A method for calibrating zero position and sensitivity of an invasive blood pressure sensor chip

Abstract

The present invention belongs to the field of production and calibration of invasive blood pressure sensor chips, and in particular to a method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip. In view of the problem that in the existing actual operation process, especially in the process of medical invasive blood pressure detection of human body, the resistance adjustment range and the resistance adjustment accuracy of a single bridge arm resistor are limited, and the bridge arm resistor is difficult to achieve perfect compensation in various use environments through the traditional method of printing thick film resistors on a carrier board and then laser adjusting the resistance, the following scheme is proposed, which includes the following steps: S1: Integrate four bridge arm resistors Ra, Rb, Rc, and Rd on an on-chip IC, and connect a pull-up resistor R1 and a pull-down resistor R2 to an off-chip power supply VDD and a ground terminal GND respectively. The present invention changes the structure of the pressure sensor and performs laser fine-tuning on the resistance on the load circuit, so that the consistency and accuracy of the pressure sensor reach a certain range.

Description

Technical Field

[0001] The invention relates to the technical field of production calibration of invasive blood pressure sensor chips, and in particular to a method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip. Background Art

[0002] Pressure sensors are indispensable in all fields of today's society. Among them, the resistance strain type pressure sensor is widely used in various industrial automatic control environments and is the most commonly used sensor in industrial practice. Its working principle is to stick the resistance strain gauge on the specific surface of the elastic element. When subjected to force, it will cause the element to produce strain changes, thereby causing changes in the resistance of the resistance strain gauge. The change in resistance is then processed by the circuit and output in the form of an electrical signal. Traditional piezoresistive pressure sensor circuits generally use Wheatstone bridge circuits, and use thick film printing technology to print the resistance paste on the carrier board. During use, the circuit is connected to an external power supply. Due to the force on the carrier board, the resistance paste printed on the carrier board will also deform, which is converted into a change in resistance. It will eventually be converted into an electrical signal through the circuit, thereby realizing the measurement of pressure. Such as Figure 1 As shown, its structure mainly consists of four varistors R with the same resistance value to form a bridge arm, and its symmetrical two ends are connected to the power supply VDD and GND respectively, and the other two symmetrical ends are connected to the output Vout+ and Vout-. In the balanced state, the two ends of Vout+ and Vout- are equal. When subjected to stress, the two resistance values ​​increase, and the pressure value can be detected by calculating the voltage difference between the two ends of the detection output. However, in the actual printing and production process of the bridge, affected by the resistance material and printing accuracy, there will be a certain error between the four resistors of the Wheatstone bridge, and with the change of the environment, especially the influence of temperature, its resistance value will become more unstable. At this time, in order to solve the deviation of the four bridge arm resistors, laser resistance adjustment is generally used to achieve the balance of the bridge arm resistors to achieve output imbalance and compensate for temperature. However, in the actual operation process, especially in the medical detection of invasive blood pressure of the human body, due to the limitations of the resistance adjustment range and resistance adjustment accuracy of a single bridge arm resistor, it is difficult to achieve perfect compensation for the bridge arm resistor in various environments of use by traditionally printing thick film resistors on the carrier board and then laser adjustment.

[0003] In view of the above problems, we found that in order to improve the accuracy of the pressure sensor and enable it to detect invasive blood pressure of the human body, its structure and processing method must be changed. We can add a circuit to the periphery of the original bridge to make the originally fixed load resistance adjustable. At the same time, with the development of semiconductor technology, pressure sensors made by the perfect combination of the piezoresistive effect of single crystal silicon and micro-machining technology came into being. They mainly use MEMS (Micro-Electro-Mechanical System) technology. The pressure sensor made of single crystal silicon generally also uses the Wheatstone bridge circuit. Its implementation principle is the combination of the piezoresistive effect and the thin plate bending theory. The measurement method also uses the Wheatstone bridge principle. The temperature coefficient of the differential output offset is compensated by bidirectional changes. Summary of the invention

[0004] The invention proposes a method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip, which solves the problem that in the existing actual operation process, especially in the medical invasive blood pressure detection process of the human body, the resistance adjustment range and adjustment accuracy of a single bridge arm resistor are limited, and the bridge arm resistor is difficult to achieve perfect compensation in various environments of use through the traditional method of printing thick film resistors on a carrier board and then laser adjusting the resistance.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip comprises the following steps:

[0007] S1: The four bridge arm resistors Ra, Rb, Rc, and Rd are integrated on the IC inside the chip, and a pull-up resistor R1 and a pull-down resistor R2 are connected to the power supply VDD and the ground terminal GND outside the chip respectively. At the same time, two parallel resistors R3 and R4 are connected to the pull-down resistor R2. The inside and outside of the chip are combined through packaging to encapsulate a complete invasive blood pressure sensor;

