A sensor and method for measuring the level of urea solution

Abstract

This invention discloses a sensor for measuring the level of urea solution, comprising a comprehensive sensing element, a level sensing unit, and a signal processing unit. The comprehensive sensing element is completely covered by the urea solution, and the level sensing unit is partially covered by the urea solution. The signal processing unit is electrically connected to both the comprehensive sensing element and the level sensing unit, and generates a second excitation signal and a third excitation signal, which are respectively sent to the comprehensive sensing element and the level sensing unit. It also receives impedance sensing signals from the comprehensive sensing element and the level sensing unit, and calculates the urea solution level based on the impedance sensing signals. This sensor can accurately measure the level of urea solution, is unaffected by urea solution sloshing or abnormal ultrasonic sensing elements, and can also diagnose IR problems where the sensor's sensed value is within the normal range but inaccurate.

Description

Technical Field

[0001] This invention belongs to the field of urea solution detection, and particularly relates to a sensor and method for measuring the level of urea solution. Background Technology

[0002] Most urea solution sensors need to be installed in a urea tank. To avoid urea solution supply problems caused by vacuum, the urea tank must have an opening to the surrounding environment, through which air comes into contact with the urea solution. Under many conditions, urea solution can generate sloshing and bubbles, which can degrade sensor performance and even temporarily disable it. When bubbles adhere to the sensor probe surface (these bubbles are difficult to dissipate on their own), they can cause the sensor to be disabled for an extended period. Furthermore, to avoid false alarms triggered by sensor problems in urea solution level readings, the sensor itself also needs to be diagnosed. Sensor diagnosis requires identifying not only the so-called Out-of-Range (OOR) problem, which causes readings to exceed the effective range, but also the so-called In-Range (IR) problem, where the sensor's sensed value is within the normal range but inaccurate. Summary of the Invention

[0003] Purpose of the invention: The technical problem to be solved by the present invention is to provide a sensor and method for measuring the level of urea solution, addressing the shortcomings of the prior art.

[0004] To solve the above-mentioned technical problems, a first aspect discloses a sensor for measuring the level of urea solution, comprising an integrated sensing element, a level sensing unit, and a signal processing unit. The integrated sensing element is completely covered by the urea solution, the level sensing unit is partially covered by the urea solution, and the signal processing unit is electrically connected to the integrated sensing element and the level sensing unit respectively.

[0005] The integrated sensing element is used to receive the second excitation signal generated by the signal processing unit, generate the first impedance sensing signal, and send the first impedance sensing signal to the signal processing unit.

[0006] The liquid level sensing unit is used to receive the third excitation signal generated by the signal processing unit, generate the second impedance sensing signal, and send the second impedance sensing signal to the signal processing unit.

[0007] The signal processing unit is used to generate a second excitation signal and a third excitation signal and send them to the integrated sensing element and the liquid level sensing unit respectively, receive the impedance sensing signal sent by the integrated sensing element and the liquid level sensing unit, and calculate the urea solution level based on the impedance sensing signal.

[0008] Furthermore, the liquid level sensing unit includes a third electrode and a fourth electrode. The urea solution between the third electrode and the fourth electrode is connected to the urea solution in the integrated sensing element. The third electrode is electrically connected to the signal processing unit through a third signal line, and the fourth electrode is electrically connected to the signal processing unit through a fourth signal line.

[0009] Furthermore, the integrated sensing element includes a first electrode and a second electrode, one end of the second electrode being electrically connected to the signal processing unit via a second signal line; and one end of the first electrode being electrically connected to the signal processing unit via a first signal line.

[0010] Furthermore, the signal processing unit includes a central processing unit and an impedance signal processing subunit. The central processing unit is used to send commands to the impedance signal processing subunit, receive the impedance sensing signal after it has been processed by the impedance signal processing subunit, and calculate the urea solution level based on the impedance sensing signal.

[0011] The impedance signal processing subunit is electrically connected to the third electrode via a third signal line and to the fourth electrode via a fourth signal line. It is used to receive a third command sent by the central processing unit, generate a third excitation signal, and send the third excitation signal to the third electrode; it also receives a second impedance sensing signal generated by the third excitation signal through the third electrode and the fourth electrode, processes it, and sends it to the central processing unit.

[0012] The impedance signal processing subunit is also electrically connected to one end of the first electrode via a first signal line and to one end of the second electrode via a second signal line. It is used to receive a second command sent by the central processing unit, generate a second excitation signal, and send the second excitation signal to the first electrode. It also receives a first impedance sensing signal generated by the second excitation signal through the first and second electrodes, processes it, and sends it to the central processing unit.

[0013] Furthermore, the signal processing unit also includes a resistance measurement module, and the liquid level sensing unit also includes a second temperature sensing element. The second temperature sensing element is used to measure the temperature of the urea solution between the third and fourth electrodes and is electrically connected to the resistance measurement module through a seventh signal line. The resistance measurement module is used to measure the resistance of the second temperature sensing element and send the resistance value to the central processing unit.

[0014] Furthermore, the sensor also includes an ultrasonic sensing element, which is completely covered by a urea solution. The urea solution between the first electrode and the second electrode is connected to the urea solution in the ultrasonic sensing element. The signal processing unit also includes an ultrasonic signal processing subunit. The ultrasonic sensing element is electrically connected to the ultrasonic signal processing subunit via a fifth signal line. The ultrasonic signal processing subunit is used to receive a first command sent by the central processing unit, generate a first excitation signal, send the first excitation signal to the ultrasonic sensing element, and receive the sensing signal generated by the ultrasonic sensing element, process it, and send it to the central processing unit.

[0015] Furthermore, the ultrasonic sensing element includes an ultrasonic transceiver unit, a first reflector, and a second reflector. The ultrasonic transceiver unit is parallel to the first reflector, and a urea solution exists between them. A urea solution exists between the ultrasonic transceiver unit and the second reflector, and their extension lines form an angle. This angle allows the second reflector to receive ultrasonic waves transmitted by the ultrasonic transceiver unit and reflect them onto the surface of the urea solution. The surface of the urea solution reflects a second ultrasonic echo back to the second reflector, which then reflects the second ultrasonic echo back to the ultrasonic transceiver unit. The first reflector receives ultrasonic waves transmitted by the ultrasonic transceiver unit, generates a first ultrasonic echo, and then reflects the first ultrasonic echo back to the ultrasonic transceiver unit. The ultrasonic transceiver unit transmits a sensing signal generated from the first and second ultrasonic echo signals to an ultrasonic signal processing subunit.

[0016] Furthermore, the resistance measurement module and the other end of the first electrode are electrically connected via a sixth signal line to measure the resistance of the first electrode and send the resistance value to the central processing unit.

[0017] Furthermore, the integrated sensing element also includes a first temperature sensing element, which is used to measure the temperature of the urea solution between the first electrode and the second electrode. It is electrically connected to a resistance measurement module via an eighth signal line. The resistance measurement module is used to measure the resistance of the first temperature sensing element and send the resistance value to the central processing unit.

[0018] The second aspect discloses a method for measuring the level of a urea solution, comprising the following steps:

[0019] Step 1: The signal processing unit generates an excitation signal and sends it to the integrated sensing element and the liquid level sensing unit.

