JP2003042871A - Semiconductor pressure detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure detecting apparatus capable of reliably shifting an external device to a fail-safe mode even if a metal diaphragm is greatly bent more than a predetermined amount due to some cause and unable to accurately detect pressure. SOLUTION: The loop height of a wire W3 for detecting signals is the highest among wires W1-W3, and the wire W3 for detecting signals is located closest to a diaphragm 34. Therefore, when the diaphragm 34 is greatly bent more than a predetermined amount toward each of the wires W1-W3, the wire W3 first comes into contact with the diaphragm 34 among the wires W1-W3. Therefore, the wire W3 for detecting signals is short-circuited to a ground level, and becomes of zero potential. An electronic control circuit unit(ECU) receives the input of the zero potential, judges that it is impossible to accurately detect pressure, and shifts to a fail-safe mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure detecting device.

[0002]

2. Description of the Related Art Conventionally, as a detecting device for detecting the pressure of a fluid such as gas or liquid, the pressure received by a stainless diaphragm contacting the fluid is transferred to a silicon diaphragm of a sensor chip via a pressure transmitting medium such as an incompressible fluid. Communicate,
A semiconductor pressure detecting device for detecting with the sensor chip is known.

Generally, this type of semiconductor pressure detecting device is
A pressure transmission medium accommodating chamber is formed by a recess formed in the housing and a metal diaphragm that seals the recess, and the pressure transmission medium is filled with the pressure transfer medium while the pressure transmission medium accommodating chamber is fixed. ing. And
In the pressure transmission medium accommodating chamber, the pair of power supply electrodes of the sensor chip are connected to the corresponding power supply terminals inserted into the housing via the power supply bonding wires. That is, the operating power supply voltage is supplied to the sensor chip through the power supply bonding wire and the power supply terminal. Also,
In the pressure transmission medium accommodating chamber, the detection signal electrode of the sensor chip is connected to the detection signal terminal which is also inserted in the housing via the detection signal bonding wire. That is, the detection signal detected by the sensor chip is output to the external device via the detection signal bonding wire and the detection signal terminal.

This type of semiconductor pressure detecting device is mounted on a fuel delivery pipe of a vehicle and detects the fuel pressure in the pipe. FIG. 6 is a circuit diagram showing an equivalent circuit of the semiconductor pressure detecting device for detecting the fuel pressure of the automobile engine and a system configuration using the semiconductor pressure detecting device. In FIG. 6, the semiconductor pressure detecting device 51 including the sensor chip 50 is connected to the positive electrode terminal of the battery B via the positive power supply line L1 and connected to the negative terminal of the battery B via the negative power supply line L2. Has been done. Further, the semiconductor pressure detecting device 51 is connected to an electronic control circuit unit (ECU) 52 via a signal line L3.

More specifically, the positive power supply electrode P1 formed on the sensor chip 50 of the semiconductor pressure detecting device 51 is connected to the positive power supply bonding wire W1, the positive power supply terminal T1 and the positive power supply line L1. Connected to the positive power supply terminal of the battery B. In addition, the negative power supply electrode P formed on the sensor chip 50
2 is a negative-side power supply bonding wire W2,
It is connected to the negative power supply terminal of the battery B through the negative power supply terminal T2 and the negative power supply line L2. Further, the detection signal electrode P3 formed on the sensor chip 50 is the detection signal bonding wire W.
3, and is connected to the ECU 52 via the detection signal terminal T3 and the signal line L3.

Then, the ECU 52 inputs the detection signal output from the semiconductor pressure detection device 51 (sensor chip 50) via the signal line L3, and calculates the fuel pressure at that time based on the detection signal.

[0007]

By the way, in the semiconductor pressure detecting device 51, if the pressure transmitting medium leaks from the pressure transmitting medium housing chamber for some reason, accurate pressure detection cannot be performed and a metal diaphragm is provided. More than a certain amount, it will bend greatly. Due to the large bending of the metal diaphragm, the diaphragm may come into contact with any of the wires W1 to W3 (the diaphragm is moved toward the pressure transmission medium accommodating chamber side by a predetermined amount or more,
Bent state).

