JP2002214220A - Water quality checker circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water quality checker circuit capable of checking not only alkalinity but also the concentration of chlorine and capable of evaluating and displaying the concentration of chlorine and alkalinity by a display means even at the time of measurement of both of the concentration of chlorine and alkalinity when water quality is evaluated and displayed by the display means. SOLUTION: If a switch SW2 is closed at the time of measurement of alkalinity, a switch SW21 is closed in connection with the on-operation of the switch SW2 and, since the voltage at the non-reversal input terminal of an operational amplifier OP3 becomes voltage divided by a resistor R8 and a variable resistor VR2, the potential of the output terminal of the operational amplifier OP3 becomes lower than that of a line A in a negative direction as compared with the voltage at the time of measurement of the concentration of chlorine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water quality checker circuit which can be used for checking both the chlorine concentration of tap water and the alkalinity of alkaline water.

[0002]

2. Description of the Related Art Conventionally, there is a method in which the chlorine concentration or alkalinity in a liquid is checked by the electromotive voltage of a pair of electrodes. Since the directions are opposite, when the chlorine concentration is substantially zero, that is, when both clean water and a liquid having a predetermined alkalinity are evaluated as “good”, the same light emitting diode is used to determine “good”. If an attempt is made to evaluate and display that there is a problem, the direction of the electromotive voltage is reversed, so that there is a problem that the circuit configuration for processing the detection signal becomes complicated.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems.
A water quality checker circuit that can check both the alkalinity and the chlorine concentration, and that can display and evaluate the water quality by the display unit when the chlorine concentration and the alkalinity are measured by the display unit. To provide.

[0004]

In order to achieve the above object, according to the first aspect of the present invention, a power supply and a different kind of metal are used to generate a voltage when immersed in a liquid to be detected. A pair of electrodes that output as a detection signal, and a negative side of the electromotive voltage when immersed in the liquid to be detected of chlorine concentration, and a positive side of the electromotive voltage when immersed in the liquid to be detected of alkalinity. Means for maintaining the potential of a connection line connecting one of the electrodes at a constant potential when viewed from the negative ground of the power supply, and the detection signal is input to a non-inverting input terminal and connected to an output terminal and an inverting input terminal. An operational amplifier for signal amplification that non-invertingly amplifies the detection signal with a gain determined by the resistance and the resistance connected between the inverting input terminal and the ground, and is connected between the positive pole of the power supply and the connection line. Series connection of multiple resistors Provided corresponding to a plurality of different divided voltage output from the voltage division circuit constituted by,
Reference voltages are respectively set by different voltage division outputs, a plurality of comparators for comparing the reference voltage with a detection signal voltage output from the operational amplifier, and an output terminal of each comparator provided corresponding to each comparator. And a power supply connected between the power supply and the output of the corresponding comparator.The display means displays the detection result. When the alkali concentration is measured, the means for switching is set to be lower than the potential of the connection line in the minus direction when measuring the alkalinity. The above calculation is performed so that the change in the detection signal voltage output from the operational amplifier until the concentration reaches Characterized in that setting the gain of the width unit.

According to a second aspect of the present invention, in the first aspect, the means for maintaining the potential of the connection line constant is:
A voltage obtained by reducing the voltage of the power supply to a predetermined voltage is input to a non-inverting input terminal, and another operational amplifier constituting a non-inverting amplifier having a gain set so as to generate substantially the same voltage at an output is provided. The connection line is connected to the output terminal of another operational amplifier.

According to a third aspect of the present invention, in the first or second aspect of the invention, as the switching means, another operational amplifier having an inverting input terminal and an output terminal connected thereto, and a non-inverting input terminal of the other operational amplifier. And voltage switching means for switching the voltage inputted to the connection line between the voltage of the connection line and the voltage lower than the connection line, and setting the potential of the output terminal of the other operational amplifier to the ground potential of the operational amplifier for signal amplification. It is characterized by having.

According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, the detection signal voltage from the operational amplifier for signal amplification is supplied to the non-inverting input terminal of each of the comparators. A reference voltage is input to each input terminal, and a comparator having a lower detection signal voltage than the reference voltage is turned on to operate the display means.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the power supply is constituted by an output of a constant voltage circuit for stabilizing a battery power supply.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment.

