A dynamic temperature compensation method for a diffused silicon water pressure sensor

Abstract

This invention discloses a dynamic temperature compensation method for diffused silicon water pressure sensors, mainly applied to temperature compensation of silicon piezoresistive pressure sensors. First, the transient thermal impedance curve of the piezoresistive core is tested using finite element simulation. Then, a Foster network is used to fit the transient thermal impedance curve, obtaining the thermal impedance network of the piezoresistive core. Next, based on the correspondence between the thermal path and the circuit, a corresponding RC network circuit is constructed according to the thermal impedance network, and this circuit is used to calculate the actual temperature of the piezoresistive chip. The temperature of the piezoresistive chip is used as the index value for temperature calibration to conduct calibration experiments, obtaining temperature calibration parameters at different temperatures. In actual operation, the amplifier gain can be adjusted according to the temperature, thereby eliminating temperature drift. This method ensures the stability of the piezoresistive pressure sensor under complex changes in ambient or medium temperature without increasing manufacturing costs.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically, to a dynamic temperature compensation method for a diffused silicon water pressure sensor. Background Technology

[0002] Pressure sensors are widely used in various fields such as automation, aerospace, and power, and are of great significance in industrial production. Piezoresistive pressure sensors, with their high linearity, high sensitivity, and stability, have become the most widely used type of pressure sensor. However, when the ambient temperature changes, piezoresistive sensors will experience temperature drift, which will bring significant errors to the actual measurement. The temperature drift of piezoresistive pressure sensors mainly comes from three aspects: first, the resistance of the piezoresistor itself is affected by temperature changes; second, the piezoresistive coefficient of the piezoresistive material is related to temperature; and third, temperature affects the amount of stress applied to the piezoresistor.

[0003] To improve the measurement accuracy of piezoresistive pressure sensors, temperature compensation of their output is essential. Currently, numerous temperature compensation methods exist for piezoresistive sensors. The principle is that the sensor output is a function of pressure and temperature. Through extensive calibration experiments, combined with specific machine learning algorithms or interpolation methods, the function of the sensor output in terms of pressure and temperature can be determined. Then, by simultaneously measuring both the temperature and the sensor output, an accurate pressure value can be determined, thereby reducing errors caused by temperature variations. However, these temperature compensation methods do not achieve optimal compensation results because the piezoresistive chip is encapsulated inside the piezoresistive core, and the chip's temperature is difficult to measure directly. Therefore, current temperature compensation methods often measure the ambient temperature and then use it for compensation, assuming that the ambient temperature is approximately equal to the piezoresistive chip temperature. This assumption holds true when the ambient temperature is relatively stable, but when the ambient temperature changes drastically, there will be a significant difference between the ambient temperature and the chip temperature, leading to a decrease in the compensation effect. Summary of the Invention

[0004] The purpose of this invention is to provide a dynamic temperature compensation method for diffused silicon water pressure sensors to solve the aforementioned problems in the prior art. Specifically, this method aims to compensate the output of a piezoresistive pressure sensor in industrial environments with drastic temperature changes, ensuring that the sensor output is largely unaffected by temperature after compensation. This improves the accuracy of the piezoresistive pressure sensor measurements.

[0005] This invention provides a dynamic temperature compensation method for a diffused silicon water pressure sensor, the method comprising:

[0006] Step S1: Measure the junction transient thermal resistance curves of the piezoresistive pressure sensor chip to the pressure transmission medium and the junction transient thermal resistance curves of the piezoresistive chip to the external environment, respectively.

[0007] Step S2: Fit the two transient thermal impedance curves obtained in step S1 with a third-order Foster network to obtain the thermal impedance network from the piezoresistive chip to the external environment and the thermal impedance network from the piezoresistive chip to the pressure transmission medium, respectively. Combine these two thermal impedance networks to obtain the overall thermal impedance network of the piezoresistive pressure sensor. The connection point of the two thermal impedance networks represents the temperature of the piezoresistive chip.

[0008] Step S3: Based on the thermal impedance network constructed in step S2, build a RC network circuit, use the output voltage of the temperature sensor as the excitation voltage of the circuit, and use the node voltage representing the piezoresistive chip in the circuit as the output voltage of the circuit.