When the metal diaphragm contacts the detection signal bonding wire W3, since the metal diaphragm is grounded through the delivery pipe, the detection signal bonding wire W3 is shorted to the ground. Then, the signal line L3 becomes 0 potential, and E
A detection signal of 0 potential is input to the CU 52. In response to the 0-potential detection signal, the ECU 52 determines that accurate pressure detection cannot be performed due to leakage of the pressure transmission medium and shifts to the fail-safe mode.

On the other hand, when the metal diaphragm contacts the plus-side power supply bonding wire W1, the plus-side power supply bonding wire W1, that is, the plus power line L1 is short-circuited to the ground. At this time, as is clear from FIG. 6, the ECU 52
The power supply voltage Vc from the battery B via the positive power supply line L1
Since c is supplied, the supply of the power supply voltage Vcc is cut off due to a short circuit, which causes a problem that the detection operation and various control operations cannot be performed.

The present invention has been made in order to solve the above problems, and an object thereof is that the metal diaphragm is largely bent by a predetermined amount or more for some reason and accurate pressure detection cannot be performed. Another object of the present invention is to provide a semiconductor pressure detecting device capable of reliably shifting the external device to the fail safe mode.

[0011]

In order to solve the above-mentioned problems, the invention according to claim 1 provides a recess formed in a connector housing provided with a power supply terminal and a detection signal terminal, and the recess. A pressure transmitting medium accommodating chamber composed of a metal diaphragm to be sealed is provided with a sensor chip for detecting the pressure received by the diaphragm via the pressure transmitting medium filled in the pressure transmitting medium accommodating chamber, and the pressure transmitting medium is also provided. A power supply bonding wire connecting the power supply electrode of the sensor chip and the power supply terminal in the housing chamber, and a detection signal bonding wire connecting the detection signal electrode of the sensor chip and the detection signal terminal. In the semiconductor pressure detecting device provided with, the diaphragm is located toward the pressure transmission medium accommodating chamber side. The amount or more, when flexed, and summarized in that the detection signal bonding wire is formed so as to be in contact with the diaphragm prior to the power supply bonding wires.

According to a second aspect of the present invention, in the semiconductor pressure detecting device according to the first aspect, the detection signal bonding wire has a loop height higher than that of the power supply bonding wire. And

The invention described in claim 3 is the invention according to claim 1 or 2.
In the semiconductor pressure detecting device described in the paragraph 1, the feed amount of the bonding wire for the detection signal by the bonding device is larger than the feed amount of the bonding wire for power supply.

The invention according to claim 4 is the invention according to claim 1 or 2.
In the semiconductor pressure detecting device according to claim 1, the power supply terminal and the detection signal terminal, each of which is provided with a connection portion to which the power supply bonding wire or the detection signal bonding wire is connected, the detection signal The gist is that the distance between the electrode and the connection portion of the detection signal terminal is made larger than the distance between the power supply electrode and the connection portion of the power supply terminal.

The invention described in claim 5 is the same as in claim 1,
The gist of the semiconductor pressure detecting device according to any one of 4 is that the mounting position of the sensor chip is restricted.

The invention according to claim 6 is the same as claim 1,
In the semiconductor pressure detecting device according to any one of 4 and 5, the position of the power supply terminal or the detection signal terminal, or the position of the power supply electrode or the detection signal electrode of the sensor chip is restricted. Use as a summary.

(Operation) According to the invention described in claim 1,
When the diaphragm bends toward the pressure transmission medium accommodating chamber by a predetermined amount or more, the detection signal bonding wire comes into contact with the diaphragm before the power supply bonding wire.
For this reason, when the diaphragm bends toward the pressure transmission medium accommodating chamber side by a predetermined amount or more for some reason, the external device is not shut off first, so that the fail-safe mode can be reliably shifted.

According to the second aspect of the present invention, the detection signal bonding wire has a loop height higher than that of the power supply bonding wire. As a result, when the diaphragm bends toward the pressure transmission medium accommodating chamber side by a predetermined amount or more for some reason, the detection signal bonding wire comes into contact with the diaphragm before the power supply bonding wire. For this reason, the power supply to the external device is not cut off first, so that the fail-safe mode can be reliably achieved.

According to the third aspect of the invention, the feed amount of the detection signal bonding wire by the bonding device is set to be larger than the feed amount of the power supply bonding wire. As a result, the loop height of the detection signal bonding wire can be made higher than the loop height of the power supply bonding wire.

