JP7157311B2 - Sensor output conversion circuit and sheet - Google Patents

Description

The present invention relates to a sensor output conversion circuit that converts the output of a sensor, and a seat provided with the sensor output conversion circuit.

Conventionally, there is known a device for estimating the seating posture of a seated person by mounting a pressure sensor on a seat on which the seated person sits (Patent Document 1).

JP-A-11-064131

However, in the prior art, since no circuit for changing the output characteristics of the pressure sensor is provided, the output characteristics of the pressure sensor are constant. The pressure applied to the pressure sensor varies greatly for each seated person, and there is a possibility that the pressure sensor cannot accurately detect the pressure. Specifically, for example, if the pressure sensor has output characteristics such that responsiveness is high when the pressure is small, and responsiveness decreases as the pressure increases, it is possible for a heavy occupant to sit on the seat. There is a risk that the accuracy of pressure detection by the pressure sensor will deteriorate when

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress deterioration in the detection accuracy of a physical quantity by a sensor by making it possible to change the output characteristics of the sensor.

In order to solve the above-described problems, the sensor output conversion circuit according to the present invention is built in the sensor, and between the sensor-side resistor whose resistance value changes according to the change in the physical quantity of the object to be measured, the power supply, and the ground, the above-mentioned A first resistor connected in series with a sensor-side resistor, an operational amplifier having a non-inverting input terminal connected to a wiring between the sensor-side resistor and the first resistor, and an output terminal and an inverting input terminal of the operational amplifier are connected. and a negative feedback circuit.
The first resistor includes a plurality of adjustment resistors and a switch for switching connection states of the plurality of adjustment resistors, and the switch can be switched based on a signal from a control device.

According to this configuration, the output value output from the operational amplifier can be changed by sending a signal from the control device to the switch, switching the switch, and switching the connection state of the plurality of adjustment resistors. The output characteristics can be changed, and deterioration of the detection accuracy of the physical quantity in the sensor can be suppressed.

Further, the switch may be provided for each of the plurality of adjustment resistors.

According to this, it is possible to increase the number of patterns of the resistance value of the first resistor, that is, the combined resistance value of the plurality of adjustment resistors, compared to a configuration in which the number of switches is smaller than the number of adjustment resistors.

Also, the switch may be a transistor.

According to this, the switch can be satisfactorily switched by a signal from the control device.

Also, the first resistor may be grounded.

Further, the plurality of adjusting resistors may have different resistance values.

According to this, it is possible to increase the number of patterns of the resistance value of the first resistor, that is, the combined resistance value of the plurality of adjustment resistors, compared to a configuration in which the plurality of adjustment resistors have the same resistance value.

Further, when the number of adjustment resistors is n, the resistance value of the k-th adjustment resistor among the n adjustment resistors may be a value obtained by multiplying the smallest resistance value by 2 ^k−1 . good.

According to this, since the resistance values of the plurality of adjustment resistors are shifted by two times in order from the lowest resistance value, the resistance value of the first resistor can be changed within an appropriate range.

Also, the plurality of adjustment resistors may be connected in parallel.

According to this, for example, when the switch is a transistor, the resistance value of the first resistor, that is, the resistance of the plurality of adjustment resistors, can be reduced even if the number of output ports is small compared to a configuration in which a plurality of adjustment resistors are connected in series. It is possible to increase the pattern of the combined resistance value of

Further, the number of adjustment resistors may be four.

Moreover, the resistance values of the four adjusting resistors may be 200Ω, 400Ω, 800Ω, and 1600Ω.

According to this, the resistance value of the first resistor can be changed in the range of 106 to 1600Ω.

A seat according to the present invention includes the sensor output conversion circuit, and includes a seat body having a seat surface for supporting a seated person.
The sensor is a pressure sensor arranged on the seat surface side of the seat body.

According to this, it is possible to change the output characteristics of the pressure sensor provided in the seat body, so that deterioration of the pressure detection accuracy of the pressure sensor due to the difference in the weight of the seated person can be suppressed.

