CN116295969A - Piezoresistive sensor sensing circuit, medical catheter and medical monitoring system - Google Patents
Piezoresistive sensor sensing circuit, medical catheter and medical monitoring system Download PDFInfo
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 13
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M25/00—Catheters; Hollow probes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K15/00—Testing or calibrating of thermometers
- G01K15/005—Calibration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/025—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning with temperature compensating means
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M25/00—Catheters; Hollow probes
- A61M2025/0001—Catheters; Hollow probes for pressure measurement
- A61M2025/0002—Catheters; Hollow probes for pressure measurement with a pressure sensor at the distal end
Abstract
The application discloses a piezoresistive sensor sensing circuit, a medical catheter and a medical monitoring system. Wherein, this sensing circuit includes: the temperature measuring unit comprises a diode or an NTC resistor and is used for measuring the temperature near the piezoresistive sensor through the diode or the NTC resistor to obtain a temperature signal; a bridge unit for detecting a pressure signal in the vicinity of the piezoresistive sensor and outputting a differential voltage based on the pressure signal; and the calculation processing unit is connected with the bridge unit and the temperature measurement unit and is used for performing temperature compensation on the differential voltage based on the temperature signal so as to obtain the compensated pressure signal. The piezoresistive sensor solves the technical problem that the piezoresistive sensor in the related art is low in accuracy.
Description
Technical Field
The application relates to the field of medical instruments, in particular to a piezoresistive sensor sensing circuit, a medical catheter and a medical monitoring system.
Background
For the measurement of the pressure in the human body, the piezoresistive sensor is mostly of a piezoresistive type, and in the application process, the most important is to ensure the linearity of the piezoresistive sensor to the pressure and the calibration of the influence of the temperature on the zero point error and the full range error of the piezoresistive sensor.
Due to the manufacturing process of the sensor, some wheatstone bridge piezoresistive sensors are subject to the influence of the sensor itself on the pressure nonlinearity and the influence of the chip ambient temperature when measuring the pressure. In addition, the sensor itself has zero offset, and different zero offsets make the output of the sensor difficult to unify.
Furthermore, piezoresistive sensors in the form of a typical wheatstone bridge have zero and full scale errors that vary with temperature. If the measurement accuracy is high, it is not negligible. Moreover, existing piezoresistive sensor sensing circuits lack protection circuits against transient voltages and electrostatic discharge, and the temperature in the body cannot be measured directly by an integrated temperature sensor on the IC.
In view of the above problems, no effective solution has been proposed at present.
Disclosure of Invention
The embodiment of the application provides a piezoresistive sensor sensing circuit, a medical catheter and a medical monitoring system, which at least solve the technical problem of low accuracy of the piezoresistive sensor in the related technology.
According to one aspect of embodiments of the present application, there is provided a piezoresistive sensor sensing circuit, comprising: the temperature measuring unit comprises a diode or an NTC resistor and is used for measuring the temperature near the piezoresistive sensor through the diode or the NTC resistor to obtain a temperature signal; a bridge unit for detecting a pressure signal in the vicinity of the piezoresistive sensor and outputting a differential voltage based on the pressure signal; and the calculation processing unit is connected with the bridge unit and the temperature measurement unit and is used for performing temperature compensation on the differential voltage based on the temperature signal so as to obtain the compensated pressure signal.
According to yet another aspect of embodiments of the present application, there is also provided a medical catheter, including: a catheter body; a sensing circuit as described above.
According to yet another aspect of embodiments of the present application, there is also provided a medical monitoring system including the medical catheter described above; and the monitoring device is used for monitoring and displaying the data detected by the sensing circuit when the medical catheter is inserted into the body of the monitored object.
According to still another aspect of the embodiments of the present application, there is further provided a method for compensating a pressure signal of a piezoresistive sensor, including measuring a temperature near the piezoresistive sensor by a temperature measurement unit of the piezoresistive sensor, to obtain a temperature signal; detecting a pressure signal in the vicinity of the piezoresistive sensor by a bridge unit of the piezoresistive sensor and outputting a differential voltage based on the pressure signal; and carrying out temperature compensation on the differential voltage based on the temperature signal to obtain the compensated pressure signal.
In the embodiment of the application, the pressure signal detected by the piezoresistive sensor is compensated, so that the technical problem that the piezoresistive sensor in the related art is low in accuracy is solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:
FIG. 1 is a schematic diagram of a piezoresistive sensor sensing circuit according to an embodiment of the present application;
FIG. 2 is a schematic diagram of another piezoresistive sensor sensing circuit according to an embodiment of the present application; the alarm interrupt unit should be in the computing processing unit
FIG. 3 is a schematic diagram of a sensing circuit employing a diode to measure temperature according to an embodiment of the present application;
fig. 4 is a circuit configuration schematic diagram of a circuit protection unit according to an embodiment of the present application;
fig. 5 is a schematic circuit configuration diagram of a temperature measurement unit and a calculation processing unit employing diodes according to an embodiment of the present application;
fig. 6A is a schematic circuit diagram of a sensing circuit for measuring temperature using NTC resistance according to an embodiment of the present application;
fig. 6B is a schematic circuit configuration diagram of a temperature measurement unit and a calculation processing unit using NTC resistors according to an embodiment of the present application;
FIG. 7 is a schematic circuit diagram of a sensing circuit employing a bridge unit to measure temperature according to an embodiment of the present application;
FIG. 8A is a schematic diagram of a sensing circuit according to an embodiment of the present application;
FIG. 8B is a schematic diagram of another sensing circuit according to an embodiment of the present application;
FIG. 8C is a schematic structural view of a medical catheter according to an embodiment of the present application;
FIG. 9 is a schematic structural view of a medical monitoring system according to an embodiment of the present application;
FIG. 10 is a flow chart of a method of compensating a pressure signal of a piezoresistive sensor according to an embodiment of the application;
fig. 11 is a schematic diagram of the effect of the temperature versus pressure calibration before and after calibration according to an embodiment of the present application.
Detailed Description
In order to make the present application solution better understood by those skilled in the art, the following description will be made in detail and with reference to the accompanying drawings in the embodiments of the present application, it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.
It should be noted that the terms "first," "second," and the like in the description and claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that embodiments of the present application described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Example 1
According to an embodiment of the present application, there is provided a piezoresistive sensor sensing circuit, as shown in fig. 1, including: a temperature measuring unit 12, a bridge unit 14, a calculation processing unit 16.
