JPS62185124A - Liquid surface detection circuit with inhibited surface contamination - Google Patents

Abstract

PURPOSE:To extend the life of a detection sensor, by detecting a liquid surface condition intermittently based on a high frequency signal to reduce the amount to be electrically decomposed and the required time. CONSTITUTION:A pair of liquid surface detecting sensor 5A and 5B are provided within the same horizontal plane on the upper side of a color forming development tank 110 and always kept immersed into a liquid. Resistors R1 and R2 each having a specified resistance value are connected between the sensors 5A and 5B and the ground and then, to a power source +V through respective switches S1 and S2. A switching signal with a specified frequency obtained from oscillators OSC and a switching signal in inverted phase I are supplied to the switch S1 and S2 respectively and an output from the sensor 5B is compared 8 with a reference voltage VREF. With such an arrangement, the lowering of the liquid surface is detected from a difference in outputs compared between the case where the liquid surface is below the sensors 5A and 5B and that where the sensors in contact with the liquid surface. This can reduce the amount of current flowing through a solution and lessens the amount of metal to be precipitated by electric decomposition thereby checking contamination of the surfaces of the sensors 5A and 5B.

Description

Detailed Description of the Invention [Industrial Application Definition] The present invention can be applied to an automatic developing device of a color image recording device that obtains a color hard copy from a color static image recorder. This invention relates to a liquid level detection circuit that suppresses surface contamination.

[Conventional technology 1 From television receivers, VTRs, video discs, etc. 11)
Various image recording apparatuses have been proposed for converting color static IL images into hard copies.

FIG. 12 is a schematic diagram showing an example of the structure, with the interior omitted, in which 10 is a printer section of an image recording apparatus, 100 is an automatic developing device, and 200 is a drying chamber for photosensitive paper on which images have been recorded. Further, 300 is a video color image display section, and the screen displays 9! A type that can still display color images is used. 400 is a signal type that can record this still image on photographic paper! Faith to convert to 6-
) is the processing section. Control what kind of still images you want to record! Keys can be selected manually from 500%.

The printer section 10 has a built-in exposure processing section for exposing still color images onto predetermined photographic paper, and the exposed photographic paper is conveyed to an automatic developing device lOO where it undergoes normally required processing such as development and fixing. The photographic paper is then transported to a drying chamber 200 in a drying state.

By the way, in such an image recording apparatus for obtaining a hard copy, as described above, in order to chemically process the photographic paper conveyed therein in the automatic developing apparatus 100,
A plurality of processing tanks are provided.

In this example, as shown in FIG. 12, four tanks are arranged in sequence in the conveying direction of photographic paper.

Reference numeral 110 denotes a color developing tank, and the developed photographic paper is then subjected to a fixing process in a bleach-fixing tank 120, and is then conveyed to first and second stabilizing tanks 130 where it is washed with water or subjected to a stabilizing process. . Therefore, these outer tanks are filled with a processing liquid necessary to carry out a predetermined chemical reaction process.

FIG. 13 shows an example of a color developing tank 110, in which a predetermined amount of developer is stored.

The color developing tank 130 is provided with a circulation pump P to agitate the developer, and a pipe 4A attached to the suction 11 side of the pump P is fitted in a liquid-tight manner to the side bottom side of the color developing tank 130. Pipe 4B attached to the outlet side
By driving a circulation pump P, which is similarly fitted liquid-tightly to the top side of the side, the liquid in the upper and lower parts of the tank is circulated. When the concentration of the liquid in the tank is made uniform by this, the temperature of the liquid in the tank, which will be described later, is also made uniform.

Now, in order to make the above-mentioned processing liquid the most likely to cause a chemical reaction on the photographic paper, we used 4PillO to 140Pill each.
It is necessary to maintain each of them at a predetermined temperature (−・constant i4).

For example, the liquid temperature of the color developing tank 110 is 39.8±0.5°C.
The bleach-fix tank 120 is maintained at 34.0 ± 4°C, and the first and second stabilizing tanks 130 and 140 are each maintained at 20°C.
Must be kept at ~35°C.

Therefore, each of these outer tanks 110 to 140 is individually provided with a temperature control device having the same configuration and configuration for adjusting the liquid temperature.

A temperature sensor 160 and a heater 170 for detecting the temperature of the liquid in the tank are installed in a liquid-tight manner inside the color developing tank 110, and a temperature control circuit (not shown) is provided outside the tank. There is.

