Pressure sensor with built-in instrument amplifier

Abstract

The utility model discloses a pressure sensor with a built-in instrument amplifier. The pressure sensor comprises a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a charge pump U4, a plurality of resistors and a plurality of capacitors. The first resistor, the second resistor, the third resistor and the fourth resistor form a Wheatstone bridge, the signal output end of the Wheatstone bridge forms a low-pass filter through a resistor and a capacitor, and a fifth capacitor is used for filtering high-frequency noise interference of a differential input channel. And then an instrument amplifier is constructed by a first operational amplifier, a second operational amplifier and a third operational amplifier to amplify and output the pressure signal. According to the pressure sensor provided by the utility model, through integrating the instrument amplifier and the charge pump designed by three operational amplifiers in the sensor, the problems of low output voltage signal, low precision, easy interference and the like of the pressure sensor are solved, and meanwhile, the pressure sensor is simple in circuit, relatively low in cost, convenient to use and wide in application range.

Description

Technical Field

[0001] The utility model relates to the technical field related to sensors, in particular to a pressure sensor with a built-in instrument amplifier. Background Art

[0002] Pressure sensors are generally used to measure the pressure of a medium (the medium can be gas or liquid). Existing pressure sensors are based on the strain effect of a resistive strain gauge, and the changing resistance value is converted into a changing voltage signal through a Wheatstone bridge circuit. However, the converted voltage signal is extremely small, so if accurate measurement is required, it is very difficult. Utility Model Content

[0003] The purpose of the utility model is to overcome the deficiencies of the prior art and provide a pressure sensor with a built-in instrument amplifier. By integrating an instrument amplifier and a charge pump designed with three operational amplifiers inside the sensor, the problems of low output voltage signal, low accuracy, and easy interference of the pressure sensor are solved.

[0004] The purpose of the utility model is achieved through the following technical solutions: A pressure sensor with a built-in instrument amplifier, comprising a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a charge pump U4, a plurality of resistors and a plurality of capacitors;

[0005] The first resistor R1 is connected in series with the fourth resistor R4, the second resistor R2 is connected in series with the third resistor R3, and the two are connected in series and then in parallel to form a Wheatstone bridge circuit; the first parallel intersection of the Wheatstone bridge circuit is connected in parallel with the positive power supply to the third capacitor C3, the second parallel intersection is connected to the ground, the first series intersection is connected in series with the negative input terminal of the first operational amplifier U1 to the fifth resistor R5, and the second series intersection is connected in series with the positive input terminal of the second operational amplifier U2 to the sixth resistor R6;

[0006] The third pin and the fifth pin of the charge pump U4 are connected in series with the first capacitor C1, the output end of the charge pump U4 is respectively connected to the negative power supply ends of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3, and the positive power supply is connected to the input end of the charge pump U4 and the positive power supply ends of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3;

[0007] The negative input terminal of the first operational amplifier U1 is connected in parallel with the fifth resistor R5 and the fourth capacitor C4, the positive input terminal of the second operational amplifier U2 is connected in parallel with the sixth resistor R6 and the sixth capacitor C6, the negative input terminal of the first operational amplifier U1 is connected in parallel with the positive input terminal of the second operational amplifier U2, the eighth resistor R8 is connected in series between the positive input terminal of the first operational amplifier U1 and the negative input terminal of the second operational amplifier U2, and the seventh resistor R7 is connected in parallel between the positive input terminal of the first operational amplifier U1 and the output terminal of the first operational amplifier U1; the negative input terminal of the second operational amplifier U2 is connected in parallel with the output terminal of the second operational amplifier U2, the twelfth resistor R12 is connected in series between the output terminal of the first operational amplifier U1 and the negative input terminal of the third operational amplifier U3, the thirteenth resistor is connected in parallel between the negative input terminal of the third operational amplifier U3 and the output terminal of the third operational amplifier U3, the tenth resistor R10 is connected in series between the output terminal of the second operational amplifier U2 and the positive input terminal of the third operational amplifier U3, and the eleventh resistor R11 is connected in series between the positive input terminal of the third operational amplifier U3 and the ground.

[0008] The fourth resistor R4 is a high-precision resistance strain gauge, and the resistance values ​​of the first resistor R1, the second resistor R2 and the third resistor R3 are equal.

[0009] The operational amplifier is LM258 or LM358, and the charge pump U4 is TPS60400DBVR.

[0010] A second capacitor C2 is connected in series between the output terminal of the charge pump U4 and the ground terminal.

[0011] The beneficial effects of the utility model are as follows: the pressure sensor with a built-in instrument amplifier of the utility model solves the problems of low output voltage signal, low accuracy, and easy interference of the pressure sensor by integrating an instrument amplifier and a charge pump designed with three operational amplifiers inside the sensor. At the same time, the pressure sensor has a simple circuit, low cost, easy use, and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a structural diagram of the pressure sensor with a built-in instrument amplifier of the utility model. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians of the art without making creative work are within the scope of protection of the present application.

[0014] The technical solution of the utility model is further explained below in conjunction with the accompanying drawings.