The temperature measuring unit 12 comprises a diode or an NTC resistor for measuring the temperature near the piezoresistive sensor through the diode or the NTC resistor to obtain a temperature signal. The temperature measuring unit 12 may include: a diode D1, both ends of the diode D1 being connected to both ends of the calculation processing unit 16; or, the device includes a fifth resistor R5, a sixth resistor R6, or a second capacitor R7, where one end of the fifth resistor R5 is connected to the computing unit 16, the other end is connected to one end of the sixth resistor R6 and one end of the second capacitor C2, the other end of the second capacitor C2 is connected to the other end of the sixth resistor R6, and the other end of the sixth resistor R6 is connected to the computing unit 16, where the sixth resistor R6 is the NTC resistor.
And a bridge unit 14 for detecting a pressure signal in the vicinity of the piezoresistive sensor and outputting a differential voltage based on the pressure signal. The bridge unit 14 includes: a sensing unit and a fixed resistance unit. The sensing unit comprises a variable resistance element for detecting the pressure near the piezoresistive sensor and outputting a pressure signal; and the fixed resistance unit is connected with the sensing unit and used for forming a Wheatstone bridge with the variable resistance element so as to acquire the differential voltage. In one example, the variable resistive element of the sensing unit includes a first variable resistor RP1 and a second variable resistor RP2.
In some examples, the bridge unit 14 includes a tenth resistor R10 and an eleventh resistor R11, one end of the tenth resistor R10 and one end of the eleventh resistor R11 are connected in series, the other end of the tenth resistor R10 is connected to the other end of the first variable resistor RP1 via the second magnetic bead FB2, and the other end of the eleventh resistor R11 is connected to the other end of the second variable resistor RP2 via the third magnetic bead FB 3.
The calculation processing unit 16 is connected to the bridge unit 14 and the temperature measuring unit 12 for temperature compensating the differential voltage based on the temperature signal to obtain the compensated pressure signal. The calculation processing unit 16 outputs the compensated pressure signal as a proportional voltage, or as a digital output in the send protocol, or as PWM, or as I2C.
The second port of the computing unit 16 is grounded, the first port is connected to a power supply, the fourth port is connected to one end of the bridge unit 14 through a fourth resistor R4 and a third resistor R3, the sixth port is connected to the other end of the bridge unit 14 through a ninth resistor R9 and an eighth resistor R8, and the fifth port is connected to a power supply port of the bridge unit 14 through a second resistor R2 and a first resistor R1.
The calculation processing unit 16 can also calibrate the pressure and zero offset of the piezoresistive sensor to obtain the compensation relationship; and then, based on the compensation relation and the differential voltage, compensating zero point errors and full range errors of the piezoresistive sensor along with temperature changes.
For example, calibrating the piezoresistive sensor at a known temperature and pressure to obtain a pressure-to-bridge influence coefficient, a temperature-to-sensitivity influence coefficient, a zero offset influence coefficient, and a pressure linearity influence coefficient; zero offset compensation, linear compensation and the temperature compensation are performed on the differential voltage based on the pressure-to-bridge influence coefficient, the temperature-to-sensitivity influence coefficient, the zero offset influence coefficient, and the pressure linearity influence coefficient. Wherein the pressure-to-bridge influence factor comprises at least one of: initial sensitivity Gain of the bridge unit at unit pressure A The method comprises the steps of carrying out a first treatment on the surface of the The temperature-to-sensitivity influence coefficient includes at least one of: temperature coefficient TC of sensitivity of the bridge unit gain Temperature quadratic coefficient SOT of sensitivity of the bridge unit tcg The method comprises the steps of carrying out a first treatment on the surface of the The zero offset influence coefficient includes at least one of: compensation B for bridge deflection of the piezoresistive sensor after calibration shift Offset zero error of the original measured reading of the bridge unit B Temperature coefficient TC for the zero point offst Temperature corrected quadratic term coefficient SOT of (2) tco The method comprises the steps of carrying out a first treatment on the surface of the The coefficient of influence on the pressure linearity includes: quadratic coefficient SOT for bridge reading nonlinearity correction B 。
In one example, the computing processing unit 16 is further configured to: a first functional relationship between the pressure and the temperature of the first variable resistor is calculated from the actual value of the first variable resistor of the sensing unit 12 and a second functional relationship between the pressure and the temperature of the second variable resistor is calculated from the actual value of the second variable resistor element of the sensing unit 12 at a plurality of different temperatures and pressures. Wherein, the first function and the second function are respectively:
R 1 ＝(1+k s1 ·ΔT)·k p1 ·P+R 0 +k T1 ·ΔT (1)
R 2 ＝(1+k s2 ·ΔT)·k p2 ·P+R 0 +k T2 ·ΔT (2)
wherein R1 and R2 are the true values of the first variable resistor and the second variable resistor respectively, R 0 For initial values, e.g. resistance initial value at 25℃under standard-atmospheric pressure, k p1 、k p2 A pressure-to-resistance influence coefficient, k, representing the influence of pressure on the first and second variable resistors, respectively s1 、k s2 A temperature-to-sensitivity influence coefficient k representing the influence of temperature on the sensitivity of the first and second variable resistors, respectively T1 、k T2 The temperature-to-resistance influence coefficient indicating the influence of temperature on the resistance values of the first and second variable resistors, respectively, Δt being a temperature-to-temperature change value, and P being a pressure.
In one example, the computing processing unit may be further connected to a display unit for displaying the output compensated pressure signal on the display unit.
In one example, the computing processing unit further includes an alarm and interrupt unit for alarming and short-circuit power-off protecting the sensing circuit in case the compensated pressure signal exceeds a pressure threshold or the compensated temperature signal exceeds a temperature threshold.
In one example, the sensing circuit further includes a circuit protection unit connected to the sensing unit and the computing processing unit 16 for performing electrostatic discharge protection on the sensing unit and the computing processing unit 16.
In one example, the sensing circuit further comprises a spike interference suppression unit 11. A spike interference suppression unit 11 connected between the sensing unit and the fixed resistance unit for filtering spike interference in the pressure signal; the peak interference suppression unit 11 includes a first magnetic bead FB1, a second magnetic bead FB2, and a third magnetic bead FB3, where one end of the first magnetic bead FB1 is connected to the calculation processing unit 16 via a first resistor R1, and the other end is connected to one ends of the first variable resistor RP1 and the second variable resistor RP2, respectively.
