CN219977522U - Electrode type liquid level sensor - Google Patents
Electrode type liquid level sensor Download PDFInfo
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- CN219977522U CN219977522U CN202321180299.4U CN202321180299U CN219977522U CN 219977522 U CN219977522 U CN 219977522U CN 202321180299 U CN202321180299 U CN 202321180299U CN 219977522 U CN219977522 U CN 219977522U
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Abstract
The utility model discloses an electrode type liquid level sensor, which comprises a power supply circuit, a square wave generating circuit, an inverting amplifying circuit, a current detecting circuit, a first electrode and a second electrode, wherein the power supply circuit is connected with the square wave generating circuit; the power supply circuit is respectively connected with the square wave generating circuit and the current detection circuit and is used for providing power supply; the output end of the square wave generating circuit is respectively connected with the first electrode and the input end of the inverting amplifying circuit, and the current detecting circuit is positioned between the output end of the inverting amplifying circuit and the second electrode. The utility model can improve the working reliability of the sensor and prolong the service life of the sensor.
Description
Technical Field
The utility model mainly relates to the technical field of liquid level detection, in particular to an electrode type liquid level sensor.
Background
With the rapid development of modern industry, the liquid level detection requirement widely exists in various industries such as petrochemical industry, metallurgy, electric power, pharmacy, environmental protection, daily life and the like, and a liquid level sensor is generated, is fixed at a specific height, and can convert the liquid level height into an electric signal for output when the liquid level is immersed at the height. The electrode type liquid level sensor is widely applied due to the simple working principle, low cost, convenient maintenance and the like.
The basic working principle of the electrode type liquid level sensor is that the conductivity of liquid is utilized, two metal electrodes on the sensor are sensing parts, and when the conductive liquid exists between the two electrodes, the two electrodes are conducted; when the two electrodes are free of conductive medium, the resistance approaches infinity. The resistance value between the electrodes is indirectly measured by detecting the current between the electrodes, so that the wading condition of the liquid level sensor is judged.
The current direct current water level sensor uses direct current to detect the liquid level, and the current carrying ions in the adopted direct current scheme can continuously move towards the electrode, so that the electrode of the sensor can be corroded and scaled due to the existence of electrolysis, the aging of the electrode is accelerated, and the service life of the sensor is directly influenced; in addition, when a direct current scheme is adopted for static or slow-flow liquid, free moving carrier ions in the liquid are reduced due to continuous movement and aggregation of carrier ions, the conductivity of the liquid between electrodes is weakened along with time, namely the resistance value of the liquid between the electrodes is continuously increased along with time, the resistance value reaches megaohm level, and the threshold resistance inside the sensor needs to be set to be larger than the resistance value of the liquid. According to the principle of resistance voltage division, the resistance between the electrodes is smaller than the internal threshold resistance, and the wading is judged, otherwise, the wading is judged. Setting a large threshold value brings hidden danger of misjudgment, and is easy to alarm in a high humidity environment.
Disclosure of Invention
The technical problem to be solved by the utility model is as follows: aiming at the technical problems existing in the prior art, the utility model provides an electrode type liquid level sensor which can improve the working reliability of the sensor and prolong the service life of the sensor.
In order to solve the technical problems, the technical scheme provided by the utility model is as follows:
an electrode type liquid level sensor comprises a power supply circuit, a square wave generating circuit, an inverting amplifying circuit, a current detecting circuit, a first electrode and a second electrode; the power supply circuit is respectively connected with the square wave generating circuit and the current detection circuit and is used for providing power supply; the output end of the square wave generating circuit is respectively connected with the first electrode and the input end of the inverting amplifying circuit, and the current detecting circuit is positioned between the output end of the inverting amplifying circuit and the second electrode.
As a further improvement of the above technical scheme:
a first voltage follower circuit is arranged between the output end of the square wave generating circuit and the first electrode, and a second voltage follower circuit is arranged between the output end of the square wave generating circuit and the current detection circuit.
The first voltage follower circuit and the second voltage follower circuit are both voltage followers.
The square wave generating circuit comprises an operational amplifier U1, a resistor R2, a resistor R3, a resistor R7 and a capacitor C1, wherein one end of the resistor R1 is connected with one end of the resistor R2 and the in-phase input end of the operational amplifier U1 respectively, the other end of the resistor R1 is connected with one end of the resistor R3 and the output end of the operational amplifier U1 respectively, one end of the capacitor C1 is connected with the other end of the resistor R3 and the anti-phase input end of the operational amplifier U1 respectively, the other end of the capacitor C1 is connected with the other end of the resistor R2 and is grounded, and the resistor R7 is connected in series with the output end of the operational amplifier U1.