[0020] Step 2: The integrated sensing element and the liquid level sensing unit receive the excitation signal generated by the signal processing unit, generate the first impedance sensing signal and the second impedance sensing signal respectively, and send them to the signal processing unit.

[0021] Step 3: The signal processing unit receives the first impedance sensing signal and the second impedance sensing signal and calculates the urea solution level.

[0022] Further, let Zsi be the impedance value corresponding to the first impedance sensing signal in step 2, and Zsl be the impedance value corresponding to the second impedance sensing signal; step 3 includes: calculating the ratio Rz between the two impedance values:

[0023] Rz=Zsi / Zsl (1)

[0024] Furthermore, in step 3, when calculating the urea solution level, a lookup table is used to compensate for nonlinear effects:

[0025] ld = Tbl(Rz) (2)

[0026] In formula (2), ld is the urea solution level value calculated in step 3, and Tbl() represents the table lookup calculation. The table value in the table lookup calculation is calibrated by the test data obtained from experiments at different urea solution concentrations.

[0027] Under conditions such as urea solution sloshing, pressure changes, and agitation, the impedance sensing value obtained using the level sensing unit and integrated sensing element can accurately measure the urea solution level.

[0028] Furthermore, in step 3, when calculating the urea solution level, a two-dimensional lookup table is used to compensate for the nonlinear effects caused by the urea solution temperature:

[0029] ld = Tbl(Rz, T227) (3)

[0030] Wherein, T227 is the urea solution temperature obtained through the second temperature sensing element, ld is the urea solution level value calculated in step 3, and Tbl() represents table lookup calculation. The table value in the table lookup calculation is calibrated by test data obtained from experiments at different urea solution concentrations and temperatures.

[0031] Furthermore, the method also includes step 4, calculating the urea solution level using the ultrasonic echo signal, including: measuring the first propagation time T of the ultrasonic wave returning to the ultrasonic transceiver unit after being reflected by the first reflector. q The second propagation time T of the ultrasonic wave, after being reflected for the first time by the second reflector, reflected a second time by the surface of the urea solution, and reflected a third time by the second reflector back to the ultrasonic transceiver unit, is... l The urea solution level is calculated using the following formula:

[0032] lu = =(h 129 -d 129 )+d 122 *Tl / T q (6)

[0033] In the formula, lu is the urea solution level calculated in step 4, and d 122 d is the distance between the ultrasonic transceiver unit and the first reflector. 129 h is the distance between the ultrasonic transceiver unit and the second reflector. 129 It is the distance from the second reflector to the bottom of the urea tank.

[0034] Urea solution levels measured using ultrasonic sensing elements are unaffected by nonlinearity and electrode variations, and can be used to calibrate urea solution levels obtained through impedance sensing values.

[0035] Furthermore, it also includes step 5, detecting whether there is a first type of abnormality in the ultrasonic sensing element. If there is a first type of abnormality, the urea solution level value ld calculated in step 3 is output; if there is no first type of abnormality, the urea solution level value lu calculated in step 4 is output.

[0036] Further, the detection of whether the ultrasonic sensing element has a first type of abnormality includes: measuring the amplitude value Lvl of the second ultrasonic echo signal that returns to the ultrasonic transceiver unit after being reflected for the first time by the second reflector, reflected for the second time by the urea solution surface, and reflected for the third time by the second reflector; comparing the amplitude value with a fifth threshold Thd_Lvll; if it is higher than the fifth threshold Thd_Lvll, it is determined that the ultrasonic sensing element does not have a first type of abnormality; otherwise, it is determined that the ultrasonic sensing element has a first type of abnormality.

[0037] By detecting the distortion of the second ultrasonic echo signal, it is possible to determine whether the ultrasonic sensing element is usable, thereby avoiding the problem of inaccurate measurement of urea solution level due to the failure of the ultrasonic sensing element.

[0038] Furthermore, it also includes step 5, detecting whether there is shaking in the urea solution; if there is shaking, then the urea solution level calculated in step 3 is executed; if there is no shaking, then the urea solution level calculated in step 4 is executed.

[0039] The detection of whether the urea solution is shaking includes: calculating the rate of change Zr of the impedance value Zsi corresponding to the first impedance sensing signal; if the Zr value is higher than the fourth threshold Thd_zrl, it is determined that the urea solution is shaking; otherwise, it is determined that the urea solution is not shaking.

[0040] Furthermore, it also includes step 5, detecting whether there is a second type of abnormality in the ultrasonic sensing element. If there is a second type of abnormality, the urea solution level value ld calculated in step 3 is output; if there is no second type of abnormality, the urea solution level value lu calculated in step 4 is output.

[0041] Further, step 5 includes: measuring the signal amplitude value S_amp of the first ultrasonic echo that returns to the ultrasonic transceiver unit after being reflected by the first reflector, and comparing it with a first threshold Thd_samp. If the value of S_amp is not higher than Thd_samp, it is determined that the ultrasonic sensing element has a second type of abnormality.

[0042] If the S_amp value is higher than Thd_samp, then measure the peak time Tpk of the first ultrasonic echo that returns to the ultrasonic transceiver unit after being reflected by the first reflector, and calculate the difference T_sft between it and the expected value Tpk0:

[0043] T_sft=Tpk-Tpk0

[0044] After obtaining the T_sft value, it is compared with the second threshold Thd_Tsft. If the T_sft value is not higher than the second threshold Thd_Tsft, it is determined that the ultrasonic sensing element has a second type of anomaly; if the T_sft value is higher than Thd_Tsft, it is determined that the ultrasonic sensing element does not have a second type of anomaly.

[0045] By detecting the distortion of the first ultrasonic echo signal, including changes in the height of the ultrasonic echo signal and the shift of the peak wave, it is possible to determine whether the ultrasonic sensing element is usable, thereby avoiding the problem of inaccurate measurement of urea concentration in urea solution due to the failure of the ultrasonic sensing element.

[0046] Furthermore, when it is determined that the ultrasonic sensing element does not exhibit any type II anomaly, the urea solution temperature Ts is measured, and the urea concentration γ of the urea solution is calculated using the first propagation time Tq of the ultrasonic wave and the urea solution temperature Ts. s .

[0047] Furthermore, when a second type of anomaly is determined to exist in the ultrasonic sensing element, the urea solution temperature Ts is measured, and the urea concentration γ of the urea solution is calculated using the impedance value Zsi corresponding to the first impedance sensing signal and the urea solution temperature Ts. s .

[0048] Furthermore, the urea solution temperature Ts is obtained by measuring the resistance Re of the first electrode, or by measuring it through the first temperature sensing element.

[0049] Furthermore, it also includes step 6, which, when it is determined that the ultrasonic sensing element does not have a second type of abnormality, uses the first impedance sensing signal to calculate the concentration of impurity ions in the urea solution, including:

[0050] The change in impedance Zsi corresponding to the first impedance sensing signal, dZsi, is calculated and defined as follows:

[0051] dZsi = (Zsi(γ i ) - Zsi(0)) / Zsi(0) (10)

[0052] Wherein, Zsi(γi) is the impedance between the first and second electrodes measured in a urea solution with an impurity ion concentration of γi, and Zsi(0) is the impedance between the first and second electrodes measured in a urea solution conforming to ISO 22241 standard; and the impurity ion concentration γi is obtained by looking up a table:

[0053] γi=Tbl(dZsi)

[0054] In the above formula, Tbl() represents table lookup calculation, and the table value in the table lookup calculation is obtained by measuring the impedance change value under different ion concentrations.