In one example, the sensing circuit further comprises a filtering unit 13 connected before the bridge unit 14 and the calculation processing unit 16 for filtering noise in the differential voltage. For example, the filter unit 13 includes a fourth resistor R4, a ninth resistor R9, a third capacitor C3, a fourth capacitor C4, and a fifth capacitor C5, where one end of the fourth resistor R4 is connected to the calculation processing unit 16, the other end is connected to the bridge unit 14, one end of the ninth resistor R9 is connected to the calculation processing unit 16, the other end is connected to the bridge unit 14, one end of the fourth capacitor C4 is connected to the fourth resistor R4 and the calculation processing unit 16, the other end is grounded, one end of the fifth capacitor C5 is connected to the ninth resistor R9 and the calculation processing unit 16, the other end is grounded, one end of the third capacitor C3 is connected to the fourth capacitor C4, and the other end is connected to the fifth capacitor C5.
The sensing circuit provided by the embodiment can calibrate and measure the piezoresistive sensor because the sensitivity and zero output offset of the piezoresistive sensor cannot be completely unified, and can compensate pressure signals based on the temperature near the piezoresistive sensor, so that the accuracy of the piezoresistive sensor is improved.
Example 2
There is further provided, in accordance with an embodiment of the present application, a piezoresistive sensor sensing circuit applied in a medical catheter for measuring blood pressure, bladder pressure, intracranial pressure, etc., as shown in fig. 2, the sensing circuit including: a temperature measuring unit 12, a bridge unit 14, a spike interference suppression unit 11, a filtering unit 13, a calculation processing unit 16, a circuit protection unit (not shown), an alarm and interrupt unit 162, a storage unit 10.
The bridge unit 14 includes a sensing unit 142 and a fixed resistance unit 144. The sensing unit 142 is for detecting a pressure within an environment and outputting a pressure signal, and includes a first pressure sensing part having a first variable resistance element RP1 and a second pressure sensing part having a second variable resistance element RP2, the resistance values of which are changed by changes in pressure and temperature.
The fixed resistance unit 144 is used to form a complete wheatstone bridge with the front-end variable resistance elements (i.e., the first variable resistance element RP1 and the second variable resistance element RP 2). In one example, the fixed resistance unit 144 includes an eleventh resistance element and a tenth resistance element, one end of the first variable resistance element is connected to one end of the second variable resistance element, and the other end of the first variable resistance element is connected to one end of the eleventh resistance element, and the processing chip U1 is connected in parallel; the other end of the second variable resistive element is connected to one end of the tenth resistive element, and the other end of the eleventh resistive element is connected to the other end of the tenth resistive element, and is grounded.
The peak interference suppression unit 11 is connected to the sensing unit 142 and the fixed resistor unit 144. In one example, the spike suppression unit 11 includes a first magnetic bead element, a second magnetic bead element, and a third magnetic bead element, where one end of the magnetic bead is connected to the wheatstone bridge, the other end is connected to the first resistor, the second magnetic bead is connected to the first variable resistor element and the eleventh resistor element, and the third magnetic bead is connected to the second variable resistor element and the tenth resistor element.
And the filtering unit 13 is connected with the bridge unit 14 and the calculation processing unit 16 and is used for filtering noise except the pressure signal. In one example, the filtering unit 13 includes a fourth resistor element, a ninth resistor element, a third capacitor element, a fourth capacitor element, and a fifth capacitor element, where one end of the fourth resistor element is connected to the processing unit, the other end of the fourth resistor element is connected to the wheatstone bridge, one end of the ninth resistor element is connected to the processing unit, the other end of the ninth resistor element is connected to the wheatstone bridge, one end of the fourth capacitor element is connected to the fourth resistor and the processing unit, the other end of the fourth capacitor element is grounded, one end of the fifth capacitor element is connected to the fourth resistor and the processing unit, the other end of the fifth capacitor element is grounded, one end of the third capacitor element is connected to the fourth capacitor element, and one end of the third capacitor element is connected to the fifth capacitor element.
The temperature measuring unit 12 senses through an external diode or external NTC resistor and transmits the sensed temperature signal to the calculation processing unit 16. The temperature measuring unit 12 may sense through an external diode or external NTC resistor, and transmit the sensed temperature signal to the calculation processing unit 16. The diode D1 and two ends of the temperature sensing unit are connected to the calculation processing unit 16, and the calculation processing unit 16 may be a chip. In one example, the temperature measuring unit 12 includes a fifth resistive element, a sixth resistive element, a second capacitive element, and a chip U1, where one end of the fifth resistive element is connected to the chip U1, the other end is connected to the sixth resistive element and the second capacitive element, the second capacitive element is connected to the sixth resistive element, one end of the sixth resistive element is connected to the fifth resistive element, and the other end is connected to the chip U1. Wherein the sixth resistive element is an NTC thermistor element.
And a storage unit 10 storing at least a compensation coefficient including a temperature to the sensing unit, a compensation coefficient of a pressure to the sensing unit, and a sensitivity compensation coefficient of a temperature to the sensing unit.
The calculation processing unit 16 includes a processing unit and a calculation unit. The processing unit is connected with the sensing unit 142 and receives the blood pressure signal measured by the sensing unit 142 and processes the measured blood pressure signal; and a calculating unit connected to the bridge unit 14, which receives the blood pressure signal processed by the processing unit and calculates a true pressure value based on the compensation relation stored in the storage unit 10.
The second port of the processing unit is grounded, the first port is connected with a power supply, the fourth port is connected with one end of a Wheatstone bridge through a fourth resistance element and a third resistance element, the sixth port is connected with the other end of the Wheatstone bridge through a ninth resistance element and an eighth resistance element, and the fifth port is connected with a power supply port of the Wheatstone bridge through the second resistance element and the first resistance element; the processing unit comprises a low-noise preamplifier, an analog-to-digital converter and a digital signal processing circuit, and a signal passing through the digital signal processing circuit is used as an output end of the processing unit.
The circuit protection unit is connected with the sensing unit and the calculating unit and is used for electrostatic discharge protection of the circuit. The circuit protection unit comprises a chip U2, a first resistor element, a third resistor element and an eighth resistor element, wherein one end of the first resistor element is connected with the first magnetic bead element, the other end of the first resistor element is connected with a first port of the chip U2, one end of the third resistor element is connected with a second port of the chip U2, the other end of the third resistor element is connected with a Wheatstone bridge, one end of the eighth resistor element is connected with a fourth port of the chip U2, the other end of the eighth resistor element is connected with the Wheatstone bridge, a fifth port of the chip U2 is connected with a power supply, and the third port of the chip U2 is grounded.
