JP2017026359A - Water quality sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water quality sensor capable of measuring conductivity of a fluid correctly.SOLUTION: A water quality sensor 10 has a constitution in which an electrode part 20 and a signal processing part 52 are integrated. The electrode part 20 is constituted by first and second electrodes arranged concentrically. The first electrode is arranged in the center position of a circle, and the second electrode has a cylindrical shape arranged on the circumference of the circle, and the electrodes are insulted by a spacer. In the vicinity of the first electrode and the second electrode, a circuit board 51 is arranged, and a measuring circuit is formed. The circuit board 51 applies a voltage between the first electrode and the second electrode, and measures an electrical characteristic of a measuring object fluid.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a water quality sensor.

  A conductivity sensor is used as a device for inspecting water quality. As a conductivity sensor for water quality inspection, there is one that includes two or four rod-shaped electrodes and measures the conductivity of a fluid between the electrodes. Furthermore, a water quality sensor having a short electrode length is also provided so that it can be used even in a thin pipe (see Patent Document 1).

JP 2009-85851 A

  The water quality sensor having the above-described configuration in which a plurality of electrodes are arranged on a straight line is easily affected by noise (underwater propagation noise) generated from machinery such as a pump and an inverter device when mounted on a metal pipe or the like. Therefore, it is difficult to accurately measure conductivity.

  For this reason, it took time and effort to attach the water quality sensor to the pipe, such as changing the joint of the pipe to resin, or attaching the water quality sensor to the pipe via an exchange adapter. Furthermore, the piping route was restricted, and it was necessary to consider the strength of the piping.

  Further, in the conventional water quality sensor, if the signal line connecting the electrode and the processing circuit for measuring the conductivity is long, the measurement error becomes large due to the parasitic resistance and parasitic capacitance of the signal line. Also, the signal line functions as a kind of antenna and is affected by noise. For this reason, accurate measurement becomes more difficult.

  This invention is made | formed in view of the said situation, and it aims at providing the water quality sensor which can measure the electrical conductivity of a fluid simply and correctly.

In order to achieve the above object, the water quality sensor of the present invention comprises:
A water quality sensor having a configuration in which an electrode part and a measurement part for measuring electrical characteristics of a fluid to be measured are integrated,
The electrode part includes a first electrode and a second electrode arranged concentrically,
The measurement unit is configured integrally with the electrode unit, is connected to the first electrode and the second electrode, and has electrical characteristics between the first electrode and the second electrode. taking measurement.

  For example, the measurement unit measures the electrical conductivity between the first electrode and the second electrode.

  For example, the first electrode has a cylindrical shape arranged at the center position of the circle, and the second electrode has a cylindrical shape arranged on the circumference of the circle.

  For example, the second electrode is formed to protrude from the first electrode, and the first electrode is disposed in a cylindrical space formed by the second electrode.

  For example, the second electrode has an opening that allows fluid to flow.

  The measurement unit includes, for example, a circuit that applies a voltage between the first and second electrodes and measures a flowing current.

  According to the present invention, since the first electrode and the second electrode are formed coaxially, and the electrode and the measurement part are formed integrally, the influence of external noise is small, and the electrical characteristics of the fluid are accurately measured. Can be measured.

It is (a) front view, (b) top view, (c) bottom view of the water quality sensor concerning Embodiment 1. FIG. It is a perspective view which notches and shows a part of water quality sensor which concerns on Embodiment 1. FIG. It is sectional drawing which shows the structure of the electrode part of the water quality sensor which concerns on Embodiment 1. FIG. FIG. 4A is a front view of the center electrode shown in FIG. 3 and FIG. FIG. 4 is a (a) front view and (b) a cross-sectional view taken along line II-II of the cylindrical external electrode shown in FIG. 3. FIG. 4A is a front view and FIG. 3B is a cross-sectional view taken along line III-III of the insulating layer shown in FIG. 3. It is a figure which shows the state which attached the water quality sensor which concerns on Embodiment 1 to piping. 1 is a circuit diagram of a water quality sensor according to Embodiment 1. FIG. It is sectional drawing which shows the thermistor arrange | positioned inside a center electrode. It is an equivalent circuit between electrodes.

