• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A liquid level sensing apparatus includes a probe (14) having a high positive temperature coefficient of resistivity. The probe (14) is connected in a circuit including an operational amplifier (A,) and a series transistor (T, which maintains the voltage across the probe (14) constant for a fixed period following switching on of the apparatus and which produces a voltage signal related to the current flowing in the probe. This voltage signal is differentiated by a differentiating circuit (R11,R12C3) to provide a signal indicating the rate of change of the voltage signal from which it is determined whether or not the probe is immersed in a cooling liquid. A warning lamp (L) is actuated by a latching switch circuit (T2, T3, T4 when the probe is not immersed. A second example is described in which the probe current is maintained at a fixed level and the rate of change of the voltage across it is monitored.
    公开号:SU963478A3
    申请号:SU792806957
    申请日:1979-08-22
    公开日:1982-09-30
    发明作者:Гордон Вильямс Дэвид；Энтони Харрис Пол
    申请人:Лукас Индастриз Лимитед (Фирма)；
    IPC主号:
    专利说明:

    I
    The invention relates to instrumentation engineering, in particular, to liquid level control devices, and can be used in mobile installations, for example, to control the level of 5 fuel in vehicle tanks.
    A liquid level detector is known, which contains a thermistor sensor, a resistance converter into an electrical signal, and a relay stage fl j.
    A disadvantage of the known device is large inertia.
    - The closest to the proposed technical essence is 15
    a liquid level detector containing a thermistor sensor, a voltage-to-resistance converter, including regulating a 1st DC voltage source 20 and a resistive divider into which a thermistor, a differentiating element connected to the output of the converter, is connected, and a relay element 2.25
    However, the device has low noise immunity.
    The purpose of the invention is to improve noise immunity and speed.
    This goal is achieved by the fact that in a device containing a sensor made in the form of a thermistor with a positive temperature coefficient of resistance, a resistance to voltage converter, including an adjustable constant voltage or current source and a resistive voltage divider, into which the thermistor is connected , as well as differential (1 urenziruyuschiy the link connected to the output of the converter, the relay element, the integrator is included, connected between the differential (1) power of the link and the relay element.
    权利要求:
    Claims (2)
    [1]
    FIG. Figure 1 shows the circuit diagram of the detector with the power supply of the sensor from an adjustable source of DC voltage for a predetermined predetermined time interval, (. 2 diagram of the indicator with a sensor circuit from a constant voltage source. The indicator is shown in Fig. 1). level control in the car's fuel tank when firing up and contains a thermistor sensor of level 1, installed in the fuel tank at a given point and resistive divider broken with resistor 2. It is made from an adjustable source of constant voltage, formed by amplifier 3 and transistor k, the base of which is connected to the output of amplifier 3. Amplifier 3 is designed to regulate the voltage for a certain period of time after each time. the sensor through diode 6 is connected to the ground bus, and the other end through diode 7 is connected to the inverting input of amplifier 3. The collector of the transistor is connected to the potential power line, and its emitter is connected to resistor 2 and Respectively connected resistor 8 and capacitor 9, which form a differentiating 1: 4 circuit with an inverting input of amplifier 10, which with a resistor 11 and a capacitor 12 forms an integrator. A relay element formed by transistors is connected to the integrator output. An indicator lamp is connected to the output circuit of which. The inverting input of the amplifier 3 is connected to the output of the master circuit time, formed by a resistor 16 and a capacitor 17. When the switch 5 is closed, the potential is exceeded at the inverting input of amplifier 3, and the potential at its inverting input is close to zero, because 17 is discharged, which biases the amplifier in a positive direction, and the transistor k opens. At the same time, the current through the sensor increases until the voltage at the inverting input y of the switch 3 becomes equal to the voltage at the non-inverting input. Thereafter, the current in the sensor is automatically adjusted to maintain this voltage until the capacitor 17 is charged to a degree to overcome the threshold value on diode 7. Thereafter, the output voltage of amplifier 3 drops, the transistor closes, and the measurement interval ends. During a period of time when a constant voltage is maintained at the sensor, the signal at the junction of resistor 2 and transistor C depends linearly on the resistance of the sensor, so that if current flows to the temperature of the sensor, the voltage at that point drops. The