The alarm and interrupt unit 162 alarms for exceeding the expected pressure or temperature while performing short circuit power-off protection. The alarm and interrupt unit can be programmed and configured through the inside of the chip U1, and the alarm signal can be output through the chip itself to achieve an alarm function; upon detection of a bridge short, the interrupt unit may interrupt power to the bridge.
The calculation processing unit may be connected to an external display unit that displays the measured pressure and temperature on a screen of the display unit based on the result of the calculation unit. In one example, the display unit includes a single-chip microcomputer processing module and a display screen module, and can display the measured ambient pressure and temperature at the same time. The singlechip is used for matching the signal output by the computing unit with the display numerical value of the display screen.
The storage unit 10 is provided in the calculation processing unit 16. The memory unit may be a read-only memory, a random access memory, or the like.
In this embodiment, based on the temperature measured by the temperature measuring unit, the temperature compensation is performed on the pressure signal measured by the sensing unit, so that the obtained pressure value is more accurate.
Example 3
According to an embodiment of the application, a piezoresistive sensor sensing circuit is also provided. The sensing circuit of the embodiment collects the pressure and the temperature in the human body environment through the forefront sensing unit, transmits the collected data to the calculation processing unit, processes and outputs the collected data according to the compensation relation stored by the storage unit, and finally displays the environmental pressure and the temperature on the display unit.
Fig. 3 is a schematic diagram of a sensing circuit employing a diode for temperature measurement according to an embodiment of the present application. The sensing circuit in fig. 3 may be divided into a bridge unit, a spike interference suppression unit, a filtering unit, a temperature measurement unit, a calculation processing unit, and a circuit protection unit.
The specific structure of each component will be described in detail below in conjunction with fig. 2 and 3.
The bridge unit 14 is powered by constant voltage or constant current or intermittent power through a U1.5 port, or by an external intermittent power supply, the components forming the bridge unit 14 are piezoresistors RP1 and RP2 and fixed resistors R11 and R12, and when the pressure or temperature changes, the resistance values of the variable resistors RP1 and RP2 change, so that the differential voltage of the U1.4 and U1.6 ports changes, the voltages at the two ends of the bridge are respectively input into a chip U1 through the U1.4 and U1.6, and the differential voltages acquired by the U1.4 and U1.6 are processed (including zero offset compensation, linear compensation and temperature compensation) in the U1 and then are output digitally. The resistors R4, R9 and the capacitors C3, C4 and C5 are filter resistors and capacitors. The resistors R1, R3, R8 and U2 form a discharge protection unit.
Fig. 4 is a schematic structural diagram of a circuit protection unit according to an embodiment of the present application. As shown in fig. 4, the circuit protection unit is a chip U2 in this embodiment, a fifth port of the chip U2 is connected to a power source, a third port is grounded, and the first, second, and fourth ports are respectively connected to a power supply terminal U2.1 and bridge signal collection terminals U2.2 and U2.4 of the bridge unit 14 for protecting the electrostatic discharge of the circuit.
Fig. 5 is a schematic structural diagram of the calculation processing unit 16 according to the embodiment of the present application. As shown in fig. 5, the calculation processing unit 16 is a chip U1 in the present embodiment. The chip U1 is supplied with power from an external power source, supplies power to the bridge unit 14, and processes the differential voltage signal input from the bridge unit 14. The chip U1 can measure temperature through an external temperature measuring diode, and can output the processed real pressure value through an Out port.
The storage unit may store values of compensation gain (sensitivity) of the bridge unit, zero compensation error of the bridge, temperature coefficient of the bridge sensitivity, temperature coefficient of the bridge zero, correction quadratic coefficient, and the like. In the present embodiment, the storage unit may be provided in the calculation processing unit, and in other embodiments, may be provided outside the calculation processing unit.
The calculation processing unit will be described in detail below.
Firstly, by measuring bridge output values at different temperatures and different pressures, data such as compensation gain (sensitivity) of the original measurement reading of the sensor bridge, compensation zero point error of the original measurement reading of the sensor bridge, temperature coefficient of the sensitivity of the sensor bridge and the temperature coefficient of the zero point of the sensor bridge are obtained. For example, at a reference temperature, measuring the output value changes of zero pressure and full pressure of the piezoresistive sensor, and obtaining compensation gain (sensitivity) data of the original measurement reading of the sensor bridge; the zero-point compensation error of the original measurement reading of the sensor bridge can be obtained by measuring the zero-point output of the sensor bridge; by measuring the values of the zero voltage and the full voltage at different temperatures, the temperature coefficient of the sensitivity of the sensor bridge and the like can be obtained.
After the above compensation relationship is obtained, the following correction formula based on the parabola of the piezoresistive sensor bridge can be used to compensate the differential voltage. Specifically, the formula for sensor bridge parabolic correction is:
B tem ＝Gain B ·(1+TC gain ·ΔT+SOT tcg ·ΔT 2 )·(K·U·Gain A -Offset B +TC offset ·ΔT+SOT tco ·ΔT 2 ) (3)
B＝(B tmp ·(1+|B tmp |·SOT B )+1)+B shift (4)
wherein, gain A An initial sensitivity gain for the bridge at unity pressure; u is the differential voltage is small; k is a quantization level processing coefficient of analog-to-digital conversion; b is the reading of the bridge unit of the corrected piezoresistive sensor; b (B) tmp An intermediate calculation of the readings of the bridge unit of the piezoresistive sensor; b (B) shift Compensation for bridge cell deflection generated by the piezoresistive sensor after calibration or packaging; gain B Compensation gain for raw measurement readings of bridge cells of piezoresistive sensors(sensitivity); offset (Offset) B Compensation zero error for the raw measurement reading of the bridge unit 14 of the piezoresistive sensor; TC (TC) gain A temperature coefficient of sensitivity of the bridge unit 14 being a piezoresistive sensor; TC (TC) offst The temperature coefficient of the zero point of the bridge unit 14, which is a piezoresistive sensor; SOT (SOT) tcg For TC gain Temperature correction quadratic term coefficient; SOT (SOT) tco For TC offst Temperature correction quadratic term coefficient; SOT (SOT) B For the quadratic coefficient for the nonlinear correction of the bridge readings, T represents the set base temperature and Δt represents the difference between the actual temperature and the base temperature.