[0008] S2: placing multiple invasive blood pressure sensors on the fixture;

[0009] S3: The fixture is not pressurized, the invasive blood pressure sensor is not powered, and the resistance between Vout+ and Vout- is measured;

[0010] S4: adjust the resistor R3;

[0011] S5: The invasive blood pressure sensor is powered on with 6Vdc and the resistor R4 is adjusted;

[0012] S6: The invasive blood pressure sensor is powered on with 2Vdc, and the resistor R1 or the resistor R2 is adjusted by judgment;

[0013] S7: Disconnect the power supply and measure the resistance between Vout+ and Vout-;

[0014] S8: The invasive blood pressure sensor is powered on with 6Vdc, the fixture is pressurized to 300mmHg, and the resistors R1 and R2 are adjusted;

[0015] S9: Cut off the pressurization of the fixture, power on 2Vdc to the invasive blood pressure sensor, and measure the voltage value between Vout+ and GND and the voltage value between Vout- and GND;

[0016] S10: Disconnect the power supply, unload the material, and the calibration is completed.

[0017] Preferably, in S1, the four bridge arm resistors Ra, Rb, Rc, and Rd are integrated on an on-chip IC using single crystal silicon using micromachining technology, and a pull-up resistor R1 and a pull-down resistor R2 are respectively connected to the off-chip power supply VDD and the ground terminal GND, and two parallel resistors R3 and R4 are connected to the pull-down resistor R2. The on-chip and off-chip are combined through packaging to package into a complete invasive blood pressure sensor.

[0018] Preferably, the resistors R1, R2, R3 and R4 are chip fixed-value resistors or metal thick film resistors printed on a glass fiber substrate or an AL2O3 ceramic substrate.

[0019] Preferably, in S3, the fixture is not pressurized, the airway is directly connected to the outside world, there is zero pressure, the air pressure inside and outside the pressure sensor is equal, the invasive blood pressure sensor is not powered, and the resistance of Vout+ and Vout- is measured and recorded as Roi.

[0020] Preferably, in S4, VDD and GND are both disconnected, and the resistor R3 is adjusted to satisfy: the resistance between Vout+ and Vout-=(300ohm+Roi) / 2.

[0021] Preferably, in S5, the invasive blood pressure sensor is powered on with 6Vdc, and the resistor R4 is adjusted to satisfy the output differential voltage of Vout+ and Vout-: Vout+-Vout-=0V+ / -5uV.

[0022] Preferably, in S6, the invasive blood pressure sensor is powered on with 2Vdc, and the adjustment resistor R1 or the resistor R2 is determined by judgment. If the voltage value between V out+ and GND is greater than 1Vdc, the resistor R1 is adjusted, and if it is less than 1Vdc, the resistor R2 is adjusted. After adjustment, the voltage value between Vout+ and GND is recorded as V1, and the voltage value between Vout- and GND is recorded as V2. At this time, it should satisfy: (V1+V2) / 2=1V+ / -1mV.

[0023] Preferably, in S7, the power supply is disconnected and the resistance between Vout+ and Vout- is measured to be 300+ / -5ohm.

[0024] Preferably, in S8, the invasive blood pressure sensor is powered on with 6Vdc, the fixture is pressurized with 300mmHg, and the resistors R1 and R2 are adjusted so that the output differential voltage of Vout+ and Vout- satisfies: Vout+-Vout-=9mV+ / -10uV.

[0025] Preferably, in S9, the pressurization of the fixture is cut off, the invasive blood pressure sensor is powered on with 2Vdc, the voltage value between Vout+ and GND is measured and recorded as V3, and the voltage value between Vout- and GND is recorded as V4. At this time, (V3+V4) / 2=1V+ / -10mV should be satisfied.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This design provides a complete solution for the calibration of invasive blood pressure sensors. Through the calibration of the entire process, it solves the problem that the traditional pressure sensor resistance adjustment method is difficult to adjust to the required accuracy for invasive blood pressure measurement of the human body. At the same time, it solves the problem that traditional pressure sensors are easily affected by temperature fluctuations after resistance adjustment.