integrator responds only to a change in voltage at the junction of resistor 2 and transistor k. A constant voltage is applied to the non-inverting input of amplifier 10, and its inverting input is connected through resistor 11 to the output of the differentiating circuit and through feedback capacitor 12 to the output of amplifier, which through the diode 18 is simultaneously connected to the output of the differentiating circuit. Positive voltage front occurring when the switch is turned on. acts in such a way that the output of amplifier 10 becomes more negative than the inverting input, so that diode 18 conducts until the voltages at the two inputs of amplifier 10 are compared. Resistor 8 limits the increase in positive voltage and thus limits the amplitude of any oscillatory transient that may occur at the output of amplifier 10. If the sensor is immersed in fuel, the voltage at the input of the differentiating circuit remains almost constant during the measurement time. On the resistor 19, the voltage is equal to the sum of the voltages on the resistor 2 with diode 7 and resistor 20. / To maintain the same voltage across the inputs of the amplifier 10, the voltage on its output should be significantly reduced, the diode 18 is in a conducting state. If the sensor is in the air, as a result of the passage of current, it heats up, its resistance increases. The input voltage of the differentiating circuit drops. During the initial transient, diode 18 performs amplifier feedback, but as the voltage starts to drop, current flows through capacitor 9 and resistor 8. The resistance value of the resistor 19 is such that it cannot pass a current sufficient to maintain the voltage on the inverting input of the amplifier 10, which tends to become more negative than the voltage on the non-inverting input. Thus, the output circuit | - the amplifier 10 becomes positive, the diode 18 is locked. In this case, the amplifier 10 operates as an integrator, and its transfer function is determined by the resistor 11 and the capacitor 12, the time constant of which is less than the time constant differentiating circuit, which significantly reduces the sensitivity to noise, which has a very short duration and has little effect on the output voltage of the amplifier. The integrator output signal is controlled by a relay stage, in the output circuit of which the indicator lamp is connected. As the output of the amplifier 10 rises, the transistor starts to open, and the positive feedback through the transistor 13 1 causes it to open fully. Thus, if at any time during the measurement period, the output signal of amplifier 10 increases significantly, transistors 13 and C open and remain in this state until the ignition switch turns on / 1 scan. The detector also includes a sensor fault detection device to which input t parallelly connected diode 20 and resistor 21, transistors 22 and 23, and resistors 2 and 25, forming a divider, to the midpoint of which is connected an em ter transistor 22. When a sensor malfunctions, for example at rupture or short to ground, these are devices o provides ignition indicator light. FIG. Figure 2 shows a diagram of a detector in which direct current flows through sensor 1, for which the sensor is connected between the emitter, trans switch l, the base of which is connected to the output of amplifier 3, and the resistor /. The common point of the sensor and resistor 22 is connected via diode 7 to the inverting input of amplifier 3 which controls the transistor. Thus, with increasing temperature, the voltage at the other end of the sensor, which is connected to the input of the differentiating circuit formed by the capacitor 9 and the resistor 8-, rises. When switched on, there is a transient which causes the amplifier (} to produce a negative signal. At the same time, feedback is provided through the diode 182. If the sensor is immersed in fuel, the input voltage of the differentiating circuit remains constant, and the current flowing through the resistor 83, causes the output signal of amplifier 10 to deflect in a positive direction with a speed that is determined by resistor 10 and capacitor 12. If the sensor is in air, the voltage signal will continue to increase even after These transients caused the output signal of the amplifier to remain low at a conducting diode 18. Otherwise, the operation of this circuit does not differ from that of the previous one. Formula of the liquid level detector containing a sensor made in the form of a thermistor with a positive temperature coefficient of resistance, the converter resistance to a voltage that includes an adjustable source of DC voltage or current and a resistive divider into which the thermistor is connected, and entsiruyuschee link. connected to the output of the converter; and a relay element, characterized in that, in order to improve the noise immunity, an integrator is inserted in it, connected between the differentiating element and the relay element. Sources of information taken into account in the examination 1. The author's certificate of the USSR N-i 6l308, cl. G 01 F 23/22, 1973.