In another example, another correction formula based on the S-curve of the piezoresistive sensor bridge can be used:
B tmp ＝Gain B ·(1+TC gain ·ΔT+SOT tcg ·ΔT 2 )·(K·U·Gain A -Offset B +TC offst ·ΔT+SOT tco ·ΔT 2 )+1 (5)
B＝(B tmp ·(1+B tem ·SOT B ))+B shift (6)
wherein, gain A An initial sensitivity gain for the bridge at unity pressure; p is the pressure; k (K) 1 Processing coefficients with the quantization level of analog-to-digital conversion A; b is the reading of the bridge unit of the corrected piezoresistive sensor; b (B) tmp An intermediate calculation of the readings of the bridge unit of the piezoresistive sensor; b (B) shift Compensation for bridge cell deflection generated by the piezoresistive sensor after calibration or packaging; gain B Compensation gain (sensitivity) for raw measurement readings of the bridge unit of the piezoresistive sensor; offset (Offset) B Compensating zero point errors for raw measurement readings of the bridge unit of the piezoresistive sensor; TC (TC) gain A temperature coefficient of sensitivity of the bridge unit being a piezoresistive sensor; TC (TC) offst A temperature coefficient of zero point of the bridge unit of the piezoresistive sensor; SOT (SOT) tcg For TC gain Temperature correction quadratic term coefficient; SOT (SOT) tco For TC offst Temperature correction quadratic term coefficient; SOT (SOT) B Is a quadratic coefficient for the nonlinear correction of the bridge readings.
The embodiment has the following beneficial effects:
in the embodiment, the pressure and zero offset of each piezoresistive sensor are calibrated, the compensation relation obtained after calibration is stored, and then the zero error and full-scale error which change along with the temperature of the piezoresistive sensor are compensated and stored, so that normalized output is achieved.
The embodiment can inhibit high-frequency noise and peak interference and filter the circuit, and can also perform electrostatic discharge protection on the sensing circuit.
This embodiment is capable of directly measuring the temperature near the piezoresistive sensor through an external diode or an external NTC resistor.
The sensing circuit in this embodiment can output signals in various forms (such as proportional voltage output, send protocol digital output, PWM output and I2C output) and display pressure and temperature on a screen, so that pressure and temperature information can be more conveniently known. In addition, the embodiment also provides an alarm function and an interrupt function.
Example 4
According to an embodiment of the application, a piezoresistive sensor sensing circuit is also provided. Fig. 6A is a schematic structural diagram of a sensing circuit for temperature measurement using NTC resistors according to an embodiment of the present application. The sensing circuit of fig. 6A is similar to the structure of the temperature measuring unit except for the difference of fig. 3, and thus, the other structures will not be described here.
Fig. 6B is a schematic structural view of the temperature measurement unit and the calculation processing unit according to the embodiment of the present application. Referring to fig. 6A and 6B, the temperature measuring unit in the present embodiment includes resistors R5 and R6 connected in series, and a capacitor C2, the capacitor C2 and the resistor R6 being connected in parallel. The other ends of the resistor R5 and the resistor R6 are connected to the port 8 and the port 14 of the calculation processing unit, respectively.
The temperature measuring unit may be powered by an external power supply or by an internal power supply, in this embodiment, by the chip U1 in fig. 6A. The chip U1 supplies power to the bridge unit through the temperature measuring unit. The temperature measuring unit is used for acquiring temperature signals, the calculation processing unit processes the acquired temperature signals to perform temperature compensation on the differential voltage, and the processed real pressure value is output through an Out port. The resistor R6 in this embodiment is an NTC resistor.
In this embodiment, the sensing of temperature can measure the relative temperature of the environment through the external NTC, so that the temperature signal can be more accurately acquired.
In this embodiment, the storage unit stores the compensation gain (sensitivity) of the sensing unit, the compensation zero point error, the temperature coefficient, the temperature or coefficient of the zero point, the quadratic term coefficient used for correction, and the like, so that a correct pressure value can be calculated based on the compensation coefficient when the calculation processing unit performs calculation, thereby improving the accuracy of measurement.
In addition, in the embodiments of the present application, the power supply to the bridge unit may be continuous power supply, and of course, in other embodiments, intermittent power supply may also be used. The display unit can be a liquid crystal display screen, an LED or the like.
Example 5
According to an embodiment of the application, a sensing circuit for measuring temperature by using the bridge is also provided. Fig. 7 is a schematic diagram of a sensing circuit employing a bridge for temperature measurement according to an embodiment of the present application. The sensing circuit in fig. 7 is different from that in fig. 3 in that a temperature measurement unit is included, and the functions of the bridge unit and the calculation processing unit in the present embodiment are thus also different from those in embodiments 3, 4. Therefore, this embodiment will focus on differences between the bridge unit and the calculation processing unit from embodiments 3 and 4, and other parts will not be described in detail.
In this embodiment, the bridge units form a wheatstone bridge, wherein the differential voltage of the wheatstone bridge is used to indicate the pressure in the vicinity of the wheatstone bridge, and the current of the wheatstone bridge is used to indicate the temperature in the vicinity of the sensing unit; and the calculation processing unit is connected with the bridge unit and is used for determining the temperature based on the magnitude of the current, calibrating the temperature and performing temperature compensation on the differential voltage based on the calibrated temperature so as to obtain a compensated pressure signal.
In some examples, the computing processing unit is further configured to: initial sensitivity Gain based on bridge at unity temperature C Compensation Gain for temperature measurement T Zero point error Offset for temperature measurement compensation T And offset compensation T for bridge temperature shift Calibrating the temperature to obtain the calibrated temperature.
In some examples, the bridge unit includes: a sensing unit including two variable resistive elements connected in parallel for detecting a pressure in the vicinity of the piezoresistive sensor and outputting a pressure signal; a fixed resistance unit including two fixed resistances connected in parallel, the two fixed resistances being connected in series with two variable resistance elements, respectively, to form the wheatstone bridge; wherein the differential voltage is a voltage between two connection points formed by connecting two fixed resistors in series with two variable resistance elements respectively; the current is the current in the path between the wheatstone power source and ground.
In some examples, the computing processing unit is further configured to: the current of the wheatstone bridge is converted into a temperature based on a pre-acquired correspondence between the historical temperature and the historical current of the bridge unit.
In some examples, the computing processing unit is further configured to: zero offset compensation, linear compensation and secondary temperature compensation are performed on the differential voltage based on a pressure versus bridge influence coefficient, a temperature versus sensitivity influence coefficient, a zero offset influence coefficient, a pressure linearity influence coefficient, and the calibrated temperature, wherein the pressure versus bridge influence coefficient, the temperature versus sensitivity influence coefficient, the zero offset influence coefficient, and the pressure linearity influence coefficient are obtained by calibrating the piezoresistive sensor with known temperatures and pressures.