According to the fourth aspect of the present invention, each terminal is provided with a connection portion to which a bonding wire is connected, and the distance between the detection signal electrode and the connection portion of the detection signal terminal is determined by the power source. The distance is larger than the distance between the electrode and the connection part of the power supply terminal. As a result, the loop height of the detection signal bonding wire can be made higher than the loop height of the power supply bonding wire.

According to the fifth aspect of the invention, the loop height of each bonding wire can be adjusted by regulating the mounting position of the sensor chip. According to the invention of claim 6, the position of the power supply terminal or the detection signal terminal or the position of the power supply electrode or the detection signal electrode of the sensor chip is regulated. Thereby, the loop height of each bonding wire can be adjusted.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is embodied in a semiconductor pressure detecting device for detecting a fuel pressure in a delivery pipe of an engine will be described below with reference to FIGS. The semiconductor pressure detecting device of the present embodiment outputs a detection signal to the ECU 52 with the same circuit configuration as described in FIG.

FIG. 1 is a side sectional view of the semiconductor pressure detecting device 11. The semiconductor pressure detection device 11 includes a sensor housing 12 made of metal and a connector housing 13 made of synthetic resin. The connector housing 13 has a base end portion fitted into the sensor housing 12, and the caulking piece 12 formed on the front end side of the sensor housing 12.
a is bent inward and pressed to be assembled.
Hereinafter, in FIG. 1, the upper side on the paper surface will be referred to as the front end and the lower side will be referred to as the base end.

The connector housing 13 is made of synthetic resin, and the plus side power supply terminal T1, the minus side power supply terminal T2 and the detection signal terminal T3 (see FIGS. 2 and 3) are insert-molded. ing. And each terminal T1-T3
Of the contact piece T1a.
T3a.

A metal plate 16 that reinforces the connector housing 13 is provided at the center of the connector housing 13 in the axial direction. Connector housing 13
A frame portion 18 is formed so as to extend on the outer peripheral portion of the base end surface 17 so as to surround the base end surface 17. As shown in FIG. 2, a chip accommodating recess 19 having a rectangular cross section is provided in the center of the base end surface 17 surrounded by the frame 18. A sensor chip 20 is fixed to the bottom surface of the chip accommodating recess 19 with an adhesive. An inclined surface 21 is formed on each of four inner side surfaces of the chip storage recess 19 so that the inside becomes narrower from the opening side toward the bottom surface of the chip storage recess 19. When the sensor chip 20 is arranged and fixed on the bottom surface of the chip housing recess 19, the inclined surface 21 is arranged so that the sensor chip 20 is guided and arranged along the slope surface 21 at the center of the bottom surface of the chip housing recess 19. Is.

The other end of each of the terminals T1 to T3 projects from the base end surface 17 surrounding the chip accommodating recess 19, and the projecting portions are referred to as connection parts T1b to T3b. And
The connecting portions T1b to T3b of the terminals T1 to T3 and the sensor chip 20 fixedly mounted in the chip accommodating recess 19 are electrically connected by a bonding wire made of aluminum. More specifically, referring to FIG.
The positive power electrode P1 is formed on the left upper surface of 0,
A minus power supply electrode P2 is formed on the lower right surface, and a detection signal electrode P3 is formed on the upper right surface. On the other hand, the connection portion T1b of the positive side power supply terminal T1
Is arranged diagonally to the left below the positive power supply electrode P1, and is connected to the connection portion T2 of the negative side power supply terminal T2.
b is arranged on the lower right side of the minus power supply electrode P2, and the connecting portion T3b of the detection signal terminal T3 is arranged on the lower right side of the detection signal electrode P3.

In the present embodiment, in the state where the sensor chip 20 is fixedly mounted in the chip accommodating recess 19, the linear distance between the plus power supply electrode P1 and the connecting portion T1b of the plus side power supply terminal T1 and the minus power supply electrode P2. The straight line distance between the negative side power supply terminal T2 and the connecting portion T2b, and the detection signal electrode P3 and the detection signal terminal T
The straight line distance between the third connecting portion T3b and the connecting portion T3b is substantially the same.