According to the present invention, since it is possible to change the output characteristics of the sensor, it is possible to suppress the deterioration of the detection accuracy of the physical quantity in the sensor.

In addition, by providing a switch for each of the plurality of adjustment resistors, the resistance value of the first resistor, that is, the combined resistance value of the plurality of adjustment resistors, can be reduced compared to, for example, a configuration in which the number of switches is smaller than the number of adjustment resistors. pattern can be increased.

Moreover, by using a transistor as the switch, the switch can be satisfactorily switched by a signal from the control device.

Further, by setting the resistance values of the plurality of adjustment resistors to different values, for example, compared to a configuration in which the plurality of adjustment resistors have the same resistance value, the resistance value of the first resistor, that is, the combination of the plurality of adjustment resistors It is possible to increase the pattern of resistance values.

In addition, by setting the resistance value of the k-th adjustment resistor among the n adjustment resistors to a value obtained by multiplying the smallest resistance value by 2 ^k−1 , the resistance values of the plurality of adjustment resistors are maximized. Since the resistance value is doubled in order from the smallest resistance value, the resistance value of the first resistor can be changed within an appropriate range.

Also, by setting the resistance values of the four adjusting resistors to 200Ω, 400Ω, 800Ω, and 1600Ω, the resistance value of the first resistor can be changed within the range of 106 to 1600Ω.

Further, by applying the sensor output conversion circuit to the pressure sensor provided on the seat, it is possible to suppress the deterioration of the pressure detection accuracy of the pressure sensor due to the difference in the weight of the seated person.

It is a figure explaining the structure of the sheet|seat which concerns on one Embodiment. It is a circuit diagram showing a sensor output conversion circuit. 4 is a graph showing the relationship between the pressure applied to the pressure sensor, the output voltage, and the resistance value of the first resistor; 4 is a circuit diagram showing a form in which a plurality of adjustment resistors are connected in series; FIG. 4 is a table showing the relationship between output states of output ports and combined resistance values in the form of series connection; 4 is a table showing the relationship between output states of output ports and combined resistance values in the form of parallel connection; 4 is a graph showing the relationship between actual combined resistance values and patterns (output states of output ports) in the form of parallel connection; 4 is a graph showing the relationship between actual combined resistance values and patterns (output states of output ports) in the form of series connection;

Next, one embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the vehicle seat S of the present embodiment is an example of a seat, and is configured as a vehicle seat installed in a vehicle, for example. The vehicle seat S includes a seat body S0, a control device 100, and a sensor output conversion circuit 40 (see FIG. 2).

The seat body S0 has a seat cushion S1 and a seat back S2. The seat cushion S1 and the seat back S2 include a cushion pad 20 and an outer skin 10 covering the cushion pad 20. As shown in FIG. The cushion pad 20 is made of urethane foam or the like and supported by a frame (not shown). The skin 10 is made of synthetic leather, fabric, or the like. The outer surface of the skin 10 serves as a seat surface that supports the seated person.

A plurality of pressure sensors PS1 to PS6 are provided under the skin 10 of the seat cushion S1 and the seat back S2. The pressure sensors PS1 to PS6 are sensors that acquire measured values for specifying the motion of the seated person sitting on the seat body S0. The pressure sensors PS1 to PS6 are arranged so as to be able to detect the state of the seat surface facing the seated person seated on the seat body S0, and acquire pressure values from the seated person sitting on the seat body S0.

Each pressure sensor PS1 to PS6 is arranged on the seat surface side of the seat body S0. Specifically, each pressure sensor PS1 to PS6 is arranged between the cushion pad 20 and the outer skin 10 . Each pair of pressure sensors PS1 to PS6 are provided symmetrically with respect to the center of the vehicle seat S in the left and right direction.
Specifically, the seat cushion S1 is provided with pressure sensors PS1 to PS3. The pressure sensor PS1 and the pressure sensor PS2 are arranged at positions corresponding to the buttocks of the seated person on the seat cushion S1. The pressure sensor PS1 and the pressure sensor PS2 constitute a first cushion sensor SC1 that measures pressure from the buttocks of the seated person. The pressure sensor PS2 is arranged slightly before the pressure sensor PS1. Note that the first cushion sensor SC1 may include only one of the pressure sensor PS1 and the pressure sensor PS2.