In some examples, the pressure-to-bridge influence factor includes the followingAt least one of: initial sensitivity Gain of the bridge unit at unit pressure A The method comprises the steps of carrying out a first treatment on the surface of the The temperature-to-sensitivity influence coefficient includes at least one of: temperature coefficient TC of sensitivity of the bridge unit gain Temperature quadratic coefficient SOT of sensitivity of the bridge unit tcg The method comprises the steps of carrying out a first treatment on the surface of the The zero offset influence coefficient includes at least one of: compensation B for bridge deflection of the piezoresistive sensor after calibration shift Offset zero error of the original measured reading of the bridge unit B Temperature coefficient TC for the zero point offst Temperature corrected quadratic term coefficient SOT of (2) tco The method comprises the steps of carrying out a first treatment on the surface of the The coefficient of influence on the pressure linearity includes: quadratic coefficient SOT for bridge reading nonlinearity correction B 。
The present example makes temperature measurements by bridge current, for example, based on the current level of the entire wheatstone bridge. The temperature and the current are in a linear relation, so that the temperature and the current can be recorded and stored at the same time during calibration. In actual use, the differential voltage signal magnitude and the current magnitude are measured simultaneously, and the temperature is determined and compensated based on the current magnitude. While the actual value of the temperature near the sensor may be output at the processing unit. The embodiment does not need to use an additional temperature measuring unit, so that the space of the sensing circuit can be saved and the cost can be saved.
Specifically, the variable resistances Rp1, rp2 of the bridge elements increase or decrease substantially linearly with increasing temperature, and the current through the loop (constant voltage powered wheatstone bridge) decreases or increases. During calibration, the magnitude of loop current is recorded based on the temperature at which the piezoresistive sensor is located. Thus, when in use, the real-time temperature can be judged according to the magnitude of the current.
In this embodiment, after obtaining the current of the wheatstone bridge and converting the current into a temperature, the calculation processing unit also calibrates the temperature. In this way, the accuracy of the detected temperature can be improved.
In some examples, the calibration equation for temperature may employ the following equation:
T tmp ＝Gain T (Gain C ·K 2 ·T+Offset T )+1
T＝(T tmp ·(1+T tmp ·SOT T ))+T shift
wherein, gain C The initial sensitivity gain of the bridge at unity temperature; p is the pressure; k (K) 2 Processing coefficients for the quantization levels of the analog-to-digital conversion; gain T Offset for compensating gain after temperature measurement result T Zero point error for compensation of temperature measurement; SOT (SOT) T A nonlinear quadratic correction coefficient for temperature; t (T) tmp Intermediate calculation results for temperature correction; t (T) shift To compensate for the offset in bridge temperature; t is the corrected temperature reading.
The calculation processing unit, after calculating the corrected temperature T, substitutes T into the equation (3) (4) or the equation (5) (6) in embodiment 3 to further perform temperature compensation, linear compensation, and/or zero offset compensation on the pressure signal. These compensation methods are the same as those of embodiment 3, and thus, will not be described here again.
According to the method, the differential voltage signal and the current are measured simultaneously through the bridge unit, the ambient temperature is judged based on the current, the obtained temperature is calibrated, and then the pressure signal corresponding to the differential voltage is compensated by utilizing the calibrated temperature, so that the actual value of the temperature near the piezoresistive sensor can be obtained without an additional temperature measuring unit, the space of a sensing circuit and the piezoresistive sensor is saved, and the cost of the piezoresistive sensor and the sensing circuit is reduced.
Example 6
Fig. 8A is a schematic structural diagram of a sensing circuit according to an embodiment of the present application, which is similar to the sensing circuit structure shown in fig. 2, and includes a temperature measurement unit, a bridge unit, a spike interference suppression unit, a filtering unit, a calculation processing unit, a circuit protection unit, an alarm and interrupt unit, and a storage unit, wherein the bridge unit includes a sensing unit 142 and a fixed resistance unit.
As shown in fig. 8A, the sensing unit 142 and the temperature measuring unit 12 of the bridge unit are disposed at the distal end of the lead 102 for extending into the body of the monitored subject to detect the pressure and temperature in the body of the monitored subject. The sensing unit 142 may also be referred to as a piezoresistive sensor.
The fixed resistance unit, the spike suppression unit, the filtering unit, the calculation processing unit, the circuit protection unit, the alarm and interrupt unit, and the memory unit of the bridge unit are integrated on the sensing circuit board 104 at the proximal end of the wire 102.
Wherein, the proximal end is the end of the wire 102 close to the monitored object, and the distal end is the end of the wire 102 far away from the monitored object.
The structure and function of the sensing circuit are the same as those of the sensing circuits in the above embodiments 2, 3, and 4, and the temperature detection unit 12 is used to detect the temperature of the internal environment of the monitored object, so that the description thereof will not be repeated here.
Example 7
Fig. 8B is a schematic diagram of another sensing circuit according to an embodiment of the present application. The sensing circuit corresponds to the circuit configuration of the sensing circuit in embodiment 5 described above, in which the pressure of the environment in the subject is detected by a bridge unit instead of a temperature detection unit.
The sensing circuit comprises a bridge unit, a peak interference suppression unit, a filtering unit, a calculation processing unit, a circuit protection unit, an alarm and interrupt unit and a storage unit, wherein the bridge unit comprises a sensing unit and a fixed resistance unit.
As shown in fig. 8B, a sensing unit 142 of the bridge unit is disposed at the distal end of the lead 102 for extending into the body of the monitored subject to detect the pressure and temperature in the body of the monitored subject.
The fixed resistance unit, the spike suppression unit, the filtering unit, the calculation processing unit, the circuit protection unit, the alarm and interrupt unit, and the memory unit of the bridge unit are integrated on the sensing circuit board 104 at the proximal end of the wire 102.
The structure and function of the sensing circuit are the same as those of the sensing circuit in the above embodiment 5, and the bridge unit is used to detect the pressure and temperature of the environment in the monitored object, so that the description thereof is omitted here.
Example 8
According to an embodiment of the present application, there is also provided a medical catheter. As shown in fig. 8C, the medical catheter includes a catheter body 106 and a sensing circuit as shown in fig. 8A or 8B.
Wherein the lead 102 is disposed within the catheter body 106, the sensing unit 142 is disposed within the distal end of the lead 102, and other units of the sensing circuit, in addition to the sensing unit 142, are integrated on a sensing chip, wherein the sensing circuit board 104 is located at the proximal end of the catheter body 106.
