JP2000136976A - Pressure-detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-detecting device that can be easily adjusted. SOLUTION: The pressure-detecting device is composed of a pressure sensor 10, a constant-current circuit 20 for supplying current to the pressure sensor 10, and an amplification circuit 30 for amplifying output from the pressure sensor 10. The pressure sensor 10 is electrically disconnected from the constant- current circuit 20. At a part where the pressure sensor 10 is connected to the amplification circuit 30, lands T1 and T2 that can input and output an electric signal are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detector using a semiconductor pressure sensor which can be easily manufactured.

[0002]

2. Description of the Related Art A pressure sensor having a Wheatstone bridge circuit composed of a plurality of gauges formed of a semiconductor resistance element formed on one surface of a diaphragm, an amplifying circuit for amplifying an electric signal from the pressure sensor according to pressure, and Is known, for example, from Japanese Patent Application Laid-Open No. 8-35898.

A pressure sensor having a structure in which a gauge is buried and protected by a filler is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-311111.
No. 1993, which is hereby incorporated by reference.

In general, 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 amplifying circuit for amplifying the output.

[0005]

In such a device, the pressure sensor, the constant current circuit, and the amplifier circuit are electrically independent of each other, and after each individual adjustment, the electrical connection is performed. Although one pressure detecting device is used, it is difficult to adjust the pressure detecting device, and this adjustment is difficult even though the overall characteristics of the pressure sensor and the amplifier circuit are particularly important.

[0006]

According to the present invention, there is provided a pressure sensor comprising a Wheatstone bridge circuit comprising a plurality of gauges on one surface of a diaphragm. A constant current circuit that supplies current thereto, and a pressure detection device including an amplifier circuit that amplifies an output from the pressure sensor, wherein the pressure sensor and the constant current circuit are electrically disconnected from each other,
A connection point between the pressure sensor and the amplification circuit has a land capable of inputting and outputting an electric signal.

According to the present invention, a pressure sensor is constituted by 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. A pressure detecting device comprising an amplifier circuit for amplifying an output from the pressure sensor, wherein the pressure sensor and the constant current circuit are electrically disconnected from each other, and a connection point between the pressure sensor and the amplifier circuit. Has a land that enables an inspection signal to be supplied to the amplifier circuit in a manufacturing process.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pressure sensor 10 is constituted by a Wheatstone bridge circuit constituted by a plurality of gauges (strain gauges) R1 to R4 on one surface of a diaphragm 2a, and a constant current circuit 20 for supplying a current to the pressure sensor 10; The pressure sensor 10 and the constant current circuit 20 are electrically disconnected from each other. The connection point between the pressure sensor 10 and the amplification circuit 30 includes:
It has lands T1 and T2 that can input and output electric signals.

A pressure sensor 10 is constituted by a Wheatstone bridge circuit comprising a plurality of gauges (strain gauges) R1 to R4 on one surface of a diaphragm 2a, and a constant current circuit 20 for supplying a current to the pressure sensor 10; And an amplification circuit 30 for amplifying the output from the pressure sensor 10.
0 and the constant current circuit 20 are electrically disconnected.
At the connection point between the pressure sensor 10 and the amplifier circuit 30, there are lands T1 and T2 that enable an inspection signal to be supplied to the amplifier circuit 30 in a manufacturing process.

Thus, the adjustment can be performed while at least the pressure sensor 10 and the amplifier circuit 30 are electrically connected, and the connection step which is a post-process of the pressure sensor 10 and the amplifier circuit 30 becomes unnecessary.

In the adjustment of the amplifier circuit 30 in a state where the pressure sensor 10 is connected, the amplification factor can be adjusted by using the lands T1 and T2. Adjustment with the amplifier circuit 30 is facilitated.

[0012]

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 will be described later, a 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.

In such a pressure detecting device, initially, the pressure sensor 10 and the constant current circuit 20 are electrically independent of each other. That is, the pressure sensor 10 and the constant current circuit 2
0 is the jumper terminal J1 between the operational amplifier OP21 and the resistor R24, and the strain gauge R3 (R4) and the resistor R23.
(R23 ') and the jumper terminal J2 (J2').

The pressure sensor 10 and the amplifier circuit 30 are arranged as shown in FIG.
As shown by, the lands T1 and T2 are electrically connected from the beginning.

The pressure sensor 10 and the constant current circuit 2
After adjusting each of the amplifier circuits 30 as necessary, a probe of a test device (not shown) is connected to the lands T1 and T2 to apply a pseudo input to the amplifier circuit 30,
8 is adjusted to determine the amplification factor of the amplifier circuit 30.

Next, jumper terminals J1 and J2 (J2 ')
After electrical connection by appropriate means such as soldering,
The offset value is determined by adjusting the resistance R33.

The adjustment of the resistors R38 and R33 is performed by laser trimming, and their resistances are made smaller.

With such a configuration, adjustment as a pressure detecting device is easy, and in particular, adjustment of the pressure sensor 10 and the amplifier circuit 30 in which comprehensive characteristics are important is easy.

[0025]

According to the present invention, the adjustment can be performed while at least the pressure sensor and the amplifier circuit are electrically connected, and the connection step which is a post-process between the pressure sensor and the amplifier circuit is unnecessary. Manufacturing becomes easier.

In the adjustment of the amplifier circuit with the pressure sensor connected, the gain can be adjusted by using the land. Therefore, the adjustment between the pressure sensor and the amplifier circuit, for which the overall characteristics are important, can be adjusted. This makes it easy to simplify the manufacturing process and reduce the cost.

[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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pressure sensor 20 Constant current circuit 30 Amplification circuit R33 Offset adjustment resistance R38 Gain adjustment resistance T1, T2 Land J1, J2, J2 'Jumper terminal

Claims (2)

[Claims] 1. A pressure sensor 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 amplifier circuit for amplifying an output from the pressure sensor. In the pressure detection device, the pressure sensor and the constant current circuit are configured in an electrically disconnected state, and a connection point between the pressure sensor and the amplification circuit has a land capable of inputting and outputting an electric signal. A pressure detecting device, characterized in that: 2. A pressure sensor comprising a Wheatstone bridge circuit composed of 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 an output from the pressure sensor. In the pressure detecting device, the pressure sensor and the constant current circuit are electrically disconnected from each other, and a connection point between the pressure sensor and the amplifier circuit is configured to transmit a test signal to the amplifier circuit in a manufacturing process. A pressure detecting device having a land that can be supplied.