JPS5810617A - Liquid level detector - Google Patents

Abstract

PURPOSE:To obtain an apparatus capable of self-protection against abnormal voltage by keeping a circuit containing a liquid level detection electrode electrically connecting to an oscillation circuit and a switching circuit, employing two current transformers. CONSTITUTION:The output of an oscillation circuit 5 is connected to the primary winding 6a of a first current transformer 6 while the secondary winding 6b thereof 6, a pair of liquid level detection electrodes 12a and 12b through the primary winding 8a of a second current transformer 8 and distributing wires 14a and 14b. The secondary winding 8b of the second current transformer 8 is connected to a switching circuit 9 comprising resistors 9a and 9b, a transistor 9c, a capacitor 9d and a relay 9e and the output of a power supply circuit 4 comprising a transformer 4a, a diode 4b and a smoothing copacitor 4c is connected to the switching circuit 9 and the oscillation circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid level detecting device for detecting the original position of water, oil, etc. stored at equal pressure in a tank, for example. ◎Generally, conventional liquid level detecting devices are the same as those of conventional liquid level detecting devices. As shown in the water level detection device in the figure, connect the external AC power supply to the primary transformer (c) of the liquid level detection device body 0), and connect the snow winding ( The AC input sides of the K-bridge rectifier) are connected in series, and a pair of electrodes (chi 1), (chi b ) are connected via electric wires (Hibiki a) and (Ilb), and this pair of electrodes (Chia) and (Chib) are placed in a water tank (9°), while the transformer (to) 3 Next, connect a rectifier diode (c) and a smoothing capacitor (b) to $111 (c), and connect a series circuit of a relay and a transistor (b) across %; The base is connected to the DC output side of the full K11 resistor (IIl, &4 and the capacitor (Ik) to the bridge rectifier via the &■ path).

In this level detection device, when the water level in the water tank (b) is zero, the resistance value between the electrodes (chi 1) and (chi b) is infinite, and the DC output side of the bridge rectifier Since no voltage appears in the transistor (to), therefore no pace current is given to the transistor (to), and the transistor (to) is in the off state and the relay is activated.Meanwhile, the water level in the water tank (y4) rises. When (b) is exceeded, water exists between the electrodes (la) and (chib), so the resistance value of water becomes K between the electrodes (chibatake) and (chib), Then the 3rd order of transformer C→
) So (ha b) → Electricity (la) → Electrode (chia) → Water → Electrode (chi b) → Electric wire (subb) → Bridge rectifier) → Transformer ()! Current flows in the path of the next winding (c)
As a result, a voltage appears on the DC output side of the bridge rectifier (to the bridge rectifier), and as a result, a pace current passes through the transistor (to), turning the transistor (2) on and activating the relay.

Depending on the operation or non-operation of this relay (b), it is possible to detect whether the water level in the aquarium (b) has changed from (b).
By controlling the alarm by opening and closing the relay contact (not shown) in (b), you can notify that the water level has reached (b), and by controlling the valve, the water supply will be stopped when the water level reaches fljK. be able to.

However, such conventional liquid level detection devices require electric wires.
), (lJb) are directly connected to the bridge rectifier) and transistor (e).In round buildings or factory areas, the electrical wires (s.a.
), (subb) are installed in piping or electric wires (lJa), (
When the length of b) becomes longer, the abnormal voltage generated in the wires (!J a) and (IJb) due to the induced lightning force (bridge rectifier) and transistor, which are relatively vulnerable to abnormal voltage. There was a risk that the (to) would be destroyed.

The present invention addresses the above points and aims to provide self-protection against abnormal voltages.