In other examples, it is also possible that the sensing unit 142 and the temperature measuring unit are provided in the distal end of the wire 102, and that other units of the sensing circuit than the sensing unit 142 are integrated on the sensing circuit board.
The structure of the sensing circuit is the same as that of the sensing circuit in the above embodiment, and thus, a description thereof will not be repeated here.
Example 9
According to an embodiment of the application, a medical monitoring system is also provided. Fig. 9 is a schematic structural diagram of a medical monitoring system according to an embodiment of the present application, as shown in fig. 9, the medical monitoring system includes a medical catheter 106 and a monitoring device 200, wherein a sensing unit 142 is disposed at a distal end of the medical catheter 106, a sensing circuit board 104 is disposed at a proximal end of the medical catheter, and other components of the sensing circuit except the sensing unit 142 are integrated on the sensing circuit board 104, and the sensing unit 142 and the sensing circuit board 104 are connected by a wire 102.
In other embodiments, the distal end of the medical catheter 106 may be provided with not only the sensing unit 142 but also a temperature measurement unit, the proximal end is provided with the sensing circuit board 104, and the sensing circuit board 104 is integrated with other components of the sensing circuit except the sensing unit 142, and the sensing unit 142 and the temperature measurement unit are connected with the sensing circuit board 104 by the wires 102.
The structure and function of the sensing circuit are similar to those of the sensing circuit in the above embodiment, and will not be repeated here.
Example 10
According to the embodiment of the application, a compensation method of the pressure signal is also provided. Fig. 10 is a flowchart of a method of compensating a pressure signal according to an embodiment of the present application, as shown in fig. 10, the method including the steps of:
Step S900, obtaining a calibration coefficient and a compensation relation through calibration.
And under the known different pressure and temperature environments, sensing differential voltage signals output by the Wheatstone bridge unit, and calibrating the piezoresistive sensor to obtain a calibration coefficient. If the bridge temperature is measured, the current signal is detected while the differential voltage signal is detected, and the calibration coefficient is obtained by calibrating the differential voltage signal and the current signal. These calibration coefficients may include, for example, data such as the compensation gain (sensitivity) of the raw measurement reading of the bridge cell, the compensation zero point error of the raw measurement reading of the bridge cell, the temperature coefficient of the sensitivity of the bridge cell, the temperature coefficient of the zero point of the bridge cell, and the like.
For example, measuring changes in output values of zero and full pressures of the piezoresistive sensor at a reference temperature can result in compensation gain (sensitivity) data for raw measurement readings of the bridge unit; the zero-position output of the bridge unit is measured, so that the compensation zero-point error of the original measurement reading of the bridge unit can be obtained; by measuring the values of the zero voltage and the full voltage at different temperatures, the temperature coefficient of the sensitivity of the bridge unit and the like can be obtained.
Based on these coefficients, a compensation relationship, for example, the compensation relationships shown in formulas (3) to (5) is established.
In step S902, a temperature signal and a pressure signal are detected.
The temperature is detected by a temperature measuring unit or by a bridge unit. At the same time as the temperature signal is obtained, the differential voltage of the wheatstone bridge of the bridge unit is detected, which is characteristic of the pressure of the environment in which the piezoresistive sensor is located.
Step S904, compensating the pressure signal with the temperature signal based on the compensation relation.
And compensating the differential voltage value output by the bridge unit by using the compensation relation to obtain a real pressure value.
The specific compensation method is the same as that in the sensing circuit in the above embodiment. For example, the compensation may be performed by using a formula for parabolic correction of the sensor bridge, and another formula for correcting the S-shaped curve of the piezoresistive sensor bridge may be used, which is not described herein.
In this embodiment, the sensing unit senses the ambient pressure and detects the ambient temperature through the temperature measuring unit or the bridge unit, then filters the pressure signal sensed by the bridge unit, and then sends the filtered pressure signal to the processing and calculating unit, and in the processing and calculating unit, the real ambient pressure value is calculated based on the compensation relation in the storage unit and the measured temperature, and finally the real ambient pressure value is output to the display unit for display.
The method in this embodiment can implement all the functions implemented by the sensing circuit in the above embodiment, and therefore, will not be described herein.
Fig. 11 is a schematic diagram showing the effects before and after calibration of the pressure by temperature. Wherein the horizontal axis represents the pressure, the left vertical axis represents the pressure value output without temperature calibration, and the right vertical axis represents the pressure value output after temperature calibration.
It should be noted that, for simplicity of description, the foregoing method embodiments are all expressed as a series of action combinations, but it should be understood by those skilled in the art that the present application is not limited by the order of actions described, as some steps may be performed in other order or simultaneously in accordance with the present application. Further, those skilled in the art will also appreciate that the embodiments described in the specification are all preferred embodiments, and that the acts and modules referred to are not necessarily required in the present application.
From the description of the above embodiments, it will be clear to a person skilled in the art that the method according to the above embodiments may be implemented by means of software plus the necessary general hardware platform, but of course also by means of hardware, but in many cases the former is a preferred embodiment. Based on such understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk), comprising several instructions for causing a terminal device (which may be a mobile phone, a computer, a server, or a network device, etc.) to perform the method described in the embodiments of the present application.
In the foregoing embodiments of the present application, the descriptions of the embodiments are emphasized, and for a portion of this disclosure that is not described in detail in this embodiment, reference is made to the related descriptions of other embodiments.
In several embodiments provided in the present application, it should be understood that the disclosed client may be implemented in other manners. The above-described embodiments of the apparatus are merely exemplary, and the division of the units, such as the division of the units, is merely a logical function division, and may be implemented in another manner, for example, multiple units or components may be combined or may be integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be through some interfaces, units or modules, or may be in electrical or other forms.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.
The foregoing is merely a preferred embodiment of the present application and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present application and are intended to be comprehended within the scope of the present application.
Claims (15)
1. A piezoresistive sensor sensing circuit, comprising:
the temperature measuring unit comprises a diode or an NTC resistor and is used for measuring the temperature near the piezoresistive sensor through the diode or the NTC resistor to obtain a temperature signal;
a bridge unit for detecting a pressure signal in the vicinity of the piezoresistive sensor and outputting a differential voltage based on the pressure signal;
and the calculation processing unit is connected with the bridge unit and the temperature measurement unit and is used for performing temperature compensation on the differential voltage based on the temperature signal so as to obtain the compensated pressure signal.
