MOS (Metal Oxide Semiconductor) geminate transistor parallel non-contact electronic water gauge circuit

Abstract

The invention discloses a non-contact electronic water gauge circuit with MOS (metal oxide semiconductor) geminate transistors connected in parallel, the circuit is composed of multi-stage water level monitoring sub-circuit cascades arranged in series at equal intervals, a voltage division circuit, a power supply, a bias power supply, a magnetic floating ball and the like, and a single-stage water level monitoring sub-circuit is composed of the MOS geminate transistors, a resistor, a magnetic resistance electronic switch and the like; and the divider resistors of the multiple stages of water level monitoring sub-circuits form a series circuit. The circuit has the advantages that the two adjacent magnetic resistance electronic switches (except the first-stage water level) are triggered at the same time, then conduction of the two pairs of MOS geminate transistors is determined, the two pairs of MOS geminate transistors are short-circuited to form corresponding divider resistors, different divider signals are output according to different short-circuited resistors, finally, the microprocessor MCU carries out analog-to-digital conversion through an ADC, and the output voltage of the two pairs of MOS geminate transistors is increased. Obtaining a voltage value and calculating water level information.

Description

Technical Field

[0001] This invention relates to the field of water level measurement, and more particularly to a non-contact electronic water level gauge circuit with parallel MOS transistors. Background Technology

[0002] An electronic water level gauge (electrode-type water level sensor) is a water level measurement sensor that uses the conductivity of water to collect water depth information through signal monitoring electrodes arranged in series at equal intervals. The signal monitoring electrodes in the acquisition circuit can determine whether the electrodes are in contact with the water body based on the potential level, and the water depth can be determined based on the number of electrodes submerged in the water.

[0003] Most electronic water level gauges on the market consist of a circuit board, a common electrode, a monitoring electrode, epoxy resin, and a metal casing. The common electrode is connected to the metal casing, and the monitoring electrode is connected to the PCB circuit board. The common electrode and the monitoring electrode are exposed to ensure good contact with water.

[0004] A reed switch has infinite resistance when open and very low resistance when closed. Reed switches are commonly used in non-contact liquid level measurement and control circuits as level sensors, widely applied in water treatment equipment, household appliances, automotive fuel level gauges, medical equipment, and other fields to control the levels of different media such as water, oil, or chemical solutions. In a level gauge, a magnetic float rises as the liquid level increases, sequentially closing the reed switches and outputting different voltage signals.

[0005] Unlike electronic water level gauges, which may have multiple electronic switches activated simultaneously, magnetic levitation balls can only trigger one reed switch to activate at a time, while the others deactivate.

[0006] Because reed switches are encapsulated in glass and are mechanical switches, their contacts have mechanical characteristics, making them prone to fatigue and short lifespan. In addition, reed switches have low resolution due to their large size, weak resistance to shock and impact, and are prone to breakage and errors during bending and forming. They are easily damaged in the design, production, transportation and use stages, and have high manufacturing costs.

[0007] Non-contact liquid level sensors typically use magnetoresistive sensors or Hall effect sensors to detect the position of the magnetic float in the liquid level sensor.

[0008] Magnetoresistive switch sensors (electronic switches, magnetoresistive chips, also known as magnetoresistive electronic switches, belong to integrated electronic circuit switches) have the characteristics of being non-contact, noiseless, highly reliable, consistent, small in size, easy to install, and improving productivity. They are often used to replace reed switches, overcoming many of the shortcomings of reed switches. As a result, magnetoresistive non-contact electronic water level gauges have appeared on the market. Compared with traditional reed switch non-contact electronic water level gauges, magnetoresistive non-contact electronic water level gauges have advantages such as high sensitivity, low power consumption, fast response, higher accuracy, and strong performance. However, the existing circuit structure logic is relatively complex. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the above-mentioned technical defects and provide a non-contact electronic water level gauge implemented using a simple combinational logic circuit.

[0010] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a non-contact electronic water level gauge circuit with parallel MOS transistors, including a cascaded water level monitoring sub-circuit arranged in series at equal intervals, a voltage divider circuit, a power supply VCC, and a bias power supply; The cascaded multi-level water level monitoring sub-circuits arranged in series at equal intervals include n levels of sub-circuits, where n is greater than 1, and each level of sub-circuit has the same structure. The first-level water level monitoring sub-circuit includes an electronic switch M1 and a magnetic sensing circuit T1. The magnetic sensing circuit T1 is connected to the bias power supply and the gate of the electronic switch M1, and controls the conduction and cutoff of the electronic switch M1. The voltage divider circuit includes signal resistors S1~Sn arranged sequentially end to end, wherein one end of the signal resistor S1 is connected to the negative terminal of the power supply VCC. One end of each of the electronic switches M1~Mn is connected together as the water level signal output terminal, outputting the water level monitoring signal Vo. The other end of the electronic switches M1~M(n-1) is respectively connected to the node VN at the connection of the signal resistor SN and S(N+1), where: N ranges from (1≤N≤n-1). The other end of Mn is connected to VCC. The magnetic sensing circuit TN (1≤N≤n) is a non-contact triggering structure composed of a magnetic float and a magnetoresistive electronic switch. When the magnetic float approaches the liquid level, it triggers the corresponding magnetoresistive electronic switch to close, controlling the conduction state of the corresponding electronic switch MN.

[0011] Preferably, the electronic switches M1~Mn are composed of MOS transistor pairs, wherein the MOS transistor pairs are PMOS transistor pairs or NMOS transistor pairs.

[0012] Preferably, the MOS pair is a PMOS pair MN and MNA, wherein: N is in the range of (1≤N≤n), the drains of the PMOS pair MN and MNA are connected to each other, the gates are connected in parallel, and the two sources are respectively used as the two ends of an electronic switch; The bias power supply is a negative bias power supply VEE, which satisfies VEE - VCC < V TP V TP This is the turn-on threshold voltage of the PMOS pair.

[0013] Preferably, the MOS pair is an NMOS pair MN and MNA, wherein: N is in the range of (1≤N≤n), the sources of the NMOS pair MN and MNA are interconnected, the gates are connected in parallel, and the two drains are respectively used as the two ends of an electronic switch; The bias power supply is a positive bias power supply VBIAS, which satisfies VBIAS > VCC + VTN, where VTN is the NMOS pair turn-on threshold voltage.

