Silicon piezoresistive pressure sensor linear optimization active analog signal processing circuit and correction method thereof

Abstract

The invention relates to the technical field of MEMS sensors, in particular to a silicon piezoresistive pressure sensor linear optimization active analog signal processing circuit and a correction method thereof, the accuracy represents the coincidence degree of an output signal of a sensor and a measured truth value, and the end-based linearity visually reflects the inherent linear characteristics of the sensor. The non-linear order of magnitude of a Wheatstone bridge type silicon piezoresistive pressure sensor is often larger than repeatability and lags for more than half order of magnitude, the non-linear order of magnitude is a primary influence factor for determining the accuracy of the sensor, and the non-linear order of magnitude of a Wheatstone bridge signal of the silicon piezoresistive pressure sensor is limited by the inherent non-linear and mutual offset effect of a bridge resistance piezoresistive effect. According to the invention, the initial nonlinearity of the sensor signal is corrected in order of magnitude by using a bridge type mode signal simulation operational amplifier gain negative feedback method, so that the accuracy of the sensor is optimized by at least half order of magnitude.

Description

Technical Field

[0001] This invention relates to the field of MEMS sensor technology, specifically to a linearly optimized active analog signal processing circuit for a silicon piezoresistive pressure sensor and its correction method. Background Technology

[0002] Accuracy is an indicator characterizing the degree to which the output signal of a sensor matches the true value of the measured quantity; it is a function of linearity, repeatability, and hysteresis. Linearity is a crucial parameter affecting accuracy; the baseline linearity of the uncompromised terminal lines directly reflects the inherent linearity of the sensor. The initial nonlinearity of a bridge-type silicon piezoresistive pressure sensor originates from the intrinsic piezoresistive effect nonlinearity of the bridge resistor in the silicon piezoresistive pressure sensor chip and the degree of mutual cancellation. The inherent nonlinearity of a typical silicon piezoresistive pressure sensor chip is often more than half an order of magnitude larger than the repeatability and mechanical hysteresis parameters, becoming the primary performance parameter limiting the accuracy of the sensor.

[0003] Unlike the characteristics of repeatability and hysteresis, which are difficult to optimize or compensate for, the inherent nonlinearity of the silicon piezoresistive pressure sensor bridge is capable of subsequent correction or compensation. To correct the initial nonlinearity of the silicon piezoresistive pressure sensor bridge and thus improve the accuracy of the bridge-type silicon piezoresistive pressure sensor, an active analog signal processing circuit and its correction method for optimizing the linearity of the bridge-type silicon piezoresistive pressure sensor are proposed. Summary of the Invention

[0004] The technical solution of this invention is as follows:

[0005] The signal of a bridge-type silicon piezoresistive pressure sensor chip can be considered as the sum of linear and nonlinear components. When the micro-deflection premise of the fixed pressure-sensing diaphragm around the sensor chip under the measured pressure is satisfied, the inherent linear nonlinear component curve of the signal often takes the shape of an upper or lower arc, with the apex or trough of the curve located at the midpoint of the measured pressure range. The arcs on both sides of the curve are symmetrical relative to the apex or trough. That is, the absolute value of the nonlinear component divides from the midpoint of the range into the lower and upper limits of the range, continuously decreasing from its maximum value to zero.

[0006] This invention utilizes the progressive modulation of the negative feedback voltage signal component of a high-linearity analog operational amplifier to cancel only the inherent terminal linear nonlinear component of the output signal of the bridge-type silicon piezoresistive pressure sensor chip. The inherent linear component of the output signal remains unchanged after the sensor is calibrated with a standard signal.

[0007] The analog signal linear optimization processing circuit design of this invention uses a high-linearity monolithic integrated quad operational amplifier. One operational amplifier is used to set the constant electrical excitation function unit of the silicon piezoresistive pressure sensor, providing constant electrical excitation to the sensitive bridge; two operational amplifiers are used to set the sensor's rated range upper limit output signal calibration function unit, modulating the resistance ratio of the series resistor between the inverting input terminals of the two operational amplifiers to differentially amplify the initial signal of the measured pressure of the sensitive bridge into a standard signal; a fourth operational amplifier is used to set the sensor's zero-point signal calibration function unit, modulating the parallel resistor between the constant electrical excitation function unit operational amplifier and the positive input terminal of the fourth operational amplifier to calibrate the initial signal of the sensitive bridge when there is no measured pressure input into the zero-point standard signal.

[0008] The gain negative feedback correction unit for the initial nonlinear component of the sensor standard signal is connected in series between the output terminal of the operational amplifier of the zero-point signal calibration function unit and the parallel terminal of the inverting input terminal of the operational amplifier of the constant electrical excitation function unit and the negative input terminal of the sensitive bridge.

