JPS5922175B2 - liquid detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid detector that has a float floating on a first liquid and detects the arrival of a second liquid on top of the first liquid.

For example, a float is floated above a first liquid such as the sea, a river, a lake, a drainage outlet, or a recess in a dike, a detection electrode is attached to the float, and the capacitance between this electrode and the first liquid is , based on the arrival of a second liquid such as petroleum, which has a dielectric constant equal to that of the J liquid, on the first liquid, a change in the capacitance between the detection electrode and the second liquid is detected, and the second liquid is detected. It has been proposed to detect the arrival of two liquids.

As a detection means, for example, a high frequency signal oscillator is provided, and this oscillates at all times, but the oscillation is controlled to stop when the second liquid arrives. This detection means is relatively complex, requires a return path through the ground as an electrical circuit, and is unstable and unreliable. The present invention proposes a liquid detector that has a simple configuration, good stability, and high reliability.

An example of a liquid detector according to the present invention will be explained below with reference to the drawings. In FIG. 1, reference numeral 11 indicates a float, which is floating on the first liquid 12.

A detection electrode 13 is attached to the float 11 near the liquid surface 12a of the first liquid. For example, as shown in FIG. 2, detection electrodes 13 are formed integrally with a metal ring T4 at appropriate angular intervals and extended downward, and this ring T4
A thread is formed on the inner peripheral surface of the float 11.
The detection electrode 13 can be attached to the float 11 by screwing it into a screw formed on the outer peripheral surface of the float 11. In this way, the position of the detection electrode 13 with respect to the first liquid 12 can be adjusted by rotating the ring T4. be able to. float 1
The bottom plate 15 has a relatively thin cylindrical shape, for example, so as to be relatively unaffected by the inclination caused by waves.
The portion is located relatively deep below the liquid level and is below the liquid level 12.
Near a, the slope with respect to the liquid level is said to be very gentle, and the upper plate IT is in the shape of a disc with a gentle slope.
There is a large hole in the center, and a lid 18 is screwed into the hole to cover it. Between this lid 18 and the upper plate 11 is o.
A ring 19 is interposed to keep the interior secret. Lid 1
A cable fixing means 21 is fixed to the center of the cable 8 , and a cable 22 is inserted through the cable fixing means 21 .
A mounting base 23 is disposed in the center of the bottom plate 15 within the float 11, a wiring board 25 is mounted on the mounting base 23 at intervals, and an electronic circuit 26 is configured on the wiring board 25.

As will be made clear later, a reed switch 2r is housed in the center of the mounting base 23 in order to prevent malfunctions when the liquid level of the first liquid 12 drops to a certain level. A ring-shaped magnet 28 is housed around this, and the reed switch 2r is kept on at all times by this magnet 28. The switch 2r is connected to an electronic circuit 26. An AC bridge circuit is provided in which one arm includes a capacitance between the detection electrode 13 and the ground, and changes in the capacitance of the detection electrode in this bridge circuit are detected.

For example, as shown in FIG. 3, a high frequency oscillator 32 including a transistor 31 is provided, and its output side is connected to a capacitor 33.
and one end of 34. These capacitors 33,
The other end of 34 is grounded through diodes 35 and 36, respectively, and is also grounded through capacitors 3r and 38. An AC bridge circuit 39 is constructed having capacitors 33, 34, 3r, and 38 as arms, respectively. This one capacitor 31 is constituted by the electrostatic capacitance Cb between the detection electrode 13 and the first liquid. If the detection electrode 13 is always in the first liquid 12, the bridge circuit 39
The capacitance value of the valley capacitor is selected so that the values are balanced.

When the first liquid 12 is water, its dielectric constant is about 80, but when a second liquid such as petroleum comes on top of the first liquid 12, the dielectric constant of petroleum is about 2 to 3, and the dielectric constant of the capacitor 3r is about 80. The capacitance decreases and the bridge circuit 39 becomes unbalanced. The arrival of the second liquid is detected by detecting that this equilibrium has been disrupted.
For example, the connection of capacitors 33 and 31. The connection point between the capacitors 34 and 38 is connected to the non-inverting input terminal and the inverting input terminal of the comparator 45 through diodes 41 and 42, and further through resistors 43 and 44, respectively.The diode 41
, the connection point of the resistor 43 is grounded through the resistor 46 and the capacitor 41, respectively, and the connection point of the diode 42 and the resistor 4
4 is grounded through a resistor 48 and a capacitor 49, and a variable resistor is interposed between the resistors 46 and 48, and this is adjusted so that the comparator circuit 45 is connected at all times, that is, in the case of only the first liquid. The transistor 51 connected to the output side is made non-conductive. That is, in a state where the detection electrode 13 faces the first liquid, the bridge circuit 39 is approximately balanced, the rectified outputs of the diodes 41 and 42 are approximately the same level, and the two inputs of the comparator circuit 45 are approximately the same, so that the output thereof In some cases, transistor 51 is prevented from conducting. The reed switch 21 described in connection with FIG. 1 is inserted in series between the diode 42 and the resistor 44. The output side of the comparator 45 is connected to the base of the transistor 51, and the collector of the transistor 51 is connected to the resistor 4.
6 to one end of the polarity matching circuit 52, and its emitter is connected to the other end of the polarity matching circuit 52 through a Zener diode 53 serving as a reference voltage source.