[0014] Preferably, the signal resistors S1~Sn are configured using an equal value sequence, an arithmetic sequence, or a geometric sequence.

[0015] Preferably, when the magnetic levitation ball is at the first level of water level, the first level magnetoresistive electronic switch T1 is closed, electronic switch M1 is turned on, and the other electronic switches M2~Mn are turned off, and the water level monitoring signal Vo is equal to the voltage at node V1. When the magnetic levitation ball is at the Nth level water level and 2≤N≤n, the N-1 and Nth level magnetoresistive electronic switches T(N-1) and TN are closed simultaneously, the electronic switches M(N-1) and MN are turned on simultaneously, the other electronic switches are turned off, the signal resistor SN is effectively short-circuited, and the water level monitoring signal Vo is equal to the voltage at node VN.

[0016] Preferably, it also includes a microprocessor (MCU), wherein the water level monitoring signal Vo is an analog voltage signal, and the single-channel ADC pin of the MCU performs analog-to-digital conversion to calculate the current liquid level height.

[0017] The advantages of this invention compared with the prior art are: it has simple combinational logic circuits, requires only one ADC digital-to-analog conversion pin in the MCU, has a high data update frequency, and can be processed into a flexible non-contact electronic water level gauge. Two circuit design schemes and theoretical analyses for PMOS and NMOS pairs are presented. MOS pairs are used as "mid-range switches" or "high-range switches" and simulation verification is performed, enriching the hardware circuit implementation methods of non-contact electronic water level gauges. Attached Figure Description

[0018] Figure 1 This is a block diagram illustrating the principle of the non-contact electronic water level gauge of the present invention. Figure 2 This is the schematic diagram of the non-contact electronic water level gauge circuit with parallel PMOS transistors of the present invention (n=12). Figure 3 This is a schematic diagram of the parallel non-contact electronic water level gauge circuit of the present invention (n=12). Figure 4 This is the schematic diagram of the parallel non-contact electronic water level gauge circuit of the present invention (n=12). Figure 5 This is a schematic diagram of the parallel NMOS transistor non-contact electronic water level gauge circuit of the present invention (n=12). Figure 6 for Figure 2 Simulation diagram of a 12-level non-contact electronic water level gauge circuit (Implementation method 1: Level 1 water level); Figure 7 for Figure 2 Simulation diagram of a 12-level non-contact electronic water level gauge circuit (Implementation method 1: four-level water level). Figure 8 for Figure 2 Simulation diagram of a 12-level non-contact electronic water level gauge circuit (Implementation method 1: seven-level water level); Figure 9 for Figure 3 Simulation diagram of a 12-level non-contact electronic water level gauge circuit (Implementation method 2: Level 1 water level); Figure 10 for Figure 3 Simulation diagram of a 12-level non-contact electronic water level gauge circuit (Implementation method 2: four-level water level); Figure 11 for Figure 3 Simulation diagram of a 12-level non-contact electronic water level gauge circuit (Implementation method 2: seven-level water level). Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings.

[0020] The principle block diagram is as follows Figure 1 As shown: Resistors S1~Sn are connected in series to form a potentiometer (voltage divider circuit). One end of electronic switches M1~Mn is connected in parallel and serves as the water level signal output terminal Vo. One end of S1 is connected to the negative terminal of the power supply. The other end of electronic switch M1 is connected to node V1 at the connection between S1 and S2. The other end of electronic switch M2 is connected to node V2 at the connection between S2 and S3. ... The other end of electronic switch M(n-1) is connected to node V(n-1) at the connection between S(n-1) and Sn. The other end of electronic switch Mn is connected to node VCC (Vn) at the connection between Sn and the power supply VCC. S1 is the low end position of the potentiometer. Electronic switches M1~Mn are equivalent to being "connected in parallel", which is equivalent to the middle (M1~M(n-1)) or high (Mn) electronic switches of the potentiometer (relative to S1).

[0021] Unlike previous magnetic reluctance non-contact electronic water level gauges where the magnetic buoy could only trigger one magnetic reluctance electronic switch at a time, this non-contact electronic water level gauge can trigger two adjacent magnetic reluctance electronic switches simultaneously (except for the first level water level). This is the innovation of this circuit.

[0022] When the magnetic levitation ball approaches the magnetoresistive electronic switch T1 (M1) (level 1 water level), only the electronic switch (MOS transistor) M1 is turned on (the other electronic switches M2~Mn are all turned off). The on-resistance of electronic switch M1 is very small (tens of milliohms, much smaller than the resistance of resistor S1), and the on-resistance voltage drop can be ignored. Resistors S1~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V1=VCC×S1 / (S1+S2+S3+…+Sn).

[0023] When the magnetic levitation ball approaches the magnetoresistive electronic switches T1 (M1) and T2 (M2) (level 2 water level), electronic switches M1 and M2 are turned on (the other electronic switches M3 to Mn are turned off). The conduction impedance of electronic switches M1 and M2 is very small (tens of milliohms, much smaller than the resistance of resistor S2), and the conduction voltage drop can be ignored. Resistor S2 is short-circuited by electronic switches M1 and M2 (it can be considered that no current flows through resistor S2), that is, V2≈V1. Resistor S1, electronic switches M1~M2, and S3~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V2=VCC×S1 / (S1+S3+…+Sn).

[0024] When the magnetic levitation ball approaches the magnetoresistive electronic switches T2 (M2) and T3 (M3) (level 3 water level), electronic switches M2 and M3 are turned on (the other electronic switches M1, M4~Mn are all turned off). The conduction impedance of electronic switches M2 and M3 is very small (tens of milliohms, much smaller than the resistance of resistor S3), and the conduction voltage drop can be ignored. Resistor S3 is short-circuited by electronic switches M2 and M3 (it can be considered that no current flows through resistor S3), that is, V3≈V2. Resistors S1 and S2, electronic switches M2~M3, and S4~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V3=VCC×(S1+S2) / (S1+S2+S4+…+Sn).

