JP2000046668A - Pressure detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly accurate pressure detection device under the application of simple constitution. SOLUTION: A maximum error ΔV2 is calculated and offset voltage is adjusted so that the error ΔV2 is within G1 to G2 or G2 to G3 as an output accuracy range. As a result, an error-temperature characteristic curve shifts upward as a whole, depending on the adjusted offset voltage, and the maximum error ΔV2 as ΔVt1 or ΔVt3 falls within G1 to G2 or G2-G3 as the output accuracy range, thereby satisfying required specification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pressure detecting device using a semiconductor sensor.

[0002]

2. Description of the Related Art A pressure sensor having a bridge circuit composed of a plurality of gauges formed of semiconductor resistance elements formed on one surface of a diaphragm, an amplifier circuit for amplifying an electric signal from the pressure sensor according to pressure, Is known, for example, from JP-A-8-35898.

In such a device, the influence of the ambient temperature change of the pressure sensor is unavoidable. For example, the offset voltage-temperature characteristic indicating the difference between the measured pressure and the actual output value with respect to the design value at the zero point or the pressure sensor has FSO meaning the difference between the actual output value and the design value in the entire measurement range
(Full Scale Out-put) It is necessary to correct temperature characteristics.

[0004]

When there is no non-linearity in the pressure-output characteristic, the normal temperature shown in FIG.
It is adjusted to a predetermined value, such as the pressure-output characteristic at 5 ° C.). The cause of the error in this case is the offset error due to the offset voltage temperature characteristic and the FSO error due to the FSO temperature characteristic.
As shown in the error-temperature characteristics shown in FIG.
(ΔVt1 or ΔVt3). This maximum error ΔV1
However, if the value falls within the range of the output accuracy, the specifications are satisfied, but if the value is too large, it may be necessary to perform some kind of correction by other means.

In FIGS. 5 and 6, V1 is a pressure P
1, V2 is the output (offset voltage) at the pressure P2, and V3 is each voltage (V) of the output at the pressure P3, and has a relationship of P1 <P2 <P3 (kg / cm2). Further, T1 to T2 (= 25) to T3 are measurable temperature ranges and have a relationship of T1 <T2 <T3 (° C.), and G1 to G2 (= 0) and G2 to G3 are ranges of output accuracy. And an error G2 (mV) at T2 (° C.).

When the pressure-output characteristic has non-linearity, as shown in FIG. 7, when one side of the temperature is adjusted, a predetermined value based on the non-linearity is applied to the other side, as in the pressure-output characteristic at normal temperature (for example, 25 ° C.). ΔV, which is an error from The error components in this case are the offset voltage temperature characteristic, the FSO temperature characteristic, and the non-linearity, and the sum of these is the maximum error ΔV2 (ΔVt1 or ΔVt1 or ΔVt1) as shown in the error-temperature characteristic shown in FIG.
Vt3). If the maximum error ΔV2 is within the range of the output accuracy, the specifications are satisfied, but if the value is too large, it is necessary to perform some kind of correction by other means. May be
Generally, it is difficult to satisfy the specifications.

In FIGS. 7 and 8, numerical values are the same as in FIGS. 5 and 6, respectively. However, V1 in FIG. 7 is not the output at the pressure P1, but the value in FIG.
The output of the pressure P1 in FIG. 7 is obtained by the sum of V1 and ΔV.

As described above, when there is non-linearity (the former) as compared with the case where there is no non-linearity (the former)
Has a larger maximum error, that is, ΔV1 << ΔV2
Therefore, it is desired to take the latter measure.

[0009]

According to a first aspect of the present invention, there is provided a vehicle starting device comprising a Wheatstone bridge circuit comprising a plurality of gauges on one surface of a diaphragm. A constant current circuit that forms a pressure sensor with a strain gauge section and supplies current thereto,
A pressure detection device comprising: an amplification circuit for amplifying an output from the pressure sensor; a temperature characteristic of an offset voltage, which is an output value at a measured pressure of zero, and a temperature of an FSO, which is an output value of the pressure sensor in an entire measurement range. The offset voltage is adjusted such that the maximum error of the error-temperature characteristic due to the influence of the ambient temperature of the pressure detecting device due to the characteristic falls within a predetermined range. In particular,
A voltage equivalent to a half of the maximum error is added to the offset voltage (Claim 3), and the adjustment of the offset voltage is performed by changing an adjustment resistor provided in the amplifier circuit. (Claim 4).