FIG. 1 shows a circuit of this embodiment. In the figure, a switch SW1 for starting measurement of chlorine concentration and a switch SW2 for starting measurement of alkalinity are connected to a battery power source 1 such as a dry battery or a secondary battery. A constant voltage circuit 2 composed of a general-purpose IC or the like is connected via a parallel circuit, and a power supply voltage stabilized by the constant voltage circuit 2 is obtained.
Is applied to a non-inverting input terminal of an operational amplifier OP1 which is divided by a resistance voltage dividing circuit to constitute a non-inverting amplifier, and a series connection of resistors R3 and R4 connected between an output terminal and an inverting input terminal of the operational amplifier OP1. The comparators CP1 to CP of the display circuit 4 for displaying the midpoint potential of the circuit in a stepwise manner in the water quality evaluation.
The ground level of the reference voltage of P5 and the ground level of the detection signal voltage due to the electromotive force generated between the sensor electrodes 3a and 3b.

A series circuit of resistors R5 and R6 is connected between the electrodes 3a and 3b, and a middle point of the series circuit is connected to a non-inverting input terminal of an operational amplifier OP2 for amplifying a detection signal. This non-inverting input terminal is also connected to the positive terminal side of the output terminal of the constant voltage circuit 2 via a capacitor C1.

The operational amplifier OP2 constitutes a non-inverting amplifier, and a variable resistor VR1 is connected between an output terminal and an inverting input terminal.
A parallel circuit composed of a response adjusting capacitor C2 is connected, and is connected between the resistance value of the variable resistor VR1 and the output terminal of an operational amplifier OP3, which will be described later, and serves as an inverting input terminal and ground (reference). The gain is set by the resistor R7,
The gain can be adjusted by the variable resistor VR1.

On the other hand, a series circuit of a variable resistor VR2 and a switch SW21 is connected between a middle point of the series circuit of the resistors R3 and R4 and the minus pole of the battery power supply 1 via a resistor R8. Resistor VR2, switch SW
The noise removing capacitor C3 is connected to the series circuit 21 and the non-inverting input terminal of the operational amplifier OP3 is connected to the connection point between the resistor R8 and the variable resistor VR2.

The operational amplifier OP3 forms a non-inverting amplifier of a voltage follower. The input voltage at the non-inverting input terminal is equal to the output voltage, and the output terminal is connected to the inverting input terminal of the operational amplifier OP2 via a resistor R7. And the potential of the ground of the operational amplifier OP2 is set to the potential of the output terminal.

The switch SW21 is a switch that is turned on / off in conjunction with the on / off of the alkalinity measurement start switch SW2, and constitutes switching means for the input voltage of the operational amplifier OP2.

The display circuit 4 has five comparators CP1 to CP1.
CP5, a current limiting resistor R11 between the output terminals of the comparators CP1 to CP5 and the positive terminal of the output terminal of the constant voltage circuit 2
, R1 to L5, etc., which constitute display means connected through R15 to R15. The positive pole at the output terminal of the constant voltage circuit 2 and the resistors R3 and R
4 and the middle point of the series circuit.
A voltage dividing circuit consisting of a series circuit of R21 is connected, and a resistor R2
The divided voltage at the connection point between the resistor 1 and the resistor R20 is determined by the comparator C
Connected as a reference voltage to the inverting input terminal of P1 and a resistor R
The divided voltage at the connection point between the resistor R20 and the resistor R19 is connected to the inverting input terminal of the comparator CP2 as a reference voltage, and the divided voltage at the connection point between the resistor R19 and the resistor R18 is connected to the inverting input terminal of the comparator CP3. Similarly, the divided voltage at the connection point between the resistors R18 and R17 is connected as a reference voltage to the inverting input terminal of the comparator CP4, and the divided voltage at the connection point between the resistors R17 and R16 is compared with the comparator CP5. Are connected as a reference voltage, and the reference voltage of the comparator CP1 to the reference voltage of the comparator CP5 are sequentially increased.

On the other hand, the non-inverting input terminals of the comparators CP1 to CP5 are connected to the output terminals of the operational amplifier OP2 via resistors R22 to R26, respectively.
2 to R26 have the same resistance value.