[0009] Step S4: Input the output voltage from step S3 to the external temperature signal input pin of the PGA309 chip, i.e., TEMP. IN The output voltage of the pressure sensor is input to the chip's V pin. IN The PGA309 chip also requires an external E pin. 2 The PROM is used to store calibration parameters; to conduct calibration experiments and to complete temperature compensation of the pressure sensor output voltage.

[0010] Optionally, the step of separately measuring the junction-shell transient thermal resistance curve of the piezoresistive pressure sensor chip to the pressure-transmitting medium and the junction-shell transient thermal resistance curve of the piezoresistive chip to the external environment includes:

[0011] The transient thermal impedance curve of the junction between the piezoresistive chip and the pressure-transmitting medium in a piezoresistive pressure sensor was determined. A physical model of the portion of the piezoresistive core from the piezoresistive chip to the pressure-transmitting medium was completed in COMSOL, ensuring the piezoresistive sensor reached a steady state at ambient temperature T1, i.e., the entire sensor temperature reached T1. A constant power P was applied to the diffused silicon piezoresistive chip, and the temperature change T of the piezoresistive chip over time was measured. j (t) and the change of shell temperature over time T c (t), the junction transient thermal impedance curve Z of the piezoresistive chip to the pressure transmission medium is calculated by formula (1). thj-c(t) The junction-shell transient thermal impedance curve of the piezoresistive pressure sensor chip to the external environment was determined using the same method.

[0012]

[0013] Optionally, step S4 includes:

[0014] The sensor is calibrated at various temperature points to obtain key temperature calibration parameters such as the output zero point and output sensitivity at that temperature. These parameters are then stored in an external E-channel. 2 In PROM;

[0015] In practical work, PGA309 is based on TEMP IN The temperature calibration index value input to the pin is used to look up the corresponding temperature calibration parameter, and the gain of the PGA309 internal amplifier is adjusted accordingly so that the output voltage is not affected by temperature changes.

[0016] Compared with the prior art, the embodiments of the present invention achieve the following beneficial effects:

[0017] This invention provides a dynamic temperature compensation method for a diffused silicon water pressure sensor, and a temperature compensation system based on a thermal impedance network. A thermal impedance network is constructed for the piezoresistive chip, and the actual temperature of the piezoresistive chip is calculated based on this network using the temperature of the pressure-transmitting medium and the ambient temperature. Temperature compensation is then performed based on the calculated temperature. Compared to other temperature compensation methods that use ambient temperature, this method achieves superior compensation results. This invention provides a temperature compensation system based on a thermal impedance network. In calculating the thermal impedance network, the correspondence between the thermal path and the circuit is utilized. A sixth-order RC network is used to complete the thermal path analysis, eliminating the need for signal processing chips such as DSPs, microcontrollers, or FPGAs. This achieves excellent calculation accuracy without increasing manufacturing costs. The temperature compensation system based on a thermal impedance network provided by this invention can be widely applied to situations with drastic changes in ambient or medium temperature. Traditional piezoresistive pressure sensor temperature compensation methods show significantly reduced compensation effectiveness under harsh ambient or medium temperature conditions. Attached Figure Description

[0018] Figure 1 This is a flowchart of the dynamic temperature compensation method for the diffused silicon water pressure sensor proposed in this invention.

[0019] Figure 2 This is a hardware structure diagram of the diffused silicon water pressure sensor core proposed in this invention.

[0020] Figure 3 The thermal impedance network diagram is the corresponding to the hardware structure diagram of the diffused silicon water pressure sensor core proposed in this invention.

[0021] Figure 4 This is a schematic diagram of the dynamic temperature compensation circuit for the diffused silicon water pressure sensor proposed in this invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings.

[0023] This invention proposes a dynamic temperature method for diffused silicon water pressure sensors. By measuring the transient thermal impedance curve of the sensor, a thermal impedance network can be established. This network can then be used to predict the temperature change of the piezoresistive chip based on the ambient temperature measurement results, thereby essentially eliminating errors caused by temperature variations. The dynamic temperature compensation system proposed in this invention utilizes the similarity between the circuit and the thermal circuit, achieving the prediction of the junction temperature of the diffused silicon chip using only a simple RC network circuit. This method is low-cost yet achieves excellent temperature compensation results. See the following embodiments for details.