Pressure sensor PS3 is located under the thigh of the seated person. The pressure sensor PS3 constitutes a second cushion sensor SC2 that measures the pressure value from the thighs of the seated person. The pressure sensor PS3 is located far forward from the pressure sensors PS1 and PS2.

The seat back S2 is provided with pressure sensors PS4 to PS6. The pressure sensor PS4 is provided at a position corresponding to the back of the seated person's waist. Pressure sensor PS5 is positioned slightly above pressure sensor PS4. Both the pressure sensor PS4 and the pressure sensor PS5 constitute a first back sensor SB1 that measures pressure from the waist of the seated person. Note that the first back sensor SB1 may include only one of the pressure sensor PS4 and the pressure sensor PS5.

The pressure sensor PS6 is arranged at a large distance above the pressure sensors PS4 and PS5. The pressure sensor PS6 is positioned corresponding to the upper back of the seated person. The pressure sensor PS6 constitutes a second back sensor SB2 that measures the pressure value from the upper back of the seated person.

Note that the pressure sensors PS1 to PS6 are, for example, elements whose electrical resistance changes according to external pressure, and the higher the pressure value, the higher (or lower) the voltage of the detection signal. The pressure sensors PS1 to PS6 may be, for example, pressure sensors in which the contact area between the pair of electrodes increases and the resistance value decreases as the input pressure increases, or the resistance distortion increases as the input pressure increases. It is possible to use a strain gauge or the like that increases the resistance value as the voltage increases. However, it is preferable to use a pressure-sensitive sensor because the pressure-sensitive sensor has a larger change in resistance value with respect to a pressure change than the strain gauge.

Each pressure sensor PS1 to PS6 is incorporated in a sensor output conversion circuit 40 (see FIG. 2), which will be described later, and is connected to the control device 100 via this sensor output conversion circuit 40. FIG. One sensor output conversion circuit 40 is provided for each of the plurality of pressure sensors PS1 to PS6 provided on the seat body S0.

A paint 31 is applied to the outer surface of the skin 10 at positions corresponding to the respective pressure sensors PS1 to PS6. Paint 31 is exposed to the outside of skin 10 by being applied to outer surface 10A of skin 10 . The color of the paint 31 is different from the color of the outer surface 10A of the skin 10. - 特許庁Specifically, for example, when the outer surface 10A of the skin 10 is black, the color of the paint 31 can be a color such as yellow that stands out against black.

Such paint 31 displays the positions of the pressure sensors PS1 to PS6 so that they can be visually recognized from the outside of the seat body S0 before the occupant sits on the vehicle seat S. As shown in FIG.

The control device 100 is connected to the pressure sensors PS1-PS6 so that pressure values can be obtained from the pressure sensors PS1-PS6. The control device 100 can transmit the information detected by each of the pressure sensors PS1 to PS6 to a target device such as a smart phone SP.

The control device 100 and the smartphone SP have a CPU, a ROM, a RAM, a rewritable non-volatile memory, etc. (not shown), and execute pre-stored programs. Note that the smartphone SP further includes a display DSP.

The controller 100 is connected to a short-range communication device 3A that enables short-range wireless communication such as Bluetooth (registered trademark) or Wi-Fi (registered trademark). The control device 100 can communicate with the smartphone SP via the short-range communication device 3A, and cooperates with an application installed in the smartphone SP to provide the smartphone SP with a predetermined screen and voice, and to receive input from the smartphone SP. It is possible to obtain the data

A system including the seat body S0, the control device 100, and the smartphone SP can provide, for example, a 100-meter run game on the smartphone SP. In this case, the control device 100 outputs a signal for causing the in-game character displayed on the display DSP to run by alternately raising and lowering the left and right legs of the seated person on the seat body S0.