[0025] When the magnetic levitation ball approaches the magnetoresistive electronic switches T(N-1) (M(N-1)) and TN(MN) (4≤N≤n-1, Nth level water level), electronic switches M(N-1) and MN are turned on (the other electronic switches M1~M(N-2) and M(N+1)~Mn are turned off). The conduction impedance of electronic switches M(N-1) and MN is very small (tens of milliohms, much smaller than the resistance of resistor SN), and the conduction voltage drop can be ignored. Resistor SN is short-circuited by electronic switches M(N-1) and MN (it can be considered that no current flows through resistor SN), that is, VN≈V(N-1). Resistors S1~S(N-1), electronic switches M(N-1)~MN, and S(N+1)~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈VN=VCC×(S1+S2+…+S(N-1)) / (S1+S2+…+S(N-1)+S(N+1)+…+Sn).

[0026] When the magnetic levitation ball approaches the magnetoresistive electronic switches T(n-1) (M(n-1)) and Tn (Mn) (nth water level), the resistor Sn is short-circuited by the electronic switches M(n-1) and Mn, and Vo≈Vn=VCC.

[0027] The monitoring water level signals obtained by the other water level monitoring sub-circuits at each level are obtained in the same manner.

[0028] In specific implementation of the present invention, Implementation

[0029] This invention discloses a non-contact electronic water level gauge circuit with parallel PMOS transistor pairs. The circuit consists of cascaded water level monitoring sub-circuits arranged in series at equal intervals, a voltage divider circuit, a power supply VCC, a negative bias power supply VEE, etc. Figure 1 The electronic switch MN (1≤N≤n) uses PMOS transistors MN and MNA, satisfying VEE-VCC<V TP V TP The turn-on threshold voltage of the PMOS transistor is shown in the schematic diagram. Figure 2 As shown (n=12 levels of water level monitoring circuit).

[0030] Unlike previous magnetic reluctance non-contact electronic water level gauges where the magnetic buoy could only trigger one magnetic reluctance electronic switch at a time, this non-contact electronic water level gauge can trigger two adjacent magnetic reluctance electronic switches simultaneously (except for the first level water level). This is the innovation of this circuit.

[0031] When the magnetic levitation ball approaches the magnetoresistive electronic switch T1 (level 1 water level), only PMOS transistors M1~M1A are turned on (the rest of the PMOS transistors are turned off). The conduction impedance of PMOS transistors M1~M1A is very small (tens of milliohms, much smaller than the resistance of resistor S1), and the conduction voltage drop is negligible. Resistors S1~Sn form a voltage divider circuit, and the conduction voltage drop of transistors M1~M1A is negligible. The output water level monitoring signal Vo≈V1=VCC×S1 / (S1+S2+S3+…+Sn).

[0032] When the magnetic levitation ball approaches the magnetoresistive electronic switch T2 (level 2 water level), PMOS transistors M1~M1A and M2~M2A are turned on (the rest of the PMOS transistors are turned off). The conduction impedance of PMOS transistors M1~M1A and M2~M2A is very small (tens of milliohms, much smaller than the resistance of resistor S2), and the conduction voltage drop is negligible. Resistor S2 is short-circuited by PMOS transistors M1~M1A and M2A~M2 (it can be considered that no current flows through resistor S2), that is, V2≈V1. PMOS resistor S1, transistors M1~M1A, PMOS transistors M2A~M2, and S3~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V2=VCC×S1 / (S1+S3+…+Sn).

[0033] As can be seen from the above analysis, when the magnetic levitation ball approaches the magnetoresistive electronic switch T3 (level 3 water level), the PMOS pairs M2~M2A and M3~M3A are turned on (the rest of the PMOS pairs are turned off). The conduction impedance of the PMOS pairs M2~M2A and M3~M3A is very small (tens of milliohms, much smaller than the resistance of resistor S3), and the conduction voltage drop can be ignored. Resistor S3 is short-circuited by PMOS pairs M2~M2A and M3A~M3 (it can be considered that no current flows through resistor S3), that is, V3≈V2. Resistors S1, S2, PMOS pairs M2~M2A, PMOS pairs M3A~M3, and S4~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V3=VCC×(S1+S2) / (S1+S2+S4+…+Sn).

[0034] When the magnetic levitation ball approaches the magnetoresistive electronic switch TN (4≤N≤n-1, Nth water level), PMOS transistors M(N-1)~M(N-1)A and MN~MNA are turned on (the remaining PMOS transistors are turned off). The on-resistance of PMOS transistors M(N-1)~M(N-1)A and MN~MNA is very small (tens of milliohms, much smaller than the resistance SN), and the on-resistance voltage drop is negligible. The resistance SN is reduced by the resistance of PMOS transistors M(N-1)~M(N-1)A. A. MNA~MN are short-circuited (it can be assumed that no current flows through resistor SN), i.e., VN≈V(N-1). Resistors S1~S(N-1), PMOS transistors M(N-1)~M(N-1), A, PMOS transistors MNA~MN, and S(N+1)~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈VN=VCC×(S1+S2+…+S(N-1)) / (S1+S2+…+S(N-1)+S(N+1)+…+Sn).

[0035] When the magnetic levitation ball approaches the magnetoresistive electronic switches T(n-1) and Tn (nth water level), the PMOS pair M(n-1), M(n-1)A, Mn, and MnA are turned on, and Vo = VCC.

[0036] The monitoring water level signals obtained by the other water level monitoring sub-circuits at each level are obtained in the same manner.

[0037] Signal resistors can be classified into equal value series resistors, arithmetic series resistors, or geometric series resistors, as detailed below.

[0038] (1) Equivalent series resistance The signal resistance of each water level monitoring sub-circuit is selected as an equal series resistance: that is, S1=S2=S3=…=Sn=R.

[0039] When the magnetic buoy approaches the magnetoresistive electronic switch T1 (level 1 water level), the magnetoresistive electronic switch T1 closes (the other magnetoresistive electronic switches are open), and only the PMOS pairs M1~M1A are turned on (the other PMOS pairs are turned off). The conduction impedance of the PMOS pairs M1~M1A is very small (tens of milliohms, much smaller than the resistance of resistor S1), and the conduction voltage drop is negligible. Resistors S1~Sn form a voltage divider circuit, and the conduction voltage drop of the pairs M1~M1A is negligible. The output water level monitoring signal Vo≈V1=VCC×S1 / (S1+S2+S3+…+Sn)=VCC / n.