[0015] like Figure 1 As shown, a pressure sensor with a built-in instrument amplifier of the utility model includes a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a charge pump U4, a plurality of resistors and a plurality of capacitors;

[0016] The first resistor R1 is connected in series with the fourth resistor R4, the second resistor R2 is connected in series with the third resistor R3, and the two are connected in series and then in parallel to form a Wheatstone bridge circuit; the first parallel intersection (point D) of the Wheatstone bridge circuit is connected in parallel with the positive power supply to the third capacitor C3, the second parallel intersection (point C) is connected to the ground, the first series intersection (point A) is connected in series with the negative input terminal of the first operational amplifier U1 to the fifth resistor R5, and the second series intersection (point B) is connected in series with the positive input terminal of the second operational amplifier U2 to the sixth resistor R6;

[0017] The third pin and the fifth pin of the charge pump U4 are connected in series with the first capacitor C1, the output end of the charge pump U4 is respectively connected to the negative power supply ends of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3, and the positive power supply VCC is respectively connected to the input end of the charge pump U4 and the positive power supply ends of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3;

[0018] The negative input terminal of the first operational amplifier U1 is connected in parallel with the fifth resistor R5 and the fourth capacitor C4, the positive input terminal of the second operational amplifier U2 is connected in parallel with the sixth resistor R6 and the sixth capacitor C6, the negative input terminal of the first operational amplifier U1 is connected in parallel with the positive input terminal of the second operational amplifier U2, the eighth resistor R8 is connected in series between the positive input terminal of the first operational amplifier U1 and the negative input terminal of the second operational amplifier U2, and the seventh resistor R7 is connected in parallel between the positive input terminal of the first operational amplifier U1 and the output terminal of the first operational amplifier U1; the negative input terminal of the second operational amplifier U2 is connected in parallel with the output terminal of the second operational amplifier U2, the twelfth resistor R12 is connected in series between the output terminal of the first operational amplifier U1 and the negative input terminal of the third operational amplifier U3, the thirteenth resistor is connected in parallel between the negative input terminal of the third operational amplifier U3 and the output terminal of the third operational amplifier U3, the tenth resistor R10 is connected in series between the output terminal of the second operational amplifier U2 and the positive input terminal of the third operational amplifier U3, and the eleventh resistor R11 is connected in series between the positive input terminal of the third operational amplifier U3 and the ground.

[0019] The fourth resistor R4 is a high-precision resistance strain gauge, and the resistance values ​​of the first resistor R1, the second resistor R2 and the third resistor R3 are equal.

[0020] The operational amplifier is LM258 or LM358, and the charge pump U4 is TPS60400DBVR. The charge pump provides a negative power supply, which can reduce the interference of power supply ripple noise on the pressure signal and improve the sensitivity of the pressure sensor.

[0021] A second capacitor C2 is connected in series between the output terminal of the charge pump U4 and the ground terminal.

[0022] All components of the utility model are inside the pressure sensor, and only communicate with other external devices through three wires: a power line, a signal line and a ground line.

Claims

1. A pressure sensor with a built-in instrument amplifier, characterized in that: It includes a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a charge pump U4, a plurality of resistors and a plurality of capacitors; The first resistor R1 is connected in series with the fourth resistor R4, the second resistor R2 is connected in series with the third resistor R3, and the two are connected in series and then in parallel to form a Wheatstone bridge circuit; the first parallel intersection of the Wheatstone bridge circuit is connected in parallel with the positive power supply to the third capacitor C3, the second parallel intersection is connected to the ground, the first series intersection is connected in series with the negative input terminal of the first operational amplifier U1 to the fifth resistor R5, and the second series intersection is connected in series with the positive input terminal of the second operational amplifier U2 to the sixth resistor R6; The third pin and the fifth pin of the charge pump U4 are connected in series with the first capacitor C1, the output end of the charge pump U4 is respectively connected to the negative power supply ends of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3, and the positive power supply is connected to the input end of the charge pump U4 and the positive power supply ends of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3; The negative input terminal of the first operational amplifier U1 is connected in parallel with the fifth resistor R5 and the fourth capacitor C4, the positive input terminal of the second operational amplifier U2 is connected in parallel with the sixth resistor R6 and the sixth capacitor C6, the negative input terminal of the first operational amplifier U1 is connected in parallel with the positive input terminal of the second operational amplifier U2, the eighth resistor R8 is connected in series between the positive input terminal of the first operational amplifier U1 and the negative input terminal of the second operational amplifier U2, and the seventh resistor R7 is connected in parallel between the positive input terminal of the first operational amplifier U1 and the output terminal of the first operational amplifier U1; the negative input terminal of the second operational amplifier U2 is connected in parallel with the output terminal of the second operational amplifier U2, the twelfth resistor R12 is connected in series between the output terminal of the first operational amplifier U1 and the negative input terminal of the third operational amplifier U3, the thirteenth resistor is connected in parallel between the negative input terminal of the third operational amplifier U3 and the output terminal of the third operational amplifier U3, the tenth resistor R10 is connected in series between the output terminal of the second operational amplifier U2 and the positive input terminal of the third operational amplifier U3, and the eleventh resistor R11 is connected in series between the positive input terminal of the third operational amplifier U3 and the ground.

2. The pressure sensor with built-in instrument amplifier according to claim 1, characterized in that: The fourth resistor R4 is a high-precision resistance strain gauge, and the resistance values ​​of the first resistor R1, the second resistor R2 and the third resistor R3 are equal.

3. The pressure sensor with built-in instrument amplifier according to claim 1, characterized in that: The operational amplifier is LM258 or LM358, and the charge pump U4 is TPS60400DBVR.

4. The pressure sensor with built-in instrument amplifier according to claim 1, characterized in that: A second capacitor C2 is connected in series between the output terminal of the charge pump U4 and the ground terminal.

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