The temperature control circuit is operated in accordance with the liquid temperature detected by the temperature sensor 160, and the supply of electricity to the heater 170 is controlled, so that the liquid temperature is always maintained at a predetermined temperature.

A pair of liquid level detection sensors 5A and 5B are provided within the same water surface on the side surface of the L portion of the color developing tank 110. This sensor is placed at a predetermined water level and is necessary for replenishing the developer that has been reduced by the development process and replenishing the wood. Therefore, it is always immersed in liquid.

A detection circuit for detecting the liquid level is separately submerged in each outer tank, and a conventional example of this detection circuit 155 is shown in FIGS. 14 and 15.

In FIG. The other detection sensor 5
B is grounded.

- When the pair of detection sensors 5A and 5B are located inside the liquid level, the detection sensors 5A and 5B are
This is equivalent to connecting both ends of 5B. Therefore, in this case, the voltage divided by R and r becomes the detection voltage.

On the other hand, when the liquid level is lower than the detection sensors 5A and 5B, there is an electrically open state between the detection sensors 5A and 5B, so in this case, the power supply voltage +■ becomes the detection voltage. .

Therefore, depending on the magnitude of this detection voltage level, it is detected that the liquid level has dropped to the minimum water position.

Figure 15 shows switch 7 between DC power supply +V and resistor R.
The configuration is the same as in Fig. 14, except that
In this case as well, a drop in the liquid level can be detected based on the same reason as described in L. For example, the switch 7 is always turned on when the water level is below the level at which liquid level detection is required.

[Problems to be Solved by the Invention] By the way, in the liquid level detection circuit 155 shown in FIG. 14, a predetermined DC current is always applied via its resistance value r unless the developer drops below the minimum water level. Flowing. On the other hand, since the chemicals such as the developer mentioned above are solutions containing electrolytes, when the developer is in the state 1E;, the electrolyte in the developer is electrolyzed, and the metal ions are detected. It will adhere and precipitate around the sensors 5A and 5B. Therefore, when automatic development processing is performed for a long time, the peripheral surfaces of the detection sensors 5A and 5B become dirty, and in the worst case, there is a problem that the liquid level cannot be reliably detected due to deposited metal.

On the other hand, in the case of FIG. 15, there is a switch 7 that is turned on when necessary, so the number of 7 points (4, etc.) decreases compared to the case of FIG. 14. However, switch 7 is turned on! L
Since the specified DC current continues to flow when the current is at
It potentially has the same drawbacks as shown in the figure.

Therefore, the present invention solves these conventional problems by significantly reducing the electrolytic temperature and time, thereby extending the life of the detection sensor and suppressing surface contamination. In this paper, we propose a liquid level detection circuit.

[Technical steps to solve the problem] In order to solve the problem mentioned above, this invention.

First and second liquid level detection sensors are attached to a portion of a reservoir for a solution containing an electrolyte, and first and second switches are provided in each detection sensor and a current path flowing through the detection sensor. The first and second detection sensors are connected to each other, and the switching is controlled in a complementary manner based on a predetermined high frequency signal, and the presence or absence of the liquid level is detected by the detection voltage output from one of the detection sensors. It is.

[Embodiment] Hereinafter, a case will be described in which the liquid level detection circuit that suppresses surface contamination according to the present invention is applied to the automatic developing device of the above-mentioned image recording apparatus.

Prior to explanation 11 of this 51IJJ, a specific example of the image recording apparatus described in 1-1 will be explained with reference to No. 10124.

In FIG. 10, a photographic paper discharge hole 201 is provided at the right end of the drying chamber 200 on the I-blood side, from which the photographic paper on which an image has been recorded is discharged.

On one side of the drying chamber 200, tanks 610 to 630 are provided to separately store replenisher solutions for replenishing a plurality of different types of chemicals necessary for developing photographic paper. The chemicals stored in the six tanks 610 to 630 are as described above, and between each tank 610 to 630 there is a replenishment water tank 640.
- 660 are provided... A sectional view taken along line BB in FIG. 10 is shown in FIG. 11.

In the figure, color photographic paper (sheet-shaped, for example, color photosensitive material photographic paper containing silver halide as one component) stored in a supply magazine 11 (hereinafter referred to as photographic paper)
12 is exposed by exposure stage 1.

Exposure stage l has color image value -''i (still image %'J)
is supplied, and the photographic paper is then exposed to these color image values.For example, a known 7-eye tube type CRT (FOT) can be used for exposure. This FOT is composed of a predetermined number of fibers, and is scanned by a predetermined number -1 in the direction of the tree f in accordance with the color image value -).