[0040] When the magnetic buoy approaches the magnetoresistive electronic switches T1 and T2 (second-level water level), the magnetoresistive electronic switches T1 and T2 close (the other magnetoresistive electronic switches are open), and the PMOS pairs M1~M1A and M2~M2A are turned on (the other PMOS pairs are turned off). The conduction impedance of the PMOS pairs M1~M1A and M2~M2A is very small (tens of milliohms, much smaller than the resistance of resistor S2), and the conduction voltage drop can be ignored. Resistor S2 is short-circuited by the PMOS pairs M1~M1A and M2A~M2 (it can be considered that no current flows through resistor S2), that is, V2≈V1. Resistor S1, pairs M1~M1A, pairs M2A~M2, and S3~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V2=VCC×S1 / (S1+S3+…+Sn)=VCC / (n-1).

[0041] From the above analysis, it can be seen that when the magnetic levitation ball approaches the magnetoresistive electronic switches T2 and T3 (at the third water level), the magnetoresistive electronic switches T2 and T3 are closed (the remaining magnetoresistive electronic switches are open), and the PMOS transistors M2~M2A and M3~M3A are turned on (the remaining PMOS transistors are turned off). The on-resistance of the PMOS transistors M2~M2A and M3~M3A is very small (tens of milliohms, much smaller than the resistance of resistor S3), and the on-resistance voltage drop can be... Neglecting the fact that resistor S3 is short-circuited by PMOS transistors M2~M2A and M3A~M3 (it can be assumed that no current flows through resistor S3), V3≈V2. Resistors S1, S2, transistors M2~M2A, transistors M3A~M3, and S4~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V3=VCC×(S1+S2) / (S1+S2+S4+…+Sn)=2VCC / (n-1).

[0042] When the magnetic buoy approaches the magnetoresistive electronic switches T(N-1) and TN (4≤N≤n-1, Nth water level), the magnetoresistive electronic switches T(N-1) and TN close (the remaining magnetoresistive electronic switches are open), and the PMOS transistors M(N-1)~M(N-1)A and MN~MNA conduct (the remaining PMOS transistors are all cut off). The conduction impedance of the PMOS transistors M(N-1)~M(N-1)A and MN~MNA is very small (tens of milliohms, much smaller than the resistance SN), and the conduction voltage drop is negligible. The resistance SN is controlled by the PMOS transistors. When tubes M(N-1)~M(N-1)A and MNA~MN are short-circuited (it can be assumed that no current flows through resistor SN), VN≈V(N-1). Resistors S1~S(N-1), tubes M(N-1)~M(N-1)A, tubes MNA~MN, and S(N+1)~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈VN=VCC×(S1+S2+…+S(N-1)) / (S1+S2+…+S(N-1)+S(N+1)+…+Sn)=VCC×(N-1) / (n-1).

[0043] When the magnetic levitation ball approaches the magnetoresistive electronic switches T(n-1) and Tn (nth water level), the PMOS pair M(n-1), M(n-1)A, Mn, and MnA are turned on, and Vo = VCC.

[0044] The water level signal monitoring data acquired by the other water level monitoring sub-circuits are all processed according to the same principle.

[0045] (2) Arithmetic series resistors Signal resistor values: Considering the ease of data processing by the MCU microprocessor after ADC conversion, the signal resistors for each stage of the water level monitoring sub-circuit are preferably selected as an arithmetic sequence resistor: S1=R, S2=2R, ..., Sn=n×R. Since ADC converters generally need to draw a certain current to operate normally, the total signal resistance is n×R, where the value of R depends on the magnitude of the current drawn by the ADC converter, and the PMOS transistor on-resistance R... DS(ON) The resistance is tens of milliohms (much smaller than the resistance R), since the signal only passes through four PMOS transistors: M(N-1)~M(N-1)A and MN~MNA, i.e., 4×R. DS(ON) With a strength on the order of tens of milliohms, R is much greater than 4 × R. DS(ON) If the total signal resistance is too large, the ADC conversion voltage error will increase; if the signal resistance is too small, the power consumption will be large. Therefore, the value of R must be appropriately balanced to meet the usage requirements, and high-precision resistors should be selected first.

[0046] The resistance of the arithmetic series is Sum = S1 + S2 + ... + Sn = n × (n + 1)R / 2. The calculation and analysis process is as follows.

[0047] When the magnetic buoy approaches the magnetoresistive electronic switch T1 (level 1 water level), the magnetoresistive electronic switch T1 closes (the other magnetoresistive electronic switches are open), and the PMOS transistors M1~M1A are turned on (the other PMOS transistors are turned off). The power supply VCC passes through Sn~S1 to the negative terminal of the power supply in sequence. The voltage drop of the PMOS transistors M1~M1A during conduction is negligible. The output water level monitoring signal Vo≈V1=VCC×S1 / (S1+S2+…+Sn)=2VCC / n / (n+1).

[0048] When the magnetic buoy approaches the magnetoresistive electronic switches T1 and T2 (level 2 water level), the magnetoresistive electronic switches T1~T2 close (the rest of the magnetoresistive electronic switches are open), and the PMOS transistors M1~M1A and M2~M2A conduct (the rest of the PMOS transistors are cut off). Resistor S2 is short-circuited by the PMOS transistors M1~M1A and M2A~M2. The conduction voltage drop of PMOS transistors M2~M2A and M1A~M1 is negligible. The current through S2 of the voltage divider signal V2 is negligible. The current through transistor M2 is negligible. 2~M2A, output water level monitoring signal Vo (almost no voltage drop), power supply VCC passes through Sn~S3, tube M2~M2A, tube M1A~M1, S1 to the negative terminal of the power supply in sequence. Resistor S1, tube M1~M1A, tube M2A~M2, S3~Sn form a voltage divider circuit. The output water level monitoring signal Vo≈V2=VCC×S1 / (S1+S3+S4+…+Sn)=VCC / (n(n+1) / 2-2)=2VCC / (n(n+1)-4).

[0049] When the magnetic levitation ball approaches the magnetoresistive electronic switches T2 and T3 (level 3 water level), the magnetoresistive electronic switches T2~T3 close (the remaining magnetoresistive electronic switches are open), and the PMOS transistors M2~M2A and M3~M3A conduct (the remaining PMOS transistors are all cut off). Resistor S3 is short-circuited by the PMOS transistors M2~M2A and M3A~M3. The conduction voltage drop of PMOS transistors M3~M3A and M2A~M2 is negligible. The current through S3 of the voltage divider signal V3 is negligible. V3 flows through transistors M3~M3A... The output water level monitoring signal Vo (with almost no voltage drop) is connected to the power supply VCC via Sn~S4, tubes M3~M3A, tubes M2A~M2, S2, and S1 to the negative terminal of the power supply. Resistors S1, S2, tubes M2~M2A, tubes M3A~M3, and S3~Sn form a voltage divider circuit. The output water level monitoring signal Vo≈V2=VCC×(S1+S2) / (S1+S2+S4+…+Sn)=3VCC / (n(n+1) / 2-3)=6VCC / (n(n+1)-6).