When playing such a game, the seated person can visually recognize the position of the paint 31 applied to the seat body S0 before sitting on the seat body S0. can be easily verified. As a result, the seated person can appropriately set his/her right and left thighs on the left and right pressure sensors PS3, so that the pressure sensors PS3 can be effectively used to enjoy the game.

As shown in FIG. 2 , the sensor output conversion circuit 40 includes a sensor side resistor Rfsr, a first resistor Rm, an operational amplifier OP, and a negative feedback circuit 41 . The sensor-side resistance Rfsr is built in the pressure sensor PS1 and is a resistance whose resistance value changes according to changes in pressure as a physical quantity to be measured. In the following description, the sensor output conversion circuit 40 corresponding to the pressure sensor PS1 will be described as a representative, and the sensor output conversion circuits 40 corresponding to the other pressure sensors PS2 to PS6 have the same structure. , the description is omitted.

The first resistor Rm is connected in series with the sensor-side resistor Rfsr between the power supply EP and the ground GND. Specifically, the end of the first resistor Rm opposite to the sensor-side resistor Rfsr is connected to the ground GND, and the end of the sensor-side resistor Rfsr opposite to the first resistor Rm is connected to the power source EP. ing.

The first resistor Rm is composed of four adjusting resistors R1 to R4 and four switches SW1 to SW4 for switching connection states of these adjusting resistors R1 to R4. The four adjustment resistors R1 to R4 are connected in parallel and have different resistance values. Specifically, the resistance value of the k-th adjusting resistor among the four adjusting resistors R1 to R4 is a value obtained by multiplying the smallest resistance value by 2 ^k−1 . In this embodiment, when the adjustment resistors R1 to R4 are arranged in ascending order of resistance, the order is R1, R2, R3, and R4. Therefore, in this embodiment, the resistance value of the first adjustment resistor R1 is the smallest value, the resistance value of the second adjustment resistor R2 is twice R1, and the resistance value of the third adjustment resistor R3 is 4 times R1. The resistance value of the fourth adjustment resistor R4 is eight times that of R1. Specifically, in this embodiment, the resistance value of the first adjustment resistor R1 is 200Ω, the resistance value of the second adjustment resistor R2 is 400Ω, the resistance value of the third adjustment resistor R3 is 800Ω, and the resistance value of the fourth adjustment resistor R3 is 800Ω. The resistance value of the adjustment resistor R4 is 1600Ω.

The switches SW1 to SW4 are transistors, and can be switched based on signals from the output ports p1 to p4 of the control device 100. FIG. The switches SW1 to SW4 are provided for the four adjusting resistors R1 to R4, respectively. Specifically, the first switch SW1 is connected in series with the first adjusting resistor R1 and is connected to the ground GND. Similarly, the second switch SW2, the third switch SW3, and the fourth switch SW4 are connected in series to the corresponding second adjustment resistor R2, third adjustment resistor R3, and fourth adjustment resistor R4, respectively, and connected to the ground GND. It is connected to the.

The operational amplifier OP is an amplifier having a non-inverting input terminal (+), an inverting input terminal (-), and one output terminal. The non-inverting input terminal (+) is connected to the wiring W between the sensor-side resistor Rfsr and the first resistor Rm. An output voltage Vout output from the output terminal is fed back to the inverting input terminal (-) via the negative feedback circuit 41 and output to the control device 100 .

The negative feedback circuit 41 is a circuit that connects the output terminal and the inverting input terminal (-) of the operational amplifier OP. In this embodiment, the negative feedback circuit 41 is configured only by wiring, but the present invention is not limited to this, and the negative feedback circuit 41 may be provided with a resistor. That is, the output terminal of the operational amplifier OP may be connected to the inverting input terminal (-) via a resistor.

