JPH07119664B2 - Leak detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak detecting device for detecting leak of non-insulating liquid such as water or a mixed liquid of water and oil.

[0002]

2. Description of the Related Art For example, under a floor of a computer room where a large number of cables are laid, or in a storage room for articles that do not like water, there should be no liquid leakage, and early detection of liquid leakage may cause malfunction of the device. Damage to goods must be prevented in advance.

Conventionally, as a device for detecting liquid leakage, there has been proposed a device including a detection line whose electric characteristic changes due to the attachment of a non-insulating liquid and a detection circuit which detects a change in the electric characteristic of the detection line. There is.

FIG. 3 shows a circuit of a general liquid leakage detection device. This device is a water leak detection device.

This detection device uses a detection line S as a detection element.
L is used. The detection line SL is a parallel line covered with a mesh, and when water enters between the meshes, the two lines conduct at that position, and the impedance between the two lines decreases. Leakage is detected by arranging this detection line on the floor and monitoring the impedance. Detection line S that is a parallel line
A voltage is applied from the power transformer 10 to one end of L, and a terminating resistor R0 is connected to the other end. The voltage from the power transformer 10 is the Zener diodes ZD1 and ZD2.
Is applied to the detection line SL via the resistor RZ. The rectifying / dividing circuit 16 rectifies the voltage across the resistor RZ with the diode D1 and the capacitor C1,
Partial pressure at 3, R4. Input ports A1 to A of the CPU 17
The divided voltage is input to 8. Therefore, when there is water leakage and the impedance of the detection line SL decreases, a high voltage is input to the input port, and when the detection line SL is disconnected, the impedance becomes extremely high, so that only a low voltage is input to the input port. . Based on this operation, when the voltage (input signal voltage) input to the input port is equal to or higher than the reference voltage Vr, it is determined that there is water leakage, and when the voltage is equal to or lower than the reference voltage Vd, it is determined that the wire is disconnected. The reference voltage values Vr and Vd are stored in the CPU 17. The input ports A1 to A8 are A / D conversion analog input ports having built-in A / D conversion circuits, and when an analog signal voltage is input, this can be converted into digital data.

[0006]

However, even if the impedance of the detection line SL is the same, the input signal voltage changes in proportion to the change in the applied voltage input from the power transformer 10. Therefore, the Zener diodes ZD1 and ZD
Although the voltage is made constant at 2, the voltage applied to the detection line SL is not exactly constant for each device because the characteristics of the Zener diode have individual variations. Therefore, the reference voltages Vr and Vd are different for each device. Therefore, the CPU 17
The reference voltage value to be stored in the memory has to be obtained by measurement for each device, which is troublesome at the time of installation.
Further, when the voltage fluctuates for some reason, the detection accuracy cannot be maintained at all.

An object of the present invention is to provide a liquid leakage detection device which can cope with voltage fluctuations by attaching a reference impedance for generating the reference voltage externally and saves the trouble of storage.

[0008]

SUMMARY OF THE INVENTION The present invention is a power supply circuit.
And a liquid leakage detection sensor whose impedance changes due to the presence of a non-insulating liquid, and the power supply for the liquid leakage detection sensor.
A first detection circuit that applies a voltage directly from the circuit to detect the voltage drop value , and the leak detection sensor detects a leak.
A reference impedance element is set to the impedance value when the said power supply to the reference impedance element
By comparing the detection value of the second detection circuit with the detection value of the second detection circuit that applies a voltage directly from the circuit and detects the voltage drop value , There is no disconnection between the judgment means for judging the presence or absence and the leak detection sensor.
The reference input set to the impedance value when
The impedance element and the reference impedance element
Directly apply voltage from the power supply circuit and detect the voltage drop value
And a detection value of the first detection circuit
By comparing the detection values of the third detection circuit,
Judgment means for judging presence / absence of disconnection of the liquid leakage detection sensor
And are provided.