FIG. 2 shows the appearance of a water quality checker using the water quality checker circuit of the present invention. A housing 5 made of a resin molded product houses the circuit shown in FIG. The main body 6 is provided with the light emitting portions of the light emitting diodes L1 to L5 of the display circuit 4 and the operating portion of the SW1 and SW2, and a pair of the front end portion formed so as to protrude forward from the front portion of the main body portion 6. Electrodes 3a, 3
and a head section 7 provided with a sensor section made of b.

The housing 5 is preferably formed of a material that does not contain an exogenous endocrine disrupting chemical substance (environmental hormone), and is formed of a resin molded product such as an ABS resin.

The head portion 7 is formed in a cylindrical shape that is long in the front-rear direction. The hollow portion inside the head portion 7 communicates with the inside of the main body 6 at the rear end side, and the front end side is opened forward. As shown in FIG. 4, the front end of the head 7 has a cylindrical shape that projects forward and has an outer diameter smaller than the outer diameter of the head 7 over the entire periphery of the opening. The fitting rib 8 is provided, and a fitting recess 9 is formed on the outer peripheral surface of the fitting rib 8 over the entire circumference. 9 are formed as fitting projections 10 protruding further to the outer peripheral side.

A fixing member 11 for securing watertightness inside and outside of the head portion 7 and fixing the terminal electrodes 3a and 3b is attached to a tip portion of the head portion 7. Fixing member 1
Numeral 1 is preferably formed of a material that does not contain environmental hormones, for example, is formed of a resin molded product such as ABS resin or the like, and is engaged with the front end side of the locking portion 12 formed in a cylindrical shape. A cylindrical projection 13 having a diameter smaller than that of the stopper 12 is formed, and a cylindrical insertion portion 14 having a diameter smaller than that of the locking part 12 is formed on the rear end side of the locking part 12.

At this time, the protruding portion 13 is formed with a front recess 15 opening forward, and the insertion portion 14 is formed with a rear recess 22 opening rearward. The concave portion 22 is partitioned by the locking portion 12.

The engaging portion 12 has two insertion holes 16 communicating the front concave portion 15 and the rear concave portion 22. Further, a concave groove 17 is formed on the entire outer periphery of the insertion portion 14 of the fixing member 11.

The fixing member 11 is attached to the front end of the head portion 7 by inserting the insertion portion 14 from the front end opening of the head portion 7 of the housing 5 as shown in FIG. The watertightness between the outer surface of the insertion portion 14 and the inner surface of the head portion 7 can be ensured by attaching the O-ring 18 to the O-ring 18.

Further, the gap between the outer surface of the insertion portion 14 and the inner surface of the head portion 7 is filled with an adhesive, and the head portion 7 and the fixing member 11 are adhered to each other. On the other hand, it can be firmly fixed and the watertightness between the outer surface of the insertion portion 14 and the inner surface of the head portion 7 can be further improved.

Two lead wires 19a and 19b are provided in the hollow portion of the head portion 7, and each of the lead wires 19a and 19b is provided.
The rear end of 19 b is pulled out to the main body 6 of the housing 5 and connected to the control unit, and the front end is fixed to the fixing member 11. Electrodes 3a and 3b are connected to the tips of the two lead wires 19a and 19b, respectively.

Here, the lead wires 19a and 19b are inserted into the insertion holes 16 of the locking portions 12 of the fixing member 11, and the rear end side of the fixing members 11 is inserted from the rear recess 22 of the insertion portion 14 through the rear end opening. Has been pulled out behind. Lead wire 19
A spherical nodule 20 larger than the inside diameter of the insertion hole 16 is formed at the distal end of the tip of each of the a and 19b.
As a result, the tips of the lead wires 19 a and 19 b are locked on the front side of the locking portion 12 in the front recess 15 of the protruding portion 13. The bump 20 at the tip of the lead wires 19a, 19b
Are embedded with the rear ends of the linear electrodes 3a and 3b, respectively, whereby the electrodes 3a and 3b are connected to the front ends of the lead wires 19a and 19b. Each of the electrodes 3 a and 3 b is disposed such that the distal end protrudes forward from the opening of the front recess 15 of the protrusion 13 of the fixing member 11.