The exposed photographic paper 12 is conveyed to the large 171e of the automatic developing device 100 via a U-turn guide RO1 and an S-shaped kite RO2 that constitute a conveyance path RO.

The conveyed photographic paper 12 has a development layer 110, a bleaching layer 1
1 layer 120. First to third stable bathtubs (rinsing layer) 130
-150 (a third stabilizing bath 150 is provided as necessary), and is sent to the drying room 200, and then transported out II 20
The photographic paper 12 discharged from holder 202-1. It will be posted on.

During a series of operations, that is, when the apparatus is normal and recording is being performed, the photographic paper [2] is automatically conveyed from the supply magazine 11 to the conveyance exit 201.

Note that the upper part of the drying chamber 200 is equipped with a
Although it may have a partially transparent structure, the photographic paper 12 is shielded from light other than the necessary light, especially from external light, from the supply magazine 11 until the stabilization process is completed in the stabilization tanks 130-150. It is configured. External light is blocked by the outer case 2, 101.

Therefore, the operator first sets the photographic paper 12, and then operates the switch provided on the operation section 500 to display the video signal as a still IF image on the attached display section 300 to obtain the desired still image. Image 1 is selected. Thereafter, by simply turning on the appropriate switch, the series of operations described in 1.
ni/＼-Tocoby will be done.

Note that after the start of the light operation, an image for selecting the next color still image may be displayed on the display section 300.

The printer section 10 is configured as follows.

Reference numeral 20 denotes a pedestal (rail), on which a removable supply magazine 11 is placed. This supply magazine 11 has an opening 11 portion 21 closed 4
22, and inside thereof is a push plate 2 which applies pressure to the loaded photographic paper 12 under the elastic force of a spring 23.
4 are provided. The photographic paper 12 is loaded with its photosensitive surface facing the opening 21 side. 25 is photographic paper 12
This is a raw mackerel board to prevent more than one mackerel from coming out when taking it out. The second roller is a presser roller that presses the photographic paper 12, and this bends the photographic paper 12 at this portion, improving the sharpness and reducing the stroke of the suction cup, which will be described later.

Reference numeral 30 denotes a take-out device for taking out the photographic paper 12, and the frame plate 3
1 has a suction cup mounting body 32 attached thereto. Two suction cups 34 are attached to the suction cup mounting body 32 so that a spring 33 provides elastic force in the L direction. Further, the inside of the suction cup mounting body 32 communicates with a reverse 1-hi valve 36 via a hose 35. 36a is a protrusion that opens the reverse 11 valve 36 when pressed.

The suction cup mounting body 32 is connected to the f1 side 41 of the slide plate 40 via two arms 38 and 39 on both sides thereof. A roller 42 is sunk in the slide plate 40, and is engaged with a guide elongated hole 31b formed on the side of the frame plate 31.

Note that a protrusion 31d with which five protrusions 36a of the reverse IF valve 36 are in contact is provided on the 11-L side 31c at the tip of the frame plate 31.

The paper feed motor 50 has a built-in speed reduction mechanism and is fixed to the frame plate 31 via a mount 51. A disk 54 is fixed to its output shaft 52, and an arm 55 is pivotally supported on the outer periphery of the disk 54. The arm 55 is a pin 57 implanted in the slide plate 40.
is supported by.

In this take-out device 30, the slide plate 40 connected by the arm 55 reciprocates once in the direction of the arrow CJj every time the paper feed motor 50 rotates and the disk 54 rotates once. During this reciprocating movement, the suction cup mount 32 receives the movement of the slide &40 via the arms 38 and 39, so the suction cup mount 32 reciprocates once in the direction of arrow F, that is, in an L-shape in the front-rear direction. Then, when the suction cup 34 returns to the frontmost position,
- The protrusion 36a of the valve 36 is attached to the protrusion 31d '17. The inside is popular and i! l! It goes through. Paper feed motor 50 at this time
The rotation position is the home position.

Therefore, in the take-out device 30, when the suction cup 34 is at the most l-position, the suction cup 34
The suction cup 3 contacts the photographic paper 12 from the 1 side, and this contact causes the suction cup 3 to
4, the photographic paper 12 is deformed by pushing it 1-1, and the photographic paper 12 is subjected to negative Il: suction 1.