Then, the positive power source electrode P1 and the connecting portion T1
A positive-side power supply bonding wire (hereinafter referred to as a positive-side wire) W1 is provided between the negative power supply electrode b and the negative power supply electrode P2 and a connecting portion T2b. A detection signal bonding wire (hereinafter referred to as a detection signal wire) W3 is connected between the detection signal electrode P3 and the connection portion T3b by a wire bonding method.

At this time, when the wires W1 to W3 are wire bonded by the wire bonding apparatus, the wire bonding is performed so that the loop heights of the wires W1 to W3 are different. More specifically, as shown in the schematic view of FIG. 4, with the surface of the sensor chip 20 as a reference,
The loop height H3 of the detection signal wire W3 is higher than the loop height H1 of the plus side wire W1. In addition,
In the present embodiment, although not shown, the negative wire W2
Has a loop height H2 equal to the loop height H1 of the plus side wire W1. Therefore, of the wires W1 to W3, the loop height of the detection signal wire W3 is the highest.

The loop height H of each wire W1 to W3
1 to H3 are adjusted by the feed amount WF of each wire W1 to W3 pulled by the bonding device at the time of wire bonding. The feed amount of the wire means each electrode P1
To P3 and the connecting portions T1b to T3b, the lengths of the wires connecting the bonding distances (the linear distances between the electrodes P1 to P3 and the connecting portions T1b to T3b) and the loop value L.
Formula regarding V WF = distance between connecting parts + LV × distance between connecting parts In the present embodiment, since the distances between the bonds are set to be substantially the same, the detection signal wire W3 is used.
The loop height H3 of the detection signal wire W3 is maximized by maximizing the loop value LV of.

On the other hand, the metal sensor housing 12
Has a screw 31 for screwing to a delivery pipe (not shown) on the outer peripheral surface of the base end portion. Further, the sensor housing 12 has a pressure introduction hole 32 formed in a central plane in a coaxial cross section and having a circular cross section. Same pressure introduction hole 3
A step-shaped sealing portion 33 is formed in an expanded manner on the tip side of 2,
A metal diaphragm 34 is airtightly joined to the sealing portion 33 together with a metal pressing member (not shown) by laser welding or the like.

When the connector housing 13 is assembled to the sensor housing 12, the concave portion surrounded by the frame portion 18 at the base end portion of the connector housing 13 is sealed by the diaphragm 34. Frame portion 18 sealed by this diaphragm 34
A recessed portion (space) surrounded by is an oil enclosure chamber 35 as a pressure transmission medium storage chamber, and the oil enclosure chamber 35 is sealed with silicone oil (not shown) as a pressure transmission medium. The silicone oil is sealed with a connector housing 13, an O-ring 36 provided on the outer periphery of the base end of the connector housing 13, a diaphragm 34, and the like.

At this time, the detection signal wire W3 has the highest loop height among the wires W1 to W3, and therefore the detection signal wire W3 is in the closest position to the diaphragm 34.

In the semiconductor pressure detecting device 11 thus constructed, the sensor housing 12 is screwed to the delivery pipe. Then, the fuel pressure in the delivery pipe is introduced into the pressure introducing hole 32, and the pressure is transmitted to the sensor chip 20 via the diaphragm 34 and the silicone-based oil,
It is detected by the sensor chip 20. Sensor chip 2
0 indicates the detected detection signal via the detection signal wire W3 and the detection signal terminal T3, and the ECU 5 shown in FIG.
Output to 2. More specifically, the detection signal terminal T3
Is connected to the ECU 52 via a signal line L3, and the detection signal detected by the sensor chip 20 is output to the ECU 52. Incidentally, the positive side power supply terminal T1 is connected to the positive terminal of the battery B via the positive power supply line L1, and the negative side power supply terminal T2 is connected to the negative power supply line L.
2 are connected to the negative terminals of the battery B via the terminals 2.

At this time, the metal sensor housing 12
Since the (diaphragm 34) is screwed to the delivery pipe and the delivery pipe is grounded, it has the same potential as the delivery pipe, that is, is grounded. on the other hand,
The sensor chip 20, the wires W1 to W3, and the terminals T1 to T3 are connected to the sensor housing 12 by a connector housing 13 made of silicone oil and synthetic resin.
Insulation is secured for the (diaphragm 34).