The sealing material 21 is filled in the rear concave portion 22 of the insertion portion 14 of the fixing member 11, so that the lead wires 19a, 19b are formed in the rear concave portion 22 of the insertion portion 14 of the fixing member 11. Has been fixed. Fixing member 1
The sealing material 23 is also filled in the front recess 15 of the first protrusion 13, whereby the protrusion 13 of the fixing member 11 is
The electrodes 3a and 3b are fixed in the front concave portion 15 of FIG. Further, the sealing members 23 and 19 ensure watertightness between the front end side and the rear end side of the fixing member 11.

The pair of electrodes 3a and 3b are connected to one electrode 3b
Is formed of a platinum wire, the other electrode 3a is formed of a silver wire,
The electrodes 3a and 3b constitute a sensor unit. Each of the electrodes 3a and 3b is formed as a buried portion embedded in the sealing material 23 in the front recess 15 of the protrusion 13 of the fixing member 11 on the rear end side, and the sealing material 23 is formed on the front end side.
Is formed as a detection portion projecting forward from the front.

The electrode 3a composed of a silver wire has a silver chloride film formed only on the surface of the detection terminal portion 7, and has no silver chloride film formed on the surface of the buried portion. No silver chloride coating is formed at the connection with the lead wire 19a, and the electrical connection between the electrode 3a and the lead wire 19a is not hindered by the silver chloride coating.

Further, a fixing member 1 is attached to the tip of the head 7.
A cap body 24 is provided so as to cover the detection terminals 7 of the electrodes 1 and the electrodes 3a and 3b, thereby protecting the detection terminals 7. As shown in FIG. 3, the cap body 24 is formed in a closed-end cylindrical shape having a closed front end and an open rear end. The outer diameter of the cap 24 is substantially the same as the outer diameter of the head 7. You. The rear end of the cap body 24 has a larger inner diameter than the front end and
Is formed as a fitted rib 25 having substantially the same size as the outer diameter of the locking portion 12 of the fitting section 12.
On the inner peripheral surface of the rear end portion, a fitting concave portion 26 that matches the fitting convex portion 10 of the fitting rib 8 of the head portion 7 is formed over the entire circumference, and the fitted concave portion 26 is formed. Further, the rear end side is formed as a fitting convex portion 27 that protrudes inward from the fitting concave portion 26 and that matches the fitting concave portion 9 of the fitting rib 8. Then, the fitting rib 25 of the cap body 24 is arranged from the outer peripheral side of the locking portion 12 of the fixing member 11 to the outer peripheral side of the fitting rib 8 of the head 7, and the fitting concave portion 9 and the fitting convex portion 2 are arranged.
7 and the fitting projection 10 and the fitting recess 26.
The cap body 24 is attached to the front end of the head part 7 by filling the gap between the fitting rib 8 and the fitted rib 25 with an adhesive. By bonding the head 24 and the head 7,
The cap body 24 can be firmly fixed to the head portion 7 and the water tightness between the fitting rib 8 and the fitted rib 25 can be ensured.

The cap body 24 is formed with two parallel and parallel slit-shaped openings 28, and the inside and outside of the cap body 24 are communicated by the openings 28. The opening 28 is formed to extend from the side surface of the cap body 24 to the opposite side surface through the front end surface. In addition, the cap body 24 has both ends of each opening 28,
A communication hole 29 communicating with the opening 28 and communicating the inside and the outside of the cap body 24 is formed. The communication hole 29 is formed to have a diameter larger than the width of each opening 28.

The slit-shaped opening 28 of the cap body 24 allows a liquid to be detected such as tap water to enter the inside of the cap body 24 when water quality is measured, thereby enabling the detection terminal 7 of the electrode 2 to be detected.
Is to be immersed in the liquid or to discharge the liquid from the inside of the cap body 24 after measuring the water quality.

The communication hole 6 discharges air from the inside of the cap body 24 at the time of measuring the water quality so that the liquid to be detected can smoothly enter the inside of the cap body 24, or the water of the cap body 24 is measured after measuring the water quality. This is to allow air to enter the inside so that the liquid is smoothly discharged from the inside of the cap body 24.

Next, the operation of the water quality checker circuit of this embodiment will be described.