[0050] When the magnetic buoy approaches the magnetoresistive electronic switches T(N-1) and TN (4≤N≤n-1, Nth water level), the magnetoresistive electronic switches T(N-1)~TN close (the rest of the magnetoresistive electronic switches are open), the PMOS pairs M(N-1)~M(N-1)A and MN~MNA conduct (the rest of the PMOS pairs are cut off), the resistor SN is short-circuited by the PMOS pairs M(N-1)~M(N-1)A and MNA~MN, the conduction voltage drop of the PMOS pairs MN~MNA and M(N-1)A~M(N-1) is negligible, the current of the voltage divider signal VN through SN is negligible, VN passes through the pairs MN~MNA, and outputs the water level monitoring signal Vo (with almost no voltage drop). The power supply VCC passes through Sn~S(N+1), transistors MN~MNA, transistors M(N-1)A~M(N-1), and S(N-1)~S1 to the negative terminal of the power supply. Resistors Sn~S(N+1), transistors MN~MNA, transistors M(N-1)A~M(N-1), and S(N-1)~S1 form a voltage divider circuit. The output water level monitoring signal Vo≈V(N-1)≈VN=VCC×(S1+S2+…+S(N-1)) / (S1+…+S(N-1)+S(N+1)+…+Sn)=VCC×(N(N-1) / 2) / (n(n+1) / 2-N)=2VCC×N(N-1) / (n(n+1)-2N).

[0051] When the magnetic levitation ball approaches the magnetoresistive electronic switches T(n-1) and Tn (nth water level), the PMOS pair Mn and MnA are turned on, and Vo = VCC.

[0052] (3) Geometric series resistance Furthermore, the voltage divider resistors S1, S2, S3~Sn can also be selected as geometric series resistors. Currently, the E48, E96, and E192 series resistors used in electronic products are geometric series resistors, with common ratios q of 1.052, 1.025, and 1.012 respectively, and their accuracy errors of ±2%, ±1%, and ±0.5% / 0.2% / 0.1% respectively. E192 resistors have high accuracy but are more expensive; we prioritize the cost-effective E96 resistors. According to the geometric series formula, the common ratio q = 1.025, and the Nth (1≤N≤n) level resistor SN = S1 × q. N-1 The total resistance of the n-level resistors is Sum = S1 + S2 + S3 + ... + Sn = S1(1 - q) n ) / (1-q).

[0053] according to Figure 1 , Figure 2 The calculation and analysis process is as follows.

[0054] When the magnetic buoy approaches the magnetoresistive electronic switch T1 (level 1 water level), the magnetoresistive electronic switch T1 closes (the other magnetoresistive electronic switches are open), the PMOS transistors M1~M1A are turned on (the other PMOS transistors are turned off), the power supply VCC passes through Sn~S1 to the negative terminal of the power supply in sequence, the voltage drop of the PMOS transistors M1~M1A is negligible, and the output water level monitoring signal Vo≈V1 is shown in equation (1): ; When the magnetic buoy approaches the magnetoresistive electronic switches T1 and T2 (second level water level), the magnetoresistive electronic switches T1~T2 are closed (the other magnetoresistive electronic switches are open), the PMOS transistors M1~M1A and M2~M2A are turned on (the other PMOS transistors are turned off), the resistor S2 is short-circuited by the PMOS transistors M1~M1A and M2A~M2, and the power supply VCC is connected to the negative terminal of the power supply through Sn~S3, transistors M2~M2A, transistors M1A~M1, and S1 in sequence. The voltage drop of the PMOS transistors M2~M2A and M1A~M1 is negligible, and the output water level monitoring signal Vo≈V2 is shown in equation (2): ; When the magnetic buoy approaches the magnetoresistive electronic switches T(N-1) and TN (3≤N≤n-1, Nth level water level), the magnetoresistive electronic switches T(N-1)~TN are closed (the other magnetoresistive electronic switches are open), the PMOS pairs M(N-1)~M(N-1)A and MN~MNA are turned on (the other PMOS pairs are turned off), the resistor SN is short-circuited by the PMOS pairs M(N-1)~M(N-1)A and MNA~MN, the power supply VCC passes through Sn~S(N+1), the pair MN~MNA, the pair M(N-1)A~M(N-1), and S(N-1)~S1 to the negative terminal of the power supply in sequence, the on-voltage drop of the PMOS pairs MN~MNA and M(N-1)A~M(N-1) is negligible, and the output water level monitoring signal Vo≈V(N-1)≈VN is as shown in equation (3): ; When the magnetic levitation ball approaches the magnetoresistive electronic switches T(n-1) and Tn (nth water level), the PMOS pair Mn and MnA are turned on, and Vo = VCC.

[0055] Therefore, we can determine the level of the monitoring electrode based on the voltage signal acquired by the MCU, and thus obtain the water level information.

[0056] ADC converter: Currently, microcontrollers have multiple built-in ADCs (M=12 / 14 / 16 / 18 / 20 bits). In order to ensure resolution, the quantization voltage difference between the first-level water level and the second-level water level must meet the condition, as shown in equation (4): ; Let X=q n -1, as shown in equation (5): ; The rearranged formula (5) is shown in formula (6): ; Solving the quadratic equation in one variable, when equation (6) holds the equality, we obtain equation (7): ; Since 4q(2 M -1)>>q 2 Simplifying the calculation of equation (7), 4q(2 M -1)+q 2 ≈4q(2 M -1), as shown in equation (8): ; If M=12 and q=1.025, the range of values ​​for n is shown in equation (9): ; The range of values ​​for the cascade series n in other cases is shown in Table 1 below.