[0024] Example 1

[0025] This invention provides a dynamic temperature compensation method for diffused silicon water pressure sensors, applicable to temperature compensation of diffused silicon pressure sensors, which can significantly reduce the temperature drift of diffused silicon pressure sensors. The method includes:

[0026] Step S1: Measure the junction transient thermal resistance curves of the piezoresistive pressure sensor chip to the pressure transmission medium and the junction transient thermal resistance curves of the piezoresistive chip to the external environment, respectively.

[0027] Step S2: Fit the two transient thermal impedance curves obtained in step S1 with a third-order Foster network to obtain the thermal impedance network from the piezoresistive chip to the external environment and the thermal impedance network from the piezoresistive chip to the pressure transmission medium, respectively. Combine these two thermal impedance networks to obtain the overall thermal impedance network of the piezoresistive pressure sensor. The connection point of the two thermal impedance networks represents the temperature of the piezoresistive chip.

[0028] Step S3: Based on the thermal impedance network constructed in step S2, build a RC network circuit, use the output voltage of the temperature sensor as the excitation voltage of the circuit, and use the node voltage representing the piezoresistive chip in the circuit as the output voltage of the circuit.

[0029] Step S4: Input the output voltage from step S3 to the external temperature signal input pin of the PGA309 chip, i.e., TEMP. IN The output voltage of the pressure sensor is input to the chip's V pin. IN The PGA309 chip also requires an external E pin. 2 The PROM is used to store calibration parameters; to conduct calibration experiments and to complete temperature compensation of the pressure sensor output voltage.

[0030] Optionally, the step of separately measuring the junction-shell transient thermal resistance curve of the piezoresistive pressure sensor chip to the pressure-transmitting medium and the junction-shell transient thermal resistance curve of the piezoresistive chip to the external environment includes:

[0031] The transient thermal impedance curve of the junction between the piezoresistive chip and the pressure-transmitting medium in a piezoresistive pressure sensor was determined. A physical model of the portion of the piezoresistive core from the piezoresistive chip to the pressure-transmitting medium was completed in COMSOL, ensuring the piezoresistive sensor reached a steady state at ambient temperature T1, i.e., the entire sensor temperature reached T1. A constant power P was applied to the diffused silicon piezoresistive chip, and the temperature change T of the piezoresistive chip over time was measured. j (t) and the change of shell temperature over time T c (t), the junction transient thermal impedance curve Z of the piezoresistive chip to the pressure transmission medium is calculated by formula (1). thj-c(t) The junction-shell transient thermal impedance curve of the piezoresistive pressure sensor chip to the external environment was determined using the same method.

[0032]

[0033] Optionally, step S4 includes:

[0034] The sensor is calibrated at various temperature points to obtain key temperature calibration parameters such as the output zero point and output sensitivity at that temperature. These parameters are then stored in an external E-channel. 2 In PROM;

[0035] In practical work, PGA309 is based on TEMP IN The temperature calibration index value input to the pin is used to look up the corresponding temperature calibration parameter, and the gain of the PGA309 internal amplifier is adjusted accordingly so that the output voltage is not affected by temperature changes.

[0036] The hardware structure diagram of the diffused silicon water pressure sensor core proposed in this embodiment of the invention is as follows: Figure 2 As shown, the silicon piezoresistive pressure sensor is mainly assembled from a stainless steel inlet head and a piezoresistive core. When measuring the pressure of the pressure-transmitting medium using the sensor, the inlet head is fixed by threads, and the pressure-transmitting medium enters the internal cavity of the sensor. Its pressure is applied to the 316L corrugated diaphragm on the piezoresistive core, and then applied to the piezoresistive chip through the silicone oil filled inside the piezoresistive core. Four identical piezoresistive resistors R are installed on the piezoresistive chip. According to the piezoresistive effect, the resistance change ΔR of the piezoresistive resistor due to pressure is... p It is directly proportional to the pressure P applied to it, and the specific relationship is as follows:

[0037] ΔR p =k·π 44 (T)·P(2)