Next, the operation of the semiconductor pressure detecting device 11 configured as described above will be described. Now, for example, if the silicone-based oil in the oil sealing chamber 35 leaks for some reason, the sensor chip 20 cannot accurately detect the pressure. On the other hand, the diaphragm 34 has each wire W
A large amount of bending is caused toward 1 to W3 by a predetermined amount or more. At this time, since the detection signal wire W3 having the highest loop height H3 is located closest to the diaphragm 34, the detection signal wire W3 is the first wire among the wires W1 to W3.
Contacts the diaphragm 34.

Therefore, the detection signal wire W3 is immediately short-circuited to the ground level and becomes 0 potential. ECU 52
Is to input this 0 potential, judge that accurate pressure detection cannot be performed due to leakage of the pressure transmission medium, and immediately shift to the fail-safe mode to execute various controls in a state where pressure detection is not possible. Become.

As a result, of the wires W1 to W3, the positive wire W1 comes into contact with the diaphragm 34 at the very front, the power supply voltage Vcc supplied to the ECU 52 is cut off, and the ECU 52 is not shifted to the fail-safe mode.
The operation of will not stop.

According to the semiconductor pressure detecting device 11 of the above embodiment, the following features can be obtained. (1) In the present embodiment, the loop height H3 of the detection signal wire W3 among the wires W1 to W3 is set to be the highest, and the detection signal wire W3 is formed on the diaphragm 34 more than the plus side wire W1 and the minus side wire W2. I tried to be close to it. That is, when the diaphragm 34 bends by a certain amount or more for some reason, the diaphragm 34 comes into direct contact with the detection signal wire W3.

Therefore, the positive wire W1 is short-circuited,
The ECU 52 does not stop its operation without shifting to the fail-safe mode. (2) In the present embodiment, the loop height H3 of the detection signal wire W3 is maximized by maximizing the loop value of the detection signal wire W3. As a result, the detection signal wire W3 can be positioned closest to the diaphragm 34.

The above embodiment may be modified as follows. -In the said embodiment, the diaphragm 3 made from stainless steel.
Although 4 is used, a diaphragm made of another material may be used as long as it is conductive.

In the above embodiment, the oil enclosure chamber 35
Silicone oil was sealed in the sensor chip 2 as the pressure transmitting medium.
Any incompressible fluid that can be transmitted to zero can be used.

In the above embodiment, each wire W1 to W
By changing the loop value at the time of wire-bonding No. 3, the loop heights H1 to H of the respective wires W1 to W3
3 was adjusted so that the loop height H3 was the highest. Instead of this, each electrode P1 to P3 and each terminal T
By adjusting the distance between the connecting portions T1b to T3b of 1 to T3, the loop height of each wire W1 to W3 is adjusted,
The loop height H3 may be the highest. That is, when each wire is pulled out with the same loop value, the loop heights H1 to H3 become higher as the distance between the electrodes P1 to P3 and the connecting portions T1b to T3b becomes larger. Therefore, the loop height H3 of the detection signal wire W3 is increased by increasing the distance between the detection signal electrode P3 and the connecting portion T3b to the maximum.
May be the highest.

The electrodes P1 to P3 and the connecting portions T1b are
The adjustment of the distances to T3b may be performed by adjusting the positions of the electrodes P1 to P3 or the connection portions T1b to T3b. The positions of the electrodes P1 to P3 may be adjusted by adjusting the position of the sensor chip 20.

For example, as shown in FIG. 5A, when the sensor chip 20 is arranged near the lower right side of the chip housing recess 19 in the drawing, the distance between the connecting portion T1b and the plus power supply electrode P1 becomes the largest, The loop height H1 of the plus side wire W1 is the highest. On the other hand, as shown in FIG.
When the sensor chip 20 is arranged closer to the upper left side of the chip housing recess 19 in the drawing, the distance between the connection portion T3b and the detection signal electrode P3 becomes the largest, and the loop height H3 of the detection signal wire W3 becomes the largest. Therefore, when the sensor chip 20 is arranged as shown in FIG.
3 is the closest position to the diaphragm 34, and when the diaphragm 34 is bent by a certain amount or more for some reason, the diaphragm 34 comes into direct contact with the detection signal wire W3.