Then, when the suction cup 34 moves in the C direction, the photographic paper 12
are sorted by the sabaki board 25, and only one sheet is taken out. When the suction cup 34 descends to the top, it moves forward and reverses 1.
Since the protrusion 36a of the 1-valve 36 comes into contact with the protrusion 31d, air flows from the outside into the reverse 1-valve 36, causing suction? ! The negative pressure adsorption at 134 is released. As a result, the photographic paper 12 is released from the suction cup 34! 4 # is done.

In this way, one sheet of photographic paper 12 is fed each time the suction cup 34 moves back and forth.

The paper feed roller 60 is used to further feed the photographic paper 12 that has been sucked and taken out by the take-out device. A paper feed sensor 61 is provided on the output 1'' side of the paper feed roller 60 to detect whether or not the photographic paper 12 has bitten into the paper feed roller 60. 63 is treated as a kite for transporting the photographic paper 12.

Exposure NIS on the side of kite handling 63? l is provided. Photographic paper 1 is placed at a position opposite to the front surface 65 of the 1st exposure stage l.
A push plate 67 is attached to the push plate 67 to allow the press plate 65 to be transported in a pressurized container.
The force of one shot is 'j-'.

The conveying roller 70 is for precisely conveying the photographic paper 12 fed to the front side 65 in the direction of
A paper discharge sensor 71 is provided on the 0 side to detect the presence or absence of paper discharge.

The photographic paper 12 that has been detected by the paper ejection sensor 71 passes through the guides RO1 and RO2 of the conveyance path RO by the rotating cola pairs 72a to 72d, and then passes through the guides RO1 and RO2 of the automatic developing device 100.
transported to e. It is desirable that the distance between the roller pairs be smaller than the length of the photographic paper 12.

The photographic paper 12 sent from the printer section IO is input 1-
The one-dot button line in Figure 0 indicates the conveyance path of the photographic paper 12 that is transported from J e into the developing tank 110.At the top of the developing tank 110, there are a photographic paper receiving roller 112 and a feeding/squeezing roller 113. A plurality of guide rollers Ill are rotationally driven within the developer tank 110. As a result, the photographic paper 12 is immersed in the developer solution contained in the tank, developed during movement for a certain period of time, and then transported to the next bleach-fix tank 120.

The bleach-fixing tank 120 includes a roller 121 for receiving and sending out photographic paper, and a guide roller 122, and the photographic paper 12 that has been developed is transported to the constant I, ' in this bleach-fixing tank 120.
It is transported while being fixed by liquid F.

The stabilized photographic paper 12 is then guided to the first to third stabilizing tanks 130-150. These stabilizing tanks contain water W or a stabilizing solution S, and by passing the photographic paper 12 through each tank, the bleaching solution F is washed away and a stabilized image is obtained. .

The photographic paper 12 that has undergone the stabilization process is squeezed and sent out by the final roller 151 to be sent to the next drying chamber 200. Inside the room, there is a group of conveying rollers that clamp and convey the photographic paper 12 that has been stabilized. After the stabilization process, the wet photographic paper 12 is transported and passed through the drying chamber 200, where it is dried by a stream of warm air. Therefore, in the drying chamber 200, there is a heater section H and a blower fan 21.
2 is provided.

The photographic paper 12 that has been conveyed through the drying chamber 200 through 'A11 is discharged to the outside from the conveyance output t1201, and is placed on the receiving stand 2021.
- to terminate the process.

Now, FIG. 1 is a connection diagram of the real part showing an example of the liquid level detection circuit according to the present invention, and there is a predetermined resistance value R between the first detection sensor 5A and the ground. A resistor R1 is connected, and this first sensing station 5A is connected to the power supply +V via a switch Sl at tSl.

Similarly, a resistor R2 having the same resistance (/i R) as described above is connected between the second detection sensor 5B and the ground, and this second detection sensor 5B is connected to the second switch S2.
Connected to power supply +■ via.

The first switch S1 is supplied with a high frequency signal (hereinafter referred to as a switching signal) of a predetermined frequency (for example, 10 KHz) from an oscillator O3C. A high frequency signal is used.

On the other hand, the second switch S2 is supplied with this switching signal whose phase is inverted at the input terminal. The output voltage obtained from the second detection sensor 5B is supplied to the voltage comparator 8 and compared with its reference voltage VREF.

The reference voltage V REF is calculated as follows, assuming that the resistance t1 of the developer is r.

0<V REF≦r/(r+R) (1).

The operation of the liquid level detection circuit configured in this way will be explained with reference to FIGS. 2 and 3.