[0038] In the formula, k is a constant, which is related to the Poisson's ratio of the silicon material and the size and structure of the silicon film, while the piezoresistive coefficient π 44 It is a function of temperature. When the temperature changes, the magnitude of the varistor also changes by ΔR. tThe four varistors on the piezoresistive chip form a Wheatstone bridge, and its output voltage is:

[0039]

[0040] As shown in the above formula, the output voltage of the Wheatstone bridge is a function of the piezoresistive chip temperature and pressure. Most current temperature compensation methods first measure the output characteristics of the pressure sensor at different temperatures, and then use some machine learning algorithms or interpolation methods to fit the output voltage as a function of temperature and pressure. The pressure can then be calculated from the output voltage and temperature. However, the piezoresistive chip is encapsulated in layers inside the piezoresistive core, and its temperature cannot be directly measured. Therefore, current methods measure the temperature of the medium or the ambient temperature to approximate the temperature of the piezoresistive chip, which will undoubtedly introduce errors into the measurement.

[0041] The dynamic temperature compensation method for the diffused silicon water pressure sensor proposed in this embodiment of the invention calculates the actual temperature of the piezoresistive chip through the thermal impedance network of the piezoresistive core. The flowchart of the dynamic temperature compensation method for the diffused silicon water pressure sensor proposed in this embodiment of the invention is as follows: Figure 1 As shown.

[0042] First, the thermal impedance network of the piezoresistive core is obtained using COMSOL simulation software. The thermal impedance network diagram corresponding to the hardware structure diagram of the diffused silicon water pressure sensor core proposed in this embodiment of the invention is as follows: Figure 3 As shown, in order to simplify the heat conduction network, the piezoresistive core can be divided into two parts. The upper part is affected by the temperature of the pressure transmission medium, while the lower part is affected by the temperature of the external environment. The thermal impedance networks from the piezoresistive chip to the pressure transmission medium and from the piezoresistive chip to the external environment are established respectively. The two parts are combined to obtain the thermal impedance network of the piezoresistive core.

[0043] Common junction temperature prediction models include Cauer and Foster types. This invention uses a third-order Foster thermal network structure to calculate the actual temperature of the piezoresistive chip. The third-order Foster thermal impedance network consists of three sets of parallel thermal resistances R and thermal capacities C. The magnitudes of the thermal resistance and thermal capacity in the thermal impedance network can be obtained by analyzing the transient thermal impedance curve Z. thj-c(t) The result is obtained by fitting, as shown in equation (4).

[0044]

[0045] In the formula, t is time, and R is... thi C thi and τ i Let τ be the thermal resistance, thermal capacity, and time constant of the i-th order thermal impedance network. i =R thi C thiIn this context, the thermal resistance and thermal capacity of each order do not have any actual physical meaning.

[0046] The transient thermal resistance curve Z thj-c(t) The transient thermal impedance curve can be obtained through experimental methods, such as using thermal impedance testing equipment like the T3Ster thermal impedance meter, or through finite element simulation. This invention uses COMSOL finite element simulation software as an example to illustrate the method for determining the transient thermal impedance curve.

[0047] To determine the transient thermal impedance curve from the piezoresistive chip to the pressure-transmitting medium in a piezoresistive core, a physical model of the upper half of the piezoresistive core is first completed. A fixed power P is applied to the piezoresistive chip in COMSOL's solid heat transfer module, and the temperature change T of the piezoresistive chip over time is measured. j (t) and the change of shell temperature over time T c (t), and then the transient thermal impedance Z can be calculated according to equation (5). thj-c(t) curve.

[0048]

[0049] After obtaining the thermal impedance network of the piezoresistive core, the temperature T0(t) of the piezoresistive chip can be calculated based on the temperature T1(t) of the pressure transmission medium and the external ambient temperature T2(t). However, to analyze this thermal path using analytical methods, it is necessary to solve multivariate differential equations. This invention utilizes the correspondence between the thermal path and the circuit (i.e., power corresponds to current, temperature corresponds to potential, thermal resistance corresponds to resistance, and thermal capacitance corresponds to capacitance) to transform the calculation of the thermal path into circuit analysis, and builds a RC circuit network according to the thermal impedance network.