[0009] After calibrating the sensor's rated zero point and upper limit output standard signals, the sensor output signal at the midpoint of the measured pressure range is tested to distinguish whether the sensor's end-base linear nonlinear curve is an upper or lower circular arc. For the inherent nonlinear component of the upper circular arc, the gain negative feedback load resistor value of the nonlinear correction unit is modulated to flip the arc apex of the nonlinear curve into a centrally symmetrical lower circular arc apex, thus reducing the absolute value of the nonlinear component by half. For the inherent nonlinear component of the lower circular arc, the modulation correction is performed in the opposite way. After each nonlinear correction, the sensor's rated zero point and upper limit output signal are recalibrated. The sensor's accuracy at room temperature is checked. If the nonlinearity meets the specified specifications, but affects the accuracy, the sensor's nonlinear component is further corrected. When both sensor linearity and accuracy meet the specified specifications, sensor linearity optimization is complete. Typically, two nonlinearity modulation corrections can optimize the initial signal end-base linearity of the sensor by more than half an order of magnitude.

[0010] Beneficial effects

[0011] In the signal analog processing circuit of the bridge-type silicon piezoresistive pressure sensor, this invention optimizes the inherent linearity of the sensor's sensing chip. By utilizing the negative feedback signal of the gain of the high-linearity final-stage operational amplifier in the circuit, the inherent nonlinear components of the sensor signal can be continuously corrected within the range of the measured pressure. This optimizes the linearity of the sensor terminal base by at least half an order of magnitude, significantly improving the accuracy and consistency of the sensor. Attached Figure Description

[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0013] Figure 1This is a functional block diagram of the active analog processing circuit for signal linear optimization of the bridge-type silicon piezoresistive pressure sensor of the present invention.

[0014] Figure 2 A schematic diagram of the nonlinear component of the signal from a bridge-type silicon piezoresistive pressure sensor before linear optimization;

[0015] Figure 3 A schematic diagram of the nonlinear component of the signal from a bridge-type silicon piezoresistive pressure sensor before linear optimization.

[0016] Figure 4 A schematic diagram of the asymptotic correction curve for the nonlinear component of the arc-shaped signal on a bridge-type silicon piezoresistive pressure sensor.

[0017] Figure 5 This is a schematic diagram of the asymptotic correction curve for the nonlinear component of the arc-shaped signal under a bridge-type silicon piezoresistive pressure sensor.

[0018] In the figure: 101, constant electrical excitation function unit; 102, rated range upper limit signal differential calibration unit; 103, final stage gain function unit; 104, zero-point signal calibration unit; 105, nonlinear correction unit. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0020] As one embodiment of the present invention, such as Figures 1-5 As shown, a linear optimization active analog signal processing circuit for a silicon piezoresistive pressure sensor is described. When designing the sensor standard signal calibration circuit, a bridge signal linear optimization function unit is set up. By utilizing the gain negative feedback function of the linear operational amplifier, the inherent nonlinearity of the sensor's initial signal is continuously corrected, and the initial accuracy of the sensor is improved by at least half an order of magnitude.

[0021] Among them, a high-linearity monolithic integrated quad operational amplifier is selected as the core device of the sensor standard signal processing circuit. One operational amplifier is set as the constant electrical excitation function unit 101 of the sensitive bridge, two operational amplifiers are set as the differential calibration function unit 102 of the upper limit output signal of the sensor rated range, and the last operational amplifier is set as the sensor final stage gain function unit 103. A zero-point signal calibration function unit 104 is set between the positive input terminal of the operational amplifier and the positive input terminal of the operational amplifier of the constant electrical excitation function unit.

[0022] Among them, a nonlinear correction unit 105 is set between the output terminal of the operational amplifier of the zero-point signal calibration unit 104 and the parallel terminal of the inverting input terminal of the operational amplifier of the constant electric excitation function unit and the negative input terminal of the sensitive bridge. The modulation gain negative feedback resistor gradually corrects the nonlinear components of the sensor output signal.

[0023] The method for continuous correction of the initial nonlinearity of sensor signals includes the following specific modulation steps:

[0024] Step 1: When the pressure being measured is at the lower limit of the rated range, calibrate the sensor output signal to the rated zero-point output value through the zero-point signal calibration unit 104, ensuring the error is within the accuracy range;

[0025] Step 2: When the measured pressure is at the upper limit of the rated range, the sensor output signal is calibrated to the rated upper limit output value through the upper limit signal differential calibration unit 102, and the error is within the accuracy range.

[0026] Step 3: Test the sensor's output value at the midpoint of the rated range of the measured pressure;

[0027] Step 4: Calculate the algebraic difference between the sensor output value at the midpoint of the rated pressure range and the corresponding value of the end base straight line to obtain the initial end base straight line nonlinearity value of the sensor standard signal at the midpoint of the rated pressure range.