[0055] In exhaust gas treatment systems, impurity ions can remain and accumulate in the SCR (Selective Catalytic Reduction) catalyst, reducing its activity and denitrification efficiency, and even causing catalyst failure. When impurity ions are present in the urea solution, ultrasonic signals are not sensitive to impurity ions and cannot detect their concentration; however, impedance sensing signals are sensitive to impurity ions, and the high sensitivity of impedance sensing elements enables them to detect low concentrations of impurities in the urea solution.

[0056] The third aspect discloses a fault detection method for a sensor used to measure the level of urea solution, comprising the following steps:

[0057] Step 1: The signal processing unit determines whether the integrated sensing element, the liquid level sensing element, and the ultrasonic sensing element have an OOR fault in impedance detection and whether there are Type I and Type II anomalies in ultrasonic detection.

[0058] Step 2: If it is determined that the integrated sensing element, liquid level sensing unit and ultrasonic sensing element do not have the OOR fault, the first type of abnormality and the second type of abnormality, the urea solution level is calculated using impedance and ultrasonic waves respectively, and the difference between the two is used to determine whether the sensor has an IR fault.

[0059] Further, step 1 includes:

[0060] The first impedance sensing signal of the integrated sensing element is acquired. If the value of the first impedance sensing signal is greater than the first maximum measurement value or less than the first minimum measurement value, it is determined that the integrated sensing element has an OOR fault.

[0061] The second impedance sensing signal of the liquid level sensing unit is acquired. If the value of the second impedance sensing signal is greater than the second maximum measurement value or less than the second minimum measurement value, it is determined that the integrated liquid level sensing unit has an OOR fault.

[0062] The amplitude value Lvl of the second ultrasonic echo signal obtained from the ultrasonic transceiver unit is measured and compared with the fifth threshold Thd_Lvll. If it is higher than the fifth threshold Thd_Lvll, it is determined that the ultrasonic sensing element does not have a first type of abnormality; otherwise, it is determined that the ultrasonic sensing element has a first type of abnormality.

[0063] The amplitude value S_amp of the first ultrasonic echo signal obtained from the ultrasonic transceiver unit is measured, and the amplitude value S_amp is compared with the first threshold Thd_samp. If S_amp is not higher than Thd_samp, it is determined that there is a second type of abnormality in the ultrasonic sensing element.

[0064] If the S_amp value is higher than Thd_samp, then measure the peak time Tpk of the first ultrasonic echo signal and calculate the difference T_sft between this peak time and the expected value Tpk0:

[0065] T_sft=Tpk-Tpk0

[0066] The T_sft value is compared with the second threshold Thd_Tsft. If T_sft is not higher than the second threshold Thd_Tsft, it is determined that the ultrasonic sensing element has a second type of anomaly; if T_sft is higher than Thd_Tsft, it is determined that the ultrasonic sensing element does not have a second type of anomaly.

[0067] Further, step 2 includes: Let Ld be the urea solution level value calculated by the integrated sensing element and the liquid level sensing unit, and Lu be the urea solution level value calculated by the ultrasonic sensing element; calculate the difference between the two, DLvl_Diff:

[0068] DLvl_Diff = abs(Li-Lu)

[0069] In the formula, abs() is the calculation of absolute value. If the value of DLvl_Diff is higher than the third threshold Thd_Ldiff, it is determined that the sensor has an IR fault; otherwise, it is determined that the sensor has not an IR fault.

[0070] Beneficial effects: This application provides a sensor for measuring the level of urea solution. It is compact and inexpensive, and can accurately measure the urea solution level even under conditions of urea solution sloshing, pressure changes, and agitation. It also enables sensor self-diagnosis, including OOR (Out of Memory) problems that cause readings to exceed the effective range and IR (Inaccurate Relative Value) problems where the sensor's sensed value is within the normal range but inaccurate. The sensor is compact and inexpensive. Attached Figure Description

[0071] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0072] Figure 1 This is a schematic diagram of the structure of a sensor for measuring the level of urea solution, provided in an embodiment of this application.

[0073] Figure 2 This is a schematic diagram of the structure of a level sensing unit for measuring the level of urea solution, provided in an embodiment of this application.

[0074] Figure 3 This is another schematic diagram of a level sensing unit for measuring the level of a urea solution, provided as an embodiment of this application.

[0075] Figure 4 This is a schematic diagram of the integrated sensing element and ultrasonic sensing element of a sensor for measuring the level of urea solution, provided in an embodiment of this application.

[0076] Figure 5 This is another structural schematic diagram of a sensor for measuring the level of urea solution, which includes a combined sensing element and an ultrasonic sensing element, as provided in an embodiment of this application.

[0077] Figure 6 This is a schematic diagram of the structure of a signal processing unit for a sensor used to measure the level of urea solution, provided in an embodiment of this application.

[0078] Figure 7 This is a schematic diagram of an ultrasonic sensor emitting ultrasonic waves and receiving a first ultrasonic echo and a second ultrasonic echo in a method for measuring the level of urea solution provided in an embodiment of this application.

[0079] Figure 8 This is a flowchart illustrating a fault detection method for a sensor used to measure the level of urea solution, as provided in an embodiment of this application. Detailed Implementation

[0080] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0081] The first embodiment of this application discloses a sensor for measuring the level of urea solution, including an integrated sensing element 100, a level sensing unit 200, and a signal processing unit (SPU) 120. The integrated sensing element 100 is completely covered by the urea solution, the level sensing unit 200 is partially covered by the urea solution, and the signal processing unit 120 is electrically connected to the integrated sensing element 100 and the level sensing unit 200 respectively.

[0082] The integrated sensing element 100 is used to receive the second excitation signal generated by the signal processing unit 120, generate the first impedance sensing signal, and send the first impedance sensing signal to the signal processing unit 120.

[0083] The liquid level sensing unit 200 is used to receive the third excitation signal generated by the signal processing unit 120, generate the second impedance sensing signal, and send the second impedance sensing signal to the signal processing unit 120.

[0084] The signal processing unit 120 is used to generate a second excitation signal and a third excitation signal and send them to the integrated sensing element 100 and the liquid level sensing unit 200 respectively, receive the impedance sensing signal sent by the integrated sensing element 100 and the liquid level sensing unit 200, and calculate the urea solution level based on the impedance sensing signal.

[0085] like Figure 1 As shown, in a specific implementation, the sensor for measuring the urea solution level can be equipped with a rubber head 80 and a base 70. Through the rubber head 80, the engine coolant flows through the coolant pipe 50 with an inlet 51 and an outlet 52 to heat the urea solution in the urea tank. The signal processing unit 120 can be set on the top of the rubber head 80 and connected to the base 70 through a cable pipe 60. The integrated sensing element 100 is connected to the base 70.