  Hereinafter, a water quality sensor according to an embodiment of the present invention will be described with reference to the drawings.

  The water quality sensor 10 according to the embodiment is shown in three views in FIGS. 1A to 1C and in a partially cutaway perspective view in FIG. 2. As shown in FIG. 2, the electrode unit 20, the electrode holding unit 30, The part 40, the main body part 50, and the connection part 60 are integrally provided.

  As shown in a cross section in FIG. 3, the electrode unit 20 includes two electrodes 21 and 22 arranged concentrically and a spacer 23 that insulates the electrodes 21 and 22 from each other.

  The electrode 21 is made of a corrosion-resistant conductive material such as stainless steel, silver, copper, brass, gold, platinum, and titanium, and is shown in a front view in FIG. 4A and in a cross-sectional view in FIG. Thus, it is formed in a bottomed cylindrical shape.

  On the other hand, the electrode 22 is formed in a cylindrical shape as shown in a front view in FIG. 5A and a sectional view in FIG. The electrode 22 is located on the circumference centered on the center electrode 21, and is made of a corrosion-resistant conductive material such as stainless steel, silver, copper, brass, gold, platinum, or titanium. Hereinafter, for distinction, the electrode 21 is referred to as a center electrode, and the electrode 22 is referred to as a cylindrical external electrode.

  The spacer 23 is formed of an insulating resin or the like, and is formed in a cylindrical shape as shown in a front view in FIG. 6A and a cross-sectional view in FIG.

  As shown in FIG. 3, the center electrode 21, the spacer 23, and the cylindrical external electrode 22 are combined so that the spacer 23 surrounds the center electrode 21 in a watertight manner, and the cylindrical external electrode 22 surrounds the spacer 23 in a watertight manner. Has been.

The tip of the center electrode 21 is located inside without protruding from the tip of the cylindrical external electrode 22. The tip of the spacer 23 is located inside the center electrode 21. For this reason, between the center electrode 21 and the cylindrical external electrode 22, the part which opposes via the fluid to be measured is formed.
Furthermore, an opening 24 through which the fluid to be measured flows is formed at a position that does not overlap with the spacer 23 of the cylindrical external electrode 22 in a 120 ° rotational symmetry.

  As shown in FIG. 3, the cylindrical external electrode 22 has a stepped portion on its inner surface, and the spacer 23 has a stepped portion on the outer periphery, and the stepped portions are in contact with each other, so that the position in the axial direction is defined. ing. Similarly, the spacer 23 has a stepped portion on the inner surface thereof, the center electrode 21 has a stepped portion on the outer periphery thereof, and the position in the axial direction is defined by contacting the stepped portions.

  The size of the center electrode 21 and the cylindrical external electrode 22 is arbitrary. For example, the center electrode 21 has an outer diameter of 4 ± 1 mm, an inner diameter of 2 mm ± 1 mm, a length of 27 ± 5 mm, and the cylindrical outer electrode 22 has an outer diameter of 11 ± 1 mm. The inner diameter is 10 ± 1 mm and the length is about 35 ± 7 mm. The distance from the tip of the center electrode 21 to the tip of the cylindrical external electrode 22 is 3 to 8 mm.

  As shown in FIGS. 1 and 2, the electrode holding portion 30 is a truncated cone-shaped member whose outer diameter decreases from the proximal end toward the distal end. The electrode holding part 30 is made of an insulating material such as plastic. The electrode holding unit 30 is mounted and held in a watertight manner so that the tip of the electrode holding unit 30 protrudes. Thereby, the space between the electrode holding part 30, the electrodes 21, 22 and the spacer 23 is sealed, and the fluid to be measured is prevented from flowing into the water quality sensor 10 during measurement.

  A male screw 32 is formed around the electrode holding unit 30 to fix the water quality sensor 10 to an opening formed in a pipe or the like.