2. The sensing circuit of claim 1, wherein the bridge unit comprises:
a sensing unit including a variable resistance element for detecting a pressure in the vicinity of the piezoresistive sensor and outputting a pressure signal;
and the fixed resistance unit is connected with the sensing unit and used for forming a Wheatstone bridge with the variable resistance element so as to acquire the differential voltage.
3. The sensing circuit of claim 1, wherein the sensing circuit comprises a plurality of sensing circuits,
the calculation processing unit outputs the compensated pressure signal in a proportional voltage mode, or in a SENT protocol mode, or in a PWM mode, or in an I2C mode;
the computing processing unit is also used for outputting and displaying the output compensated pressure signal on the display unit.
4. A sensing circuit according to claim 3, wherein the computing processing unit further comprises an alarm and interrupt unit for alerting and short circuit power-down protecting the sensing circuit in case the compensated pressure signal exceeds a pressure threshold or the compensated temperature signal exceeds a temperature threshold.
5. The sensing circuit of claim 2, further comprising a circuit protection unit coupled to the sensing unit and the computing processing unit for electrostatic discharge protection of the sensing unit and the computing processing unit.
6. The sensing circuit of claim 2, wherein the sensing circuit further comprises:
the peak interference suppression unit is connected between the sensing unit and the fixed resistance unit and is used for filtering peak interference in the pressure signal; and/or
And the filtering unit is connected between the bridge unit and the calculation processing unit and is used for filtering noise in the differential voltage.
7. The sensing circuit of claim 6, wherein the sensing circuit comprises a plurality of sensing circuits,
the variable resistance element of the sensing unit includes a first variable resistance RP1 and a second variable resistance RP2;
the peak interference suppression unit comprises a first magnetic bead FB1, a second magnetic bead FB2 and a third magnetic bead FB3, wherein one end of the first magnetic bead FB1 is connected with the calculation processing unit through a first resistor R1, and the other end of the first magnetic bead FB1 is respectively connected with one ends of the first variable resistor RP1 and the second variable resistor RP2;
the bridge unit includes a tenth resistor R10 and an eleventh resistor R11, one end of the tenth resistor R10 and one end of the eleventh resistor R11 are connected in series, the other end of the tenth resistor R10 is connected to the other end of the first variable resistor RP1 via the second magnetic bead FB2, and the other end of the eleventh resistor R11 is connected to the other end of the second variable resistor RP2 via the third magnetic bead FB 3.
8. The sensing circuit of claim 6, wherein the filtering unit includes a fourth resistor R4, a ninth resistor R9, a third capacitor C3, a fourth capacitor C4, and a fifth capacitor C5, one end of the fourth resistor R4 is connected to the computing unit, the other end is connected to the bridge unit, one end of the ninth resistor R9 is connected to the computing unit, the other end is connected to the bridge unit, one end of the fourth capacitor C4 is connected to the fourth resistor R4 and the computing unit, the other end is grounded, one end of the fifth capacitor C5 is connected to the ninth resistor R9 and the computing unit, the other end is grounded, one end of the third capacitor C3 is connected to the fourth capacitor C4, and the other end is connected to the fifth capacitor C5.
9. The sensing circuit of claim 1, wherein the temperature measurement unit comprises:
a diode D1, both ends of the diode D1 being connected to both ends of the calculation processing unit; or (b)
A fifth resistor R5, a sixth resistor R6, or a second capacitor R7, where one end of the fifth resistor R5 is connected to the calculation processing unit, the other end is connected to one end of the sixth resistor R6 and one end of the second capacitor C2, the other end of the second capacitor C2 is connected to the other end of the sixth resistor R6, and the other end of the sixth resistor R6 is connected to the calculation processing unit, where the sixth resistor R6 is the NTC resistor.
10. The sensing circuit of claim 1, wherein the second port of the computing unit is grounded, the first port is connected to a power supply, the fourth port is connected to one end of the bridge unit through a fourth resistor R4 and a third resistor R3, the sixth port is connected to the other end of the bridge unit through a ninth resistor R9 and an eighth resistor R8, and the fifth port is connected to a power supply port of the bridge unit through a second resistor R2 and a first resistor R1.
11. The sensing circuit of claim 1, wherein the computing processing unit is further configured to: zero offset compensation, linear compensation and the temperature compensation are performed on the differential voltage based on a pressure-versus-bridge influence coefficient, a temperature-versus-sensitivity influence coefficient, a zero offset influence coefficient, and a pressure linearity influence coefficient, wherein the pressure-versus-bridge influence coefficient, the temperature-versus-sensitivity influence coefficient, the zero offset influence coefficient, and the pressure linearity influence coefficient are obtained by calibrating the piezoresistive sensor with known temperature and pressure.
12. The sensing circuit of claim 11, wherein the sensing circuit comprises a plurality of sensing circuits,
The pressure-to-bridge influence factor includes at least one of: initial sensitivity Gain of the bridge unit at unit pressure A ；
The temperature-to-sensitivity influence coefficient includes at least one of: temperature coefficient TC of sensitivity of the bridge unit gain、 Temperature quadratic coefficient SOT of sensitivity of the bridge unit tcg ；
The zero offset influence coefficient includes at least one of: compensation B for bridge deflection of the piezoresistive sensor after calibration shift Offset zero error of the original measured reading of the bridge unit B Temperature coefficient TC for the zero point offst Temperature corrected quadratic term coefficient SOT of (2) tco ；
The coefficient of influence on the pressure linearity includes: quadratic coefficient SOT for bridge reading nonlinearity correction B 。
13. A medical catheter for insertion into a body of a subject, comprising:
a catheter body;
the sensing circuit of any one of claims 1 to 12, a sensing unit of the sensing circuit being provided at one end of the catheter body, other components of the sensing circuit being provided at the other end of the catheter body, the sensing unit being connected to the other components by wires.
14. A medical monitoring system, comprising:
the medical catheter of claim 13;
and the monitoring device is used for monitoring and displaying the data detected by the sensing circuit when the medical catheter is inserted into the body of the monitored object.
15. A method of compensating a pressure signal of a piezoresistive sensor, comprising:
measuring the temperature near the piezoresistive sensor through a temperature measuring unit of the piezoresistive sensor to obtain a temperature signal;
detecting a pressure signal in the vicinity of the piezoresistive sensor by a bridge unit of the piezoresistive sensor and outputting a differential voltage based on the pressure signal;
and carrying out temperature compensation on the differential voltage based on the temperature signal to obtain the compensated pressure signal.
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