Figure 2 shows the operation when the liquid level is equal to or higher than the detection sensors 5A and 5B, and the first and second switches 31 and 32 are complementary switching controlled as shown in Figures A and B. Therefore, the electric capacitors at points a and b: Va and vb are C in the same figure.
, D. This is because the liquid surface is not in contact with the detection sensor, so its +j4 end is in an open state.

Therefore, the comparison output has the same waveform as that shown in the second diagram.

On the other hand, when the first and second detection sensors are in contact with the liquid surface, when the first switch 31 is turned on, the people detection sensor 5A,
A predetermined current is shunted to resistors R1 and R2 connected to 5B. As a result, the output 'Hvb' becomes r/(r+R), and a voltage waveform as shown in the third diagram is obtained.

On the other hand, since the quasi-voltage of comparator 8 is selected as shown in equation (1), the comparison output in this case is always "H".
It can be obtained at the level of

Therefore, a low level of the liquid level can be detected from the difference in these comparison outputs.

4 is a modification of FIG. 1, 514 is a waveform diagram illustrating the operation when the liquid level is not in contact, and FIG. 6 is a diagram illustrating the operation when the liquid level is in contact.

In this example, the first and second detection sensors 5A.

This is the case when 5B is sunk to the ground side. 1st and 2nd
The detection sensors 5A and 5B are not in contact with the liquid surface.
In the contact state, the detection voltage vb becomes a voltage 1') in the opposite phase to the switching signal t) supplied to the second switch S2 as shown in FIG. A staircase waveform output that is repeated at the switching period is obtained. Therefore, as the reference voltage VREF supplied to the voltage comparator 8, (r/r+R) V<VREF
By setting <V (2), the comparison output (DC) at a predetermined level is ignored in the contact state, so that the liquid level detection becomes 11f due to the difference in the comparison output.

Also in this embodiment, a high frequency signal of about 10 KH/ is used as the switching signal.

]The frequency at switching 0 shown in 2 is just an example.
If it is a high frequency signal within the range of about 1 to 100KH/,
Either can be used.

Incidentally, the embodiments shown in FIGS. 1 and 4 are both cases where switching signals SL and S2 with a duty ratio of 50% are used.

The example shown in FIG. 7 is 1-
In this case, the energization period is shorter than in the case described above.

8 and 9 are explanatory diagrams of the circuit operation, with FIG. 8 showing waveforms of various parts when the liquid surface is not in contact, and FIG. 9 showing waveforms at various parts when the liquid surface is in contact.

In FIG. 7, first and second detection sensors 5A, 5
The connection relationship between B and the first and second switches S1 and S2 is the same as that shown in FIG. 4, so a description thereof will be omitted. In this example, a frequency of about 1 Hz is used. 0 oscillator O that operates the first and second detection sensors 5A and 5B once every second in the case of IH, and once every 2 seconds in the case of 0.5H1.
The oscillation frequency of the SC can be changed depending on the comfort.

This output pulse is supplied to a first mono-multivibrator (hereinafter referred to as "mono-multi") MMI to form a first mono-multi vibrator (hereinafter referred to as mono-multi) output Sa having a predetermined width as shown in FIG. 8B. This first monomulti output Sa is supplied as a first switching signal to the first switch Sl.

The first mono-multi output Sa is further configured in circuit with the first mono-multi MMI and is supplied to a second mono-multi MM2 which operates at tL of the pulse, and is supplied to the second mono-multi MM2 shown in FIG. 8C. A monomulti output sb is formed. This second monomulti output sb is supplied as a switching signal t) to the second switch S2. The pulse widths of both the first and second monomulti outputs Sa and Sb are preferably 1 m5ec or more.

The first monomulti output Sa is also supplied as a latch pulse to a latch circuit that latches the detection voltage vb.

Now, in the case of this configuration, since the on and off timings of the first and second switches SL and S2 are different, it is possible to maintain a state in which the liquid level is not in contact with the first and second detection sensors 5A and 5B. ! In the system, "II" flows through the developer solution.
i, Detection of one point a, b because no flow path is formed 'l+
! , JI: V a and V b are both the 8th diagram, E
becomes.

On the other hand, the first and second detection sensors 5A and 5B
When is in contact with the liquid surface, the following happens.

That is, when the first switch SL is on, the current flows in the direction of the arrow X in FIG. 7, and when the second switch S2 is on, the current flows in the direction of the arrow X, so that the detected voltage Va, Vb is E in the ninth diagram. Therefore, ノ, (
The quasi voltage V REF is set as shown in equation (1), and the latch timing of the latch circuit is controlled by the switching signal.
,>Sa, a latch output of "H" will be obtained when the liquid surface is not in contact, and a latch output of "L" will be obtained when the liquid surface is in contact. Liquid level detection becomes ++ (1) at bolt separation.