[0086] In this embodiment, as Figure 2 As shown, the liquid level sensing unit 200 includes a third electrode 220 and a fourth electrode 205. The urea solution between the third electrode 220 and the fourth electrode 205 is connected to the urea solution in the integrated sensing element 100. The third electrode 220 is electrically connected to the signal processing unit 120 via a third signal line 222, and the fourth electrode 205 is electrically connected to the signal processing unit 120 via a fourth signal line 223. The positions of the third electrode 220 and the fourth electrode 205 are not specifically limited in this embodiment, as long as there is no electrical short circuit between the two electrodes. The impedance of the third electrode 220 and the fourth electrode 205 can change with temperature. Specifically, the third electrode 220 and the fourth electrode 205 can be made of materials such as stainless steel (e.g., 304, 304L, 316, 316L) or Hastelloy (nickel-molybdenum-chromium-tungsten alloy).

[0087] In this embodiment, as Figure 4 As shown, the integrated sensing element 100 includes a first electrode 130 and a second electrode 125. One end of the second electrode 125 is electrically connected to the signal processing unit 120 through a second signal line 123; one end of the first electrode 130 is electrically connected to the signal processing unit 120 through a first signal line 128.

[0088] In this embodiment, as Figure 6 As shown, the signal processing unit 120 includes a central processing unit 230 and an impedance signal processing subunit 250. The central processing unit 230 is used to send commands to the impedance signal processing subunit 250, receive the impedance sensing signal after it has been processed by the impedance signal processing subunit 250, and calculate the urea solution level based on the impedance sensing signal.

[0089] The impedance signal processing subunit 250 is electrically connected to the third electrode 220 via the third signal line 222 and to the fourth electrode 205 via the fourth signal line 223. It is used to receive the third command sent by the central processing unit 230, generate the third excitation signal, and send the third excitation signal to the third electrode 220; receive the second impedance sensing signal generated by the third excitation signal through the third electrode 220 and the fourth electrode 205, process it, and send it to the central processing unit 230; the fourth electrode 205 is grounded.

[0090] The impedance signal processing subunit 250 is also electrically connected to one end of the first electrode 130 via a first signal line 128 and to one end of the second electrode 125 via a second signal line 123. It is used to receive a second command sent by the central processing unit 230, generate a second excitation signal, and send the second excitation signal to the first electrode 130. It also receives a first impedance sensing signal generated by the second excitation signal through the first electrode 130 and the second electrode 125, processes it, and sends it to the central processing unit 230.

[0091] In one alternative implementation, the signal processing unit 120 further includes a resistance measurement module 260, such as... Figure 3 As shown, the liquid level sensing unit 200 further includes a second temperature sensing element 227, which is used to measure the temperature of the urea solution between the third electrode 220 and the fourth electrode 205, and is electrically connected to the resistance measurement module 260 through the seventh signal line 226; the resistance measurement module 260 is used to measure the resistance of the second temperature sensing element 227 and send the resistance value to the central processing unit 230.

[0092] In this embodiment, the sensor further includes an ultrasonic sensing element, which is completely covered by a urea solution. The urea solution between the first electrode 130 and the second electrode 125 is connected to the urea solution in the ultrasonic sensing element. The signal processing unit 120 further includes an ultrasonic signal processing subunit 240. The ultrasonic sensing element is electrically connected to the ultrasonic signal processing subunit 240 via a fifth signal line 115. The ultrasonic signal processing subunit 240 is used to receive a first command sent by the central processing unit 230, generate a first excitation signal, send the first excitation signal to the ultrasonic sensing element, and receive the sensing signal generated by the ultrasonic sensing element, process it, and send it to the central processing unit 230.

[0093] In this embodiment, as Figure 4 As shown, the ultrasonic sensing element includes an ultrasonic transceiver unit 112, a first reflector 122, and a second reflector 129. The ultrasonic transceiver unit 112 and the first reflector 122 are parallel, and a urea solution exists between them. The ultrasonic transceiver unit 112 and the second reflector 129 are separated by a urea solution, and their extension lines form an angle. This angle allows the second reflector 129 to receive the ultrasonic waves transmitted by the ultrasonic transceiver unit 112 and reflect them onto the surface of the urea solution. The surface of the urea solution reflects a second ultrasonic echo back to the second reflector 129, which then reflects the second ultrasonic echo back to the ultrasonic transceiver unit 112. The first reflector 122 receives the ultrasonic waves transmitted by the ultrasonic transceiver unit 112, generates a first ultrasonic echo, and then reflects the first ultrasonic echo back to the ultrasonic transceiver unit 112. The ultrasonic transceiver unit 112 sends the sensing signal generated by the first and second ultrasonic echo signals to the ultrasonic signal processing subunit 240. For example, the second electrode 125 includes a horizontal portion and an inclined portion. A mounting surface 110 is provided above the end of the horizontal portion of the second electrode 125 away from the inclined portion. An ultrasonic transceiver unit 112 is disposed close to the mounting surface 110. A first reflector 122 may be disposed at the end of the horizontal portion of the second electrode 125 near the inclined portion. A second reflector 129 is disposed close to the inclined portion of the second electrode 125.

[0094] In one alternative implementation, the impedance of the first electrode 130 and the second electrode 125 varies with temperature. Specifically, the first electrode 130 and the second electrode 125 can be made of materials such as stainless steel (e.g., 304, 304L, 316, 316L) or Hastelloy (nickel-molybdenum-chromium-tungsten alloy). The other end of the resistance measurement module 260 and the first electrode 130 are electrically connected via a sixth signal line 126 for measuring the resistance of the first electrode 130 and sending the resistance value to the central processing unit 230.

[0095] In another alternative implementation, such as Figure 5As shown, the integrated sensing element 100 also includes a first temperature sensing element 135, which is used to measure the temperature of the urea solution between the first electrode 130 and the second electrode 125. It is electrically connected to the resistance measurement module 260 through the eighth signal line 127. The resistance measurement module 260 is used to measure the resistance of the first temperature sensing element 135 and send the resistance value to the central processing unit 230.

[0096] The second embodiment of this application discloses a method for measuring the level of a urea solution, including the following steps:

[0097] Step 1: The signal processing unit 120 generates an excitation signal and sends it to the integrated sensing element 100 and the liquid level sensing unit 200.

[0098] Step 2: The integrated sensing element 100 and the liquid level sensing unit 200 receive the excitation signal generated by the signal processing unit 120, generate the first impedance sensing signal and the second impedance sensing signal respectively, and send them to the signal processing unit 120.

[0099] Step 3: The signal processing unit 120 receives the first impedance sensing signal and the second impedance sensing signal and calculates the urea solution level.

[0100] In this embodiment, the impedance value corresponding to the first impedance sensing signal in step 2 is Zsi, and the impedance value corresponding to the second impedance sensing signal is Zsl; step 3 includes: calculating the ratio Rz between the two impedance values:

[0101] Rz=Zsi / Zsl (1).

[0102] In one alternative implementation, when calculating the urea solution level in step 3, a lookup table is used to compensate for nonlinear effects:

[0103] ld = Tbl(Rz) (2)

[0104] In formula (2), ld is the urea solution level value calculated in step 3, and Tbl() represents the table lookup calculation. The table value in the table lookup calculation is calibrated by the test data obtained from experiments at different urea solution concentrations.