[0057]

[0058] If the spacing between the signal monitoring electrodes is 1 cm, then M = 16, q = 1.012, and n = 119 are selected. Currently, a non-contact electronic water level gauge with a cascade number of n = 100 can meet the requirements. However, the drawback is that more than 100 types of resistors need to be soldered. The number of cascaded stages obtained with the same ADC bit depth is less than that of Implementation Method 1 under the same signal resistance. Therefore, Implementation Method 1 is preferred. Implementation

[0059] The difference between Implementation Method 2 and Implementation Method 1 lies in the selection of MOS pair types: Implementation Method 1 uses PMOS pairs, while Implementation Method 2 uses NMOS pairs.

[0060] This invention discloses another NMOS transistor parallel parallel non-contact electronic water level gauge circuit. This circuit consists of cascaded water level monitoring sub-circuits arranged in series at equal intervals, a voltage divider circuit, a power supply VCC, a positive bias power supply VBIAS, etc. Figure 1 The electronic switch MN (1≤N≤n) uses an NMOS pair MN~MNA, which must satisfy VBIAS>VCC+V TN V TN The NMOS transistor's turn-on threshold voltage is shown in the schematic diagram. Figure 3The diagram shows a water level monitoring circuit with n=12 levels. The first-level water level monitoring sub-circuit (located at the lowest point of the non-contact electronic water level gauge) consists of NMOS transistors M1~M1A, resistors S1 and R1, and a magnetoresistive electronic switch T1. The positive bias power supply VBIAS and resistor RG are common components. In the circuit, one end of the magnetoresistive electronic switch T1 is connected to both R1 and the gate (G) of NMOS transistors M1~M1A. The other end is connected to the positive bias power supply VBIAS through current-limiting resistor W1 and resistor RG. The drain (D) of NMOS transistor M1 is connected to one end of voltage divider resistor S1 (node ​​V1). The other end of voltage divider resistor S1 and R1 is connected to the negative terminal of the power supply. The drain (D) of NMOS transistor M1A is the water level monitoring signal output terminal Vo.

[0061] An arithmetic series resistor is used as the signal resistor for each level of the water level monitoring sub-circuit.

[0062] When the magnetic buoy approaches the magnetoresistive electronic switch T1 (level 1 water level), the magnetoresistive electronic switch T1 closes (the other magnetoresistive electronic switches are open), and the voltage at the gate (X1) of the NMOS transistors M1~M1A is high (R1 is much larger than W1, VBIAS×R1 / (W1+R1)≈VBIAS is high), and the voltage difference V between the gate and source of the NMOS transistors M1~M1A... GS The voltage V is greater than the turn-on threshold voltage of NMOS transistor M1. TN V GS ≈VBIAS-VCC>V TN NMOS transistors M1~M1A are turned on (the rest of the NMOS transistors are turned off), and the on-resistance is very small (tens of milliohms, much smaller than the resistance of resistor S1). The voltage divider signal V1 outputs the monitoring signal Vo through the low-impedance path (NMOS transistors M1~M1A). Its on-resistance drop is negligible. Resistors S1~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V1=VCC×S1 / (S1+S2+…+Sn)=2VCC / (n(n+1))=2VCC / n / (n+1).

[0063] When the magnetic buoy approaches the magnetoresistive electronic switches T1 and T2 (at the second water level), the magnetoresistive electronic switches T1-T2 close (the remaining magnetoresistive electronic switches are open), and the NMOS transistors M1-M1A and M2-M2A conduct (the remaining NMOS transistors are all off). Resistor S2 is short-circuited by the NMOS transistors M1-M1A and M2A-M2. The on-state voltage drop of the NMOS transistors M2-M2A and M1A-M1 is negligible, and the current through S2 of the voltage divider signal V2 is negligible. Ignoring the fact that V2 passes through transistors M2~M2A, the power supply VCC, and then through Sn~S3, transistors M2~M2A, transistors M1A~M1, and S1 to the negative terminal of the power supply, the resistors S1, transistors M1~M1A, transistors M2A~M2, and S3~Sn form a voltage divider circuit, and the output water level monitoring signal Vo≈V2=VCC×S1 / (S1+S3+S4+…+Sn)=VCC / (n(n+1) / 2-2)=2VCC / (n(n+1)-4).

[0064] When the magnetic buoy approaches the magnetoresistive electronic switches T2 and T3 (level 3 water level), the magnetoresistive electronic switches T2~T3 close (the remaining magnetoresistive electronic switches are open), and the NMOS transistors M2~M2A and M3~M3A conduct (the remaining NMOS transistors are all off). Resistor S3 is short-circuited by the NMOS transistors M2~M2A and M3A~M3. The on-state voltage drop of the NMOS transistors M3~M3A and M2A~M2 is negligible. The current through S3 of the voltage divider signal V3 is negligible. For tubes M3~M3A, the power supply VCC passes sequentially through Sn~S4, tubes M3~M3A, tubes M2A~M2, S2, and S1 to the negative terminal of the power supply. Resistors S1, S2, tubes M2~M2A, tubes M3A~M3, and S4~Sn form a voltage divider circuit. The output water level monitoring signal Vo≈V2=VCC×(S1+S2) / (S1+S2+S4+…+Sn)=3VCC / (n(n+1) / 2-3)=6VCC / (n(n+1)-6).

[0065] When the magnetic buoy approaches the magnetoresistive electronic switches T(N-1) and TN (4≤N≤n, Nth water level), the magnetoresistive electronic switches T(N-1)~TN close (the remaining magnetoresistive electronic switches are open), and the NMOS transistors M(N-1)~M(N-1)A and MN~MNA conduct (the remaining NMOS transistors are all cut off). Resistor SN is short-circuited by the NMOS transistors M(N-1)~M(N-1)A and MN~MNA. The on-state voltage drop of the NMOS transistors MN~MNA and M(N-1)A~M(N-1) is negligible. The current of the voltage divider signal VN through SN is negligible. VN flows through transistors MN~MNA, and the power supply VCC flows through S in sequence. n~S(N+1), tubes MN~MNA, tubes M(N-1)A~M(N-1), and S(N-1)~S1 are connected to the negative terminal of the power supply. Resistors Sn~S(N+1), tubes MN~MNA, tubes M(N-1)A~M(N-1), and S(N-1)~S1 form a voltage divider circuit. The output water level monitoring signal Vo≈V(N-1)≈VN=VCC×(S1+S2+…+S(N-1)) / (S1+…+S(N+1)+S(N+2)+…+Sn)=VCC×(N(N-1) / 2) / (n(n+1) / 2-N)=2VCC×N(N-1) / (n(n+1)-2N).

