JP2010060395A - Flow cell for liquid sensor such as dissolved oxygen sensor and water quality analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce flow rate influence in a liquid sensor by increasing the flow rate of a liquid as a measuring object supplied by a DO (dissolved oxygen) sensor to increase the replacement speed of the liquid as a measuring object in the vicinity of a sensor surface of the DO sensor. <P>SOLUTION: This flow cell 3 for the DO sensor supplies a liquid as a measuring object to the DO sensor. The flow cell includes: a flow cell body 31 housing the DO sensor and having a supply port P1 for supplying the liquid as a measuring object to the interior thereof; and a throttling structure provided on the flow cell body 31 to form an opening opposite to the DO sensor and communicated with the supply port P1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flow cell for a liquid sensor that supplies a liquid to be measured to a liquid sensor such as a dissolved oxygen sensor, and water quality of, for example, the ocean, rivers / lakes, dams, well water / ground water, urban sewage, factory sewage, agricultural water, aquaculture, etc. The present invention relates to a water quality analyzer for analyzing water.

  As shown in Patent Document 1, a conventional water quality analyzer uses a diaphragm type galvanic cell type or a diaphragm type polarographic diaphragm electrode method as a dissolved oxygen sensor.

  This dissolved oxygen sensor is provided with an oxygen permeable membrane that allows oxygen to permeate at the tip of a cylindrical casing, forms a chamber partitioned from the outside by the oxygen permeable membrane, and contains an internal solution (electrolyte) in the chamber. While being accommodated, the positive electrode (working electrode) and the negative electrode (counter electrode) are disposed in the internal liquid. Then, oxygen dissolved in the liquid to be measured passes through an oxygen permeable membrane (hereinafter also referred to as a sensor surface) exposed to the outside, and is reduced by reacting with the positive electrode. At this time, a reduction current proportional to the dissolved oxygen concentration is generated, and the dissolved oxygen concentration in the liquid to be measured is measured by measuring the reduction current.

  However, the dissolved oxygen sensor of the diaphragm electrode method has a problem that the sensitivity of the sensor is affected by the flow rate of the liquid to be measured passing near the sensor surface (measurement region). Specifically, the smaller the flow rate of the liquid to be measured, the worse the sensor sensitivity. When the flow rate of the liquid to be measured exceeds a predetermined value, the sensor sensitivity becomes substantially constant.

  That is, if the flow rate of the measurement target liquid is small and the measurement target liquid from which dissolved oxygen has been removed by the oxygen permeable membrane stays without being replaced by a new measurement target liquid, the supply speed of the dissolved oxygen to the positive electrode is reduced. There is a problem that the reaction speed cannot be caught up, the reduction current generated at the positive electrode is reduced, and the sensitivity of the dissolved oxygen sensor is deteriorated. This becomes a more significant problem because the larger the dissolved oxygen sensor, the longer it takes to replace the liquid to be measured near the sensor surface.

  Thus, considering only the replacement of the measurement target liquid in the vicinity of the sensor surface, it is conceivable to simply reduce the area of the sensor surface (oxygen exchange membrane) of the dissolved oxygen sensor.

  However, if the area of the sensor surface is reduced, insoluble substances such as silver chloride generated by the internal liquid enter between the working electrode and the oxygen permeable film, and oxygen that has passed through the oxygen permeable film moves to the positive electrode. There is a problem of preventing that. If it does so, the reduction current produced in a positive electrode will become small, the output of a dissolved oxygen sensor will become small, and also there exists a problem that S / N ratio will worsen. Further, when the measurement target liquid is sewage or the like, there is a problem that foreign matter adheres to the sensor surface and the area of the sensor surface is narrowed, and the permeation of dissolved oxygen from the measurement target liquid is hindered.

