JPH062113Y2 - Liquid level relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a liquid level relay used in combination with a pump or the like to control a liquid level in a tank.

(B) Conventional Technology There are various types of relays used for liquid level control, but in recent years, electrode-bar type liquid level relays have become the mainstream. This type of liquid level relay is provided with at least three electrode rods having different lengths, each of which is suspended in a tank, and the longest first electrode rod is used as a ground electrode. For example, the shortest third electrode is used. The rod is used as an electrode for stopping water supply, the second electrode rod of medium length is used as an electrode for starting water supply, and when the liquid level drops to below the lower limit liquid level, a gap between the first electrode rod and the second electrode rod Since the conduction is OFF, in response to this OFF, the water supply pump is turned ON and water supply is started. The water level rises due to this water supply, and when the tip of the third electrode rod is exceeded, the third electrode rod will also be submerged in the liquid, and the first and third electrode rods will be in a conductive state. The water supply pump stops operating in response to.

(C) Problems to be solved by the device In the conventional liquid level relay, a short circuit may occur between adjacent electrode rods due to foreign matter containing water, or the electrode may drop out for some reason after long-term use. Sometimes. The electrode rods in which such a short circuit or dropout occurs are not specific to a plurality of electrode rods and are miscellaneous, and these abnormalities cannot be detected.

This invention was made by paying attention to the above problems, and in addition to the original control system, by detecting the current flowing through each electrode rod, when a short circuit or dropout of the electrode rod occurs, It is an object of the present invention to provide a liquid level relay that can easily detect these abnormalities.

(D) Means and Actions for Solving Problems The liquid level relay of the present invention is provided with a plurality of electrode rods for detecting the liquid level, and these electrode rods are connected to the relay unit part while the electrode rods are connected. Is installed in the liquid level detection area of a tank, etc., and in the case of controlling external equipment depending on the presence or absence of current flowing in each electrode rod, connect a resistor between the relay unit and the electrode rod, and measure the voltage across this resistor. It is derived and used as a detection signal of the current flowing through the electrode rod.

In this liquid level relay, the relay contacts are opened and closed depending on the presence / absence of current flowing through each electrode rod to control the external device, and the voltage drop across the resistor differs depending on the presence / absence of current flowing through the electrode rod. The presence or absence of current flowing through each electrode rod is detected from the voltage across each resistor. Therefore, by logically processing the output voltage obtained from both ends of these resistors, it is possible to detect a short circuit or a drop of each electrode rod.

(E) Embodiment Hereinafter, the present invention will be described in more detail with reference to embodiments.

FIG. 1 is a connection diagram of a liquid level relay showing an embodiment of the present invention. In the figure, three relay units 1, 2, 3
And six electrode rods E ₁ , E ₂ , E ₃ , E ₄ , E ₅ and E ₆
Shows the case of using.

Resistances r ₁ , r ₂ , ..., R ₆ are connected in series to the electrode rods E ₁ , E ₂ , ..., E ₆ , respectively.
The other ends of ₁ , r ₂ , ..., R ₆ are relay contacts R ₁ , R ₂ ,
..., connected to the common terminal c of R ₆ .

Therefore, the electrode rod E ₁ is connected to the relay unit 1 via the resistor r ₁ and the relay contact R ₁ . Further, the electrode rod E ₂ is connected to the relay unit 1 via the resistance r ₂ and the relay contacts R ₂ and U ₁ . Further, the electrode rod E ₃ is connected to the relay unit 2 via the resistor r ₃ and the relay contact R ₃ , and similarly the electrode rod E ₄ is connected to the relay unit 3 via the resistor r ₄ and the relay contact R _4. Has been done. The electrode rod E ₅ has a resistance r ₅ , relay contacts R ₅ , and U _3.
Is connected to the relay unit 3 via
₆ is a resistor r ₆ , a relay contact R ₆ , and a coil L,
It is connected to relay unit 1. Resistances r ₁ , r ₂ ,
..., electrode rods E ₁ connected from both ends of r ₆ ,
When a current flows through E ₂ , ..., E ₆ , the voltage drop causes
The current detection voltages V ₁ , V ₂ , ..., V ₆ are output. However, each electrode bar _{E 1,} E 2, ..., the resistance _r 1 in series _{E 6,} r 2, ..., connection configuration except that connects _{r 6} is
It is an example of what is conventionally used, and is not particularly new.