In the sensor output conversion circuit 40, when the control device 100 controls the power supply EP to apply the voltage Vpp to the sensor-side resistor Rfsr and the first resistor Rm that are connected in series, the voltage Vpp changes between the sensor-side resistor Rfsr and the first resistor Rm. 1 resistor Rm. As a result, the potential between the sensor-side resistor Rfsr and the first resistor Rm, that is, the voltage Vin applied to the first resistor Rm is expressed by the following equation (1).
Vin={Rm/(Rfsr+Rm)}·Vpp (1)

When this voltage Vin is input to the non-inverting input terminal (+) of the operational amplifier OP, the output voltage Vout is output to the control device 100 from the output terminal of the operational amplifier OP. Here, since the negative feedback circuit 41 consists only of wiring, the output voltage Vout is represented by the following equation (2).
Vout=Vin={Rm/(Rfsr+Rm)}·Vpp (2)

Here, the resistance value of the first resistor Rm changes to various values by switching the switches SW1 to SW4. The resistance value of the first resistor Rm is represented by the following formula (3).
Rm= ₁ /(p1/R1+p2/ _R2 +p3/R3+p4/ _R4 ) ( ₃ )
p ₁ to p ₄ : 0 or 1

Here, p ₁ to p ₄ are values indicating the output states (HIGH/LOW) of the signals output from the output ports p1 to p4 to the switches SW1 to SW4, and correspond to ON/OFF of the respective switches SW1 to SW4. ing. In this circuit, when the outputs of the output ports p1 to p4 are set to HIGH, the switches SW1 to SW4 are turned ON to connect the adjustment resistors R1 to R4 to the ground GND. Further, when the outputs of the output ports p1 to p4 are set to LOW, the switches SW1 to SW4 are turned OFF to disconnect the adjustment resistors R1 to R4 from the ground GND. In equation (3), 0 is substituted for p ₁ to p ₄ when the switches SW1 to SW4 are OFF, and 1 is substituted for them when the switches SW1 to SW4 are ON.

In the present embodiment, since each of the adjustment resistors R1 to R4 is 200Ω, 400Ω, 800Ω, and 1600Ω, the combined resistance value of the adjustment resistors R1 to R4, that is, the resistance value of the first resistor Rm, is in the range of 106 to 1600Ω. can be switched with

By switching the resistance value of the first resistor Rm in this manner, the characteristics of the output voltage Vout, which is the output value of the pressure sensor PS1, can be switched as shown in FIG. FIG. 3 is a graph in which the horizontal axis represents the pressure applied to the pressure sensor PS1 and the vertical axis represents the output voltage Vout.

From the graph of FIG. 3, in the range where the pressure applied to the pressure sensor PS1 is a small value such as 0 to F1, the larger the resistance value of the first resistor Rm, the larger the slope of the output voltage Vout. becomes higher. Further, in a range where the pressure applied to the pressure sensor PS1 is a medium value such as F1 to F2, the slope of the output voltage Vout is substantially constant regardless of the resistance value of the first resistor Rm. In the range where the pressure applied to the pressure sensor PS1 has a large value such as F2 to F3, the smaller the resistance value of the first resistor Rm, the steeper the slope of the output voltage Vout and the higher the responsiveness and resolution.

Therefore, for example, when the weight of the seated person is small, the control device 100 turns on the fourth switch SW4 and turns off the other switches SW1 to SW3 to set the resistance value of the first resistor Rm to 1600Ω. , the responsiveness of the pressure sensor PS1 can be enhanced. Further, for example, when the weight of the seated person is large, the control device 100 turns on all the switches SW1 to SW4 to set the resistance value of the first resistor Rm to 106Ω, thereby improving the responsiveness of the pressure sensor PS1. can be raised.

As described above, according to the sensor output conversion circuit 40 of the present embodiment, the following effects can be obtained.
By switching the connection state of the four adjustment resistors R1 to R4 with the switches SW1 to SW4, the output value of the pressure sensor PS1 output from the operational amplifier OP can be changed, so the output characteristics of the pressure sensor PS1 can be changed. It is possible to suppress the deterioration of the pressure detection accuracy of the pressure sensor PS1.

