JPS61129531A - Electrostatic capacity type level gauge - Google Patents

Abstract

PURPOSE:To detect accurately an entry of water into a tank and to annunciate that by putting on a warning lamp by providing an abnormality warning circuit which generates an abnormality warning signal when the electrostatic capacity of a sensor part increases abnormally. CONSTITUTION:A level gauge is constituted by connecting an electrostatic capacity type sensor part 1 having a couple of electrodes 11 to be put in the tank 17 to a monostable multivibrator 2 and varies the output pulse width of the monostable multivibrator 2 according to the electrostatic capacity of the sensor part 1. Then its output pulse signal is passed through an integration circuit 3 to generates an integral signal and a display corresponding to the integral signal is made on the level meter 4. Further, the abnormality warning circuit 5 is added, and consequently if water mixes with the fuel in the tank 17 and enters the gap between the electrodes 11, the electrostatic capacity between them increases abruptly and the circuit 5 generates an abnormality warning signal to put on the warning lamp 6, thus annunciating the entry of the water into the tank.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a capacitive level meter for detecting liquid levels in various fuel tanks and the like.

<Conventional technology> There is a capacitance level meter as a level meter that measures the remaining amount in various fuel tanks. The capacitance between the electrodes, which is determined by the size, shape, relative position of the electrodes, and the dielectric constant of the intervening substances (for example, fuel and air), is measured as the liquid level.

<Problems to be Solved by the Invention> However, when measuring the level of fuel with a dielectric constant of about 2.5 using a capacitance type level meter, water with a dielectric constant of about 60 to 7o is used. If it gets into the tank and accumulates at the bottom of the tank, the dielectric constant of the substance interposed between the electrodes increases dramatically, causing the capacitance between the electrodes to increase significantly, causing the level gauge needle to swing out beyond the full tank. This will make it impossible to accurately measure the level in the tank. Therefore, in such a case, the inside of the tank must be cleaned and the water must be drained immediately. Therefore, conventionally, water detection type level meters have been manufactured that have an electrode in the sensor part to detect the water in the tank, and detect the water in the tank by changing the electrical resistance between the electrodes. The seed bar meter requires a dedicated water detection electrode and detection circuit, which poses problems such as an increase in the size of the sensor section and a complicated structure.

<Means for Solving the Problems> The present invention takes the above points into consideration and is constructed as follows.

That is, in the capacitive level meter of the present invention, as shown in the overall configuration diagram of FIG. The output pulse reflex width of the monostable multivibrator 2 is changed according to the capacitance of the sensor section 1, and this output pulse signal is passed through the integration circuit 3 and sent to the level meter 4 according to the integral signal created. The capacitance type level meter that performs display is provided with an abnormality alarm circuit 5 that generates an abnormality alarm signal and lights up an alarm lamp 6 when the capacitance of the sensor section 1 becomes abnormally high.

With this configuration, when water accumulates in the tank and the capacitance of the sensor unit 1 increases abnormally, an abnormality alarm circuit is generated from the abnormality alarm circuit 5, the alarm lamp 6 is lit, and water is discharged into the tank. Alerts the ingress of water.

<Example> Embodiments of the present invention will be described below based on the drawings.

[First Embodiment] In Fig. 2, 17 is a tank for storing fuel, etc. A pair of plate-shaped electrodes 11, which will become the sensor part 1, are inserted into the tank 17 and fixed at predetermined relative positions. The electrode 11 is connected to a measuring circuit 18, and the level meter 4 is connected to the output side of the measuring circuit 18.

FIG. 3 shows a circuit diagram of this measuring circuit 18, in which 2L is a monostable multivibrator, and the above-mentioned electrode 1 serves as a capacitor that determines the pulse width of the pulse signal output from the monostable multivibrator.
1 is connected. 22 is a clock oscillator that generates a clock pulse signal, and is connected to send a clock signal to the monostable multivibrator 21 and to another monostable multivibrator 23 via an inverter 24 and an AND gate 25. . Note that the width of the high level output of the monostable multivibrator 21 is set to be shorter than one cycle of the clock signal even when full tank is detected.

The output side of the monostable multivibrator 21 is the inverter 2
6 to the AND gate 25, and also to the resistor 31 of the integrating circuit 3 via another AND gate 27.

The monostable multivibrator 23 is triggered by the rising edge of the clock signal sent from the AND gate 25 and outputs a high-level signal for a certain period of time. capacitor C connected to.

capacity is set. Further, the output side of this monostable multivibrator 23 is connected to an AND gate 27, and is also connected to the base of a transistor 52 in an abnormality alarm circuit 5 via an inverter 51, and the collector of the transistor 52 is connected to an alarm lamp 6. be done. on the other hand,
A resistor 31 and a capacitor 32 of the integrating circuit 3 are connected to an operational amplifier 33, and a level meter 4 is connected to this side of the operational amplifier 33.

