A pressure acquisition calibration circuit and method based on Wheatstone bridge

Abstract

The present invention provides a pressure acquisition calibration circuit and method based on a Wheatstone bridge in the technical field of pressure sensor, wherein the circuit comprises a main control chip, a power amplifier module, a Wheatstone bridge, and an output module; the main control chip, the power amplifier module, the Wheatstone bridge, and the output module are connected in sequence; the power amplifier module comprises an operational amplifier U2A, an operational amplifier U2B, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R9, a capacitor C1, a capacitor C2, and a capacitor C3; the resistor R2 is connected to the main control chip, the capacitor C2, and the pin 3 of the operational amplifier U2A; the pin 1 of the operational amplifier U2A is connected to one end of the resistor R3 and one end of the resistor R9, the pin 2u is connected to one end of the resistor R4 and the other end of the resistor R9, and the pin 8 is connected to the capacitor C1; the pin 5 of the operational amplifier U2B is connected to the other end of the resistor R3 and one end of the capacitor C3, the pin 6 is connected to one end of the resistor R1, and the pin 7 is connected to the other end of the resistor R1 and the Wheatstone bridge. The advantages of the present invention are: the pressure calibration accuracy is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and in particular to a pressure acquisition and calibration circuit and method based on a Wheatstone bridge. Background Art

[0002] Pressure sensors are widely used in industry, including aviation, aerospace, military industry, petrochemical industry, electric power, etc. With the progress of the times, the requirements for the accuracy of pressure collection are getting higher and higher.

[0003] The accuracy of pressure acquisition is determined by two aspects. One is the device offset error of the pressure acquisition circuit itself. The offset error directly determines whether the small signal provided by the pressure sensor can be accurately converted into a digital pressure value, and also reflects the accuracy range of the pressure acquisition circuit. The second is whether the excitation voltage provided to the pressure sensor is accurate enough, which affects whether the feedback voltage value itself is biased.

[0004] The excitation voltage can be corrected by using a high-precision power reference chip or actually measuring the real excitation voltage. The offset error of the pressure acquisition circuit device itself needs to be calibrated. The small voltage converted by most pressure sensors is in the range of 0 to 20mV, but it is traditionally impossible to provide a low-cost and stable supply of small voltage values ​​in this range of 0 to 20mV, which affects the pressure calibration accuracy.

[0005] Therefore, how to provide a pressure acquisition calibration circuit and method based on a Wheatstone bridge to improve the pressure calibration accuracy has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a pressure acquisition calibration circuit and method based on a Wheatstone bridge to improve the pressure calibration accuracy.

[0007] In a first aspect, the present invention provides a pressure acquisition and calibration circuit based on a Wheatstone bridge, comprising a main control chip, a power amplifier module, a Wheatstone bridge and an output module;

[0008] The main control chip, the power amplifier module, the Wheatstone bridge and the output module are connected in sequence;

[0009] The power amplifier module includes an operational amplifier U2A, an operational amplifier U2B, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R9, a capacitor C1, a capacitor C2 and a capacitor C3;

[0010] One end of the resistor R2 is connected to the main control chip, and the other end is connected to the capacitor C2 and the pin 3 of the operational amplifier U2A; the pin 1 of the operational amplifier U2A is connected to one end of the resistor R3 and one end of the resistor R9, the pin 2u is connected to one end of the resistor R4 and the other end of the resistor R9, and the pin 8 is connected to one end of the capacitor C1; the pin 5 of the operational amplifier U2B is connected to the other end of the resistor R3 and one end of the capacitor C3, the pin 6 is connected to one end of the resistor R1, and the pin 7 is connected to the other end of the resistor R1 and the Wheatstone bridge.

[0011] Further, the Wheatstone bridge includes a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a capacitor C4;

[0012] One end of the resistor R5 is connected to one end of the capacitor C4, one end of the resistor R6 and the power amplifier module, and the other end is connected to one end of the resistor R7 and the output module; one end of the resistor R8 is connected to the other end of the resistor R6 and the output module, and the other end is connected to the other end of the capacitor C4 and the other end of the resistor R7.

[0013] Furthermore, the output module includes an output interface J1, a capacitor C5 and a capacitor C6;

[0014] Pin 2 of the output interface J1 is connected to one end of the capacitor C5 and one end of the capacitor C6, pin 3 is connected to the other end of the capacitor C5 and the Wheatstone bridge, and pin 4 is connected to the other end of the capacitor C6 and the Wheatstone bridge.