  In addition, there has been considered a method in which a dedicated flow cell that accommodates a dissolved oxygen sensor is provided, a measurement target liquid at a constant flow rate is supplied into the flow cell, and dissolved oxygen in the measurement target liquid is measured by the dissolved oxygen sensor. The flow cell includes a bottomed cylindrical flow cell main body, a supply port provided on the bottom wall side of the side wall of the flow cell main body, and a discharge port provided on the opening side of the side wall of the flow cell main body. The supply port is connected to a supply hose whose tip is immersed in, for example, a lake, and a pump is provided on the supply hose.

However, it only supplies a constant flow rate of the measurement target liquid into the flow cell body, and does not take into account the flow rate of the measurement target liquid on the sensor surface of the dissolved oxygen sensor, and the measurement target liquid stays in the vicinity of the dissolved oxygen sensor. Therefore, there is a problem that the dissolved oxygen in the liquid to be measured cannot be measured with high accuracy.
JP 2000-97930 A

  Therefore, the present invention has been made to solve the above problems all at once, and the main point is to quickly replace the measurement target liquid in the measurement area of the liquid sensor and reduce the influence of the flow rate in the liquid sensor. This is an issue to be solved.

  That is, the flow cell for a liquid sensor of the present invention is a flow cell for a liquid sensor that supplies a liquid to be measured to the liquid sensor, and has a supply port for accommodating the liquid sensor and supplying the liquid to be measured therein. A flow cell body; and a throttle structure provided in the flow cell body, forming an opening facing the liquid sensor, and communicating with the supply port. Here, “communication with the supply port” means not only that the communication is directly connected to the supply port, but also that the communication is connected via another member such as a pipe, or communication through a space. Including.

  In such a case, the liquid to be measured flows into the liquid sensor from the opening provided facing the liquid sensor, so that the liquid to be measured in the measurement area of the liquid sensor can be replaced quickly. The influence of the flow rate of the liquid to be measured by the sensor can be reduced. Therefore, the liquid to be measured can be accurately measured by the liquid sensor.

  In order to make effective use of the existing flow cell body, to reduce the manufacturing cost, and to make it possible to easily configure the throttle structure, the throttle structure is provided in the flow cell body, and the liquid sensor It is desirable to form from the partition plate which has an aperture_diaphragm | restriction which opposes. At this time, an aperture is formed in which the aperture is provided to face the liquid sensor.

  As a specific embodiment of the liquid sensor, a dissolved oxygen sensor is desirable. A dissolved oxygen sensor measures dissolved oxygen in a liquid to be measured in the vicinity of the film by an oxygen permeable membrane. The smaller the flow rate of the liquid to be measured, the worse the sensor sensitivity, and the flow rate of the liquid to be measured. Has a characteristic that the sensor sensitivity becomes substantially constant when the value becomes equal to or greater than a predetermined value.

  As a specific embodiment of the arrangement of the throttle holes that makes the effect of the present invention remarkable, it is desirable to be provided facing the measurement region for measuring the liquid to be measured by the liquid sensor. Is preferably provided opposite to the oxygen permeable membrane as the sensor surface.

  The water quality analyzer according to the present invention is a water quality analyzer comprising a sensor body having a dissolved oxygen sensor, and a flow cell provided in the sensor body and supplying a measurement target liquid having a constant flow rate to the dissolved oxygen sensor. The flow cell is attached to the sensor main body so as to accommodate the dissolved oxygen sensor, and has a supply port for supplying a measurement target liquid and a discharge cell for discharging the measurement target liquid, A partition plate provided in the flow cell main body and partitioning the supply port and the discharge port and having a throttle hole facing the sensor surface of the dissolved oxygen sensor.

  In order to easily and reliably position the dissolved oxygen sensor and the throttle hole when the flow cell is mounted so that the liquid to be measured flows into the sensor surface of the dissolved oxygen sensor, the flow cell is inserted into the sensor body. It is desirable to provide a fixed positioning mechanism for positioning the dissolved oxygen sensor and the throttle hole in the attached state.

  In addition, when the sensor main body further includes at least a conductivity sensor or a turbidity sensor, the measurement target liquid may not easily circulate due to the structure of the sensor. At this time, in order to circulate the liquid to be measured in the conductivity sensor or the turbidity sensor, the partition plate is a conductivity sensor throttle hole facing the conductivity sensor or a turbidity sensor facing the turbidity sensor. It is desirable to have a throttle hole for use.