  The hexagonal head 40 is formed integrally with the electrode holding part 30 at the proximal end of the electrode holding part 30. By rotating the hexagonal head 40 with a wrench or the like, the male screw 32 formed on the electrode holding unit 30 is screwed into the insertion hole 111 formed on the pipe 110 or the like as shown in FIG. 20 can be inserted into the pipe 110 in a watertight manner.

  The main body 50 is formed integrally with the hexagonal head 40 and has a cubic shape. A signal processing unit that measures the electrical characteristics of the fluid to be measured by applying a voltage between the center electrode 21 and the cylindrical external electrode 22 and measuring a current flowing between the electrodes inside the main body 50. 52 is formed. The signal processing unit 52 includes a circuit board 51 on which an electronic circuit is formed. The circuit board 51 is composed of a printed wiring board or the like. Therefore, the circuit board 51 is disposed at a position very close to the center electrode 21 and the cylindrical external electrode 22, for example, a position of several mm to 3 cm.

  As shown in FIG. 8, a measurement circuit including an AC oscillator 71, a resistor 72, an absolute value amplifier (amplifier) 73, a signal processing circuit 74, and the like is formed on the circuit board 51.

  The AC oscillator 71 and the resistor 72 are connected in series, and one end is connected to the center electrode 21 via a conductor (not shown) and the other end is connected to the cylindrical external electrode 22 via a short signal line. In FIG. 8, one end of the AC oscillator 71 is connected to the center electrode 21, the other end of the AC oscillator 71 is connected to one end of the resistor 72, and the other end of the resistor 72 is connected to the cylindrical external electrode 22 via a short signal line. It is connected to the.

  The voltage across the resistor 72 is applied to two input terminals of an absolute value amplifier (amplifier) 73. The absolute value amplifier 73 amplifies the voltage across the resistor 72 by an absolute value. The output of the absolute value amplifier 73 is supplied to the signal processing circuit 74.

The signal processing circuit 74 smoothes the output signal of the absolute value amplifier 73, A / D (analog / digital) converts this, and performs digital arithmetic processing, thereby interposing between the center electrode 21 and the cylindrical external electrode 22. The electrical characteristics such as conductivity of the fluid to be measured are obtained, and a digital signal indicating the obtained value is output.
It should be noted that any known method can be used as a method for obtaining electrical characteristics such as conductivity.

  The signal processing circuit 74 includes a temperature compensation circuit for compensating a measurement error due to a temperature change. The temperature compensation circuit compensates the measurement value (conductivity of the measurement target fluid) based on the temperature of the measurement target fluid detected by the temperature sensor 75 such as a thermistor. As schematically shown in FIG. 9, the temperature sensor 75 is disposed inside and at the tip of the bottomed cylindrical center electrode 21, and is connected to the signal processing circuit 74 by a signal line 76. With such an arrangement, it is possible to accurately measure the temperature of the fluid to be measured. Also, the signal line 76 can be short.

  The connection unit 60 bundles a cable 61 including a power supply line, an earth line, an output line of the signal processing circuit 74 and the like supplied from the outside.

  Next, an example of a procedure for obtaining the electrical conductivity of the fluid in the pipe using the water quality sensor 10 having the above configuration will be described.

  First, as shown in FIG. 7, in order to attach the water quality sensor 10 to the pipe 110, an insertion hole 111 having substantially the same diameter as the distal end portion (small diameter portion) of the electrode holding portion 30 is formed. A tap may be cut on the inner surface of the insertion hole 111.

  Subsequently, the male screw 32 of the electrode holding unit 30 is screwed into the insertion hole 111 by inserting the tip of the electrode holding unit 30 of the water quality sensor 10 into the insertion hole 111 and rotating the hexagonal head 40 with a wrench or the like. Thereby, the electrode part 20 is watertightly fixed in the piping 110.

  Subsequently, the fluid to be measured is caused to flow in the pipe 110. As a result, the fluid to be measured also flows into the space formed by the cylindrical external electrode 22, the center electrode 21, and the spacer 23. However, the cylindrical external electrode 22 has a shape surrounding the central electrode 21, and the fluid flow in the region between the central electrode 21 and the cylindrical external electrode 22 is relatively gentle.