Next, the operation of the capacitive level meter having the above configuration will be explained with reference to the timing chart in FIG. 4.The clock signal CK1 is constantly applied from the clock oscillator 22 to the monostable multivibrator 21, and its output Q1 is , is triggered to a high level by the rising edge of the clock signal CKI, and the width of the high level increases as the fuel in the tank 17 increases and the capacitance of the electrode increases. Then, the output Q1 of the monostable multivibrator 21 is integrated by passing through the integrating circuit 3 from the AND gate 27, and the operational amplifier 83 outputs an output signal OF at a level corresponding to the liquid level in the tank. The signal OF is sent to the level meter 4, which displays the fuel level I in the tank 17. On the other hand, the monostable multivibrator 23 has an output Q of the monostable multivibrator 21.
The logical sum of the inverted signal of 1 and the inverted signal of clock signal CKl is applied as the clock signal GK2, and the monostable multivibrator 21 is triggered at the rising edge of this clock signal CK2, and the high level width of its output Q2 is equal to that of the first clock. Since it is set longer than one cycle of signal CKl,
As shown in FIG. 4, the output Q2 of the monostable multivibrator 21 does not fall to a low level but remains at a high level when level detection is performed normally and the clock signal CK2 is generated normally. Therefore, a low V voltage is applied to the base of the transistor 52 of the abnormality alarm circuit 5, and the alarm lamp 6 is not lit.

However, if water gets mixed into the fuel in the tank 17 and enters between the electrodes 11, the capacitance between them increases dramatically, and the output Q1 of the monostable multivibrator 21 does not fall to a low level but remains at a high level. It will remain as it is. Therefore, and gate 25
Since the clock signal OK2 outputted from remains at a low level, the monostable multivibrator 23 is not triggered and its output Q2 immediately falls to a low level. Therefore, the output of the AND gate 27 becomes low level as the output Q2 decreases, so the output OP of the operational amplifier 33 which has passed through the integrating circuit 3 rises instantaneously when water is detected, but falls to a low level after several m5ec. level meter 4
Stop the level instruction without shaking out. on the other hand,
When water is detected, the monostable multivibrator 23
Since the output Q"2 falls to a low level, an inverter 51 is connected to the base of the transistor 52 of the abnormal alarm circuit 5
A high level and high voltage is applied through the collector circuit, a current flows through the collector circuit, the alarm lamp 6 is lit, and an alarm indicating water contamination is issued.

[Second Embodiment] FIG. 5 is a circuit showing another embodiment, and No. 6 is a timing chart showing its operation. In this example, electrode 1
The output side of the monostable multivibrator 21 to which 1 is connected is directly connected to the integrating circuit 3, and the output side of the integrating circuit 3 is connected to the level meter 4 via the operational amplifier 33 in the same manner as described above. Furthermore, operation amplifier 33
The output side of is connected to a comparator 34, the other input side of the comparator 34 is connected to a circuit for applying a reference voltage, the output side is connected to the base of a transistor 35, and the alarm lamp 6 is connected to its collector. be done. Note that the reference voltage of the comparator 34 is set approximately halfway between the voltage level of the output OP of the operational amplifier 33 when the fuel in the tank is full and the same voltage level when the level meter 4 swings out when water is detected. be done.

Next, to explain its operation with reference to FIG.
Outputs Renu signal. The output Q is integrated via the integrating circuit 3 and the operational amplifier 33, and the output OF of the operational amplifier 33 becomes a voltage level corresponding to the fuel level in the tank and is sent to the level meter 4, which measures the fuel level. indicate. On the other hand, when water gets into the tank and the capacitance between the electrodes 11 increases dramatically, the output Q of the monostable multivibrator 21 drops to a low level and remains at a high level, and the output OP of the operational amplifier 33 changes to the level meter 4. It rises until it shakes out. Then, the output OF exceeds the reference voltage applied to the comparator 34,
A high level signal is sent from the comparator 34 to the transistor 35.
, the transistor 35 becomes conductive and the alarm lamp 6 is turned on.
lights up to notify you of water contamination.

Although the plate electrode 11 is used in the sensor section 1 in the above embodiment, it is of course possible to use a cylindrical electrode 12 made of a cylinder and a metal rod inside the cylinder, as shown in FIG.

<Effects of the Invention> As explained above, according to the capacitance level meter of the present invention, water contamination in a tank can be accurately detected without providing a special electrode or complicated circuit in the sensor section. This can be notified by lighting an alarm lamp. Further, according to the first embodiment, it is possible to prevent the level meter from swinging out due to a sharp increase in the capacitance of the electrode due to water intrusion.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the present invention, Figs. 2 to 7 show embodiments of the invention, Fig. 2 is an explanatory diagram of a tank and a level meter, Fig. 3 is a circuit diagram of a measuring circuit, and Fig. 7 is an illustration of a tank and a level meter. Fig. 4 is a timing chart showing the operation of the same circuit, Fig. 5 is a circuit diagram of another embodiment, Fig. 6 is a timing chart showing the operation of the same circuit, and Fig. 7 is a perspective view of electrodes of another embodiment. It is. ■...Sensor part, 2...Monostable multivibrator, 3...Integrator circuit, 4...Level meter, 5...
Abnormal IF alarm circuit, 6... Alarm lamp. Patent application Jin-Aisan Kogyo Co., Ltd. Figure 1 @ Figure 2 Figure 4 @ 6 Figure Run 43W Figure 7

Claims (1)

[Claims] A capacitive sensor section with a pair of electrodes inserted into a tank is connected to a monostable multivibrator, and the output pulse width of the monostable multivibrator is varied according to the capacitance of the sensor section. In a capacitive level meter that passes the output pulse signal through an integrating circuit and displays it on a level meter according to the integrated signal generated, an abnormality alarm signal is generated when the capacitance of the sensor section increases abnormally. A capacitive level meter characterized by being equipped with an abnormality alarm circuit that lights up an alarm lamp when an abnormality occurs.