JP3461232B2 - Liquid 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 a leak of non-insulating liquid such as water or a mixed liquid of water and oil.

[0002]

2. Description of the Related Art Conventionally, there must be no leakage of liquid, particularly non-insulating liquid, such as in a computer room or article storage, and when there is leakage, it can be detected early to prevent malfunction of the device or damage to the article. In places where protection is required, various leak detection devices are used that consist of a detection line whose electrical characteristics change due to the adhesion of non-insulating liquid and a detection circuit that detects changes in the electrical characteristics of the detection line. , Or have been proposed. The present applicant has also made several proposals, including Japanese Utility Model Application Laid-Open No. 57-97265 (Japanese Utility Model Publication No. 64-5241) and Japanese Patent Application Laid-Open No. 4-301732, which have been implemented.

These are, for example, as shown in FIG. 6, a leak detection sensor 1 whose impedance changes due to the presence of a non-insulating liquid, and a detection circuit 30 which detects a leak due to a change in the impedance of the leak detection sensor. Be prepared. Then, when direct current is used, electrolytic corrosion or polarization occurs in the liquid leakage detection sensor, so normally the alternating current power supply 2 is used to detect the change in impedance between the electrode lines of the liquid leakage detection sensor 1 against the reference value. In FIG. 6, the leak sensor 1 includes at least one pair of electrode wires 1 arranged substantially in parallel.
a and 1b, which are connected in series with the reference resistor R _{S at the} starting end thereof. Also, a resistor R _E for impedance adjustment is connected to the normal termination.

The detection circuit 30 may be, for example, a real public shokoku 64-5.
The liquid leakage detection device of No. 241 includes a voltage conversion unit 31, a determination unit 32, and an alarm unit 33. The voltage of the AC power supply 2 is divided by the line impedance of the liquid leakage detection sensor 1 and the reference resistance R _S to obtain the reference resistance R _S and the AC power supply 2
If the voltage is constant, the change in the line impedance of the leak detection sensor 1 can be detected by monitoring the line AC voltage of the leak detection sensor 1. Therefore, the line-to-line AC voltage is converted into a DC voltage by the voltage converting means 31, and this voltage is compared with the reference voltage in the judging means 32. The determination means 32 is composed of, for example, an operational amplifier and a reference voltage circuit that supplies a reference voltage to the operational amplifier, and the DC voltage input from the voltage conversion means 31 is a predetermined lower limit reference value V.
When it drops below _L, it is judged as a leak. Further, there is a possibility that the liquid leakage cannot be detected when the sensor is disconnected for some reason. Therefore, the determination unit is the voltage conversion unit 3.
It also has a function of determining disconnection when the DC voltage input from 1 exceeds a predetermined upper limit reference value V _U. The adjustment resistance R _E is adjusted so that these upper and lower reference values are values that can be easily set by the determination means 32.

[0005]

However, the liquid leakage detection device malfunctions due to the voltage fluctuation of the AC power supply. That is, although the upper and lower reference values are given by the voltage values V _U and V _L and are fixed to a predetermined value, the voltage V between the electrode lines 1a and 1b is
_{Since B} varies with the variation of the power supply voltage, the variation causes an error. To eliminate such errors,
For example, the leak detecting device of Jitsukaihei 4-301732 is
Instead of fixedly setting the reference value with the voltage comparison circuit or storing it inside the CPU, an external resistor having upper and lower limit reference impedance values is used, and the voltage value generated at both ends of this external resistor is used as the reference value. Is stored in the CPU. In this way, the voltage generated across the external resistor becomes the reference voltage value, and this reference voltage value fluctuates in proportion to the power supply voltage together with the impedance between the electrode lines, so that malfunction due to fluctuations in the power supply voltage does not occur. However, there is a problem that an external resistor must be provided separately. Further, when there are a plurality of liquid leakage detection sensors, especially when monitoring different types of liquid leakage detection sensors, the reference value must be changed for each, so the number of external resistors increases and the circuit becomes complicated.