According to a second aspect of the present invention, a pressure sensor is constituted by a strain gauge section comprising a Wheatstone bridge circuit constituted by a plurality of gauges on one surface of a diaphragm, and a constant current circuit for supplying a current thereto. And an amplifier circuit for amplifying the output from the pressure sensor, wherein the temperature characteristic of the offset voltage, which is the output value at the zero point of the measured pressure, and the FSO, which is the output value of the pressure sensor in the entire measurement range. Error due to the ambient temperature of the pressure detecting device due to the non-linearity of the temperature characteristics of the pressure sensor and the pressure-output characteristics of the pressure sensor.
The offset voltage is adjusted so that the maximum error of the temperature characteristic falls within a predetermined range. In particular, a voltage equivalent to half of the maximum error is added to the offset voltage (claim 3), and the offset voltage is adjusted by changing an adjustment resistor provided in the amplifier circuit. It is characterized in that it is performed (claim 4).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pressure detecting device is a pressure sensor 10 according to the present invention.
And a constant current circuit 20 for supplying a current to the pressure sensor 10
And an amplifier circuit 30 for amplifying the output from the pressure sensor 10.

The maximum error ΔV2 of the pressure sensor 10 is calculated, and G1 to G2 or G2 to G3 within the range of the output accuracy.
The offset voltage V2 ′ is adjusted so as to fall within the range.

As a result, the error-temperature characteristics are shifted upward as a whole, and the maximum error ΔV2 falls within the range of G1 to G2 or G2 to G3 within the range of the output accuracy, so that the specifications can be easily satisfied. it can.

Although this is effective as a means for satisfying specifications when the pressure sensor 10 has non-linearity, it can be similarly applied when there is no non-linearity. In that case, The error can be suppressed smaller than in the conventional example, and a more accurate pressure detecting device can be provided.

The value added to the offset voltage is ΔV2 / 2
Not only is it necessary to adjust the offset voltage so that the maximum error of the error-temperature characteristic falls within a predetermined range, but when adjusting the offset voltage V2 ′, the maximum error Δ
It is desirable to add half of V2 to make V2 ′ = V2 + ΔV2 / 2, so that the initial characteristics are not significantly impaired.

Further, such an adjustment is made by adjusting the resistance R3 of the amplifier circuit 30.
The operation is facilitated by performing the variable operation of 3.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the accompanying drawings.

FIG. 1 shows the structure of a pressure sensor 10, in which a semiconductor type strain gauge section 2 is fixed on a substrate 1 on which a circuit section (hybrid integrated circuit) described later such as an amplifier circuit is formed. The electrode formed on the strain gauge portion 2 is bonded to the electrode formed on the strain gauge portion 2 with a wire 3 such as a gold wire, the frame 4 is assembled around the strain gauge portion 2, and a filler 5 such as silicon oil is injected. Further, the lid 6 covering the upper part thereof is fixed to the frame 4.

The strain gauge section 2 has four strain gauges R1 to R4 formed on the upper surface of a strain generating section 2b of a diaphragm 2a by a semiconductor film forming technique.
As described later, the Wheatstone bridge circuit is configured so that the pressure sensor 10 outputs an electric signal corresponding to the pressure received by the strain generating unit 2b.

FIG. 2 is a circuit diagram of a pressure detecting device including the pressure sensor 10, wherein 20 is a constant current circuit, and 30 is an amplifier circuit.

The constant current circuit 20 converts the power supply voltage E into a resistor R2.
1, the voltage is divided by R22, the voltage is divided via the operational amplifier OP21, the current I is supplied by the pressure sensor 10, and the current is fed back to the operational amplifier OP21 from the middle point between the pressure sensor 10 and the resistor R23 connected in series thereto. Thus, the constant current drive is performed with the current I to the pressure sensor 10 being a constant value. The resistor R22 is a variable operational amplifier OP21.
Are the input voltage adjustment resistors. The resistances R23 and R23 are zero-offset voltage adjustment resistors of the variable pressure sensor 10. Further, a resistor R24 is connected between the output of the operational amplifier OP21 and the ground side of the resistor R23, and the resistor R24 is a variable resistor for adjusting the FSO temperature characteristic of the pressure sensor 10. The resistance R25 is equal to the resistance R2.
These resistors are connected between 3, 23 'and ground.

A resistor R26 is connected in parallel to at least one strain gauge R2 of the pressure sensor 10, and the resistor R26 is a variable resistor for adjusting the offset temperature characteristic of the pressure sensor 10. Note that the resistor R26
Is built in the pressure sensor 10 in FIG. 2, but is actually provided in the constant current circuit 20.

The amplifier circuit 30 is connected to the output side of the pressure sensor 10, and has at least a differential amplifier OP31 and a feedback resistor R31 connected to the minus terminal.
The power supply voltage divided by the resistors R32 and R33 is
It is connected to the plus terminal of the operational amplifier OP31 via. Generally, in order to suppress the influence of the temperature change of the pressure sensor 10, two operational amplifiers OP32 and OP33 and a resistor R3
5 and R36 are connected to the operational amplifiers OP32 and OP33.
Are connected to the output of the pressure sensor 10, and each minus terminal is connected by a resistor R37. And
The amplification factor adjustment resistor R38 of the amplification circuit 30 is an operational amplifier OP
32 is connected as a feedback resistor to the minus terminal.