The input side of the polarity matching circuit 52 is connected to a power source 56 through transmission lines 54 and 55. The polarity matching circuit 52 is the circuit 5
A diode is connected so that the collector side of the transistor 51 always has a positive potential even if the polarity of the connection between the transistor 2 and the transmission lines 54 and 55 is changed. Both ends of the output side of the polarity matching circuit 52 are connected to operating power supply terminals of the comparator 45, oscillation circuit 32, etc. through a constant voltage circuit 57. In addition, capacitor 33, 3r1 diode 35,
41 constitutes a voltage doubler rectifier circuit, and similarly a capacitor 34
, 38, and diodes 36 and 42 constitute a voltage doubler rectifier circuit. When the detection electrode 13 is in the first liquid 12, the bridge circuit 39 is balanced as described above, and the output of the comparator 45 does not cause the transistor 51 to conduct. The current flowing is small.

However, when the second liquid arrives on top of the first liquid 12 and enters the detection electrode 13 and the second liquid, the level at the non-inverting input end of the comparator 45 increases compared to the level at the inverting input end. The output is at a significantly high level, approximately close to the positive power supply voltage, causing transistor 51 to conduct, thereby causing a relatively large current to flow in transmission lines 54 and 55. For example, an ammeter 58 is inserted in series with the transmission lines 54 and 55, and the arrival of the second liquid can be detected based on the state of the vibration. According to this configuration, fluctuations in the power supply voltage and fluctuations in the oscillation frequency of the oscillation circuit 32 affect the capacitors 33, 34, 36, 31, and 38 almost uniformly, so there is no fear that the balance will be lost. It has good stability and can perform highly reliable detection without being affected by changes in the temperature. Since the electric circuit is composed only of the float 11 portion, the stability of the circuit operation is good. Further, only the detection electrode 13 may be used as the electrode. The dielectric constant of a liquid generally decreases with increasing temperature.

Therefore, to prevent malfunctions due to temperature changes, for example, the following steps may be taken. As shown in FIG. 4, a liquid chamber 61 is provided in the bottom plate 15 of the float, and water is placed inside the liquid chamber 61 so that the temperature of this water matches that of the first liquid 12. A pair of electrodes 62 and 63 are provided, and the capacitance of these electrodes 62 and 63 through the liquid in the liquid chamber 61 is used as the capacitance of the capacitor 38 in FIG. Alternatively, a temperature compensation capacitor may be inserted as the capacitor 38. When the capacitance of the detection electrode 13 with respect to the first liquid changes due to a temperature change, the capacitance between the electrodes 62 and 63 changes at the same time, and the bridge circuit 39 is always maintained in an equilibrium state, making it less susceptible to temperature changes. Become something. Placing the float 11 requires a guide to prevent it from drifting away.

For example, a guide 64 as shown in FIG. 5 is provided. The guide 64 has a cable holder 65 at its upper center and a receiving part 66 at its bottom.
6, as shown in FIG. 6 and FIG. 1, respectively, approximately 90
One end of each support arm 67 is attached with a second angular spacing, for example by screwing. Both ends of the guide rod 68 are fixed to corresponding ones of the other ends of the support arm 67, respectively. The guide rod 68 is fixed, for example, by making the ends of the arm 67 into a forked shape, placing the guide rod therebetween, and tightening the two ends with bolts and nuts6. float guide 64
is constructed by assembling a holder 65, a receiving portion 66, an arm 67, and a guide rod 68. Therefore, it is easy to carry.
Further, the height of the receiving portion 66 can be easily adjusted. As shown in FIG. 5, a guide 64 is disposed within a so-called bit 69, which is a recess within the dike, and a ring-shaped permanent magnet 10 is accommodated in a receiving portion 66.