In addition to disconnection, it may be necessary to check the state of the leak detection sensor. For example,
This is because if the impedance of the sensor changes due to changes in the surrounding environment or natural deterioration of the electrodes and insulation of the sensor, the above reference value must be changed. In order to make it easier to absorb the liquid leakage, for example, when a liquid leakage detection sensor having a braided body made of a liquid absorbing thread on the outer periphery is used, the impedance is 20 kΩ in a normal state, and the lower limit reference value Z
_{When L is set} to 5 kΩ, if the floor is waxed, the impedance will be about 10 kΩ. Then, when the humidity is high, such as on a rainy day, even if there is no leakage, it will fall below the lower limit reference value Z _{L of} 5 kilo ohms, and it will be judged as leakage.

Therefore, in order to prevent such a malfunction, the user has to regularly check the impedance of the leak sensor. Such maintenance is usually performed using a hand-held type DC resistance measuring instrument, but an accurate check cannot be performed because the value is larger than the AC impedance due to the influence of polarization and the like. Further, in order to obtain an accurate value of impedance, an expensive measuring instrument such as an alternating current impedance measuring instrument must be prepared, and there is a problem that it takes time and effort for measurement. And in the place where many leak detection sensors are installed,
The labor of maintenance also increased in proportion to the number, giving a heavy burden to the user.

The present invention has been made to solve the above problems, and the invention of claim 1 is to detect malfunction such as external resistance due to fluctuation of power supply voltage in detection of liquid leakage, disconnection and the like. An object of the present invention is to provide a leak detection device that can be prevented without using any parts. In addition to the object of the invention of claim 1, the invention of claim 2 does not require an expensive measuring instrument or excessive labor for maintenance, and is capable of accurately grasping the impedance of the leak detection sensor. For the purpose of providing. And the invention of claim 3 is the above-mentioned claim 2.
In addition to the object of the present invention, in a liquid leakage detection device in which a large number of liquid leakage detection sensors are installed and monitored at the same time, it is possible to select a desired liquid leakage detection sensor and display its impedance. An object is to provide a liquid detection device. Further, in addition to the object of the invention of claim 3 described above, an object of the invention of claim 4 is to provide a liquid leakage detection device capable of displaying the impedance of the liquid leakage detection sensor at a desired time.

[0009]

In order to achieve the above-mentioned object, the invention of claim 1 uses a leak detecting sensor whose impedance changes due to the presence of a non-insulating liquid, and a change in the impedance of the leak detecting sensor. In a liquid leakage detection device comprising a detection circuit for detecting liquid leakage, wherein the liquid leakage detection sensor forms a series circuit connected in series with an AC power source together with a reference resistance, the detection circuit includes a leakage circuit of the series circuit. Two voltage conversion means for converting at least two AC voltages among three AC voltages generated between electrodes of the liquid detection sensor, both ends of the reference resistance of the series circuit and both ends of the series circuit, and the two voltage conversion means. A calculation means for calculating the impedance of the leak detection sensor from the DC voltage converted by the two voltage conversion means, and the calculation result of the calculation means is compared with a predetermined criterion. To leakage and is characterized by comprising a determination means for determining presence or absence of disconnection or the like.

Further, the invention according to claim 2 is the liquid leakage detection device according to claim 1, characterized in that the detection circuit has a display means for displaying the impedance calculated by the calculation means. It is a thing.

Here, the leak detection sensor means a sensor having at least a pair of electrodes, and the impedance between the electrodes changes due to the presence of a non-insulating liquid. The electrodes are described in the section of the prior art. It is not limited to such a linear shape. Further, the impedance of the leak detection sensor when the electrodes are linear is the impedance seen from the position of the starting end or the like connected in series with the reference resistance. When the impedance adjusting resistor R _E is connected to the terminal end, for example, it means the impedance as seen from the connection position such as the starting end of the liquid leakage detection sensor in that state. The voltage conversion means takes out a predetermined AC voltage from the series circuit, converts it into a DC voltage, and enables processing by the calculation means. The computing means is configured to include the two DC voltages input from the two voltage converting means and the value R of the reference resistance stored in advance.
_{From S} and _S , the impedance Z _S of the leak detection sensor is calculated using the equation described below.