[0015] Furthermore, the model of the main control chip is STM32F429ZGT6LQFP-144.

[0016] Furthermore, the operational amplifier U2A and the operational amplifier U2B are both of model TLV2316IDR.

[0017] In a second aspect, the present invention provides a pressure acquisition calibration method based on a Wheatstone bridge, comprising the following steps:

[0018] Step S1, connecting the output module to the pressure acquisition circuit to be calibrated;

[0019] Step S2, setting two calibration points based on the range of the pressure acquisition circuit, and the main control chip outputs corresponding voltage values ​​to the pressure acquisition circuit based on the calibration points;

[0020] Step S3, acquiring the first voltage output value and the second voltage output value collected by the pressure collection circuit, and collecting the first voltage actual value and the second voltage actual value output by the calibration circuit through a high-precision voltmeter;

[0021] Step S4, calculating a correction factor based on the first voltage output value, the second voltage output value, the first voltage actual value and the second voltage actual value according to a first-order function, and writing the correction factor into the pressure acquisition circuit to perform a calibration operation;

[0022] Step S5, setting a number of review points based on the measurement range, and reviewing and optimizing the correction factor based on each of the review points;

[0023] Step S6: record the calibration log in real time, and store and back up the calibration log.

[0024] Furthermore, in step S4, the correction factor is calculated based on the first voltage output value, the second voltage output value, the first voltage actual value and the second voltage actual value as follows:

[0025] Vb1=Va1*k+b;

[0026] Vb2=Va2*k+b;

[0027] Among them, Vb1 represents the actual value of the first voltage; Vb2 represents the actual value of the second voltage; Va1 represents the first voltage output value; Va2 represents the second voltage output value; k and b both represent correction factors.

[0028] Furthermore, in step S5, the review points are 1%, 10%, 20%, 50%, and 90% of the measuring range.

[0029] The advantages of the present invention are:

[0030] A main control chip, a power amplifier module, a Wheatstone bridge and an output module are set, and the main control chip, the power amplifier module, the Wheatstone bridge and the output module are connected in sequence; a rail-to-rail dual operational amplifier (op amp U2A and op amp U2B) is set through the power amplifier module for amplification to achieve twice the gain; a controllable small voltage value can be output by setting the resistance configuration of the Wheatstone bridge; common-mode interference is suppressed by capacitors C5 and C6 of the output module, so that a stable voltage acquisition value can be provided, which ultimately greatly improves the pressure calibration accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0032] Figure 1 The invention discloses a circuit principle block diagram of a pressure acquisition and calibration circuit based on a Wheatstone bridge.

[0033] Figure 2 It is a circuit diagram of the power amplifier module of the present invention.

[0034] Figure 3 It is a circuit diagram of the Wheatstone bridge of the present invention.

[0035] Figure 4 It is a circuit diagram of the output module of the present invention.

[0036] Figure 5 The present invention is a flow chart of a pressure acquisition and calibration method based on a Wheatstone bridge. DETAILED DESCRIPTION

[0037] The technical solution in the embodiment of the present application has the following general idea: a rail-to-rail dual operational amplifier is set up through the power amplifier module for amplification to achieve twice the gain; a controllable small voltage value can be output by setting the resistance configuration of the Wheatstone bridge; common-mode interference is suppressed by the capacitors C5 and C6 of the output module, and a stable voltage acquisition value can be provided to improve the pressure calibration accuracy.

[0038] Please refer to Figures 1 to 5 As shown, a preferred embodiment of a pressure acquisition and calibration circuit based on a Wheatstone bridge of the present invention includes a main control chip, a power amplifier module, a Wheatstone bridge and an output module;

[0039] The main control chip, the power amplifier module, the Wheatstone bridge and the output module are connected in sequence;

[0040] The power amplifier module includes an operational amplifier U2A, an operational amplifier U2B, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R9, a capacitor C1, a capacitor C2 and a capacitor C3;

[0041] One end of the resistor R2 is connected to the main control chip, and the other end is connected to the capacitor C2 and the pin 3 of the operational amplifier U2A; the pin 1 of the operational amplifier U2A is connected to one end of the resistor R3 and one end of the resistor R9, the pin 2u is connected to one end of the resistor R4 and the other end of the resistor R9, and the pin 8 is connected to one end of the capacitor C1; the pin 5 of the operational amplifier U2B is connected to the other end of the resistor R3 and one end of the capacitor C3, the pin 6 is connected to one end of the resistor R1, and the pin 7 is connected to the other end of the resistor R1 and the Wheatstone bridge.