Especially in this embodiment, it is possible to change the output characteristics of the pressure sensors PS1 to PS6 provided on the seat body S0 used as a controller for operating the in-game character displayed on the smartphone SP. Therefore, deterioration of the pressure detection accuracy of the pressure sensors PS1 to PS6 due to the difference in the weight of the seated person can be suppressed, and the same operability can be provided to various seated persons of different weights.

Since the switches SW1 to SW4 are provided for the four adjustment resistors R1 to R4, respectively, the resistance value of the first resistor Rm, that is, the four adjustment resistors, is smaller than, for example, a configuration in which the number of switches is smaller than the number of adjustment resistors. It is possible to increase the number of patterns of combined resistance values of the resistors R1 to R4.

Since the switches SW1 to SW4 are transistors, the switches SW1 to SW4 can be satisfactorily switched by signals from the control device 100. FIG.

By setting the resistance values of the four adjustment resistors R1 to R4 to different values, the resistance value of the first resistor Rm, that is, the four adjustment resistors can be reduced compared to a configuration in which the four adjustment resistors have the same resistance value, for example. The patterns of combined resistance values of R1 to R4 can be increased.

By setting the resistance value of the k-th adjustment resistor among the four adjustment resistors R1 to R4 to the value obtained by multiplying the smallest resistance value by 2 ^k−1 , the resistance values of the four adjustment resistors R1 to R4 are obtained. However, the resistance value of the first resistor can be changed within an appropriate range because the resistance value of the first resistor is shifted by two times in order from the smallest resistance value.

Since the resistance values of the four adjusting resistors R1 to R4 are set to 200Ω, 400Ω, 800Ω, and 1600Ω, the resistance value of the first resistor Rm can be changed within the range of 106 to 1600Ω.

Although the embodiments of the present invention have been described above, the present invention can be modified as appropriate and implemented as shown in other forms below. In the following description, members having substantially the same structure as those of the above-described embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

In the above embodiment, a plurality of adjustment resistors R1 to R4 are connected in parallel, but the present invention is not limited to this, and may be connected in series. For example, as shown in FIG. 4, five adjusting resistors R11 to R15 may be connected in series.

Specifically, in the form of FIG. 4, the first resistor Rm is composed of five adjustment resistors R11 to R15 and four switches SW1 to SW4 for switching the connection state of these adjustment resistors R11 to R15. The five adjustment resistors R11 to R15 are connected in series and have the same resistance value, eg, 200Ω. Specifically, the first adjustment resistor R11 is connected in series with the sensor-side resistor Rfsr, the second adjustment resistor R12 is connected in series with the first adjustment resistor R11, and the third adjustment resistor R13 is connected in series with the second adjustment resistor R13. is connected in series with a resistor R12. The fourth adjustment resistor R14 is connected in series with the third adjustment resistor R13, and the fifth adjustment resistor R15 is connected in series with the fourth adjustment resistor R14 and ground GND.

The switches SW1 to SW4 are transistors, and can be switched based on signals from the output ports p1 to p4 of the control device 100. FIG. The first switch SW1 is connected to the wiring between the first adjustment resistor R11 and the second adjustment resistor R12, and is also connected to the ground GND. The second switch SW2 is connected to the wiring between the second adjustment resistor R12 and the third adjustment resistor R13, and is also connected to the ground GND.

The third switch SW3 is connected to the wiring between the third adjustment resistor R13 and the fourth adjustment resistor R14, and is also connected to the ground GND. The fourth switch SW4 is connected to the wiring between the fourth adjustment resistor R14 and the fifth adjustment resistor R15, and is also connected to the ground GND.