Assuming that the DC voltages corresponding to the three AC voltages generated at both ends of the reference resistance, between the electrodes of the liquid leakage detection sensor and at both ends of the series circuit are V _A , V _B and V _C , respectively, R _S : Z _{Since S} = V _A : V _B , Z _S = R _S × (V _B / V _A ) (1) Since V _C = V _A + V _B , instead of V _A in equation (1) When V _C is used, Z _S = R _S × [V _B / (V _C −V _B )] (2) Further, when V _C is used instead of V _{B in} the equation (1), Z _S = R _S × [ _{(V C -V a) / V} a ] (3) or Z _S = R _S × [(V _C / V _a) -1] (3) 'or of the formula (1), (2), (3) The same result can theoretically be obtained by using either of the formulas [or (3) '].

In the conventional leak detection device of FIG. 6, when the power supply voltage fluctuates, the voltage between the electrode lines fluctuates, which causes malfunction. However, in the leak detection device of the present invention, the power supply voltage fluctuates. However, since the DC voltages V _A , V _B and V _C fluctuate in proportion, no malfunction occurs. For example, if the power supply voltage is V _C
To η × V _C , V _A and V _{B become} η × V _A and η × V _B , respectively, and as is apparent from the equation (1), Z _S = R _S × [(η × V _B ) / (Η × V _A )] = R _S ×
(V _B / V _A ) That is, since the value of Z _S does not change even if the power supply voltage changes, no malfunction occurs. Further, in the conventional device, there is no mechanism for measuring the impedance itself of the liquid leakage detection sensor, but in the liquid leakage detection sensor of the present invention, the impedance itself of the liquid leakage detection sensor can be measured by simply modifying the conventional device. Since it is possible to measure and display the impedance, the user can know the impedance directly from the leak detection device itself without using another measuring device.

According to a third aspect of the present invention, in the liquid leakage detection device according to the second aspect, a plurality of the series circuits of the liquid leakage sensor and the reference resistance are connected in parallel to the AC power supply, and the detection circuits are provided with the respective ones. It is characterized in that it has selection means for selecting a desired series circuit among the series circuits, and the display means displays the impedance of the liquid leakage detection sensor in the selected series circuit.

Therefore, the desired liquid leakage detecting sensor is selected from the plurality of series circuits by the sensor selecting means, and its impedance is measured and displayed.

According to a fourth aspect of the present invention, in the liquid leakage detection device according to the third aspect, the detection circuit includes a mode for sequentially detecting liquid leakage and disconnection of the plurality of liquid leakage detection sensors and a desired series circuit. It is characterized in that it has an output switching means for selecting one of the modes for measuring and displaying the impedance of the liquid leakage detection sensor.

Unlike the leak detection mode, the impedance display mode which does not need to be activated at all times can be selected by the output switching means only when necessary.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described based on illustrated examples. FIG. 1 is a diagram showing an embodiment of the present invention when there is one leak detection sensor. In FIG.
Reference numeral 1 denotes a liquid leakage detection sensor, in which the electrode wires 1a and 1b are arranged substantially parallel to each other, and is insulated by, for example, a liquid-permeable insulator and covered with a braided body made of a liquid-absorbent thread. 2 is AC power supply,
R _S is a reference resistor and R _E is a terminating resistor for impedance adjustment. Reference resistor R _S and the leakage AC to the series circuit of the sensor 1 power source 2 is connected, with the variation of the impedance of the leak detection sensor 1, the connection point between the reference resistor R _S and the leakage detection sensor 1 T Potential fluctuates. The detection circuit 3 includes a first voltage conversion unit A, a second voltage conversion unit B, a calculation unit 4, a determination unit 5, an alarm unit 6 and a display unit 7. The AC voltage between the electrode lines (between T and G) of the liquid leakage detection sensor 1 is input to the second voltage conversion means B, and the DC voltage V _B corresponding thereto is output. Further, the first voltage converting means A is supplied with the potential difference across the reference resistor R _S (between P and T) and outputs a DC voltage V _A corresponding thereto.