  Subsequently, operating power is supplied from the outside, the AC oscillator 71 is activated, and an AC voltage is applied between the center electrode 21 and the cylindrical external electrode 22 via the resistor 72.

  Subsequently, operating power is supplied from the outside, the AC oscillator 71 is activated, and an AC voltage is applied between the center electrode 21 and the cylindrical external electrode 22 via the resistor 72.

An equivalent circuit between the center electrode 21 and the cylindrical external electrode 22 can be expressed as shown in FIG. Here, R is the interelectrode resistance, Cp is the interelectrode capacitance + cable capacitance, and Cs is the polarization capacitance.
The signal processing circuit 74 obtains the conductivity of the fluid to be measured from the equivalent circuit and the obtained measurement value, and outputs it through the cable 61.

  According to the water quality sensor 10 having the above configuration, since a current flows between the center electrode 21 and the closed cylindrical external electrode 22, almost no current wraps around. In addition, the current flow path is in a region surrounded by the cylindrical external electrode 22 and is shielded by the cylindrical external electrode 22, and is less affected by electromagnetic noise from the outside.

  In addition, the water quality sensor 10 supports the electrode unit 20 and the signal processing unit 52 with a casing, and integrates from detection of a signal to measurement of electrical characteristics of a fluid to be measured by signal processing as one portable device. The configuration is as follows. Therefore, it is not necessary to transmit the detection signal to an external signal processing device in order to obtain the electrical characteristics of the measurement fluid. For this reason, the wiring which connects the center electrode 21, the cylindrical external electrode 22, and the circuit board 51 can be very short. For this reason, the parasitic capacitance of the wiring is small, and a circuit for canceling the capacitance component is not required in the signal processing unit 52, and accurate measurement is possible. In the case of conductivity measurement, since the conductor resistance becomes very small due to the shortening of the wiring, there is no measurement error.

  Since the temperature sensor 75 such as a thermistor is positioned in the hollow portion of the center electrode 21, the temperature response of the measurement-measuring fluid is excellent.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation and application are possible. For example, the shapes of the center electrode 21 and the cylindrical external electrode 22 are not limited to the above embodiment. For example, the center electrode 21 may have a rod shape without a hollow portion therein. Further, the cylindrical external electrode 22 may have a protruding amount similar to that of the center electrode 21. Further, the shape, number, arrangement, and the like of the opening 24 are arbitrary. For example, a slit shape or the like may be used.

The configuration of the signal processing unit 52 is also arbitrary. For example, although the example using the absolute value amplifier 73 has been shown, a rectifier circuit and an amplifier may be used in combination.
Although an example of digital signal processing has been shown, analog signal processing may be used.

  Although an example of measuring conductivity as an index representing water quality has been shown, other electrical characteristics may be measured. For example, the resistance value (1 / conductivity) may be measured.

DESCRIPTION OF SYMBOLS 10 Water quality sensor 20 Electrode part 21 Center electrode 22 Cylindrical external electrode 30 Electrode holding part 40 Hexagon head 50 Main-body part 51 Circuit board 60 Connection part

Claims (6)

A water quality sensor having a configuration in which an electrode part and a measurement part for measuring electrical characteristics of a fluid to be measured are integrated,
The electrode part includes a first electrode and a second electrode arranged concentrically,
The measurement unit is configured integrally with the electrode unit, is connected to the first electrode and the second electrode, and has electrical characteristics between the first electrode and the second electrode. taking measurement,
Water quality sensor.   The water quality sensor according to claim 1, wherein the measurement unit measures conductivity between the first electrode and the second electrode.   3. The water quality according to claim 1, wherein the first electrode is disposed at a center position of a circle, and the second electrode has a cylindrical shape disposed on a circumference of the circle. Sensor. The second electrode is formed so as to protrude from the first electrode,
The water quality sensor according to claim 3, wherein the first electrode is disposed in a cylindrical space formed by the second electrode.   5. The water quality sensor according to claim 3, wherein the second electrode has an opening that allows fluid to flow therethrough.   The water quality sensor according to claim 1, wherein the measurement unit includes a circuit that applies a voltage between the first and second electrodes and measures a flowing current.

Images