opening 7a hinge 10 SOI substrate 12 silicon support layer 13 insulating layer 14 silicon active layer 15 external electrode 20 gap 24 atmospheric pressure of outside air 4 (pressure fluctuation)
25 Air pressure inside the cavity 5 (air pressure fluctuation)
26 Displacement of pressure receiving portion 6 30 Through hole 34 Air pressure of outside air 4 (air pressure fluctuation)
35 Air pressure inside the cavity 5 (air pressure fluctuation)
36 Displacement of pressure receiving portion 6 40 Opening of cavity opening 44 Air pressure of outside air 4 (air pressure fluctuation)
45 Air pressure inside the cavity 5 (air pressure fluctuation)
46 displacement of pressure receiving unit 6 50 analog unit 52 reference resistor 53 variable resistor 54 fixed resistor 55 bridge circuit 56 amplifier 57 filter 60 microcomputer 61 A/D
62 Pressure calculator 68 Adhesive sealed bag 69 Adhesive

Claims (4)

a pressure-receiving portion that is displaced by receiving a pressure difference between the inside of the cavity and the outside air;
a displacement detection unit that detects and outputs the displacement of the pressure receiving unit;
A method of driving a pressure sensor comprising
the cavity comprises a sealable cavity opening;
opening the cavity opening when the pressure sensor is not driven;
A pressure sensor driving method, wherein the cavity opening is sealed when the pressure sensor is driven. The cavity opening is composed of a lid that can be opened and closed,
When the pressure sensor is not driven, the lid is opened to open the cavity opening,
2. The pressure sensor driving method according to claim 1 , wherein the lid is closed to seal the cavity opening when the pressure sensor is driven. The cavity opening is composed of an openable and closable slide plate,
When the pressure sensor is not driven, the slide plate is moved to open the cavity opening,
2. The pressure sensor driving method according to claim 1 , wherein when driving the pressure sensor, the slide plate is moved to seal the cavity opening. A sealing adhesive is disposed near the cavity opening,
2. The pressure sensor driving method according to claim 1 , wherein the sealed adhesive is released to seal the cavity opening before driving the pressure sensor.

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