[0066] When the magnetic buoy approaches the magnetoresistive electronic switches T(n-1) and Tn (nth water level), the electronic switch Mn is turned on, and Vo = VCC.

[0067] The monitoring water level signals obtained by the other water level monitoring sub-circuits at each level are obtained in the same manner.

[0068] Similar to Implementation Method 1, when the signal resistance of each water level monitoring sub-circuit is a geometric series, please refer to Implementation Method 1 for details, which will not be repeated here.

[0069] When using a chip-based solution, a single PMOS transistor (without a body diode) integrated within the chip can be used to replace it. Figure 2 PMOS transistors in the middle, such as Figure 4 As shown, please refer to Implementation Method 1 for details. Alternatively, a single NMOS transistor (without a body diode) integrated within the chip can be used to replace it. Figure 3 NMOS transistors in the middle, such as Figure 5 As shown, please refer to Implementation Method 1 and Implementation Method 2 for details.

[0070] Furthermore, for cases where the non-contact electronic water level gauge triggers multiple (more than two) magnetoresistive electronic switches at the same time, please refer to the above implementation method for details, which will not be repeated here. Implementation

[0071] according to Figure 2 , Figure 3The circuit was simulated and tested using National Instruments' Multisim simulation software (version V14.0). The PMOS transistor selected was from ON Semiconductor, model NVTFS5124PLTAG, with a minimum turn-on threshold voltage of V. TP(MIN) =-1.5V, maximum value V TP(MIN) =-2.5V, typical value V not given. TP The conduction current can reach -6A, and the conduction impedance R DS(ON) =260mΩ (V) GS =-10V), R DS(ON) =380mΩ (V) GS =-4.5V), let's take the turn-on threshold voltage V. TP =-2.5V. The NMOS transistor used is from NXP, model BSP030, with a minimum turn-on threshold voltage of V. TN(MIN) =1V, maximum value V TN(MAX) =2.8V, typical value not given in V TN The conduction current reaches 10A, and the conduction impedance R DS(ON) =30mΩ (V) GS =10V), R DS(ON) =50mΩ (V) GS =4.5V), let's take the turn-on threshold voltage V. TN =2.8V.

[0072] When n=12, for ease of calculation, the signal resistance of each water level monitoring sub-circuit is selected as an arithmetic series resistance: S1=R=100Ω, S2=2R=200Ω, ..., S12=12×R=1200Ω, power supply VCC=3.3V, negative bias power supply VEE=-10V, positive bias power supply VBIAS=10V; the magnetic levitation ball has its own magnet. When the magnetic levitation ball is close to the magnetoresistive electronic switch TN, T(N-1)~TN is closed, and the MOS pair MN~MNA is turned on; when the magnetic levitation ball is away from the magnetoresistive electronic switch, TN and T(N-1)~TN are open, and the MOS pair MN~MNA is turned off. The simulation is shown below.

[0073] Implementation Method 1: Simulation (1) When the magnetic levitation ball approaches the magnetoresistive electronic switch T1 (level 1 water level): the magnetoresistive electronic switch T1 is closed (the other magnetoresistive electronic switches are open), the PMOS transistors M1~M1A are turned on (the other PMOS transistors are turned off), the power supply VCC passes through S12~S1 to the negative terminal of the power supply in sequence, and the output water level monitoring signal Vo=42.323mV (measured with a multimeter). The specific simulation is as follows: Figure 6As shown, it is consistent with the theoretical voltage Vo=2VCC / (n(n+1))=2VCC / 12 / 13=42.3mV, with a relative error of approximately 0.05%.

[0074] (2) When the magnetic levitation ball approaches the magnetoresistive electronic switches T3 and T4 (level 4 water level): magnetoresistive electronic switches T3~T4 are closed (the rest of the magnetoresistive electronic switches are open), PMOS transistors M3~M3A and M4~M4A are turned on (the rest of the PMOS transistors are turned off), resistor S4 is short-circuited by PMOS transistors M3~M3A and M4A~M4, and power supply VCC is connected to the negative terminal of the power supply through S12~S5, transistors M4~M4A, transistors M3A~M3, and S3~S1 in sequence, and the output water level monitoring signal Vo=267.831mV (measured with a multimeter). The specific simulation is as follows. Figure 7 As shown, the result is consistent with the theoretical voltage Vo = VCC × (N(N-1) / 2) / (n(n+1) / 2-N) = 6VCC / (78-4) = 0.267V, with a relative error of approximately 0.31%.

[0075] (3) When the magnetic levitation ball approaches the magnetoresistive electronic switches T6 and T7 (7th level water level): magnetoresistive electronic switches T6~T7 are closed (the rest of the magnetoresistive electronic switches are open), PMOS transistors M6, M6A, and M7~M7A are turned on (the rest of the PMOS transistors are turned off), and the power supply VCC passes through S12~S8, transistors M7~M7A, transistors M6A~M6, and S6~S1 to the negative terminal of the power supply in sequence, and outputs a water level monitoring signal Vo=976.208mV (measured with a multimeter). The specific simulation is as follows: Figure 8 As shown: It is consistent with the theoretical voltage Vo=VCC×(N(N-1) / 2) / (n(n+1) / 2-N)=21VCC / (78-7)=0.976V, with a relative error of about 0.02%.

[0076] Therefore, we can determine the level of the monitoring electrode based on the voltage signal acquired by the MCU, and thus obtain the water level information. The simulation test data for 12 water levels are shown in Table 2.

[0077]

[0078] Implementation Method Two: Simulation (1) When the magnetic levitation ball approaches the magnetoresistive electronic switch T1 (level 1 water level): the magnetoresistive electronic switch T1 is closed (the other magnetoresistive electronic switches are open), the NMOS transistors M1 and M1A are turned on (the other NMOS transistors are turned off), the power supply VCC passes through S12~S1 to the negative terminal of the power supply in sequence, and the output water level monitoring signal Vo=42.279mV (measured with a multimeter). The specific simulation is as follows: Figure 9As shown, it is consistent with the theoretical voltage Vo=2VCC / (n(n+1))=2VCC / 12 / 13=42.3mV, with a relative error of approximately -0.05%.