[0028] The present invention changes the structure of the pressure sensor and performs laser fine-tuning on the resistance on the load circuit, so that the consistency and accuracy of the pressure sensor reach a certain range. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A conventional pressure sensor circuit diagram of a method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip proposed by the present invention;

[0030] Figure 2 A circuit diagram of an invasive blood pressure sensor combined with a chip metal film resistor and a calibration method for zero position and sensitivity of an invasive blood pressure sensor chip proposed by the present invention;

[0031] Figure 3 The present invention provides a flow chart of an invasive blood pressure sensor calibration method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0033] Embodiment 1

[0034] Reference Figure 2-3A method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip comprises the following steps:

[0035] S1: The four bridge arm resistors Ra, Rb, Rc, and Rd are integrated on the IC inside the chip, and a pull-up resistor R1 and a pull-down resistor R2 are connected to the power supply VDD and the ground terminal GND outside the chip respectively. At the same time, two parallel resistors R3 and R4 are connected to the pull-down resistor R2. The inside and outside of the chip are combined through packaging to encapsulate a complete invasive blood pressure sensor;

[0036] S2: placing multiple invasive blood pressure sensors on the fixture;

[0037] S3: The fixture is not pressurized, the invasive blood pressure sensor is not powered, and the resistance between Vout+ and Vout- is measured;

[0038] S4: adjust the resistor R3;

[0039] S5: The invasive blood pressure sensor is powered on with 6Vdc and the resistor R4 is adjusted;

[0040] S6: The invasive blood pressure sensor is powered on with 2Vdc, and the resistor R1 or the resistor R2 is adjusted by judgment;

[0041] S7: Disconnect the power supply and measure the resistance between Vout+ and Vout-;

[0042] S8: The invasive blood pressure sensor is powered on with 6Vdc, the fixture is pressurized to 300mmHg, and the resistors R1 and R2 are adjusted;

[0043] S9: Cut off the pressurization of the fixture, power on 2Vdc to the invasive blood pressure sensor, and measure the voltage value between Vout+ and GND and the voltage value between Vout- and GND;

[0044] S10: Disconnect the power supply, unload the material, and the calibration is completed.

[0045] Embodiment 2

[0046] Reference Figure 2 , four bridge arm resistors are integrated on the IC using single crystal silicon using micromachining technology. In the figure, Ra, Rb, Rc, and Rd are four bridge arm resistors integrated on the chip. At the same time, in order to further improve the accuracy of the bridge arm resistors and deal with the situation of bridge arm resistor imbalance, a pull-up resistor R1 and a pull-down resistor R2 are connected to the off-chip power supply VDD and the ground terminal GND respectively. At the same time, two parallel resistors R3 and R4 are connected to the pull-down resistor R2. These four off-chip resistors can be fixed-value chip resistors or metal thick film resistors printed on a glass fiber substrate or an AL2O3 ceramic substrate. The on-chip and off-chip are combined through packaging to form a complete invasive blood pressure sensor. After the final combination, its structure is as follows Figure 2Here we explore the calibration scheme after packaging.

[0047] A method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip comprises the following steps:

[0048] S1: Before batch calibration, the following equipment must be prepared: 1. Laser resistance trimmer; 2. A fixture that matches the invasive blood pressure sensor package and is connected to an external precision gas supply and fixed on the laser resistance trimmer; 3. Resistance and voltage measuring equipment;

[0049] S2: Place multiple packaged products on the fixture;

[0050] S3: The pressure fixture is not pressurized, and the airway is directly connected to the outside world (zero pressure, the air pressure inside and outside the pressure sensor is equal);

[0051] S4: VDD and GND are disconnected, and the resistance between Vout+ and Vout- is measured and recorded as Roi;

[0052] S5: VDD and GND are both disconnected, and R3 is adjusted to satisfy: the resistance between Vout+ and Vout- = (300ohm + Roi) / 2;

[0053] S6: VDD and GND are powered on with 6Vdc, and R4 is adjusted to meet the output differential voltage of Vout+ and Vout-: Vout+-Vout-=0V+ / -5uV;

[0054] S7: VDD and GND are powered on with 2Vdc. If the voltage between Vout+ and GND is greater than 1Vdc, adjust the resistor R1. If it is less than 1Vdc, adjust the resistor R2. After adjustment, the voltage between Vout+ and GND is recorded as V1, and the voltage between Vout- and GND is recorded as V2. At this time, the following should be satisfied:

[0055] (V1+V2) / 2=1V+ / -1mV;

[0056] S8: VDD and GND are disconnected and tested. At this time, the resistance between Vout+ and Vout- should be 300+ / -5ohm;

[0057] S9: VDD and GND are powered on with 6Vdc, and the fixture is provided with 300mmHg air pressure by the air source. At the same time, the laser adjusts the resistors R1 and R2 so that the output differential voltage of Vout+ and Vout- satisfies: Vout+-Vout-=9mV+ / -10uV;

[0058] S10: Cut off the gas supply to the fixture, power on VDD and GND to 2Vdc, measure the voltage between Vout+ and GND and record it as V3, and the voltage between Vout- and GND and record it as V4. At this time, (V3+V4) / 2=1V+ / -10mV should be satisfied;

[0059] S11: Disconnect the power supply, unload the material, and the calibration is completed.