The current detection circuit comprises an alternating current input optocoupler and a resistor R5, wherein the input end of the alternating current input optocoupler is connected in series between the output end of the inverting amplification circuit and the second electrode, one end of the power supply circuit is connected with one side of the output end of the alternating current input optocoupler, and the other side of the output end of the alternating current input optocoupler is grounded through the resistor R5.
The inverting amplifier circuit is an inverting amplifier.
The first electrode and the second electrode are both fixed on a fixed seat.
The first electrode and the second electrode are fixed on the fixing seat in a glass sintering mode.
Compared with the prior art, the utility model has the advantages that:
the alternating-current positive and negative square waves are generated by the square wave generating circuit, and the equal alternating-current square waves with adjustable frequency are applied to the two detection electrodes, so that the liquid resistance between the two electrodes is kept stable and kept small, the threshold setting of wading judgment of the sensor can be reduced, the risk of false alarm of the liquid level sensor is reduced, and the working reliability of the sensor is improved; in addition, the moving direction of the conductive ions between the two electrodes is driven by the alternating current between the electrodes, so that the conductive ions do not continuously flow to one electrode, the oxidation corrosion speed of the electrode is greatly slowed down, and the service life of the liquid level sensor is prolonged.
One of the output signals of the square wave generating circuit is input into the inverting amplifier to generate the mirrored positive and negative square waves, when one electrode is positive voltage, the other electrode is negative voltage, so that the driving capacity of the electrode to liquid is doubled, and the problem of limited driving capacity of the positive and negative square waves on one side is solved.
The internal circuit and the external signal are fully isolated by adopting a voltage follower mode between the square wave signal and the electrode, so that external interference is effectively isolated, and the generation of square waves is prevented from being influenced by the fact that external electromagnetic interference is led in from the electrode.
Drawings
FIG. 1 is a schematic circuit diagram of a level sensor of the present utility model in an embodiment.
Fig. 2 is a schematic structural view of a first electrode and a second electrode according to an embodiment of the present utility model.
Legend description: 1. a square wave generating circuit; 2. an inverting amplifier circuit; 3. a first voltage follower circuit; 4. a second voltage follower circuit; 5. a current detection circuit; 6. a first electrode; 7. a second electrode; 8. a fixing seat.
Detailed Description
The utility model is further described below with reference to the drawings and specific examples.
As shown in fig. 1 and 2, an electrode type liquid level sensor according to an embodiment of the present utility model includes a power supply circuit, a square wave generating circuit 1, an inverting amplifying circuit 2 (such as an inverting amplifier U2), a current detecting circuit 5, a first electrode 6 and a second electrode 7; the power supply circuit is respectively connected with the square wave generating circuit 1 and the current detection circuit 5 and is used for providing power supply; the output end of the square wave generating circuit 1 is respectively connected with the first electrode 6 and the input end of the inverting amplification circuit 2, and the current detection circuit 5 is positioned between the output end of the inverting amplification circuit 2 and the second electrode 7; in addition, a first voltage follower circuit 3 (U4 in fig. 1) is provided between the output terminal of the square wave generating circuit 1 and the first electrode 6, and a second voltage follower circuit 4 (U3 in fig. 1) is provided between the output terminal of the square wave generating circuit 1 and the current detecting circuit 5. Wherein the first voltage follower circuit 3 and the second voltage follower circuit 4 are both voltage followers.
The alternating current positive and negative square waves are generated by the square wave generating circuit 1, and the equal alternating current square waves with adjustable frequency are applied to the two detection electrodes, so that the liquid resistance between the two electrodes is kept stable and kept small, the threshold setting of wading judgment of the sensor can be reduced, the risk of false alarm of the liquid level sensor is reduced, and the working reliability of the sensor is improved; in addition, the moving direction of the conductive ions between the two electrodes is driven by the alternating current between the electrodes, so that the conductive ions do not continuously flow to one electrode, the oxidation corrosion speed of the electrode is greatly slowed down, and the service life of the liquid level sensor is prolonged.
One of the output signals of the square wave generating circuit 1 is input into the inverting amplifier to generate the mirrored positive and negative square waves, when one electrode is positive voltage, the other electrode is negative voltage, so that the driving capacity of the electrode to liquid is doubled, and the problem of limited driving capacity of the positive and negative square waves on one side is solved.
Because the electrode can be contacted with an external medium, an interference signal can be introduced to disturb the generation of square wave signals, an internal circuit is fully isolated from an external signal by adopting a voltage follower mode between the square wave signals and the electrode, and external interference is effectively isolated, so that the generation of square waves is prevented from being influenced by the fact that external electromagnetic interference is led in from the electrode.