[0105] In another alternative implementation, when calculating the urea solution level in step 3, a two-dimensional lookup table is used to compensate for the nonlinear effects caused by the urea solution temperature.

[0106] ld = Tbl(Rz, T227) (3)

[0107] Wherein, T227 is the urea solution temperature obtained by the second temperature sensing element 227, which is calculated by the signal processing unit 120 by obtaining the resistance of the second temperature sensing element 227, ld is the urea solution level value calculated in step 3, and Tbl() represents table lookup calculation. The table value in the table lookup calculation is calibrated by test data obtained from experiments at different urea solution concentrations and temperatures.

[0108] In this embodiment, step 4 is also included, which calculates the urea solution level using the ultrasonic echo signal, including: measuring the first propagation time T of the ultrasonic wave returning to the ultrasonic transceiver unit 112 after being reflected by the first reflector 122 from the ultrasonic transceiver unit 112. q The second propagation time T of the ultrasonic wave, after being reflected for the first time by the second reflector 129, reflected a second time by the surface of the urea solution, and reflected a third time by the second reflector 129 back to the ultrasonic transceiver unit 112, is as follows: l The urea solution level is calculated using the following formula:

[0109] lu = =(h 129 -d 129 )+d 122 *T l / T q (6)

[0110] In the formula, lu is the urea solution level calculated in step 4, and d 122 d is the distance between the ultrasonic transceiver unit 112 and the first reflector 122. 129 h is the distance between the ultrasonic transceiver unit 112 and the second reflector 129. 129 It is the distance from the second reflector 129 to the bottom of the urea tank.

[0111] In one optional implementation, step 5 is further included: detecting whether there is a first type of abnormality in the ultrasonic sensing element; if there is a first type of abnormality, the urea solution level value ld calculated in step 3 is output; if there is no first type of abnormality, the urea solution level value lu calculated in step 4 is output.

[0112] The detection of whether the ultrasonic sensing element has a first type of anomaly includes: measuring the amplitude value Lvl of the second ultrasonic echo signal 183 that returns to the ultrasonic transceiver unit 112 after being reflected for the first time by the second reflector 129, reflected a second time by the urea solution surface, and reflected a third time by the second reflector 129. Figure 7As shown, the amplitude value is compared with the fifth threshold Thd_Lvll. If it is higher than the fifth threshold Thd_Lvll, it is determined that the ultrasonic sensing element does not have a type I anomaly; otherwise, it is determined that the ultrasonic sensing element has a type I anomaly. The fifth threshold Thd_Lvll can be set according to the signal amplitude range during normal use.

[0113] In another optional implementation, step 5 is also included: detecting whether there is shaking in the urea solution; if there is shaking, then the urea solution level calculated in step 3 is executed; if there is no shaking, then the urea solution level calculated in step 4 is executed.

[0114] The detection of whether the urea solution is sloshing includes: calculating the rate of change Zr of the impedance value Zsi corresponding to the first impedance sensing signal; if the Zr value is higher than the fourth threshold Thd_zrl, it is determined that the urea solution is sloshing; otherwise, it is determined that the urea solution is not sloshing. The fourth threshold Thd_zrl can be set according to the signal amplitude range during normal use.

[0115] In another alternative implementation, step 5 is also included: detecting whether there is a second type of anomaly in the ultrasonic sensing element; if there is a second type of anomaly, the urea solution level value ld calculated in step 3 is output; if there is no second type of anomaly, the urea solution level value lu calculated in step 4 is output.

[0116] Step 5 includes: measuring the amplitude value S_amp of the first ultrasonic echo signal 182 that returns to the ultrasonic transceiver unit 112 after being reflected by the first reflector 122, such as... Figure 7 As shown, it is compared with the first threshold Thd_samp. If the S_amp value is not higher than Thd_samp, it is determined that the ultrasonic sensing element has a second type of abnormality. The first threshold Thd_samp can be set to be slightly higher than the maximum value of S_amp in the operating temperature range (e.g., -11℃ to -85℃).

[0117] If the S_amp value is higher than Thd_samp, then measure the peak time Tpk of the first ultrasonic echo that returns to the ultrasonic transceiver unit 112 after being reflected by the first reflector 122, and calculate the difference T_sft between it and the expected value Tpk0:

[0118] T_sft=Tpk-Tpk0

[0119] After obtaining the T_sft value, it is compared with the second threshold Thd_Tsft. If the T_sft value is not higher than the second threshold Thd_Tsft, the ultrasonic sensing element is determined to have a type II anomaly; if T_sft is higher than Thd_Tsft, the ultrasonic sensing element is determined not to have a type II anomaly. The normal value Tpk0 is determined by the pulse width of the ultrasonic excitation signal and can be set to half the pulse width of the excitation signal. The second threshold Thd_Tsft can be set to the width of one or several carrier pulses.

[0120] In some embodiments, when it is determined that the ultrasonic sensing element does not have a type II anomaly, the urea solution temperature Ts is measured, and the urea concentration γ of the urea solution is calculated using the first propagation time Tq of the ultrasonic wave and the urea solution temperature Ts. s .

[0121] In other embodiments, when a second type of anomaly is determined to exist in the ultrasonic sensing element, the urea solution temperature Ts is measured, and the urea concentration γ of the urea solution is calculated using the impedance value Zsi corresponding to the first impedance sensing signal and the urea solution temperature Ts. s .

[0122] The urea solution temperature Ts is obtained by measuring the resistance Re of the first electrode 130 or by measuring the first temperature sensing element 135.

[0123] In this embodiment, step 6 is also included: when it is determined that the ultrasonic sensing element does not have a second type of abnormality, the concentration of impurity ions in the urea solution is calculated using the first impedance sensing signal, including:

[0124] The change in impedance Zsi corresponding to the first impedance sensing signal, dZsi, is calculated and defined as follows:

[0125] dZsi = (Zsi(γ i ) - Zsi(0)) / Zsi(0) (10)

[0126] Wherein, Zsi(γi) is the impedance between the first electrode 130 and the second electrode 125 measured in a urea solution with an impurity ion concentration of γi, and Zsi(0) is the impedance between the first electrode 130 and the second electrode 125 measured in a urea solution conforming to ISO 22241 standard; and the impurity ion concentration γi is obtained by looking up a table:

[0127] γi=Tbl(dZsi)

[0128] In the above formula, Tbl() represents table lookup calculation, and the table value in the table lookup calculation is obtained by measuring the impedance change value under different ion concentrations.

[0129] The third embodiment of this application discloses a fault detection method for a sensor used to measure the level of urea solution, such as... Figure 8 As shown, it includes the following steps:

[0130] Step 1: The signal processing unit 120 determines whether the integrated sensing element 100, the liquid level sensing unit 200 and the ultrasonic sensing element have an OOR fault in impedance detection and whether there are first-type and second-type abnormalities in ultrasonic detection.

[0131] Step 2: If it is determined that the integrated sensing element 100, the liquid level sensing unit 200 and the ultrasonic sensing element do not have the OOR fault, the first type of abnormality and the second type of abnormality, the urea solution level is calculated using impedance and ultrasonic waves respectively, and the difference between the two is used to determine whether the sensor has an IR fault.