[0009]

The liquid leakage detection device of the present invention is provided with a liquid leakage detection sensor and a first detection circuit for detecting the impedance of the liquid leakage detection sensor, and the liquid leakage state and disconnection of the sensor.
Two reference impedance elements set to the impedance of the state and second and third detection circuits for detecting the impedance of the reference impedance elements are provided. Voltages are supplied to the first, second and third detection circuits from the same power supply circuit. Therefore, when the power supply voltage changes, the voltages supplied to the first, second and third detection circuits also change, and the detection signal voltage also changes. When judging whether the impedance of the leak detection sensor is normal or not, it is possible to compare the impedance of the reference impedance element detected at that time with the impedance of the reference impedance element that is detected at the same time, rather than comparing with the preset reference value. It is possible to cancel the detection error and make an accurate determination. Also,
The trouble of storing the reference voltage value in the device can be saved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of a water leak detection device according to an embodiment of the present invention. In this device, the same parts as those of the circuit shown in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the eight rectification voltage dividing circuits 16 are connected to the analog switch 15. The analog switch 15 is connected to the input port and the output port of the CPU 17. The analog switch 15 selectively operates the eight rectifying / dividing circuits 16 according to an instruction from the CPU 17 as a CP.
Connect to U17. The rectification voltage dividing circuit 16 corresponds to the first detection circuit of the present invention. Further, two rectification voltage dividing circuits 31 and 41 are further connected to this input port. Standard impedances 30 and 40 are connected to the rectification voltage dividing circuits 31 and 41. Standard impedance 3
0 is set to be substantially equal to the impedance when the detection line SL is short-circuited due to water leakage, and the output of the rectification voltage dividing circuit 31 becomes the reference voltage Vr. Also, the standard impedance 40
Is almost equal to the impedance when the detection line SL is broken, and the output of the rectification voltage dividing circuit 41 is the reference voltage V.
It becomes d.

The relay drive circuit 18 is a circuit for turning on / off a relay for operating an external alarm device or the like when water leakage is detected or a wire break is detected. The display signal drive circuit 19 is a display unit (display unit) 2 in the monitoring room.
1 is a circuit that operates the relay unit 22.

FIG. 2 is a flow chart showing the general operation of the CPU 17. This operation is repeatedly executed at regular time intervals. First, the reference voltages Vr and Vd by the standard impedances 30 and 40 and the rectification voltage dividing circuits 31 and 41 are detected (n1, n2). Next, 1 is set to the pointer i (n3), and VAi is detected (n4). Where VA
i is the input terminal Ai of the analog switch 15 (i = 1
Up to 8). This VAi is compared with the reference voltages Vr, Vd (n5, n6). If VAi ≧ Vr, the impedance of the detection line SLi is too low.
That is, the water leak warning operation is executed assuming that there is water leak (n10). The water leak alarm operation is an operation of sounding an acoustic alarm such as a buzzer and displaying on the display that water leaks near the detection line. On the other hand, VAi ≦ Vd
If so, the impedance of the detection line SLi is too high. That is, the disconnection alarm operation is executed assuming that the disconnection has occurred (n11). The above operation is repeatedly executed within the range of i = 1 to 8 (n7, n8).

In the above operation, the reference voltages Vr and Vd were first applied only once, but the respective detection lines (SL1 to SL8)
It may be performed each time the impedance is detected.

[0014]

As described above, according to the liquid leakage detection device of the present invention, a reference value for determining liquid leakage or disconnection is obtained by an external reference impedance, and a voltage for detecting this impedance is used for liquid leakage detection. By making it common to the voltage for detecting the impedance of the sensor, the detection signal voltage and the detection voltage of the reference impedance fluctuate in parallel even if the voltage fluctuates, so that a constant detection accuracy can always be maintained. . Further, since it is not necessary to store the reference voltage value in the liquid leakage detection device, there is an advantage that labor for manufacturing and installing can be saved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a water leak detection device according to an embodiment of the present invention,

FIG. 2 is a flowchart showing the operation of the CPU of the water leakage detection device,

FIG. 3 is a circuit diagram of a conventional water leakage detection device.

[Explanation of symbols]

SL-detection line, 10-power transformer, 30,40-reference impedance, 16,31,41-rectification voltage dividing circuit.

Claims (1)

[Claims] 1. A power supply circuit, a leak detection sensor whose impedance changes due to the presence of a non-insulating liquid, and a voltage which is directly applied to the leak detection sensor from the power supply circuit to detect the voltage drop value . No. 1 detection circuit, a reference impedance element set to an impedance value when the leak detection sensor detects a leak, and a voltage is directly applied to the reference impedance element from the power supply circuit. A second detection circuit that detects the voltage drop value ; a determination unit that determines the presence or absence of liquid leakage by comparing the detection value of the first detection circuit with the detection value of the second detection circuit; Impedance value when the leak detection sensor is disconnected
A reference impedance element is set to direct electrodeposition from the power supply circuit to the reference impedance element
Third detection circuit for applying pressure to detect the voltage drop value
And the detection value of the first detection circuit and the detection value of the third detection circuit.
By comparing the output values, the leakage detection sensor can be disconnected.
A liquid leakage detection device comprising: a determination unit that determines the presence or absence of a line .