According to this configuration, since the liquid level is detected by the short pulse width switching signals -3a and Sb that operate according to the oscillation period of the oscillation zosc, the energization period is significantly shortened.

Metal deposition by electrolysis can be further reduced by +7) and power consumption can be further reduced than in the cases of FIGS. 1 and 4.

In the above, an example was shown in which the present invention was applied to a liquid level detection circuit used in an automatic developing device of an image recording device.
The technical field to which this invention is applied is not limited to the example described above, but in an IB tank for storing a solution containing an electrolyte,
It goes without saying that this method can also be applied when it is necessary to detect the liquid level state.

[Effects of the Invention] As explained above, according to the present invention, since the liquid level 7JTi is detected intermittently based on the high-frequency signal, it is possible to detect meteorites flowing in the solution more easily than before. As a result, the metal clay deposited by electrolysis can be significantly reduced.

Contamination on the surfaces of the pair of detection sensors 5A and 5B can be effectively suppressed. From this, the liquid level detection is
You can avoid the worst situation, such as getting stuck in a needle.

Therefore, according to the invention, the detection sensor 5A.

5B length) It is possible to achieve improved lifespan and reduced power consumption.

[Brief explanation of drawings]

FIG. 1 is a connection diagram showing an example of the liquid level detection circuit according to the present invention, FIGS. 2 and 3 are waveform diagrams for explaining the operation thereof, and FIG. 4 is a connection diagram showing an example of the liquid level detection circuit according to the present invention. FIG. 5 and FIG. 6 are waveform diagrams for explaining the operation thereof. FIG. 7 is a connection diagram showing still another example of the liquid level detection circuit according to the present invention, and FIGS. Fig. 9 is a waveform diagram for explaining its operation, Fig. 10 is a partial perspective view of an image recording device to which this system can be applied, Fig. 11 is a sectional view taken along line B-B, and Fig. 12 is an image recording device. FIG. 13 is a perspective view of a storage tank used in this image recording device; FIG. 14 and FIG. 15 are respectively a liquid level detection circuit applied to this image recording device. FIG. 2 is a connection diagram showing a conventional example. 1...Exposure stage 12...Photographic paper 11O...Color developer tank 20...Bleach-fix tank 130-150 units/1st to 3rd stabilizing tank 5A , 5
B...First and second detection sensor r...Dispute・Resistance value of solution SL, S2・φ・First and second switch O3C
... Oscillator 8 ... ゛, L voltage comparison condition R1, R2 ... Resistance window Sa, Sb ... Switching signal - MMI1M
M2・Φ First and second mono multi-pie break L...φ・ Applicant of latch circuit patent Roku Konishi Photography Co., Ltd. Figure 2A (Switch No. 7"4) -"-11 1---F
--1---Ding-1-6 top "■Yu"" B (λ Eve + 72A Kichigo) C (杞-*6Va) Ding-down T-ding 0 (Ftt4JLVb) 3
figure. (, ++-, +>7”/l (possible 1f Higuchi) “B (Suiken 7...>-”-m-1---1111-111-111 [-1]- 1. Figure 4 Figure 8 E (Embarrassing Pregnancy) 1] "--■-" Figure 9 Figure 14 Figure 15 "--■]

Claims (5)

[Claims] (1) Part of the reservoir tank containing the electrolyte contains the first and second
A first liquid level detection sensor is installed in each of the above detection sensors and a current path flowing through the detection sensor.
and a second switch are connected, and the switching of these first and second detection sensors is controlled in a complementary manner based on a predetermined high frequency signal, and the presence or absence of the liquid level is determined by the detection voltage output from the one detection sensor. A liquid level detection circuit that suppresses surface contamination. (2) Liquid level detection with reduced surface contamination as set forth in claim 1, wherein the first and second switches are connected between the detection sensor and a power source. circuit. (3) The liquid level detection circuit with reduced surface contamination as claimed in claim 1, wherein the first and second switches are connected between the detection sensor and ground. (4) The surface according to claim 1, 2, or 3, wherein the first and second switches are controlled to turn on and off in synchronization. Liquid level detection circuit with reduced dirt. (5) The surface according to claim 1, 2, or 3, wherein the first and second switches are controlled to be turned on and off in an asynchronous state. Liquid level detection circuit with reduced dirt.