In this form, the resistance value of the first resistor Rm is represented by the following equation (4).
Rm=R11+p1·[R12 ₊ p2· _{ R13+p3· ₍ R14+p4·R15)}] ( ₄ )
p ₁ to p ₄ : 0 or 1

It should be noted that the numerical values substituted for p ₁ to p ₄ in equation (4) are opposite to those in the above embodiment. That is, in equation (4), 0 is substituted for p ₁ to p ₄ when the switches SW1 to SW4 are ON, and 1 is substituted for them when the switches SW1 to SW4 are OFF. According to this embodiment, as shown in FIG. 5, the resistance of the first resistor Rm is changed according to the output state (HIGH/LOW) of the signals of the respective output ports p1 to p4, that is, the ON/OFF state of the respective switches SW1 to SW4. The value (combined resistance value) can be proportionally changed to 200Ω, 400Ω, 600Ω, 800Ω, and 1000Ω.

In the form of series connection, only five patterns of the resistance value (combined resistance value) of the first resistor Rm can be created for the four output ports p1 to p4. Also, the number of adjusting resistors must be five.

On the other hand, in the form of parallel connection, as shown in FIG. 6, 16 patterns of combined resistance values can be created for four output ports p1 to p4. More specifically, in the parallel connection mode, when the number of output ports is n, ²ⁿ patterns of combined resistance values can be created. can do a lot. Furthermore, in the form of parallel connection, only four adjustment resistors are required, and cost reduction can be achieved. In the embodiment of FIG. 6, the resistance values of the adjustment resistors R1 to R4 are different from those in the above embodiment, and the combined resistance value range is 66.7 to 1 kΩ.

However, in the form of parallel connection, there are combined resistance values that are close to each other, such as combined resistance values of 125Ω and 111Ω for patterns 9 and 10 shown in FIG. Therefore, as shown in FIG. 7, depending on the manufacturing error of the adjustment resistors R1 to R4, there is a possibility that a pattern in which the magnitude relationship of the combined resistance value is reversed may occur. Here, in FIG. 7, the graph indicated by the solid line is the graph when the manufacturing error is approximately 0, and the graph indicated by the broken line is the graph when there is the manufacturing error.

On the other hand, in the form of series connection, as shown in FIG. 5, by greatly shifting the combined resistance value of each pattern, for example, by shifting by 200Ω, as shown in FIG. Even if a manufacturing error occurs in ~R15, the magnitude relationship of the combined resistance value will not be reversed. Here, in FIG. 8, the graph indicated by the solid line is the graph when the manufacturing error is approximately 0, and the graph indicated by the broken line is the graph when there is the manufacturing error.

In the above-described embodiment, the vehicle seat S used in a vehicle such as an automobile was exemplified as a seat, but the present invention is not limited to this, and other seats such as a legless chair used indoors such as a house can be used. It may be a child, a chair, or the like.

In the above embodiment, the sensor-side resistor Rfsr is connected to the power supply EP and the first resistor Rm is connected to the ground GND. , the first resistor Rm may be connected to the power supply EP, and the sensor-side resistor Rfsr may be connected to the ground GND.

In the above embodiment, the pressure sensors PS1 to PS6 were exemplified as sensors, but the present invention is not limited to this, and the sensors are sensors having sensor-side resistance whose resistance value changes according to changes in the physical quantity to be measured. Any sensor may be used. For example, the sensor may be a temperature sensor having a sensor-side resistance whose resistance value changes according to changes in temperature.

In the above embodiment, the number of adjustment resistors R1 to R4 is four, but the present invention is not limited to this. good too. Also, the number of switches may be appropriately changed according to the number of adjustment resistors. Also, the resistance values of the adjusting resistors R1 to R4 can be arbitrarily set. If the number of adjustment resistors is n, the resistance value of the k-th adjustment resistor among the n adjustment resistors may be set to a value obtained by multiplying the smallest resistance value by 2 ^k−1 . Here, k: 1 to n.

Also, the plurality of adjusting resistors may be connected in series, or may be connected in a combination of series and parallel.