The position of the sensor chip 20 can be adjusted by
Alternatively, the inclined surface 21 may be formed so that the sensor chip 20 is arranged at a specific position. In addition, the sensor chip 2 is controlled by arranging the sensor chip 20 in a specific position when the sensor chip 20 is arranged in the chip accommodating recess 19 with a large degree of freedom in the position where the sensor chip 20 can be arranged.
The zero position may be adjusted.

In the above embodiment, the semiconductor pressure detecting device for detecting the fuel pressure of the engine is embodied, but the invention may be applied to a semiconductor pressure detecting device for detecting other pressures.

[0048]

As described in detail above, according to the present invention,
Even if the metal diaphragm is largely bent by a certain amount or more for some reason and accurate pressure detection cannot be performed, the external device can be reliably shifted to the fail-safe mode.

[Brief description of drawings]

FIG. 1 is an overall side sectional view of a semiconductor pressure detecting device.

FIG. 2 is a bottom view of the connector housing.

FIG. 3 is a plan view of a semiconductor pressure detection device.

FIG. 4 is a schematic diagram for explaining a bonding condition of an aluminum wire.

FIG. 5 is an explanatory view of the arrangement position of the sensor chip,
FIG. 7A is an explanatory diagram for a case where the distance between the detection signal electrode and the connection portion of the detection signal terminal is small, and FIG. 9B is for explaining a case where the distance between the detection signal electrode and the connection portion of the detection signal terminal is large.

FIG. 6 is a block diagram showing an electrical configuration of a semiconductor pressure detecting device.

[Explanation of symbols]

P1 ... Positive power supply electrode, P2 ... Negative power supply electrode, P3
... detection signal electrode, T1 ... plus side power supply terminal, T2 ... minus side power supply terminal, T3 ... detection signal terminal, W1 ... plus side power supply bonding wire, W2 ... minus side power supply bonding wire, W3 ... Bonding wire for detection signal, 11
... Semiconductor pressure detecting device, 20 ... Sensor chip, 34 ... Diaphragm, 35 ...

Continued front page    (72) Inventor Tatsuya Nakamura             1-1 Asahi-cho, Kariya city, Aichi             Machine Co., Ltd. F term (reference) 2F055 AA21 BB20 CC02 DD04 EE13                       FF45 GG22 GG43

Claims (6)

[Claims] 1. A diaphragm receives pressure in a pressure transmission medium accommodating chamber which is composed of a recess formed in a connector housing provided with a power supply terminal and a detection signal terminal and a metal diaphragm for sealing the recess. A sensor chip for detecting pressure through a pressure transmission medium filled in the pressure transmission medium accommodation chamber is provided, and a power supply for connecting the power supply electrode of the sensor chip and the power supply terminal to the pressure transmission medium accommodation chamber. In the semiconductor pressure detecting device provided with a bonding wire for use and a detection signal bonding wire for connecting the detection signal electrode of the sensor chip and the detection signal terminal, the diaphragm moves toward the pressure transmission medium accommodating chamber by a predetermined amount. As described above, when the detection signal bonding wire bends, Semiconductor pressure detecting device, characterized in that before the use the bonding wire is formed so as to contact the diaphragm. 2. The semiconductor pressure detecting device according to claim 1, wherein the detection signal bonding wire has a loop height higher than that of the power supply bonding wire. 3. The semiconductor pressure detecting device according to claim 1, wherein a feed amount of the detection signal bonding wire by the bonding device is larger than a feed amount of the power supply bonding wire. Semiconductor pressure sensing device. 4. The semiconductor pressure detecting device according to claim 1, wherein the power supply terminal and the detection signal terminal are connected to the power supply bonding wire or the detection signal bonding wire, respectively. A semiconductor pressure is provided in which a distance between the detection signal electrode and the connection portion of the detection signal terminal is larger than a distance between the power supply electrode and the connection portion of the power supply terminal. Detection device. 5. The semiconductor pressure detecting device according to claim 1, wherein the mounting position of the sensor chip is regulated. 6. The semiconductor pressure detecting device according to claim 1, wherein the power supply terminal or the detection signal terminal is located, or the power supply electrode of the sensor chip. Alternatively, the semiconductor pressure detecting device is characterized in that the position of the detection signal electrode is regulated.