The computation unit 4, the output voltage V _A and from a reference resistor R _S to the output voltage stored in advance and V _B of the second voltage converting means B of the formula (1) of the first voltage converting means A The impedance Z _S is calculated by The AC voltage V _A ′ across the reference resistor R _S of the series circuit (between P and T).
Alternatively, instead of the AC voltage V _B ′ between the electrode lines of the liquid leakage detection sensor 1 (between T and G), the AC voltage V _C ′ between both ends (between P and G) of the series circuit is taken out and used as a DC voltage V _C. The impedance Z _S may be calculated from the converted value using the equation (2) or the equation (3) [or (3) ′]. The determination means 5 stores a lower limit reference value Z _L that determines liquid leakage when the impedance Z _S value is lower than that and an upper limit reference value Z _U that determines disconnection when the impedance Z _S exceeds the value, and is input from the calculation means 4. The value of the impedance Z _S that is applied is compared with these criteria. When the impedance Z _S is less than the lower limit reference value Z _L , a leak signal is output, and when the impedance Z _S exceeds the upper limit reference value Z _U , a disconnection signal is output. The alarm unit 6 displays an alarm that requires liquid leakage or disconnection according to the type of signal input from the determination unit 5.

The display means 7 displays the value of the impedance Z _S output from the calculation means 4 by an appropriate means. Therefore, the user does not need to use a measuring device that is separate from the leak detecting device, and the impedance of the leak detecting sensor 1 is normal or abnormal simply by looking at the display means 7 of the leak detecting device. You can know

FIG. 2 shows a first voltage converting means A and a second voltage converting means A.
It is a figure which shows one specific example of the voltage conversion means B of FIG. In FIG. 2, the first voltage converting means A comprises a buffer A1, a subtracting means A2 and an AC / DC converting means A3, and the second voltage converting means is a buffer B1, a non-inverting amplifier circuit B2,
It is composed of AC / DC converting means B3. The power supply potential V _P is input to the inverting input terminal of the operational amplifier OP1 of the subtracting means A2, and the potential V _T of the connection point T between the reference resistance R _S and the leak detection sensor 1 is input to the non-inverting input terminal, The difference is AC /
It is output to the DC converting means A3. Further, the potential V _T of the connection point T is input to the inverting input terminal of the operational amplifier OP2 of the non-inverting amplifier circuit B2, the ground potential is input to the non-inverting input terminal, and the difference between them is the AC / DC converting means B3. Is output to. The AC / DC converting means A3 and the AC / DC converting means B3 are each composed of two operational amplifiers OP3, OP4 or OP5, OP6, two rectifying elements D1, D2 or D3, D4, and a capacitor C1 or C2. It forms a wave rectifying / smoothing circuit and outputs a DC voltage V _A or V _B.

As the calculating means 4 and the determining means 5, for example, a CPU is used as in the second embodiment described later, but a wired logic circuit may be used. As the alarm means, a means such as blinking of an LED or the like, a bell, a voice notification or the like is used, and as the display means, a digital display such as an LED or a liquid crystal or an analog display such as an instrument panel or a recorder is used.