[0060] In this embodiment, the resistor R1 is 300-1000Ω, the resistor R2 is 300-1000Ω, the resistor R3 is 10-100Ω, the resistor R4 is 10-100Ω, the resistor Ra is 200-300Ω, the resistor Rb is 200-300Ω, the resistor Rc is 200-300Ω, and the resistor Rd is 200-300Ω.

[0061] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip, characterized in that: The following steps are involved: S1: The four bridge arm resistors Ra, Rb, Rc, and Rd are integrated on the IC inside the chip, and a pull-up resistor R1 and a pull-down resistor R2 are connected to the power supply VDD and the ground terminal GND outside the chip respectively. At the same time, two parallel resistors R3 and R4 are connected to the pull-down resistor R2. The inside and outside of the chip are combined through packaging to encapsulate a complete invasive blood pressure sensor; S2: placing multiple invasive blood pressure sensors on the fixture; S3: The fixture is not pressurized, the invasive blood pressure sensor is not powered, and the resistance between Vout+ and Vout- is measured; S4: adjust the resistor R3; S5: The invasive blood pressure sensor is powered on with 6Vdc and the resistor R4 is adjusted; S6: The invasive blood pressure sensor is powered on with 2Vdc, and the resistor R1 or the resistor R2 is adjusted by judgment; S7: Disconnect the power supply and measure the resistance between Vout+ and Vout-; S8: The invasive blood pressure sensor is powered on with 6Vdc, the fixture is pressurized to 300mmHg, and the resistors R1 and R2 are adjusted; S9: Cut off the pressurization of the fixture, power on 2Vdc to the invasive blood pressure sensor, and measure the voltage value between Vout+ and GND and the voltage value between Vout- and GND; S10: disconnect the power supply, unload the material, and the calibration is completed; In the S1, four bridge arm resistors Ra, Rb, Rc, and Rd are integrated on a chip IC using single crystal silicon by using micromachining technology, and a pull-up resistor R1 and a pull-down resistor R2 are connected to the power supply VDD and the ground terminal GND outside the chip respectively, and two parallel resistors R3 and R4 are connected to the pull-down resistor R2, and the inside and outside of the chip are combined by packaging to encapsulate a complete invasive blood pressure sensor; The resistors R1, R2, R3 and R4 are fixed-value chip resistors or metal thick film resistors printed on a glass fiber substrate or an AL2O3 ceramic substrate; In S3, the fixture is not pressurized, the airway is directly connected to the outside world, zero pressure, the air pressure inside and outside the pressure sensor is equal, the invasive blood pressure sensor is not powered, and the resistance between Vout+ and Vout- is measured and recorded as Roi.

2. The method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip according to claim 1, characterized in that: In S4, VDD and GND are both disconnected, and the resistor R3 is adjusted to satisfy: the resistance between Vout+ and Vout- = (300ohm + Roi) / 2.

3. The method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip according to claim 1, characterized in that: In S5, the invasive blood pressure sensor is powered on with 6Vdc, and the resistor R4 is adjusted to satisfy the output differential voltage of Vout+ and Vout-: Vout+-Vout-=0V+ / -5uV.

4. The method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip according to claim 1, characterized in that: In S6, the invasive blood pressure sensor is powered on with 2Vdc, and the resistor R1 or the resistor R2 is adjusted by judgment. If the voltage value between Vout+ and GND is greater than 1Vdc, the resistor R1 is adjusted. If it is less than 1Vdc, the resistor R2 is adjusted. After adjustment, the voltage value between Vout+ and GND is recorded as V1, and the voltage value between Vout- and GND is recorded as V2. At this time, it should satisfy: (V1+V2) / 2=1V+ / -1mV.

5. The method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip according to claim 1, characterized in that: In S7, the power supply is disconnected and the resistance between Vout+ and Vout- is measured to be 300+ / -5ohm.

6. The method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip according to claim 1, characterized in that: In S8, the invasive blood pressure sensor is powered on with 6Vdc, the fixture is pressurized with 300mmHg, and the resistors R1 and R2 are adjusted so that the output differential voltage of Vout+ and Vout- satisfies: Vout+-Vout-=9mV+ / -10uV.

7. The method for calibrating the zero position and sensitivity of an invasive blood pressure sensor chip according to claim 1, characterized in that: In S9, the pressurization of the fixture is cut off, the invasive blood pressure sensor is powered on with 2Vdc, the voltage value between Vout+ and GND is measured and recorded as V3, and the voltage value between Vout- and GND is recorded as V4. At this time, (V3+V4) / 2=1V+ / -10mV should be satisfied.

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