When the float 11 comes into contact with the receiving portion 66, the magnetic field of the magnet 28 on the reed switch 27 in FIG. 1 is canceled out by the magnet 10, so that the reed switch 21 is turned off. By selecting the height of the receiving portion 66, the position where the float 11 is placed in the malfunction prevention state can be adjusted, and the float 11 is held in the receiving portion 66 even when the liquid level decreases. In this held state, the reed switch 2T is turned off, so even if the first liquid is not present in FIG. 3 and the capacitance of the capacitor 37 is significantly reduced, the switch 2r is turned off. The input level at the input terminal becomes O, and the level at the inverting input terminal is higher than this, so the output of the comparator 45 is held negative, and the transistor 46
There is no conduction. That is, there is no risk of malfunction due to the arrival of the first liquid. In this way, the float is placed inside the float guide 64 to prevent the float from flowing, but when it rains, the rainwater flows between the guide rod 68 of the float guide and the float 1.
When the liquid flows to the surface of the float opposite to the electrode 13 through the part in contact with the second liquid, the peripheral surface of the float 11 becomes electrically at the same potential as the guide rod 68, and as shown in FIG. 1, regardless of the presence of the second liquid, There is a possibility that the arrival of the second liquid will not be detected because the capacitance facing the electrode 13 is not reduced.

From this point, the upper plate 1 of the float in Figure 1
The hood 13 is integrally constructed by extending the hood 7 and bending its peripheral edge downward, and a gap is provided between the periphery of the hood 13 and the peripheral surface of the float so that the first liquid does not come in contact with the hood 13. By preventing rainwater from reaching the device, it is possible to prevent previous malfunctions. According to this invention, the thickness of the liquid layer of the second liquid to be detected can be adjusted.

That is, unless a layer of the second liquid arrives that is so thick that the detection electrode 13 is inserted deeply into the first liquid, detection cannot be performed, resulting in a decrease in sensitivity. In order to transmit the capacitance of the detection electrodes 13 to the ground in this column part to the internal electronic circuit 26, a wire may be directly connected to the metal ring R4, but in that case, a hole is formed in the float 11. Since the lead wire has to be passed through the opening, the problem of airtightness of the flow port 1 arises. Therefore, it is preferable to attach a ring-shaped electrode 15 to the inner peripheral surface of the float 11 facing the ring R4, and to connect the electrode 13 to the circuit 26 through capacitive coupling between the ring 74 and the electrode 75. A gap is provided between the detection electrode 13 and the male circumferential surface of the float without contacting the first liquid 12, to prevent continuous formation of slag due to floating matter between them. In addition, in FIGS. 4 and 5, in order to lead out the cable 22 from above,
In order to prevent force from being applied to the float 11 through the cable 22 and causing it to malfunction, the cable 22 is fixed at the position of the holder 65, and a margin is provided for the cable 22 between the holder 65 and the float 11. Eliminate instability such as malfunction or non-operation. Furthermore, since the transmission lines 54 and 55 are used for supplying operating power to the oscillation circuit 32 and comparison circuit 45 and for transmitting the detection signal, the cost can be reduced accordingly. Also, the detection electrode 13
is attached to the circumferential wall of the float 11, so that even if the liquid to be detected clumps at room temperature, such as heavy oil, the arrival of the liquid can be detected. Moreover, the area of the detection electrode 13 can be increased, and it is less susceptible to the effects of slag and dirt.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a liquid detector according to the present invention, FIG. 2 is a perspective view showing the detection electrode of FIG. 1 and its mounting part, and FIG. 3 is a connection showing an example of the electric circuit part 4 is a sectional view showing the main parts of another example of a liquid detector according to the present invention, FIG. 5 is a front view showing a float arranged on a float guide, and FIG. 6 is an enlarged view of its holder. FIG. 7 is an enlarged plan view of the receiving portion. 11: float, 12: first liquid, 13: detection electrode, 32
: Oscillation circuit, 39: AC bridge, 45: Comparison circuit.

Claims (1)

[Claims] 1. A float floating in a first liquid, with its lower end in contact with the first liquid, and attached to the outer peripheral wall of the float with a space provided between the lower end and the outer peripheral surface of the float. An AC bridge circuit that includes a detection electrode and a capacitance between the detection electrode and ground in one arm, and a change in the capacitance caused by a second liquid arriving on top of the first liquid. A liquid detector comprising means for detecting a change in the output of the bridge circuit as the arrival of the second liquid, and means for adjusting the vertical position of the detection electrode with respect to the float.