In a specific embodiment, the current detection circuit 5 includes an ac input optocoupler U5 and a resistor R5, wherein an input end of the ac input optocoupler is connected in series between an output end of the inverting amplifier circuit 2 and the second electrode 7, one end of the power supply circuit is connected to one side of the output end of the ac input optocoupler, and the other side of the output end of the ac input optocoupler is grounded through the resistor R5. When the first electrode 6 and the second electrode 7 are immersed in the liquid, the loop is conducted, at the moment, the light output end of the optocoupler is conducted, and the wading condition can be judged through the voltages at the two ends of the R5.
As the sensing of the water entering state of the sensor is realized by detecting current, the AC optocoupler is adopted to convert the signal into a voltage signal, and the voltage output signal is more stable through optocoupler isolation.
In a specific embodiment, the square wave generating circuit 1 includes an operational amplifier U1, a resistor R2, a resistor R3, a resistor R7 and a capacitor C1, wherein one end of the resistor R1 is connected to one end of the resistor R2 and the in-phase input end of the operational amplifier U1, the other end of the resistor R1 is connected to one end of the resistor R3 and the output end of the operational amplifier U1, one end of the capacitor C1 is connected to the other end of the resistor R3 and the inverting input end of the operational amplifier U1, the other end of the capacitor C1 is connected to the other end of the resistor R2 and grounded, and the resistor R7 is connected in series to the output end of the operational amplifier U1. The power supply circuit mainly generates positive and negative power supplies with equal voltage values, wherein the positive power supply VCC supplies power to the positive power supply of the operational amplifier U1 and the current detection circuit 5, and the negative power supply VSS supplies power to the negative power supply of the operational amplifier U1 for generating alternating current square waves.
Specifically, the square wave generating circuit 1 is used to generate alternating positive and negative square waves. A square wave generating circuit constructed based on a rail-to-rail operational amplifier matched with peripheral resistance and capacitance is shown in figure 1 by utilizing a capacitance charge-discharge principle. Since the operational amplifier U1 (operational amplifier U1 for short) cannot be balanced completely, the operational amplifier will output high or low level after power-up. Suppose that the operational amplifier U1 outputs a high level U 0 The voltage across R2, i.e. the in-phase input voltage of the operational amplifier U1, is U R2 ＝R2/(R2+R2)·U 0 . Due to the voltage U across the capacitor C1 C1 Can not mutate and transportInverting input voltage U of amplifier U1 C1 Will gradually increase when U C1 >U R2 When the operational amplifier U1 outputs a low level-U 0 At this time, the in-phase input voltage of the operational amplifier U1 is U R2 ＝-R2/(R2+R2)·U 0 Capacitor C1 begins to discharge, inverting input voltage U C1 Reduced to U C1 <U R2 ＝-R2/(R2+R2)·U 0 When the operational amplifier outputs a high level U 0 The charge and discharge time of the capacitor is equal, and the operational amplifier outputs square waves. Since the visible square wave is generated from the charge-discharge process of the capacitor C1, and the oscillation frequency depends on C1 and R3, the frequency calculation formula is f approximately 1/1.39RC. R1, R2, R3 and C1 can be adjusted according to specific application conditions.
Because the conductive characteristics of different liquids under different working conditions are different, the sensitivity threshold of the liquid level sensor can be improved through three ways: 1. adjusting C1 and R3 to improve the square wave vibration frequency. As the direct current power-on time is increased, the liquid resistance is obviously increased, and the unidirectional power-on time is shortened by increasing the square wave frequency, so that the purpose of reducing the liquid resistance between the electrodes is achieved; 2. an optocoupler U5 with higher current transmission ratio is selected, namely the ratio of output current to input current, and even if the current of the input end is smaller, the output end can pass through larger current; 3. the resistance value of R5 is increased, and the voltage at two ends of R5 is increased by utilizing the principle of resistance voltage division.
The sensitivity threshold of the sensor is adaptively adjusted according to different use scenes so as to meet the complex field application condition.
In one embodiment, the first electrode 6 and the second electrode 7 are fixed on a fixing base 8. Specifically, the first electrode 6 and the second electrode 7 are fixed on the fixing base 8 by glass sintering. The 316L gold-plated electrodes are adopted as the electrodes, so that the corrosion resistance of salt mist and acid-base liquid is improved. In addition, the two electrodes are fixed together by adopting a sintering tube seat mode. The insulation resistance between the electrodes directly relates to the judgment of the sensor on the wading condition, and the performances of the fixed structural strength of the electrodes, the air tightness of the internal circuit, the structural appearance and the like are considered. Because glass sintering has good insulativity, can reach thousands of megaohms, is almost completely insulated, and leads the connection between the glass and the electrode to be perfect and the air tightness to be ensured to be perfect by sintering the two electrodes at high voltage. In addition, considering the condition of comdenstion water, the surface of glass can accomplish enough smoothness, and the drop of water is difficult for adhesion to cause the electrode mistake to switch on at the surface to smooth surface is also convenient for clean.