FIG. 3 is an explanatory view of another embodiment of the present invention. In FIG. 3, the difference from the embodiment of FIG. 1 is that there are a plurality of liquid leakage detection sensors, and a mechanism for selecting a desired liquid leakage detection sensor by using the switching circuit 8, the CPU 11, and the sensor selection switch 9 is added. That is the point. That is, the connection terminals S1, S2 ... Sn to which the leak detection sensor is connected and the reference resistors R _S1 , R _S2 ... R _Sn.
The connection parts P1, P2 ... Pn are connected to the switching circuit 8
Connected to the input terminals T1, T2 ... Tn of the sensor, and sequentially or arbitrarily selecting the leak detection sensor to be detected by a command from the sensor selection switch 9 and / or the CPU 11, and the selected x-th leak detection sensor. Is connected to the output terminal Q of the switching circuit 8 connected to the input terminal Tx.

The first voltage converting means A and the second voltage converting means B are the same as those in the embodiment shown in FIG.
Is embodied as The calculation means 4 and the determination means 5 are composed of the CPU 11. So C
The operation of the PU 11 will be described with reference to the flowchart shown in FIG. Now, it is assumed that n leak detecting sensors are connected to this leak detecting device. First, the switching circuit 8 is instructed to select the input terminal T1 to be connected to the output terminal Q (N0 to N1). One of the potentials of the input terminal T1 is input to the first voltage conversion means A via the output terminal Q, and the AC voltage between both ends (P0-P1) of the reference resistor R _S1 is supplied to the first voltage conversion means A. CP as DC voltage V _A via
It is input to U11 and the other is the first leak detection sensor S.
The first line-to-line (between P1 and G) AC voltage is input to the second voltage converting means B and converted into a DC voltage V _B to be converted into a CPU.
11 is input. DC voltage V input to CPU 11
_A and V _B are digitized by an A / D converter (not shown), respectively, and the impedance Z _S is calculated by the calculation unit according to the calculation formula (1) stored in the storage unit in the CPU 11 (N2). The calculated impedance Z _S is compared with the lower limit reference value Z _L and the upper limit reference value Z _{U of} the impedance stored in the storage unit, and Z _S <Z _L
If so, it is judged as a leak, and if Z _S > Z _U, it is judged as a wire break (N
3). When it is determined that the liquid is leaking or the wire is broken, the alarm means is instructed to issue the necessary alarms (N4, N
5).

After the above judgment is completed, it is checked whether or not the sensor selection switch 9 selects the input terminal T1 (N6). When selected, the display means 4 is instructed to display the calculated Z _S (N7). After that, the same processing is sequentially performed on the input terminals T2 and thereafter, and after the processing up to the input terminal Tn, the processing returns to the terminal T1 (N8 to N1).
0). Here, step N2 corresponds to the calculating means 4, and step N3 corresponds to the determining means 5. And step N
1, step N6, the switching circuit 8 and the sensor selection switch 9 (see FIG. 3) constitute the sensor selection means. Since it is not necessary to display the impedance for all of the plurality of leak detection sensors at the same time, by providing the sensor selection means as described above, the impedance can be displayed and checked only for the sensors that need to be checked in a timely manner. .

As still another embodiment, the operation of a device provided with an output switching means for arbitrarily switching between detection of liquid leakage, disconnection, etc. and display of impedance is shown in FIG.
This will be described with reference to the flowchart of. In FIG. 5, first, it is checked whether the output changeover switch 10 (see FIG. 3) is selected between the leak detection mode and the impedance display mode (S0 to S1). If the detection result output is selected, the input terminal T is the same as in the case of FIG.
Starting from 1, step S corresponding to steps N1 to N5
2 to S6 are executed, and then step N8 in the case of FIG.
Steps S7 to S9 corresponding to N10 are executed. Then, when the scanning up to the input terminal Tn is completed, it is checked again whether the output changeover switch 10 selects the leak detection mode or the impedance display mode (S1). If the impedance display is selected, the input terminal selected by the sensor selection switch 9 at that time is connected to the output terminal Q (S10), and the impedance is calculated (S11) and displayed (12). , And returns to step S1.