[0132] In this embodiment, step 1 includes:

[0133] The first impedance sensing signal of the integrated sensing element 100 is acquired. If the value of the first impedance sensing signal is greater than the first maximum measurement value (such as the signal value measured when the circuit is open) or less than the first minimum measurement value (such as the signal value measured when the circuit is short), it is determined that the integrated sensing element 100 has an OOR fault.

[0134] The second impedance sensing signal of the liquid level sensing unit 200 is acquired. If the value of the second impedance sensing signal is greater than the second maximum measurement value (such as the signal value measured when the circuit is open) or less than the second minimum measurement value (such as the signal value measured when the circuit is short), it is determined that the integrated liquid level sensing unit 200 has an OOR fault.

[0135] When the integrated sensing element 100 or the integrated liquid level sensing unit 200 has an OOR fault, the status flag Stat_LI = 1 can be used to indicate that there is no OOR fault. When neither the integrated sensing element 100 nor the integrated liquid level sensing unit 200 has an OOR fault, the status flag Stat_LI = 0 can be used to indicate that there is no OOR fault.

[0136] The amplitude value Lvl of the second ultrasonic echo signal acquired from the ultrasonic transceiver unit 112 is measured and compared with the fifth threshold Thd_Lvll. If it is higher than the fifth threshold Thd_Lvll, it is determined that the ultrasonic sensing element does not have a first type of abnormality; otherwise, it is determined that the ultrasonic sensing element has a first type of abnormality. The fifth threshold Thd_Lvll can be set according to the signal amplitude range during normal use.

[0137] The amplitude value S_amp of the first ultrasonic echo signal obtained from the ultrasonic transceiver unit 112 is measured, and the amplitude value S_amp is compared with the first threshold Thd_samp. If S_amp is not higher than Thd_samp, it is determined that the ultrasonic sensing element has a second type of abnormality. The first threshold Thd_samp can be set to be slightly higher than the maximum value of S_amp in the operating temperature range (e.g., -11℃ to -85℃).

[0138] If the S_amp value is higher than Thd_samp, then measure the peak time Tpk of the first ultrasonic echo signal and calculate the difference T_sft between this peak time and the expected value Tpk0:

[0139] T_sft=Tpk-Tpk0

[0140] The T_sft value is then compared with the second threshold Thd_Tsft. If T_sft is not higher than the second threshold Thd_Tsft, the ultrasonic sensing element is determined to have a type II anomaly; if T_sft is higher than Thd_Tsft, the ultrasonic sensing element is determined not to have a type II anomaly. The normal value Tpk0 is determined by the pulse width of the ultrasonic excitation signal and can be set to half the pulse width. The second threshold Thd_Tsft can be set to the width of one or several carrier pulses.

[0141] When the ultrasonic sensing element has a first-class or second-class abnormality, the status flag Stat_LU = 1 can be used to indicate it; otherwise, the status flag Stat_LU = 0 can be used.

[0142] In this embodiment, step 2 includes: Let Ld be the urea solution level value calculated by the integrated sensing element 100 and the liquid level sensing unit 200, and Lu be the urea solution level value calculated by the ultrasonic sensing element; calculate the difference between the two, DLvl_Diff.

[0143] DLvl_Diff = abs(Li-Lu)

[0144] In the formula, abs() is the calculation of the absolute value. If the value of DLvl_Diff is higher than the third threshold Thd_Ldiff, the sensor is determined to have an IR fault, which can be represented by the fault flag Fault_LR = 1; otherwise, the sensor is determined not to have an IR fault, which can be represented by the fault flag Fault_LR = 0. The third threshold Thd_Ldiff can be set according to the error limit range required by OBD or design specifications.

[0145] In its specific implementation, this application provides a computer storage medium and a corresponding data processing unit. The computer storage medium can store a computer program, which, when executed by the data processing unit, can run the invention's content regarding a method for measuring urea solution level and a fault detection method for a sensor used to measure urea solution level, as well as some or all of the steps in various embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0146] Those skilled in the art will clearly understand that the technical solutions in the embodiments of the present invention can be implemented using computer programs and their corresponding general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of computer programs, i.e., software products. These computer program software products can be stored in a storage medium and include several instructions to cause a device containing a data processing unit (which may be a personal computer, server, microcontroller, MUU, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0147] This invention provides a sensor and method for measuring the level of urea solution. Many methods and approaches exist for implementing this technical solution; the above description is merely a specific embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A sensor for measuring the level of a urea solution, characterized in that, The system includes a comprehensive sensing element (100), a liquid level sensing unit (200), an ultrasonic sensing element, and a signal processing unit (120). The comprehensive sensing element (100) and the ultrasonic sensing element are completely covered by urea solution, and the urea solution in the comprehensive sensing element (100) and the urea solution in the ultrasonic sensing element are connected. The liquid level sensing unit (200) is partially covered by urea solution, and the signal processing unit (120) is electrically connected to the comprehensive sensing element (100), the ultrasonic sensing element, and the liquid level sensing unit (200). The integrated sensing element (100) is used to receive the second excitation signal generated by the signal processing unit (120), generate the first impedance sensing signal, and send the first impedance sensing signal to the signal processing unit (120). The liquid level sensing unit (200) is used to receive the third excitation signal generated by the signal processing unit (120), generate the second impedance sensing signal, and send the second impedance sensing signal to the signal processing unit (120). The ultrasonic sensing element is used to receive the first excitation signal generated by the signal processing unit (120), generate a sensing signal, and send the sensing signal to the signal processing unit (120). The signal processing unit (120) is used to generate a first excitation signal, a second excitation signal, and a third excitation signal and send them to the ultrasonic sensing element, the integrated sensing element (100), and the liquid level sensing unit (200), respectively. It also receives the impedance sensing signal sent by the integrated sensing element (100) and the liquid level sensing unit (200) and the sensing signal sent by the ultrasonic sensing element. If the ultrasonic sensing element is abnormal or the urea solution is sloshing, the urea solution level is calculated based on the impedance sensing signal. If there is no abnormality in the ultrasonic sensor or the urea solution is not shaking, the urea solution level is calculated using the sensing signal sent by the ultrasonic sensor. Detecting whether urea solution is shaking includes: calculating the rate of change Zr of the impedance value Zsi corresponding to the first impedance sensing signal; if the Zr value is higher than the fourth threshold Thd_zrl, it is determined that the urea solution is shaking; otherwise, it is determined that the urea solution is not shaking.

2. The sensor for measuring the level of urea solution according to claim 1, characterized in that, The liquid level sensing unit (200) includes a third electrode (220) and a fourth electrode (205). The urea solution between the third electrode (220) and the fourth electrode (205) is connected to the urea solution in the integrated sensing element (100). The third electrode (220) is electrically connected to the signal processing unit (120) through a third signal line (222), and the fourth electrode (205) is electrically connected to the signal processing unit (120) through a fourth signal line (223).

3. A sensor for measuring the level of urea solution according to claim 2, characterized in that, The integrated sensing element (100) includes a first electrode (130) and a second electrode (125). One end of the second electrode (125) is electrically connected to the signal processing unit (120) via a second signal line (123); one end of the first electrode (130) is electrically connected to the signal processing unit (120) via a first signal line (128).