Therefore, the feature of the liquid level relay of this embodiment is that the resistances r ₁ and r are respectively connected in series to the electrode rods E ₁ , E ₂ , ..., E _6.
2 , ..., R ₆ are connected, the voltage drop is derived, and the presence or absence of current is detected.

These resistors _{r 1, r 2, ...,} r 6 , the electrode rod _{E 1,} E 2 to the tank 4, ..., while installing the _{E 6,} depending on the water level in the tank 4, each electrode bar _E 1, E _The currents flowing through ₂ , ..., E ₆ are detected. Since the mode of the presence or absence of the current flowing through each electrode rod E ₁ , E ₂ , ..., E ₆ changes depending on the water level in the tank 4 as well as due to a short circuit between the electrode rods or a dropout of each electrode rod, , V ₆ , can be detected by the logical processing of the derived voltages V ₁ , V ₂ , ..., V ₆ . next,
An example of the case where the abnormality determination is performed by the logical processing of the voltage across the resistor will be described.

For convenience, the liquid level relay of FIG. 1, the electrode rod _E 1, E
The abnormality determination between ₂ , ..., E ₅ , that is, the abnormality determination in the electrode configuration shown in FIG. 2 will be described.

The following case is assumed as an operation mode different from the normal operation.

When the electrode rod _{E 3} is ON, i.e. when there is a voltage output across the resistor _{r 3,} electrode rod _{E 2, E 3, E 4} , E 5 is all if not ON → A.

If the electrode rod E ₂ does not turn on within 0.5 seconds when the electrode rod E ₁ is ON, that is, when there is a voltage output across the resistor r ₁ , or when the electrode rod E ₁ is ON, the electrode rod E ₂ ,
When E ₄ and E ₅ are not ON → Set to B.

When the electrode rod E ₄ is ON, that is, when there is a voltage output across the resistor r ₄ and the electrode rod E ₅ does not turn on within 0.5 seconds, or when the electrode rod E ₄ is ON, the electrode rod E ₂ ,
If E ₅ is not ON → Set as C.

When the electrode rod E ₂ is OFF, and the electrode rod E ₁ is OFF within 0.5 seconds, set as → D.

When the electrode rod E ₅ is OFF, and the electrode rod E ₄ is OFF within 0.5 seconds, set to E.

When the above phenomenon A occurs, possible abnormalities include, as shown in FIG. 3, the electrode rod E ₁ falling off, the electrode rods E ₂ and E ₃ short-circuited,
The electrode rods E ₃ and E ₄ are short-circuited, and the electrode rods E ₃ and E ₅ are short-circuited. When the phenomenon B occurs, possible abnormalities are a short circuit between the electrode rods E ₁ and E ₅ , and a dropout of the electrode rods E ₂ or E ₅ . Further, when the phenomenon C occurs, a possible abnormality is the detachment of the electrode rod E ₅ . When phenomenon D occurs, a possible anomaly is a short circuit between electrode rods E ₁ and E ₂ . Further, the abnormality that may cause the development E is a short circuit between the electrode rods E ₄ and E ₅ .

From the above, the voltage V ₁ across the resistors r ₁ , r ₂ , ..., R ₅ is
Input V ₂ , ..., V ₅ to the logic circuit,
The input corresponding to each electrode rod is the phenomenon A, B, C,
If it is set so that a specific logic state output can be obtained at D or E, if a short circuit or disconnection of the electrode rod occurs at the logic circuit output, the alarm is activated or the safety device is activated. it can.

FIG. 4 shows a circuit diagram of an example of a logic circuit that outputs a specific logic state signal when the phenomena A, B, C, D, and E occur.