[0042] The Wheatstone bridge includes a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a capacitor C4;

[0043] One end of the resistor R5 is connected to one end of the capacitor C4, one end of the resistor R6 and the power amplifier module, and the other end is connected to one end of the resistor R7 and the output module; one end of the resistor R8 is connected to the other end of the resistor R6 and the output module, and the other end is connected to the other end of the capacitor C4 and the other end of the resistor R7.

[0044] The Wheatstone bridge uses a resistance configuration of 750Ω, 12Ω and 750Ω, 10Ω, and the voltage value of S+ and S- is V=VsetOUT*[R7 / (R5+R7)-R8 / (R6+R8)]. This voltage value is provided to the pressure acquisition circuit to be calibrated for calibration. By adjusting the output value of VsetOUT, a controllable small voltage value can be obtained.

[0045] The output module includes an output interface J1, a capacitor C5 and a capacitor C6;

[0046] Pin 2 of the output interface J1 is connected to one end of the capacitor C5 and one end of the capacitor C6, pin 3 is connected to the other end of the capacitor C5 and the Wheatstone bridge, and pin 4 is connected to the other end of the capacitor C6 and the Wheatstone bridge.

[0047] The model of the main control chip is STM32F429ZGT6LQFP-144. The present invention uses its two built-in 12-bit buffered DAC channels to convert two digital signals into two analog voltage signal outputs. When its built-in BUFF is not enabled, the minimum output is 0.5mV and the maximum output is 3.299V. The redundant interfaces can expand the communication module according to the use requirements to realize the control of the host computer.

[0048] The operational amplifier U2A and the operational amplifier U2B are both TLV2316IDR models, and can output a maximum voltage of 5V.

[0049] A preferred embodiment of a pressure acquisition and calibration method based on a Wheatstone bridge of the present invention comprises the following steps:

[0050] Step S1, connecting the output module to the pressure acquisition circuit to be calibrated;

[0051] Step S2, two calibration points are set based on the range of the pressure acquisition circuit, and the main control chip outputs corresponding voltage values ​​to the pressure acquisition circuit based on the calibration points; for example, if the range is 0-10mV, the calibration points are set to 1mV and 7mV;

[0052] Step S3, acquiring the first voltage output value and the second voltage output value collected by the pressure collection circuit, and collecting the first voltage actual value and the second voltage actual value output by the calibration circuit through a high-precision voltmeter;

[0053] The model of the high-precision voltmeter can be 34461A, with a resolution of 6.5 digits, and a DCV accuracy of 0.003% RD + 0.003% FS at 100mV, which is equivalent to 10mV 30,000 accuracy, and can be calibrated to a target accuracy of 1000;

[0054] In a specific implementation, the collection of the first voltage output value, the second voltage output value, the first voltage actual value and the second voltage actual value needs to wait for a preset time to ensure the accuracy of the collection, for example, waiting for 2000mS;

[0055] Step S4, calculating a correction factor based on the first voltage output value, the second voltage output value, the first voltage actual value and the second voltage actual value according to a first-order function, and writing the correction factor into the pressure acquisition circuit to perform a calibration operation;

[0056] Step S5, setting a number of review points based on the measurement range, and reviewing and optimizing the correction factor based on each of the review points; that is, reviewing and optimizing the voltage output value and the actual voltage value based on each of the review points;

[0057] Step S6: record the calibration log in real time, store and back up the calibration log to facilitate later tracing and troubleshooting.

[0058] In step S4, the correction factor is calculated based on the first voltage output value, the second voltage output value, the first voltage actual value and the second voltage actual value as follows:

[0059] Vb1=Va1*k+b;

[0060] Vb2=Va2*k+b;

[0061] Among them, Vb1 represents the actual value of the first voltage; Vb2 represents the actual value of the second voltage; Va1 represents the first voltage output value; Va2 represents the second voltage output value; k and b both represent correction factors.

[0062] In step S5, the review points are 1%, 10%, 20%, 50%, and 90% of the measuring range.

[0063] In summary, the advantages of the present invention are:

[0064] A main control chip, a power amplifier module, a Wheatstone bridge and an output module are set, and the main control chip, the power amplifier module, the Wheatstone bridge and the output module are connected in sequence; a rail-to-rail dual operational amplifier (op amp U2A and op amp U2B) is set through the power amplifier module for amplification to achieve twice the gain; a controllable small voltage value can be output by setting the resistance configuration of the Wheatstone bridge; common-mode interference is suppressed by capacitors C5 and C6 of the output module, so that a stable voltage acquisition value can be provided, which ultimately greatly improves the pressure calibration accuracy.