4. A sensor for measuring the level of urea solution according to claim 3, characterized in that, The signal processing unit (120) includes a central processing unit (230) and an impedance signal processing subunit (250). The central processing unit (230) is used to send commands to the impedance signal processing subunit (250), receive the impedance sensing signal after it has been processed by the impedance signal processing subunit (250), and calculate the urea solution level based on the impedance sensing signal. The impedance signal processing subunit (250) is electrically connected to the third electrode (220) via the third signal line (222) and to the fourth electrode (205) via the fourth signal line (223). It is used to receive the third command sent by the central processing unit (230), generate the third excitation signal, and send the third excitation signal to the third electrode (220); receive the second impedance sensing signal generated by the third excitation signal through the third electrode (220) and the fourth electrode (205), process it, and send it to the central processing unit (230). The impedance signal processing subunit (250) is also electrically connected to one end of the first electrode (130) via a first signal line (128) and to one end of the second electrode (125) via a second signal line (123). It is used to receive a second command sent by the central processing unit (230), generate a second excitation signal, and send the second excitation signal to the first electrode (130). It also receives a first impedance sensing signal generated by the second excitation signal through the first electrode (130) and the second electrode (125), processes it, and sends it to the central processing unit (230).

5. A sensor for measuring the level of urea solution according to claim 4, characterized in that, The signal processing unit (120) further includes a resistance measurement module (260), and the liquid level sensing unit (200) further includes a second temperature sensing element (227). The second temperature sensing element (227) is used to measure the temperature of the urea solution between the third electrode (220) and the fourth electrode (205), and is electrically connected to the resistance measurement module (260) through the seventh signal line (226). The resistance measurement module (260) is used to measure the resistance of the second temperature sensing element (227) and send the resistance value to the central processing unit (230).

6. A sensor for measuring the level of urea solution according to claim 4 or 5, characterized in that, The urea solution between the first electrode (130) and the second electrode (125) is connected to the urea solution in the ultrasonic sensing element; the signal processing unit (120) further includes an ultrasonic signal processing subunit (240), and the ultrasonic sensing element is electrically connected to the ultrasonic signal processing subunit (240) through the fifth signal line (115); the ultrasonic signal processing subunit (240) is used to receive the first command sent by the central processing unit (230), generate the first excitation signal, send the first excitation signal to the ultrasonic sensing element, and receive the sensing signal generated by the ultrasonic sensing element, process it and send it to the central processing unit (230).

7. A sensor for measuring the level of urea solution according to claim 6, characterized in that, The ultrasonic sensing element includes an ultrasonic transceiver unit (112), a first reflector (122), and a second reflector (129). The ultrasonic transceiver unit (112) and the first reflector (122) are parallel, and there is a urea solution between them. There is a urea solution between the ultrasonic transceiver unit (112) and the second reflector (129), and the extension lines of the two form an angle. The angle allows the second reflector (129) to receive the ultrasonic waves sent by the ultrasonic transceiver unit (112) and reflect them to the surface of the urea solution. The surface of the urea solution reflects a second ultrasonic echo to the second reflector (129), and the second reflector (129) then reflects the second ultrasonic echo back to the ultrasonic transceiver unit (112). The first reflector (122) receives the ultrasonic waves sent by the ultrasonic transceiver unit (112), generates a first ultrasonic echo, and then reflects the first ultrasonic echo back to the ultrasonic transceiver unit (112). The ultrasonic transceiver unit (112) sends the sensing signal generated by the first ultrasonic echo and the second ultrasonic echo signal to the ultrasonic signal processing subunit (240).

8. A sensor for measuring the level of urea solution according to claim 7, characterized in that, The other end of the resistance measurement module (260) and the first electrode (130) are electrically connected via a sixth signal line (126) for measuring the resistance of the first electrode (130) and sending the resistance value to the central processing unit (230).

9. A sensor for measuring the level of urea solution according to claim 7, characterized in that, The integrated sensing element (100) further includes a first temperature sensing element (135), which is used to measure the temperature of the urea solution between the first electrode (130) and the second electrode (125). It is electrically connected to the resistance measurement module (260) via the eighth signal line (127). The resistance measurement module (260) is used to measure the resistance of the first temperature sensing element (135) and send the resistance value to the central processing unit (230).

10. A method for measuring the level of a urea solution, applied to a sensor for measuring the level of a urea solution as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: The signal processing unit (120) generates an excitation signal and sends it to the integrated sensing element (100) and the liquid level sensing unit (200). Step 2: The integrated sensing element (100) and the liquid level sensing unit (200) receive the excitation signal generated by the signal processing unit (120), generate the first impedance sensing signal and the second impedance sensing signal respectively, and send them to the signal processing unit (120). Step 3: The signal processing unit (120) receives the first impedance sensing signal and the second impedance sensing signal and calculates the urea solution level.

11. The method for measuring the level of a urea solution according to claim 10, characterized in that, In step 2, the impedance value corresponding to the first impedance sensing signal is Zsi, and the impedance value corresponding to the second impedance sensing signal is Zsl; step 3 includes: calculating the ratio Rz between the two impedance values. Rz=Zsi / Zsl (1).

12. A method for measuring the level of a urea solution according to claim 11, characterized in that, In step 3, when calculating the urea solution level, a lookup table is used to compensate for nonlinear effects: ld = Tbl(Rz) (2) In formula (2), ld is the urea solution level value calculated in step 3, and Tbl() represents the table lookup calculation. The table value in the table lookup calculation is calibrated by the test data obtained from experiments at different urea solution concentrations.

13. A method for measuring the level of a urea solution according to claim 11, characterized in that, In step 3, when calculating the urea solution level, a two-dimensional lookup table is used to compensate for the nonlinear effects caused by the temperature of the urea solution. ld = Tbl(Rz, T227) (3) Wherein, T227 is the urea solution temperature obtained by the second temperature sensing element (227), ld is the urea solution level value calculated by step 3, and Tbl() represents table lookup calculation. The table value in the table lookup calculation is calibrated by test data obtained from experiments at different urea solution concentrations and temperatures.

14. A method for measuring the level of a urea solution according to claim 12 or 13, characterized in that, The method also includes step 4, which calculates the urea solution level using the ultrasonic echo signal, including: measuring the first propagation time T of the ultrasonic wave returning to the ultrasonic transceiver unit (112) after being reflected by the first reflector (122). q The second propagation time T of the ultrasonic wave from the ultrasonic transceiver unit (112) after the first reflection by the second reflector (129), the second reflection by the surface of the urea solution, and the third reflection by the second reflector (129) back to the ultrasonic transceiver unit (112) is as follows. l The urea solution level is calculated using the following formula: lu = =(h 129 -d 129 )+d 122 *T l / T q (6) In the formula, lu is the urea solution level calculated in step 4, and d 122 d is the distance between the ultrasonic transceiver unit (112) and the first reflector (122). 129 h is the distance between the ultrasonic transceiver unit (112) and the second reflector (129). 129 It is the distance from the second reflector (129) to the bottom of the urea tank.

15. A method for measuring the level of a urea solution according to claim 14, characterized in that, It also includes step 5, which detects whether there is a first type of abnormality in the ultrasonic sensing element. If there is a first type of abnormality, the urea solution level value ld calculated in step 3 is output; if there is no first type of abnormality, the urea solution level value lu calculated in step 4 is output.