[0028] Step 5: If the algebraic difference > 0, modulate the gain negative feedback resistor value of the nonlinear correction unit 105 to reduce the sensor's output value at the midpoint of the measured pressure's rated range, with the reduction value being twice the algebraic difference. If the algebraic difference < 0, conversely, modulate the gain negative feedback resistor value of the nonlinear correction unit 104 to increase the sensor's output value at the midpoint of the measured pressure's rated range, with the increase value being twice the absolute value of the algebraic difference.

[0029] Step 6: Repeat Step 1 and Step 2. After calibrating the sensor output signal to the rated zero point value and the upper limit of the range output value, and ensuring that the error is within the accuracy range, measure the nonlinearity of the sensor after correction.

[0030] Step 7: If the sensor nonlinearity does not meet the specified index, repeat steps 3, 4 and 5 to continue correcting the sensor nonlinearity until it meets the index.

[0031] Step 8: Test the sensor accuracy at room temperature. If the nonlinearity meets the specified index, but affects the accuracy, repeat steps 1 to 7 to ensure that both the sensor linearity and accuracy meet the specified index.

[0032] In the signal analog processing circuit of the bridge-type silicon piezoresistive pressure sensor, this invention optimizes the inherent linearity of the sensor's sensing chip. By utilizing the negative feedback signal of the gain of the high-linearity final-stage operational amplifier in the circuit, the inherent nonlinear components of the sensor signal can be continuously corrected within the range of the measured pressure. This optimizes the linearity of the sensor terminal base by at least half an order of magnitude, significantly improving the accuracy and consistency of the sensor.

[0033] The foregoing description illustrates and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A silicon piezoresistive pressure sensor linearization active analog signal processing circuit, characterized by: When designing the sensor standard signal calibration circuit, the bridge signal linear optimization function unit is set, the linear operational amplifier gain negative feedback function is used to continuously correct the inherent nonlinearity of the sensor initial signal, and the sensor initial accuracy is at least improved by half an order of magnitude.

2. A linearized active analog signal processing circuit for a silicon piezoresistive pressure sensor according to claim 1, characterized in that: The high linearity single-chip integrated four operational amplifier is designed and selected as the core device of the sensor standard signal processing circuit, one operational amplifier is set as the sensitive bridge constant electric excitation function unit (101), two operational amplifiers are set as the sensor rated range upper limit output signal differential calibration function unit (102), and the last operational amplifier is set as the sensor final stage gain function unit (103). The zero signal calibration function unit (104) is set between the operational amplifier positive input end and the constant electric excitation function unit operational amplifier positive input end.

3. A linearized active analog signal processing circuit for a silicon piezoresistive pressure sensor according to claim 2, characterized in that: The nonlinearity correction unit (105) is set between the zero signal calibration unit (104) operational amplifier output end and the constant electric excitation function unit operational amplifier reverse input end and the sensitive bridge input negative pole parallel end, the gain negative feedback resistance of the modulation correction unit (105) is adjusted, and the nonlinearity component of the sensor output signal is corrected in an asymptotic manner.

4. A linearized active analog signal processing circuit for a silicon piezoresistive pressure sensor according to any one of claims 1 to 3, characterized in that: The sensor signal initial nonlinearity continuous correction method includes the following specific modulation steps: Step one: when the measured pressure is the lower limit value of the rated range, the zero signal calibration unit (104) is used to calibrate the sensor output signal to the rated zero output value, and the error is within the accuracy range; Step two: when the measured pressure is the upper limit value of the rated range, the rated range upper limit signal differential calibration unit (102) is used to calibrate the sensor output signal to the rated upper limit output value, and the error is within the accuracy range; Step three: test the sensor signal output value when the measured pressure is the midpoint of the rated range; Step four: calculate the algebraic difference between the sensor output value at the midpoint of the rated pressure range and the corresponding value of the end-based working straight line to obtain the end-based initial nonlinearity value of the sensor standard signal in the rated pressure range; Step five: if the algebraic difference is > 0, adjust the gain negative feedback resistance value of the nonlinearity correction unit (105) to reduce the output value of the sensor at the midpoint of the measured pressure rated range by 2 times the algebraic difference value, and if the algebraic difference is < 0, adjust the gain negative feedback resistance value of the nonlinearity correction unit (105) to increase the output value of the sensor at the midpoint of the measured pressure rated range by 2 times the absolute value of the algebraic difference value; Step six: repeat steps one and two to calibrate the sensor output signal to the rated zero value and the range upper limit output value within the accuracy range, and then measure the corrected nonlinearity of the sensor; Step seven: if the sensor nonlinearity does not meet the specified index, repeat steps three, four and five to continue correcting the sensor nonlinearity until it meets the requirements; Step eight: detect the sensor accuracy at room temperature, if the nonlinearity meets the specified index but the accuracy does not meet the specified index, repeat steps one to seven to make the sensor linearity and accuracy meet the specified index at the same time.

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