[0079] (2) When the magnetic levitation ball approaches the magnetoresistive electronic switches T3 and T4 (level 4 water level): magnetoresistive electronic switches T3 and T4 are closed (the rest of the magnetoresistive electronic switches are open), NMOS transistors M3, M3A, M4, and M4A are turned on (the rest of the NMOS transistors are turned off), resistor S4 is short-circuited by NMOS transistors M3, M3A, M4A, and M4, and power supply VCC is connected to the negative terminal of the power supply through S12~S5, transistors M4, M4A, M3A, M3, and S3~S1 in sequence, and the output water level monitoring signal Vo = 267.3mV (measured with a multimeter). The specific simulation is as follows. Figure 10 As shown, the result is consistent with the theoretical voltage Vo = VCC × (N(N-1) / 2) / (n(n+1) / 2-N) = 6VCC / (78-4) = 0.267V, with a relative error of approximately 0.11%.

[0080] (3) When the magnetic levitation ball approaches the magnetoresistive electronic switches T6 and T7 (7th water level): magnetoresistive electronic switches T6 and T7 are closed (the rest of the magnetoresistive electronic switches are open), NMOS transistors M6, M6A, M7, and M7A are turned on (the rest of the NMOS transistors are turned off), and the power supply VCC passes through S12~S8, transistors M7, M7A, M6A, M6, and S6~S1 to the negative terminal of the power supply in sequence, outputting a water level monitoring signal Vo=974.6mV (measured with a multimeter). The specific simulation is as follows: Figure 11 As shown: It is consistent with the theoretical voltage Vo=VCC×(N(N-1) / 2) / (n(n+1) / 2-N)=21VCC / (78-7)=0.976V, with a relative error of approximately -0.14%.

[0081] Therefore, we can determine the level of the monitoring electrode based on the voltage signal acquired by the MCU, and thus obtain the water level information. The simulation test data for 12 water levels are shown in Table 3.

[0082]

[0083] Comparing the simulation test data in Tables 2 and 3, the NMOS electronic switch has superior performance and smaller relative error compared to the PMOS electronic switch due to its lower on-resistance.

[0084] This circuit consists of the following external connections: power supply VCC, water level monitoring signal Vo, power supply negative terminal, negative bias power supply, magnetic levitation ball, etc. The output water level monitoring signal Vo is an analog signal that needs to be processed by ADC. Therefore, the analog signal replaces the digital signal, which has the characteristics of ultra-low power consumption and strong anti-interference.

[0085] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0086] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0087] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A parallel non-contact electronic water level gauge circuit with MOS transistors, characterized in that: This includes a cascaded water level monitoring sub-circuit arranged in series at equal intervals, a voltage divider circuit, a power supply VCC, and a bias power supply. The cascaded multi-level water level monitoring sub-circuits arranged in series at equal intervals include n levels of sub-circuits, where n is greater than 1, and each level of sub-circuit has the same structure. The first-level water level monitoring sub-circuit includes an electronic switch M1 and a magnetic sensing circuit T1. The magnetic sensing circuit T1 is connected to the bias power supply and the gate of the electronic switch M1, and controls the conduction and cutoff of the electronic switch M1. The voltage divider circuit includes signal resistors S1~Sn arranged sequentially end to end, wherein one end of the signal resistor S1 is connected to the negative terminal of the power supply VCC. One end of each of the electronic switches M1~Mn is connected together as the water level signal output terminal, outputting the water level monitoring signal Vo. The other end of the electronic switches M1~M(n-1) is respectively connected to the node VN at the connection of the signal resistor SN and S(N+1), where: N ranges from (1≤N≤n-1). The other end of the electronic switch Mn is connected to VCC. The magnetic sensing circuit is a non-contact triggering structure composed of a magnetic float and a magnetoresistive electronic switch. When the magnetic float approaches the liquid level, it triggers the corresponding magnetoresistive electronic switch to close, thereby controlling the conduction state of the corresponding electronic switch Mn.

2. The non-contact electronic water level gauge circuit with parallel MOS transistors according to claim 1, characterized in that: The electronic switches M1~Mn are composed of MOS transistor pairs, wherein the MOS transistor pairs are either PMOS transistor pairs or NMOS transistor pairs.

3. The parallel non-contact electronic water level gauge circuit of MOS transistors according to claim 2, characterized in that: The MOS pair consists of PMOS transistors MN and MNA, where N is in the range of (1≤N≤n). The drains of PMOS transistors MN and MNA are connected to each other, and their gates are connected in parallel. The two sources are used as the two ends of an electronic switch. The bias power supply is a negative bias power supply VEE, which satisfies VEE - VCC < V TP V TP This is the turn-on threshold voltage of the PMOS pair.

4. The parallel non-contact electronic water level gauge circuit of MOS transistors according to claim 2, characterized in that: The MOS pair consists of NMOS pairs MN and MNA, where N ranges from 1 to N to n. The sources of the NMOS pairs MN and MNA are interconnected, their gates are connected in parallel, and their two drains serve as the two ends of an electronic switch. The bias power supply is a positive bias power supply VBIAS, which satisfies VBIAS > VCC + V TN V TN This is the turn-on threshold voltage for the NMOS pair.

5. The non-contact electronic water level gauge circuit with parallel MOS transistors according to claim 1, characterized in that: The signal resistors S1~Sn are configured using an equal value sequence, an arithmetic sequence, or a geometric sequence.

6. The non-contact electronic water level gauge circuit with parallel MOS transistors according to claim 2, characterized in that: When the magnetic levitation ball is at the first level of water level, the first level magnetoresistive electronic switch T1 is closed, electronic switch M1 is turned on, and the other electronic switches M2~Mn are turned off. The water level monitoring signal Vo is equal to the voltage at node V1. When the magnetic levitation ball is at the Nth level water level and 2≤N≤n, the N-1 and Nth level magnetoresistive electronic switches T(N-1) and TN are closed simultaneously, the electronic switches M(N-1) and MN are turned on simultaneously, the other electronic switches are turned off, the signal resistor SN is effectively short-circuited, and the water level monitoring signal Vo is equal to the voltage at node VN.

7. A parallel non-contact electronic water level gauge circuit according to any one of claims 1-6, characterized in that: It also includes a microprocessor (MCU), where the water level monitoring signal Vo is an analog voltage signal, and the single-channel ADC pin of the MCU performs analog-to-digital conversion to calculate the current liquid level height.

Images