  As described above, according to the present invention, it is possible to increase the replacement speed of the liquid to be measured in the measurement region of the liquid sensor and reduce the influence of the flow rate in the liquid sensor.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the configuration of the water quality analyzer 100 of the present embodiment.

<Device configuration>
The water quality analyzer 100 according to the present embodiment continuously measures measurement items such as pH, conductivity, dissolved oxygen concentration, turbidity, and water temperature simultaneously. As shown, a sensor main body 2 having a plurality of liquid sensors (liquid sensors) for water quality measurement, and a flow cell fixed to the sensor main body 2 and supplying a liquid to be measured with a flow rate of a predetermined value or more to the liquid sensor. 3 and an instrument main body 4 electrically connected to the sensor main body 2 via a waterproof electric cable CA. For example, when analyzing the quality of seawater, the seawater sucked from the sea is circulated in the flow cell 3.

  First, the sensor body 2 and the instrument body 4 will be described.

  As shown in FIG. 1, the sensor body 2 has a generally rotating body shape, a mounting block body 21 to which a plurality of types of liquid sensors are attached, a calculation unit having a power source and a memory function unit, and calculated water quality measurement data. And the like, and a storage unit 22 including a computing device that incorporates a data logger for recording the time-series and the like. In addition, the attachment block body 21 and the container 22 such as a computing device constitute a watertight case.

  Specifically, as shown in FIG. 1, a dissolved oxygen sensor 5 using a diaphragm-type polarographic method, a turbidity sensor 6 using a transmission scattering method, for example, an alternating current quadrupole method is used at the lower end of the mounting block body 21. The conductivity sensor 7 and the temperature sensor (not shown) are provided so as to face the same direction. That is, each sensor is provided at the lower end in a direction in which the central axis directions substantially coincide. In addition, although not shown, a pH sensor composed of a pH glass electrode for pH measurement and a comparative electrode using a high concentration (3.3 mol / L) KCl internal solution, and a redox potential using the comparative electrode. A redox electrode or the like for measurement may be provided.

  In addition, the measurement principle of each sensor is not limited to the above, and another measurement principle may be used. In addition, a sensor or an electrode provided on the attachment block body 21 such as the dissolved oxygen sensor 5 is generally exchangeable with respect to the attachment block body 21 in consideration of deterioration or unforeseen damage accompanying use. It is a formula and is easy to replace.

  The meter body 4 includes a display unit for displaying measurement data from the sensor body 2, a power key, a function key, a measurement start / end key, a calibration key, a select key, an up / down key, and the like. Then, when the measurement target liquid is circulated in the flow cell 3, measurement data based on the output from each measurement sensor is recorded in the memory function unit, and the measurement value is displayed on the display unit.

  Next, the flow cell 3 will be described in detail.

  As shown in FIGS. 1 and 2, the flow cell 3 is detachably attached to the sensor body 2 and supplies a measurement target liquid having a constant flow rate to the dissolved oxygen sensor 5, the turbidity sensor 6, and the conductivity sensor 7. A flow cell main body 31 attached to the sensor main body 2 and a diaphragm structure provided in the flow cell main body 31. The internal volume of the flow cell 3 attached to the sensor body 2 is, for example, 400 ml.

  The flow cell main body 31 has a bottomed cylindrical shape, and has a substantially rotating body shape having substantially the same opening as the outer surface of the sensor main body 2 (specifically, the mounting block body 21). Specifically, the cylindrical member 311 having both ends opened, the lower member 312 that closes one end of the cylindrical member 311, and the other end of the cylindrical member 311 are attached to the sensor body 2. An upper member 313. The cylindrical member 311, the lower member 312, and the upper member 313 are all formed of a synthetic resin such as vinyl chloride, and the cylindrical member 311 is positioned at the positions of the sensors 5, 6, and 7 and throttle holes 321, 322, and 323 described later. It is transparent to confirm the relationship, and the lower member 312 and the upper member 313 are formed using a material capable of blocking light from the outside, or are colored black, for example, to block light from the outside. A light-shielding process is performed. And the opening part of the flow cell main body 31, specifically, the opening part formed by the upper member 313 is fixed to the outer surface of the sensor main body 2 (specifically, the attachment block body 21), thereby the attachment block body 21. A measurement sensor including a dissolved oxygen sensor 5, a turbidity sensor 6 and a conductivity sensor 7 provided in the inside is housed inside.