The following is an example of the present invention based on nine drawings and one drawing.
To explain, it is the main body of the lII'i liquid level detection device, and the external AC power supply! Power input terminal 1m, 3b to connect
The transformer 4a to which the K primary winding is connected and this transformer 4
A power supply circuit 4 consisting of nine diodes 4b connected in series to the 102nd winding and a smoothing capacitor 4c connected in parallel to this series circuit, an oscillation circuit 2 which oscillates using the output voltage of this power supply circuit 4 as a power supply, and this oscillation circuit The output of 1*I line 6a
A second current transformer having a primary winding 1 connected in series to the winding 6 of the current transformer 6 and connected to the detection terminals 7m and 7b. The secondary winding 8b of this third current transformer is connected to the input KII and the electric line 4.
b0 which houses the switching circuit @ supplied with power from
In addition, the switching circuit is the secondary winding of the second transformer.
bK resistor 9a connected in parallel and secondary winding 8 of this current transformer 8
bK resistor b connected in series, secondary winding lbK pace, and transistor j connected through this resistor 9b
It consists of a relay 9. connected in parallel between l'io and the base and emitter of this transistor 9c, a capacitor t9d, and a relay 9 connected in series between the collector and emitter of the transistor 9@ and connected in parallel to the output of the power supply circuit 4, When a predetermined voltage is output from the secondary winding lb of the current transformer 8, the transistor 9e drives the switching 4 and operating relay 9. The vagina is a container such as a tank for storing water or oil, n is a liquid such as water or oil stored in a container 10, and sL2&*ub is a pair of electrodes housed in the container 10, and these electrodes 12a and ulb are Reference numerals 014a and 14b are supported by insulators so as not to melt. Reference numerals 014a and 14b are electrical wires for connecting the detection terminals 7m and 7b of the main body 1 and the electrodes 11a and 11.

To explain this operating state, when the liquid level in the container 10 is below the higher position W1 of the electrodes 12m, 1! The resistance value between the primary winding 6b of the first current transformer 6 and the second current transformer #I is infinite.
The current Fi does not flow through the primary winding 11aK of Il, and the switching circuit 9 does not operate. On the other hand, when the liquid level in the container rises to a position W1 or higher, liquid n is present between the electrodes 11m and 11b, and the electrode line a.

1! has the resistance value of the blsflK liquid 11, and therefore the current transformation of wGl generated by the output of the oscillation circuit 2.
The current in the eighth winding 6b of the second current transformer is the primary winding 8a of the second current transformer.
→Wire Ma→Electrode 12a→Liquid 11→Electrode 1! By flowing through the path b → electric cable ub → secondary winding sob of the first current transformer 6, voltage is output to the secondary winding sob of the second current transformer l, and the switching circuit 9 performs a switching operation. do. Therefore, depending on the operating state of this switching circuit 9, the liquid level of the liquid n stored in the container W can be detected. For example, if a valve is controlled by this switching circuit, the liquid level can be adjusted between the spear and the water with the position W1 as the boundary. You can take care of yourself.

In this way, the present invention allows the output of the oscillation circuit to be transferred to the first current transformer 6.
Connect the primary winding 6aK of this current transformer, and connect the secondary winding Ml of this current transformer.
) to the primary winding of the second current transformer and the wiring wire 14
A pair of liquid level detection voltages via 114b @! 1m12b, the second current transformer 80 secondary winding 8b is connected to the switching circuit 1i1, and the switching circuit 9 and the output of the oscillation circuit MK power supply circuit 4 are connected. From the current transformer 6, 1IF-, the secondary winding 6b of the first current transformer 6, the primary winding 8a of the second current transformer 8, and the wiring wire 14
m*14b and liquid level detection electrode 12a.

Since there is no electrical connection between the circuit 12b and the oscillation circuit and switching circuit 9, there is less damage to electrical parts due to abnormal voltage generated in the wiring wires 14m and 14bK compared to conventional ones. , for wiring [#11148,
14b is housed in the same electric tube as other power lines or electric light lines, or when the wiring wires 14a and 14b are lengthened, an effective liquid level detection device can be provided.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the liquid level detecting device of the present invention, and FIG. 2 is a circuit diagram showing a conventional liquid level detecting device. 4... Power supply circuit, 5... Oscillation circuit, 6... First current transformer, 6a... Primary winding, eb... Secondary winding, 8
...Second current transformer, 8a...Primary winding, 8b...
Secondary winding, 9... Switching circuit, 11-... Liquid, 121 and 12b... Liquid level detection electrode, 14m and 1
4b... Wiring wire. Patent applicant Matsushita Electric Works Co., Ltd.

Claims (1)

[Claims] Connect the output of the oscillator circuit to the primary winding of the current transformer IIl,
The 8th winding of this current transformer is connected to a pair of liquid level detection electrodes KII via the primary winding of the 8th current transformer and a wiring wire, and the 8th order winding of the third current transformer is connect to the switching circuit,
Connect the output of the power supply circuit to this switcher circuit and the oscillation circuit to form a liquid level detection device.