    [2]
    2. USSR author's certificate N 574b23, cl. G 01 F 23/22, 1976 (prototype).
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    同族专利:
    公开号 | 公开日
    AU4988179A|1980-02-28|
    ZA794052B|1980-08-27|
    CA1125886A|1982-06-15|
    AU531106B2|1983-08-11|
    EP0008508A1|1980-03-05|
    US4283719A|1981-08-11|
    JPS5531993A|1980-03-06|
    IN151991B|1983-09-17|
    ES483603A1|1980-04-01|
    DE2961163D1|1982-01-07|
    BR7905390A|1980-05-20|
    EP0008508B1|1981-10-28|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US2742634A|1953-07-21|1956-04-17|Republic Aviat Corp|Supervisory circuit for ambient condition detector|
    US2901740A|1956-11-23|1959-08-25|Specialties Dev Corp|Electrical network automatically responsive to a change in condition|
    GB1096278A|1964-04-28|1967-12-20|Dipstix Ltd|Improvements in or relating to liquid level indicators|
    US3376568A|1964-09-29|1968-04-02|Gen Motors Corp|Transistor switching circuit|
    US3547145A|1966-05-16|1970-12-15|Walter Holzer|Apparatus for sensing levels in containers holding liquids|
    FR2085952B3|1970-04-09|1974-02-15|Beck Stephane Andre|
    US3740740A|1972-01-12|1973-06-19|Us Army|Liquid cryogen detector|
    GB1450895A|1972-11-17|1976-09-29|Lucas Electrical Ltd|Liquid level detection systems|
    GB1480349A|1973-12-28|1977-07-20|Apv Co Ltd|Liquid detectors|
    US3911744A|1974-04-10|1975-10-14|Liquidometer Corp|Liquid level gauging apparatus|
    US3943767A|1974-07-22|1976-03-16|American Magnetics, Inc.|Level detector system for cryogenic liquids|
    FR2325909A1|1975-09-23|1977-04-22|Jaeger|Automatic oil level sensor for vehicles - uses fast response level detector, electronic threshold switch and alarm system|
    FR2367276B1|1976-10-06|1979-02-23|Jaeger|
    DE2645743C2|1976-10-09|1985-11-07|Vdo Adolf Schindling Ag, 6000 Frankfurt|Liquid level measuring device|
    US4102191A|1976-11-19|1978-07-25|Harris Roger J|Digital fuel gauge|
    US4185207A|1977-08-15|1980-01-22|Ab Svensk Nivakontroll|Amplifier system with alternate inputs|DE3133421C2|1981-08-24|1985-10-24|Vdo Adolf Schindling Ag, 6000 Frankfurt|Device for electrically monitoring the level of a liquid contained in a container|
    FR2514134B2|1981-10-07|1984-01-13|Jaeger|
    US4506258A|1982-05-20|1985-03-19|Gulf & Western Manufacturing Company|System for detecting low liquid level and probe therefor|
    US4591839A|1982-05-20|1986-05-27|Gulf & Western Manufacturing Company|System for detecting low liquid level and probe therefor|
    US4497205A|1982-12-17|1985-02-05|Gulf & Western Manufacturing Company|Method and apparatus for automatically sensing the level of a liquid in a reservoir|
    US4654646A|1985-02-22|1987-03-31|Wickes Manufacturing Company|Modular liquid level sensor having integral electronics|
    US4771271A|1987-03-11|1988-09-13|Ford Motor Company|Silicon based low level liquid sensor having a fast response time|
    GB2231961A|1989-05-18|1990-11-28|Peng Wen Bing|Liquid level sensing circuit|
    JPH0324425A|1989-06-20|1991-02-01|Murata Mfg Co Ltd|Displacement-amount measuring apparatus|
    FR2690245A1|1992-04-21|1993-10-22|Sagem|A method of controlling the level of a liquid by resistive element and circuit for carrying out the method.|
    DE4330924C1|1993-09-13|1994-11-17|Loh Kg Rittal Werk|Cooling device for a switching cabinet or an electronics housing|
    ITTO20020601A1|2002-07-10|2004-01-12|Olivetti I Jet Spa|DETECTION SYSTEM OF THE LEVEL OF A LIQUID IN A TANK|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    GB7834265|1978-08-23|
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