[0065] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A pressure acquisition calibration circuit based on a Wheatstone bridge, characterized in that: It includes a main control chip, a power amplifier module, a Wheatstone bridge and an output module; The main control chip, the power amplifier module, the Wheatstone bridge and the output module are connected in sequence; The power amplifier module includes an operational amplifier U2A, an operational amplifier U2B, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R9, a capacitor C1, a capacitor C2 and a capacitor C3; One end of the resistor R2 is connected to the main control chip, and the other end is connected to the capacitor C2 and the pin 3 of the operational amplifier U2A; the pin 1 of the operational amplifier U2A is connected to one end of the resistor R3 and one end of the resistor R9, the pin 2u is connected to one end of the resistor R4 and the other end of the resistor R9, and the pin 8 is connected to one end of the capacitor C1; the pin 5 of the operational amplifier U2B is connected to the other end of the resistor R3 and one end of the capacitor C3, the pin 6 is connected to one end of the resistor R1, and the pin 7 is connected to the other end of the resistor R1 and the Wheatstone bridge.

2. A pressure acquisition and calibration circuit based on a Wheatstone bridge as claimed in claim 1, characterized in that: The Wheatstone bridge includes a resistor R5, a resistor R6, a resistor R7, a resistor R8 and a capacitor C4; One end of the resistor R5 is connected to one end of the capacitor C4, one end of the resistor R6 and the power amplifier module, and the other end is connected to one end of the resistor R7 and the output module; one end of the resistor R8 is connected to the other end of the resistor R6 and the output module, and the other end is connected to the other end of the capacitor C4 and the other end of the resistor R7.

3. A pressure acquisition and calibration circuit based on a Wheatstone bridge as claimed in claim 1, characterized in that: The output module includes an output interface J1, a capacitor C5 and a capacitor C6; Pin 2 of the output interface J1 is connected to one end of the capacitor C5 and one end of the capacitor C6, pin 3 is connected to the other end of the capacitor C5 and the Wheatstone bridge, and pin 4 is connected to the other end of the capacitor C6 and the Wheatstone bridge.

4. A pressure acquisition and calibration circuit based on a Wheatstone bridge as claimed in claim 1, characterized in that: The model of the main control chip is STM32F429ZGT6LQFP-144.

5. The pressure acquisition and calibration circuit based on Wheatstone bridge according to claim 1, characterized in that: The operational amplifier U2A and the operational amplifier U2B are both of TLV2316IDR.

6. A pressure acquisition calibration method based on a Wheatstone bridge, characterized in that: The method requires the use of a calibration circuit as claimed in any one of claims 1 to 5, comprising the following steps: Step S1, connecting the output module to the pressure acquisition circuit to be calibrated; Step S2, setting two calibration points based on the range of the pressure acquisition circuit, and the main control chip outputs corresponding voltage values ​​to the pressure acquisition circuit based on the calibration points; Step S3, acquiring the first voltage output value and the second voltage output value collected by the pressure collection circuit, and collecting the first voltage actual value and the second voltage actual value output by the calibration circuit through a high-precision voltmeter; Step S4, calculating a correction factor based on the first voltage output value, the second voltage output value, the first voltage actual value and the second voltage actual value according to a first-order function, and writing the correction factor into the pressure acquisition circuit to perform a calibration operation; Step S5, setting a number of review points based on the measurement range, and reviewing and optimizing the correction factor based on each of the review points; Step S6: record the calibration log in real time, and store and back up the calibration log.

7. A pressure acquisition and calibration method based on a Wheatstone bridge as claimed in claim 6, characterized in that: In step S4, the correction factor is calculated based on the first voltage output value, the second voltage output value, the first voltage actual value and the second voltage actual value as follows: Vb1=Va1*k+b; Vb2=Va2*k+b; Among them, Vb1 represents the actual value of the first voltage; Vb2 represents the actual value of the second voltage; Va1 represents the first voltage output value; Va2 represents the second voltage output value; k and b both represent correction factors.

8. A pressure acquisition and calibration method based on a Wheatstone bridge as claimed in claim 6, characterized in that: In step S5, the review points are 1%, 10%, 20%, 50%, and 90% of the measuring range.

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