  Further, a supply port P1 for supplying a liquid to be measured therein is provided on the bottom side of the side wall of the flow cell body 31 (specifically, the side wall of the lower member 312). The side wall 313 is provided with a discharge port P2 for discharging the liquid to be measured from the inside. The supply port P1 and the discharge port P2 are provided substantially perpendicular to the side wall of the flow cell main body 31 and are provided in the same direction. A supply hose H1 whose tip is immersed in water such as a lake is connected to the supply port P1. A pump is provided on the supply hose H1, and the liquid to be measured sucked up from the water is supplied into the flow cell main body 31 through the supply port P1. The discharge port P2 is provided with a discharge hose H2 whose tip is immersed in water such as a lake.

  With such a configuration, the liquid to be measured sucked up from the water by the pump is supplied into the flow cell main body 31 through the supply port P1, and each component is measured by the dissolved oxygen sensor 5 or the like. After the measurement, the discharge port P2 is measured. Is discharged to the lake by the discharge hose H2.

  The throttle structure is constituted by a partition plate 32, and the partition plate 32 is provided inside the flow cell main body 31 and has a flat plate shape that partitions the supply port P <b> 1 and the discharge port P <b> 2 in the flow cell main body 31. That is, in the state in which the flow cell 3 is attached to the sensor body 2, the partition plate 32 divides the space formed by the flow cell 3 and the sensor body 2 into a space communicating with the supply port P1 and a space communicating with the discharge port P2. Divide. More specifically, the space formed by the sensor body 2 and the flow cell body 31 is a space on the supply port P1 side that does not include a measurement sensor, and a space on the discharge port P2 side that includes a measurement sensor (at least Divided into a space containing the dissolved oxygen sensor 5, turbidity sensor 6 and conductivity sensor 7). The partition plate 32 is made of a synthetic resin such as vinyl chloride, like the flow cell main body 31, and is made of a light shielding process or a light shielding material. The partition plate 32 of this embodiment is provided between the cylindrical member 311 and the lower member 312, and specifically, is sandwiched between the cylindrical member 311 and the lower member 312 when the lower member 312 is fixed to the cylindrical member 311. .

  The partition plate 32 is formed with a plurality of throttle holes 321, 322, and 323. In particular, as shown in FIG. 1, they are provided to face the dissolved oxygen sensor 5, the turbidity sensor 6, and the conductivity sensor 7, respectively. The throttle holes 321, 322, and 323 increase the replacement speed of the liquid to be measured in each measurement region of the dissolved oxygen sensor 5, the turbidity sensor 6, and the conductivity sensor 7.

  The dissolved oxygen sensor throttle hole 321 is formed to face the sensor surface 51 (specifically, the oxygen permeable film) of the dissolved oxygen sensor 5. Specifically, the throttle hole 321 is formed so that the opening direction of the throttle hole 321 faces the sensor surface 51 of the dissolved oxygen sensor 5, and the central axis of the throttle hole 321 is formed to substantially coincide with the central axis of the dissolved oxygen sensor 5. ing. As a result, the liquid to be measured that has passed through the dissolved oxygen sensor throttle hole 321 flows substantially perpendicularly to the sensor surface 51 of the dissolved oxygen sensor 5. That is, the measurement target liquid that has passed through the dissolved oxygen sensor throttle hole 321 flows substantially perpendicularly to the measurement region in which the dissolved oxygen is measured by the dissolved oxygen sensor 5.