In the figure, amplifier 11 _-1, 11 _-2, to ... 11 _-5,
The voltage across the resistors r ₁ , r ₂ , ..., R ₅ is V ₁ , V ₂ ,.
V ₅ is input correspondingly. Amplifier 1
1 _-1 , 11 _-2 , ..., 11 _-5 are signals V ₁ , V ₂ , ..., V
₅ is above a predetermined level, that is, the electrode rod E ₁ ,
When the current flowing through E ₂ , ..., E ₅ is equal to or larger than a predetermined value, a high signal (logic “1”) is output. These amplifiers 11 _-1 ,
The outputs of 11 _-2 , ..., 11 _-5 are the NOT circuit 1 respectively.
2 _-1 , 12 _-2 , ..., 12 _-5 and NO circuit 13 _-1 , 1
_3-2, ..., via the 13 _-5, one end of the input of the AND circuits 14 and 15, the other end of the AND circuits 14, 15, 16, is connected to one end of the input of the AND circuits 16 and 17. Also, N
The output of the OT circuit 12 _-1 is connected to the preset input terminal PR of the flip-flop 20 via the delay circuit 18 and the other end of the input of the AND circuit 17. The output of the NOT circuit 12 _-2 is the flip-flop 20.
Connected to the clear terminal CL. Similarly, the output of the NOT circuit 12 _-4 is connected to the preset terminal PR of the flip-flop 21 via the delay circuit 19, and also the NOT circuit
The output of the circuit 12 _-5 is connected to the clear terminal CL of the flip-flop 21. AND circuits 14, 15, 1
Output terminals of the flip-flops 6 and 17 and the flip-flops 20 and 21 are commonly connected via the diodes d ₁ , d ₂ , ..., D ₆ and are connected to one end of the resistor R ₁ . Resistance R
₁ is also grounded via a resistor R ₂ . The midpoint of connection between the resistors R ₁ and R ₂ is connected to the base of the transistor 22, and the emitter of the transistor 22 is grounded. A light emitting diode 23 and a relay 24 are connected between the power supply + V and the collector of the transistor 22.

In the above embodiment, when the logic state of the voltage across each resistor is predetermined, in response to this, as a circuit that outputs an abnormality detection signal, a circuit composed of a logical element such as a NOT circuit, an AND circuit, and a flip-flop. However, a logic process may be performed using a microcomputer instead of the illustrated logic circuit.

Further, in this invention, the resistance is connected to the electrode rods of the liquid level relay, so that the number of electrode rods, the mode of abnormality, etc. are not limited to those in the above embodiment.

(F) Effect of the device According to this device, since the current flowing through the electrode rod is detected by using the voltage drop due to the resistance, the presence or absence of the current can be detected regardless of the signal of the control part of the liquid level relay. In addition, it is possible to reliably detect a short circuit, a drop or the like of the electrode rod. Further, since the current flowing through the electrode rod can be detected digitally, the subsequent complicated signal determination processing can be performed using a microcomputer or the like, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a connection diagram of a liquid level relay showing an embodiment of the present invention, FIG. 2 is a diagram for explaining a phenomenon when the liquid level relay of the embodiment is not normal, and FIG. FIG. 4 is a diagram showing a correlation between the above phenomenon and a short circuit between electrode rods and the dropout of each electrode. FIG. 4 shows the voltage across the resistance of the liquid level relay of the embodiment.
It is a circuit diagram showing an example of a logic circuit for determining the presence or absence of abnormality. 1, 2, 3: Relay unit, 4: Tank, E ₁ · E ₂ ···· E ₆ : Electrode rod, r ₁ · r ₂ ···· r ₆ : Resistance.

Claims (1)

[Scope of utility model registration request] 1. A plurality of electrode rods for detecting a liquid level are provided, and while these electrode rods are connected to a relay unit part, the electrode rods are installed in a liquid level detection area and the current flowing through each electrode rod is Depending on the presence or absence, in a liquid level relay that controls an external device, a resistor is connected between the relay unit and the electrode rod, the voltage across this resistor is derived, and this is used as a detection signal of the current flowing through the electrode rod. Liquid level relay to be.