Because the electrode is a sensing part of the liquid level signal, the performance of the sensor is influenced by the performance of the sensor such as appearance structure, insulativity, sealing degree, air leakage rate and the like. The electrodes are fixed by adopting the glass sintering mode, so that the reliable fixation of the two electrodes is ensured; and secondly, the glass has good insulativity, can be tightly sealed with the electrode in a sintering mode, can avoid vapor and liquid from penetrating into the sensor through the electrode, and can cope with various high-low temperature complex working conditions.
The whole circuit of the utility model has simple principle and easy realization, adopts common electronic devices in the circuit, is economical and practical, and can be applied to a plurality of places.
The above is only a preferred embodiment of the present utility model, and the protection scope of the present utility model is not limited to the above examples, and all technical solutions belonging to the concept of the present utility model belong to the protection scope of the present utility model. It should be noted that modifications and adaptations to the utility model without departing from the principles thereof are intended to be within the scope of the utility model as set forth in the following claims.
Claims (8)
1. An electrode type liquid level sensor is characterized by comprising a power supply circuit, a square wave generating circuit (1), an inverting amplifying circuit (2), a current detecting circuit (5), a first electrode (6) and a second electrode (7); the power supply circuit is respectively connected with the square wave generating circuit (1) and the current detection circuit (5) and is used for providing power supply; the output end of the square wave generating circuit (1) is respectively connected with the first electrode (6) and the input end of the inverting amplifying circuit (2), and the current detecting circuit (5) is positioned between the output end of the inverting amplifying circuit (2) and the second electrode (7).
2. Electrode type liquid level sensor according to claim 1, characterized in that a first voltage follower circuit (3) is arranged between the output of the square wave generating circuit (1) and the first electrode (6), and a second voltage follower circuit (4) is arranged between the output of the square wave generating circuit (1) and the current detecting circuit (5).
3. Electrode level sensor according to claim 2, characterized in that the first voltage follower circuit (3) and the second voltage follower circuit (4) are both voltage followers.
4. An electrode type liquid level sensor as claimed in claim 1, 2 or 3, wherein the square wave generating circuit (1) comprises an operational amplifier U1, a resistor R2, a resistor R3, a resistor R7 and a capacitor C1, one end of the resistor R1 is connected with one end of the resistor R2 and the non-inverting input terminal of the operational amplifier U1 respectively, the other end of the resistor R1 is connected with one end of the resistor R3 and the output terminal of the operational amplifier U1 respectively, one end of the capacitor C1 is connected with the other end of the resistor R3 and the inverting input terminal of the operational amplifier U1 respectively, the other end of the capacitor C1 is connected with the other end of the resistor R2 and is grounded, and the resistor R7 is connected in series with the output terminal of the operational amplifier U1.
5. An electrode type liquid level sensor according to claim 1, 2 or 3, wherein the current detection circuit (5) comprises an ac input optocoupler and a resistor R5, an input end of the ac input optocoupler is connected in series between an output end of the inverting amplification circuit (2) and the second electrode (7), one end of the power supply circuit is connected with one side of an output end of the ac input optocoupler, and the other side of the output end of the ac input optocoupler is grounded via the resistor R5.
6. An electrode level sensor according to claim 1 or 2 or 3, characterized in that the inverting amplifier circuit (2) is an inverting amplifier.
7. An electrode level sensor according to claim 1, 2 or 3, characterized in that the first electrode (6) and the second electrode (7) are both fixed to a fixed seat (8).
8. Electrode-type liquid level sensor according to claim 7, characterized in that the first electrode (6) and the second electrode (7) are fixed to the holder (8) by means of glass sintering.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202321180299.4U CN219977522U (en) | 2023-05-16 | 2023-05-16 | Electrode type liquid level sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202321180299.4U CN219977522U (en) | 2023-05-16 | 2023-05-16 | Electrode type liquid level sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN219977522U true CN219977522U (en) | 2023-11-07 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202321180299.4U Active CN219977522U (en) | 2023-05-16 | 2023-05-16 | Electrode type liquid level sensor |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN219977522U (en) |
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2023
- 2023-05-16 CN CN202321180299.4U patent/CN219977522U/en active Active
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