First, when checking the chlorine concentration of tap water, the switch SW1 is turned on and the head section 7 is immersed in tap water which is a liquid to be detected. An electromotive voltage is generated between the electrodes 3a and 3b in the cap body 24 immersed in tap water according to the chlorine concentration. In this case, the electrode 3a becomes a positive pole, and a voltage is generated in the resistor R6 by the electromotive voltage, and this voltage is input to the operational amplifier OP2 as a detection signal at the non-inverting input terminal and is amplified in a non-inverting manner.

On the other hand, the output voltage from the constant voltage circuit 2 is equal to the resistance R
1 and a resistor R2, which are divided and stepped down, and the voltage across the resistor R2 is non-inverted and amplified by the operational amplifier OP1. Here, the resistance values of the resistors R4 and R3 connected to the output terminal and the inverting input terminal of the operational amplifier OP1 are set so that the voltage of the connection line A connected to the middle point thereof is substantially equal to the voltage of both ends of the resistor R2. It is set to be voltage.

Since the switch SW21 is off, the voltage at the output terminal of the operational amplifier OP3 becomes the voltage input to the non-inverting input terminal, that is, the voltage of the connection line A. Therefore, the potential of this output terminal and the connection line A
, The operational amplifier OP2 has a gain determined by the resistance of the variable resistor VR1 and the resistance of the resistor R7 connected between the inverting input terminal and the output terminal of the operational amplifier OP3. The detection signal voltage generated at both ends is amplified.

The detection signal voltage amplified by the operational amplifier OP3 is input to the display circuit 4 and compared with reference voltages set in the comparators CP1 to CP5.
Then, in the comparator in which the detection signal voltage does not exceed the reference voltage, the output terminal is set to the “L” level, and the light emitting current flows through the light emitting diode connected to the output terminal. In other words, the higher the chlorine concentration of the water to be measured, the more the electrodes 3a, 3
The electromotive voltage generated during b increases, and the voltage across the resistor R6 increases. Therefore, the number of comparators exceeding the reference voltage increases, and the number of light emitting diodes that emit light decreases. Therefore, when all of the light emitting diodes L1 to L5 are lit, the chlorine concentration is nearly zero and the water quality evaluation is “good”.
It can be seen that the smaller the number of lightings, the higher the chlorine concentration and the worse the water quality evaluation. Also, before immersing the head unit 7 in tap water, the capacitor C1 is charged from the time when the switch SW1 is turned on, and the light-emitting diodes L1 to L5 are sequentially turned on slowly with the charging, so that the operation can be checked by this lighting. It has become. This operation is performed only when measuring the chlorine concentration, and is not performed when measuring the alkalinity described later.

The checker circuit of the present invention can check not only the chlorine concentration of the tap water but also the degree of alkalinity of the alkali-produced water. In this case, the switch SW2 is turned on and the chlorine of the tap water is detected in the liquid to be detected. What is necessary is just to soak the head part 7 like the density check.

That is, the switch SW21 is turned on in conjunction with the ON operation of the switch SW2, and the voltage at the non-inverting input terminal of the operational amplifier OP3 is switched to the voltage divided by the resistor R8 and the variable resistor VR2. The potential of the output terminal of the operational amplifier OP3 becomes lower in the minus direction than the potential of the connection line A as compared with the concentration measurement.

On the other hand, during the alkali measurement, the electrodes 3a,
The direction of the electromotive voltage between the terminals 3b and 3b is opposite to the direction of the chlorine concentration measurement, and the higher the alkalinity, the higher the operational amplifier O
The detection signal voltage input to the non-inverting input terminal of P2 increases in the negative direction with respect to the potential of the connection line A.

Here, the potential at the output terminal of the operational amplifier OP3 is set so that the light emitting diodes L1 to L5 are fully turned on when the alkalinity is higher than a predetermined level, and are completely turned off when the alkalinity is lower than the predetermined level. , Variable resistor VR
2, the detection signal voltage input to the non-inverting input terminal of the operational amplifier OP3 increases in the negative direction with respect to the connection line A when the alkalinity is higher than a predetermined value. By making the potential of the output terminal sufficiently higher in the minus direction than the potential of the connection line A, the potential difference between the non-inverting input terminal of the operational amplifier OP2 to which the detection signal is input and the ground is reduced, and the potential of the operational amplifier OP2 is reduced. The amplified detection signal voltage output from the output terminal has a value substantially close to the voltage of the connection line A. As a result, when the alkalinity is equal to or higher than a predetermined value, the input voltages of the non-inverting input terminals of all the comparators CP1 to CP5 fall below the reference voltage, and the comparator CP1
To CP5 are all at "L" level, and all the light emitting diodes L1 to L5 are turned on.