The output changeover switch 10 and step S1 correspond to the output changeover means of the present invention. By providing such an output switching means, it is possible to select the impedance display mode with the output switching switch 10 only when the impedance needs to be checked and to select the leak detection sensor to be checked with the sensor selection switch 9. Of course, unlike the case of FIG. 4, it is not necessary to check the necessity of displaying the impedance each time the scanning of the detection result is completed, and it is sufficient to display the impedance only when the output changeover switch 10 requests the display of the impedance. Useless confirmation steps can be omitted, and abnormality detection of a plurality of sensors and impedance display can be efficiently performed.

[0028]

As described above, the leak detecting device according to the first aspect of the present invention can measure the impedance itself of the leak detecting sensor by simply modifying the conventional device. Since this is possible, it is possible to easily prevent malfunctions due to fluctuations in the power supply voltage in the detection of liquid leakage, disconnection, etc. without using parts such as external resistors. In addition to the effect of the invention of claim 1, the leak detecting device of the invention of claim 2 can display the impedance itself of the leak detection sensor, so that the user can use another expensive It is possible to efficiently and accurately know the accurate impedance directly from the liquid leakage detection device without using a measuring instrument or excessive labor, and if the impedance changes, the reference value can be easily changed accordingly. .

According to the invention of claim 3, in addition to the effect of the invention of claim 2, even if there are a plurality of leak detecting sensors, only the leak detecting sensor of a desired series circuit is selected by the sensor selecting means from among them. Then, the impedance can be measured and displayed, which is efficient.

Further, according to the invention of claim 4, in addition to the effect of claim 3, the impedance display mode which does not need to be constantly operated is different from the detection mode of liquid leakage or the like only when it is necessary by the output switching means. It is more efficient because it can be arbitrarily selected.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a specific example of voltage conversion means of the present invention.

FIG. 3 is an explanatory diagram of another embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of the leak detection device of the present invention.

FIG. 5 is a flowchart showing another operation of the leak detection device of the present invention.

FIG. 6 is an explanatory diagram of a conventional leak detection device.

[Explanation of symbols]

1 Leak detection sensor 2 AC power supply 3 detection circuit 4 computing means 5 Judgment means 6 warning means 7 Display means 8 switching circuits 9 Sensor selection switch 10 Output selector switch 11 CPU A first voltage conversion means B Second voltage conversion means

Claims (4)

(57) [Claims] 1. A liquid leakage detection sensor whose impedance changes due to the presence of a non-insulating liquid, and a detection circuit which detects liquid leakage due to a change in the impedance of the liquid leakage detection sensor. In a liquid leakage detection device that is connected in series with an AC power source together with a reference resistance to form a series circuit, the detection circuit includes electrodes of a liquid leakage detection sensor of the series circuit, both ends of the reference resistance of the series circuit and the series. A plurality of voltage conversion means for converting at least two AC voltages among the three AC voltages generated at both ends of the circuit into a DC voltage, and the impedance of the leak detection sensor from the DC voltages converted by the plurality of voltage conversion means. And a judging means for judging the presence or absence of liquid leakage, disconnection, etc. by comparing the calculation result of the calculating means with a predetermined judgment standard. A leak detection device. 2. The liquid leakage detection device according to claim 1,
The liquid leakage detection device, wherein the detection circuit includes a display unit that displays the impedance calculated by the calculation unit. 3. The liquid leakage detection device according to claim 2,
A plurality of the series circuits of the leak sensor and the reference resistance are connected in parallel to the AC power source, the detection circuit has a selection means for selecting a desired series circuit among the series circuits, the display means A leak detecting device for displaying the impedance of a leak sensor in a selected series circuit. 4. The liquid leakage detection device according to claim 3,
The detection circuit, one of a mode for sequentially detecting the leakage of the liquid leakage detection sensor of the plurality of series circuits, disconnection, etc., and a mode for measuring and displaying the impedance of the desired leakage detection sensor of the series circuit. A leak detection device having an output switching unit for selection.