16. The method for measuring the level of a urea solution according to claim 15, characterized in that, The method for detecting whether the ultrasonic sensing element has a first type of abnormality includes: measuring the amplitude value Lvl of the second ultrasonic echo signal that returns to the ultrasonic transceiver unit (112) after the first reflection from the ultrasonic transceiver unit (112) through the second reflector (129), the second reflection from the urea solution surface, and the third reflection from the second reflector (129), and comparing the amplitude value with the fifth threshold Thd_Lvll. If it is higher than the fifth threshold Thd_Lvll, it is determined that the ultrasonic sensing element does not have a first type of abnormality; otherwise, it is determined that the ultrasonic sensing element has a first type of abnormality.

17. A method for measuring the level of a urea solution according to claim 14, characterized in that, The process also includes step 5, which detects whether the urea solution is shaking. If shaking is present, the urea solution level calculated in step 3 is executed; if shaking is absent, the urea solution level calculated in step 4 is executed.

18. A method for measuring the level of a urea solution according to claim 14, characterized in that, It also includes step 5, which detects whether there is a second type of abnormality in the ultrasonic sensing element. If there is a second type of abnormality, the urea solution level value ld calculated in step 3 is output; if there is no second type of abnormality, the urea solution level value lu calculated in step 4 is output.

19. A method for measuring the level of a urea solution according to claim 18, characterized in that, Step 5 includes: measuring the signal amplitude value S_amp of the first ultrasonic echo that returns to the ultrasonic transceiver unit (112) after being reflected by the first reflector (122), and comparing it with the first threshold Thd_samp. If the value of S_amp is not higher than Thd_samp, it is determined that the ultrasonic sensing element has a second type of abnormality. If the S_amp value is higher than Thd_samp, the peak time Tpk of the first ultrasonic echo that returns to the ultrasonic transceiver unit (112) after being reflected by the first reflector (122) is measured, and the difference T_sft between it and the expected value Tpk0 is calculated: T_sft=Tpk-Tpk0, After obtaining the T_sft value, it is compared with the second threshold Thd_Tsft. If the T_sft value is not higher than the second threshold Thd_Tsft, it is determined that the ultrasonic sensing element has a second type of anomaly; if the T_sft value is higher than Thd_Tsft, it is determined that the ultrasonic sensing element does not have a second type of anomaly.

20. A method for measuring the level of a urea solution according to claim 19, characterized in that, When it is determined that the ultrasonic sensing element does not have a type II anomaly, the urea solution temperature Ts is measured, and the urea concentration φ of the urea solution is calculated using the first propagation time Tq of the ultrasonic wave and the urea solution temperature Ts. s .

21. A method for measuring the level of a urea solution according to claim 19, characterized in that, When a second type of abnormality is determined in the ultrasonic sensing element, the urea solution temperature Ts is measured, and the impedance value Zsi corresponding to the first impedance sensing signal and the urea solution temperature are used as the basis for the measurement. Ts Calculate the urea concentration of the urea solution. s .

22. A method for measuring the level of a urea solution according to claim 20 or 21, characterized in that, The temperature of the urea solution Ts It can be obtained by measuring the resistance Re of the first electrode (130) or by measuring the first temperature sensing element (135).

23. The method for measuring the level of a urea solution according to claim 19, characterized in that, The method also includes step 6, which, when it is determined that the ultrasonic sensing element does not have a second type of abnormality, uses the first impedance sensing signal to calculate the concentration of impurity ions in the urea solution, including: The change in impedance Zsi corresponding to the first impedance sensing signal, dZsi, is calculated and defined as follows: dZsi = (Zsi(𝛾 i ) - Zsi(0)) / Zsi(0) (10) Wherein, Zsi(𝛾i) is the impedance between the first electrode (130) and the second electrode (125) measured in a urea solution with an impurity ion concentration of 𝛾i, and Zsi(0) is the impedance between the first electrode (130) and the second electrode (125) measured in a urea solution conforming to ISO 22241 standard; and the impurity ion concentration 𝛾i is obtained by looking up a table: 𝛾i = Tbl(dZsi) In the above formula, Tbl() represents table lookup calculation, and the table value in the table lookup calculation is obtained by measuring the impedance change value under different ion concentrations.

24. A fault detection method for a sensor used to measure the level of a urea solution, applied to the sensor for measuring the level of a urea solution as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1, the signal processing unit (120) determines whether the integrated sensing element (100), the liquid level sensing unit (200) and the ultrasonic sensing element have an OOR fault in impedance detection and whether there are first-type and second-type abnormalities in ultrasonic detection. Step 2: If it is determined that the integrated sensing element (100), the liquid level sensing unit (200) and the ultrasonic sensing element do not have the OOR fault, the first type of abnormality and the second type of abnormality, the urea solution level is calculated using impedance and ultrasonic waves respectively, and the difference between the two is used to determine whether the sensor has an IR fault.

25. A fault detection method for a sensor used to measure the level of urea solution according to claim 24, characterized in that, Step 1 includes: The first impedance sensing signal of the integrated sensing element (100) is obtained. If the value of the first impedance sensing signal is greater than the first maximum measurement value or less than the first minimum measurement value, it is determined that the integrated sensing element (100) has an OOR fault. The second impedance sensing signal of the liquid level sensing unit (200) is acquired. If the value of the second impedance sensing signal is greater than the second maximum measurement value or less than the second minimum measurement value, it is determined that the integrated liquid level sensing unit (200) has an OOR fault. The amplitude value Lvl of the second ultrasonic echo signal obtained from the ultrasonic transceiver unit (112) is measured and compared with the fifth threshold Thd_Lvll. If it is higher than the fifth threshold Thd_Lvll, it is determined that the ultrasonic sensing element does not have a first type of abnormality; otherwise, it is determined that the ultrasonic sensing element has a first type of abnormality. The amplitude value S_amp of the first ultrasonic echo signal obtained from the ultrasonic transceiver unit (112) is measured, and the amplitude value S_amp is compared with the first threshold Thd_samp. If S_amp is not higher than Thd_samp, it is determined that the ultrasonic sensing element has a second type of abnormality. If the S_amp value is higher than Thd_samp, then measure the peak time Tpk of the first ultrasonic echo signal and calculate the difference T_sft between this peak time and the expected value Tpk0: T_sft=Tpk-Tpk0, The T_sft value is compared with the second threshold Thd_Tsft. If T_sft is not higher than the second threshold Thd_Tsft, it is determined that the ultrasonic sensing element has a second type of anomaly; if T_sft is higher than Thd_Tsft, it is determined that the ultrasonic sensing element does not have a second type of anomaly.

26. A fault detection method for a sensor used to measure the level of urea solution according to claim 25, characterized in that, Step 2 includes: Let Ld be the urea solution level value calculated by the integrated sensing element (100) and the liquid level sensing unit (200), and Lu be the urea solution level value calculated by the ultrasonic sensing element. Calculate the difference between the two, DLvl_Diff: DLvl_Diff = abs(Li-Lu), In the formula, abs() is the calculation of absolute value. If the value of DLvl_Diff is higher than the third threshold Thd_Ldiff, it is determined that the sensor has an IR fault; otherwise, it is determined that the sensor has not an IR fault.

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