Further, the lower the alkalinity of the liquid to be detected, the lower the electromotive voltage in the negative direction, and the lower the detection signal voltage in the negative direction input to the non-inverting input terminal of the operational amplifier OP2. The potential difference between the non-inverting input terminal of OP2 and the ground increases, and the amplified detection signal voltage output from the output terminal of the operational amplifier OP3 increases. Therefore, the higher the alkalinity of the liquid to be measured, the greater the number of comparators whose voltage at the non-inverting input terminal exceeds the reference voltage, and the less the number of light emitting diodes that emit light. That is, the light emitting diodes L1 to L
When all 5 are lit, the degree of alkalinity is higher than a predetermined level and the water quality evaluation is “good”. Conversely, the smaller the number of lights, the lower the degree of alkalinity and the water quality evaluation is “bad”. You can see that it is.

In this embodiment, the light emitting diodes L1 to L
Although the water quality evaluation is displayed with the number of lights of 5,
The information may be displayed using a liquid crystal display or the like.

[0046]

According to the first aspect of the present invention, there is provided a power supply, a pair of electrodes formed of different kinds of metals, and generates a voltage when immersed in a liquid to be detected and outputs the voltage as a detection signal; The potential of the connection line connecting one of the electrodes that is on the negative side of the electromotive voltage when immersed in the liquid to be detected and becomes the positive side of the electromotive voltage when immersed in the liquid for the alkalinity is A means for maintaining a constant potential when viewed from the negative ground of the power supply, and the detection signal is input to the non-inverting input terminal, and is connected between the inverting input terminal and the resistor connected to the output terminal and the inverting input terminal. A signal amplification operational amplifier that non-inverts and amplifies a detection signal with a gain determined by a resistor, and a voltage divider circuit configured by a series circuit of a plurality of resistors connected between the positive pole of the power supply and the connection line Output from A plurality of comparators are provided corresponding to the different divided voltage outputs, the reference voltages are respectively set by the different divided voltage outputs, and the comparators compare the reference voltage with the detection signal voltage output from the operational amplifier. A display means for displaying a detection result, which is provided between the output terminal of each comparator and the power supply, is driven in accordance with the output of the corresponding comparator, and is provided corresponding to the comparator; The potential of the ground is set to the potential of the connection line at the time of measuring the chlorine concentration, and at the time of measuring the alkalinity, there is provided a means for switching and setting the potential in the minus direction to be lower than the potential of the connection line. And the change of the detection signal voltage of the operational amplifier from the case where the measured chlorine concentration is substantially zero to the case where the measured chlorine concentration exceeds a predetermined concentration. Since the gain of the operational amplifier is set to be substantially the same, an evaluation display of water quality from a case where the chlorine concentration of tap water is substantially zero to a predetermined concentration, and a case where the alkalinity such as alkali-produced water is higher than a predetermined level. Since the same display means can be used to evaluate and display water quality up to a predetermined level without switching comparators, measurement of chlorine concentration and measurement of alkalinity with the same electrode and simple circuit configuration There is an effect that a water quality checker circuit capable of performing the above can be realized.

According to a second aspect of the present invention, in the first aspect, the means for maintaining the potential of the connection line constant is provided by inputting a voltage obtained by reducing the voltage of the power supply to a predetermined voltage to a non-inverting input terminal. Since another operational amplifier constituting a non-inverting amplifier whose gain is set to generate substantially the same voltage at the output is formed, and the connection line is connected to the output terminal of the other operational amplifier, the detection signal A circuit for keeping the voltage ground potential constant can be easily realized.

According to a third aspect of the present invention, in the first or second aspect of the invention, as the switching means, another operational amplifier having an inverting input terminal and an output terminal connected thereto, and a non-inverting input terminal of the other operational amplifier. And voltage switching means for switching the voltage inputted to the connection line between the voltage of the connection line and the voltage lower than the connection line, and setting the potential of the output terminal of the other operational amplifier to the ground potential of the operational amplifier for signal amplification. So,
With the operational amplifier and the simple voltage switching means, the water quality evaluation display can be performed in the same way by the same operational amplifier for signal amplification, the comparator, and the same display means when measuring the chlorine concentration and when measuring the alkalinity degree. A circuit can be realized.