A description will now be given of the compensation when such a configuration has nonlinearity, that is, when the maximum error is large.

In the conventional example, the offset voltage is set to a predetermined value V2 (see FIG. 7), and a maximum error ΔV2 is generated (see FIG. 8). In this embodiment, the maximum error ΔV2 is calculated. G1 to G within the range of output accuracy
The offset voltage V2 'is adjusted so as to fall within the range of G2 or G2 to G3, and desirably, to be located at the center of the output accuracy range G1 to G3. Specifically, the maximum error ΔV2
V2 ′ = V2 + ΔV2 / 2 (see FIG. 3).

As a result, the error-temperature characteristic becomes ΔV2 /
2, that is, the error G2 ′ at the temperature T2 becomes the error G2
2, the characteristic is shifted upward by ΔV2 / 2 from Δ2.
The maximum error ΔV2 that is Vt1 or ΔVt3 falls within G1 to G2 or G2 to G3 within the range of the output accuracy and can easily satisfy the specifications (see FIG. 4).

It is needless to say that the same can be applied to the case where there is no non-linearity. In this case, the error can be reduced to half of the conventional example,
A more accurate pressure detection device can be provided.

Of course, the value added to the offset voltage is ΔV
It is sufficient that the offset voltage is adjusted so that the maximum error of the error-temperature characteristic is not limited to 2/2 but falls within a predetermined range, and it is needless to say that the offset voltage is equivalent to half of the maximum error. The voltage component is a limit value that does not significantly impair the initial characteristics.

Such adjustment is performed by varying the resistance R33. Of course, the resistors R23, R2 of the constant current circuit 20
The offset voltage can be adjusted by changing 3 ′, but if the adjustment is made by the amplifier circuit 30 on the output side, the adjustment including the temperature characteristic of the amplifier circuit 30 can be made easier. The value can be changed reliably, which is convenient.

[0030]

According to the present invention, an accurate pressure detecting device can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a pressure sensor according to an embodiment of the present invention.

FIG. 2 is an overall circuit diagram of the embodiment.

FIG. 3 is a pressure-output characteristic diagram of the embodiment.

FIG. 4 is an error-temperature characteristic diagram of the embodiment.

FIG. 5 is a pressure-output characteristic diagram of a conventional example.

FIG. 6 is an error-temperature characteristic diagram of the conventional example.

FIG. 7 is a pressure-output characteristic diagram of another conventional example.

FIG. 8 is an error-temperature characteristic diagram of the conventional example.

[Explanation of symbols]

 Reference Signs List 10 pressure sensor 20 constant current circuit 30 amplifier circuit R1 to R4 strain gauge R24 FSO temperature characteristic adjustment resistor R26 offset temperature characteristic adjustment resistor R33 characteristic adjustment resistor

Claims (4)

[Claims] 1. A pressure sensor is constituted by a strain gauge section comprising a Wheatstone bridge circuit constituted by a plurality of gauges on one surface of a diaphragm, and a constant current circuit for supplying a current to the pressure sensor, and an output from the pressure sensor. In a pressure detecting device comprising an amplifying circuit for amplifying, a temperature characteristic of an offset voltage at which a measured pressure is an output value at a zero point, and an FSO which is an output value of the pressure sensor in an entire measurement range.
A pressure error adjusting unit that adjusts the offset voltage such that a maximum error of an error-temperature characteristic due to an influence of an ambient temperature of the pressure detecting device due to the temperature characteristic falls within a predetermined range. 2. A pressure sensor comprising a strain gage section comprising a Wheatstone bridge circuit comprising a plurality of gauges on one surface of a diaphragm, and a constant current circuit for supplying a current to the pressure sensor, and an output from the pressure sensor. In the pressure detecting device comprising an amplifying circuit for amplifying, a temperature characteristic of an offset voltage at which a measured pressure is an output value at a zero point, a temperature characteristic of an FSO which is an output value of an entire measurement range of the pressure sensor, and a pressure of the pressure sensor. -An error due to the influence of the ambient temperature of the pressure detection device due to having non-linearity in the output characteristics-the offset voltage is adjusted so that the maximum error of the temperature characteristics falls within a predetermined range. . 3. The method according to claim 1, wherein a voltage corresponding to a half of said maximum error is added to said offset voltage.
Or the pressure detecting device according to claim 2. 4. The pressure detection device according to claim 1, wherein the adjustment of the offset voltage is performed by changing an adjustment resistor provided in the amplifier circuit.