[0050] The structure diagram of the dynamic temperature compensation circuit for the diffused silicon water pressure sensor proposed in this embodiment of the invention is as follows: Figure 4 As shown, this circuit requires two temperature sensors to measure the temperature of the pressure-transmitting medium and the temperature of the external environment, respectively. Both sensors provide voltage output, and their output voltage provides excitation for the RC network. Figure 4 U1 and U2 in the figure represent the output voltages of the pressure transmission medium temperature sensor and the external ambient temperature sensor, respectively. U1 and U2 are proportional to T1 and T2, respectively. Therefore, U0 is proportional to the piezoresistive chip temperature T0. Next, U0 is input to the external temperature signal input terminal of PGA309 as the temperature calibration index value.

[0051] Afterwards, calibration experiments were conducted. When the chip temperature changes, the zero-point output and sensitivity of the sensor will drift. In the calibration experiment, the PGA309 records the zero-point output and sensitivity at different temperatures. The chip temperature is the temperature calibration index value, and the zero-point output and sensitivity are the temperature calibration parameters. In actual operation, the PGA309 can look up the corresponding parameters according to the index value and adjust the gain of its internal amplifier accordingly to eliminate temperature drift.

[0052] It will be readily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for dynamic temperature compensation of a diffused silicon water pressure sensor, characterized in that, The method includes: Step S1: Measure the junction transient thermal resistance curves of the piezoresistive pressure sensor chip to the pressure transmission medium and the junction transient thermal resistance curves of the piezoresistive chip to the external environment, respectively. Step S2: Fit the two transient thermal impedance curves obtained in step S1 with a third-order Foster network to obtain the thermal impedance network from the piezoresistive chip to the external environment and the thermal impedance network from the piezoresistive chip to the pressure transmission medium, respectively. Combine these two thermal impedance networks to obtain the overall thermal impedance network of the piezoresistive pressure sensor. The connection point of the two thermal impedance networks represents the temperature of the piezoresistive chip. Step S3: Based on the thermal impedance network constructed in step S2, build a RC network circuit. This circuit requires two temperature sensors to measure the temperature of the pressure transmission medium and the temperature of the external environment, respectively. The two sensors use voltage output, and their output voltage provides excitation for the RC network. The node voltage representing the piezoresistive chip in the circuit is used as the output voltage of the circuit. Step S4: input the output voltage in step S3 to the external temperature signal input pin of PGA309 chip, i.e. pin, and the output voltage of the pressure sensor is input to the pin of the chip, and the PGA309 chip also needs to be externally connected to for storing calibration parameters; perform calibration experiments to complete temperature compensation of the output voltage of the pressure sensor.

2. The dynamic temperature compensation method for a diffused silicon water pressure sensor according to claim 1, wherein, The measurement of the junction-shell transient thermal impedance curves of the piezoresistive pressure sensor chip to the pressure-transmitting medium and the junction-shell transient thermal impedance curves of the piezoresistive chip to the external environment includes: The transient thermal impedance curve of the junction between the piezoresistive chip and the pressure-transmitting medium in a piezoresistive pressure sensor was determined. A physical model of the portion of the piezoresistive core from the piezoresistive chip to the pressure-transmitting medium was completed in COMSOL, enabling the piezoresistive sensor to operate under ambient temperature conditions. The temperature reaches a steady state, meaning the temperature of the entire sensor reaches a certain level. A constant power P is applied to a diffused silicon piezoresistive chip, and the temperature change of the piezoresistive chip over time is measured. and the change in shell temperature over time The transient thermal impedance curve of the junction between the piezoresistive chip and the pressure transmission medium is calculated using formula (1). The junction-shell transient thermal impedance curve of the piezoresistive pressure sensor chip to the external environment was determined using the same method. （1）。 3. The dynamic temperature compensation method for a diffused silicon water pressure sensor according to claim 1, characterized in that, Step S4 includes: The sensor is calibrated at various temperature points to obtain the output zero point and output sensitivity at those temperatures, and these parameters are stored in an external device. In PROM; In practical work, PGA309 is based on The temperature calibration index value input to the pin is used to look up the corresponding temperature calibration parameter, and the gain of the PGA309 internal amplifier is adjusted accordingly so that the output voltage is not affected by temperature changes.

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