In the above embodiment, the switches SW1 to SW4 are composed of transistors, but the present invention is not limited to this, and may be composed of any switch that can be switched based on a signal from the control device. For example, ICs of relays, FETs, and digital circuits (AND circuits, OR circuits, and XOR circuits) may be used as switches.

Each element described in the above embodiment and modifications may be implemented in any combination.

40 Sensor output conversion circuit 41 Negative feedback circuit 100 Control device EP Power supply GND Ground OP Operational amplifier PS1 to PS6 Pressure sensor R1 to R4 Adjustment resistor Rfsr Sensor side resistor Rm First resistor SW1 to SW4 Switch

Claims (8)

A sensor-side resistance that is built into the sensor and whose resistance value changes according to changes in the physical quantity to be measured;
a first resistor connected in series with the sensor-side resistor between a power supply and ground;
an operational amplifier in which wiring between the sensor-side resistor and the first resistor is connected to a non-inverting input terminal;
A sensor output conversion circuit comprising a negative feedback circuit connecting the output terminal and the inverting input terminal of the operational amplifier,
The first resistor is
connected in parallel a plurality of adjustment resistors;
A switch for switching the connection state of the plurality of adjustment resistorsA switch provided for each of the plurality of adjustment resistorsConsists of
A plurality of adjusting resistors are each connected to ground through a switch,
The sensor output conversion circuit, wherein the switch is switchable based on a signal from a control device. A sensor-side resistance that is built into the sensor and whose resistance value changes according to changes in the physical quantity to be measured;
a first resistor connected in series with the sensor-side resistor between a power supply and ground;
an operational amplifier in which wiring between the sensor-side resistor and the first resistor is connected to a non-inverting input terminal;
A sensor output conversion circuit comprising a negative feedback circuit connecting the output terminal and the inverting input terminal of the operational amplifier,
The first resistor is
connected in series a plurality of adjustment resistors;
A switch for switching the connection state of the plurality of adjustment resistorsa plurality of switches with one end connected between each adjusting resistorConsists of
The other end of each switch is connected to ground,
The sensor output conversion circuit, wherein the switch is switchable based on a signal from a control device. 3. The sensor output conversion circuit according to claim 1, wherein said switch is a transistor. 4. The sensor output conversion circuit according to claim 1 , wherein the plurality of adjustment resistors have different resistance values. When the number of adjustment resistors is n, the resistance value of the k-th adjustment resistor among the n adjustment resistors is a value obtained by multiplying the smallest resistance value by 2 ^k−1 . 5. The sensor output conversion circuit according to claim 4 . 2. The sensor output conversion circuit according to claim 1, wherein the number of said adjustment resistors is four. 7. The sensor output conversion circuit according to claim 6 , wherein resistance values of the four adjusting resistors are 200Ω, 400Ω, 800Ω, and 1600Ω. A seat body having a seat surface that supports a seated personWhen,arranged on the seat surface side of the seat bodySENsaWhen,Sensor output conversion circuitand a controller;A seat comprising
The sensor output conversion circuit is
a sensor-side resistor that is built in the sensor and whose resistance value changes according to changes in the physical quantity to be measured;
a first resistor connected in series with the sensor-side resistor between a power supply and ground;
an operational amplifier in which wiring between the sensor-side resistor and the first resistor is connected to a non-inverting input terminal;
a negative feedback circuit connecting the output terminal and the inverting input terminal of the operational amplifier,
The first resistor is
a plurality of adjustment resistors;
A switch for switching connection states of the plurality of adjustment resistors, the switch being switchable based on a signal from the control device,
The control device is
determining whether the weight of the seated person is equal to or less than a predetermined value based on information from the sensor;
when it is determined that the weight of the seated person is equal to or less than a predetermined value, controlling the switch to set the resistance value of the first resistor to the first resistance value;
When it is determined that the weight of the seated person is not equal to or less than the predetermined value, the switch is controlled to set the resistance value of the first resistor to a second resistance value smaller than the first resistance value.A sheet characterized by:

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