According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, a detection signal voltage from the operational amplifier for signal amplification is supplied to a non-inverting input terminal of each of the comparators.
A reference voltage is input to the inverting input terminal of each of the comparators, and a comparator having a lower detection signal voltage than the reference voltage is turned on to operate the display means, so that it is possible to check the operation before measurement when measuring the chlorine concentration. effective.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the power supply is constituted by an output of a constant voltage circuit for stabilizing the battery power supply. Circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention.

FIG. 2 is a side view of a water quality checker using the above.

FIG. 3A is an enlarged cross-sectional view of a water quality checker using the same as above, in which a part of a head portion is omitted. (B) is an enlarged side view which can omit a part of head part of a water quality checker using the same as the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery power supply 2 Constant voltage circuit 3a, 3b electrode 4 Display circuit OP1 to OP3 Operational amplifier SW1, SW2, SW21 Switch CP1 to CP5 Comparator L1 to L5 Light emitting diode

Claims (5)

[Claims] 1. A power source, a pair of electrodes made of different kinds of metals, and generating a voltage when immersed in a liquid to be detected and outputting the voltage as a detection signal; When viewed from the minus ground of the power supply, the potential of the connection line that connects one electrode that is on the minus side of the electromotive voltage when immersed and becomes the plus side of the electromotive voltage when immersed in the liquid to be detected for alkalinity is A means for maintaining a constant potential, and the detection signal is input to a non-inverting input terminal, and is detected by a gain determined by a resistor connected between the output terminal and the inverting input terminal and a resistor connected between the inverting input terminal and the ground. An operational amplifier for signal amplification for non-inverting amplification of a signal, and a plurality of different voltages output from a voltage dividing circuit configured by a series circuit of a plurality of resistors connected between a positive pole of the power supply and the connection line. For partial pressure output A plurality of comparators are provided corresponding to the respective comparators, and reference voltages are respectively set by different divided outputs, and a plurality of comparators are provided for comparing the reference voltage with a detection signal voltage output from the operational amplifier. And a display unit that is connected between the output terminal of each comparator and the power supply, is driven according to the output of the corresponding comparator, and displays a detection result.
When the potential of the ground of the operational amplifier is set to the potential of the connection line when measuring the chlorine concentration, and when measuring the alkalinity, there is provided a means for switching and setting the potential in the minus direction to be lower than the potential of the connection line. The gain of the operational amplifier was set so that the change in the detection signal voltage output from the operational amplifier from when the measured chlorine concentration was substantially zero to when the measured chlorine concentration reached the predetermined concentration or more was substantially the same. A water quality checker circuit, characterized in that: And a means for maintaining the potential of said connection line constant so that a voltage obtained by stepping down the voltage of said power supply to a predetermined voltage is inputted to a non-inverting input terminal so that substantially the same voltage is generated at an output. 2. The water quality checker circuit according to claim 1, wherein the circuit is constituted by another operational amplifier constituting the set non-inverting amplifier, and the connection line is connected to an output terminal of the another operational amplifier. 3. The switching means includes another operational amplifier having an inverting input terminal and an output terminal connected thereto, and a voltage input to a non-inverting input terminal of the other operational amplifier, the voltage of the connection line and the voltage of the connection line. 3. A voltage switching means for switching to a lower voltage, wherein the potential of the output terminal of the other operational amplifier is set to the ground potential of the operational amplifier for signal amplification. Water quality checker circuit. 4. A detection signal input from the operational amplifier for signal amplification to a non-inverting input terminal of each comparator, a reference voltage to an inverting input terminal of each comparator, and a detection signal input from the reference voltage. The water quality checker circuit according to any one of claims 1 to 3, wherein the display means is operated by turning on a comparator having a low voltage. 5. The power supply according to claim 1, wherein said power supply comprises an output of a constant voltage circuit for stabilizing a battery power supply.
A water quality checker circuit according to any one of claims 1 to 4.