  The turbidity sensor throttle hole 322 is formed to face the internal space of the measurement cell 61 of the turbidity sensor 6. More specifically, the central axis of the throttle hole 322 is formed so as to substantially coincide with the central axis of the measurement cell 61. As a result, the liquid to be measured that has passed through the turbidity sensor throttle hole 322 easily flows into the measurement cell 61 that is the measurement region. A light source 62, a transmitted light detector 63, and a scattered light detector (not shown) are provided on the side periphery of the measurement cell 61.

  The conductivity sensor aperture 323 is formed to face the voltage application electrode 71 and the voltage detection electrode 72 of the conductivity sensor 7. More specifically, it is formed to face the internal space of the casing 73 that accommodates the voltage application electrode 71 and the voltage detection electrode 72. As a result, the liquid to be measured that has passed through the conductivity sensor throttle hole 323 easily flows into the casing 73 that is the measurement region. Note that both the measurement cell of the turbidity sensor 6 and the casing of the conductivity sensor 7 are open toward the bottom side of the flow cell main body 31.

  The dissolved oxygen sensor throttle hole 321, the turbidity sensor throttle hole 322, and the conductivity sensor throttle hole 323 may have the same shape or different shapes.

  Further, as shown in FIG. 1, the water quality analyzer 100 of the present embodiment attaches the flow cell 3 to the sensor main body 2 and positions the dissolved oxygen sensor 5 and the dissolved oxygen sensor throttle hole 321 in the attached state. A positioning mechanism 8 is provided. The positioning mechanism 8 includes an engaging portion 81 provided on one side of the sensor body 2 or the flow cell 3 and an engaged portion 82 provided on the other side of the sensor body 2 or the flow cell 3.

  The engaged portion 82 of the present embodiment is a plurality of engaging pins provided on the outer peripheral surface of the mounting block body 21 of the sensor main body 2, and the engaging portion 81 is a flow cell main body as shown in FIG. 31 (specifically, the upper member 313) is a plurality of substantially L-shaped engagement grooves provided on the inner peripheral surface. With such a configuration, the flow cell body 31 is inserted into the sensor body 2 along the engagement grooves 81 so that the engagement grooves 81 are fitted to the engagement pins 82, and the flow cell body 31 is moved to a predetermined position. After insertion, by rotating along the engagement groove 81, the engagement groove 81 and the engagement pin 82 are locked, and the flow cell body 31 is fixed to the sensor body 2, and the dissolved oxygen sensor 5. The throttle holes 321, 322, and 323 are positioned with respect to the turbidity sensor 6 and the conductivity sensor 7, respectively. In addition, the engagement groove 81 is substantially L-shaped to prevent the flow cell body 31 from being detached from the mounting block 21 due to an increase in internal pressure when the measurement target liquid is supplied into the flow cell body 31. be able to.

  In addition, a seal member such as an O-ring that seals the sensor main body 2 and the flow cell main body 31 in a liquid-tight manner when attached is provided on the inner peripheral surface of the opening of the flow cell main body 31.

  Next, the sensor sensitivity (DO instruction value) of the dissolved oxygen sensor when the flow cell of the present embodiment is used with respect to the flow rate to the flow cell, and the sensor sensitivity (DO instruction value) of the dissolved oxygen sensor when the conventional flow cell is used. ) Is shown in FIG. In addition, FIG. 3 has shown the variation | change_quantity of the instruction | indication value of the flow volume of 100-500 ml / min on the basis of 500 ml / min in which the sensor sensitivity of a dissolved oxygen sensor becomes substantially the same. As can be seen from this figure, the indicated value change amount of the dissolved oxygen sensor using the flow cell of this embodiment is significantly smaller than the indicated value change amount of the dissolved oxygen sensor using the conventional flow cell. I understand. That is, in the flow cell of the present embodiment, the dissolved oxygen sensor is configured to flow through the dissolved oxygen throttle hole toward the dissolved oxygen sensor and increase the replacement rate of the measured solution in the measurement region. Sensor sensitivity equivalent to the sensor sensitivity when the flow rate to the measurement region is large can be realized. For example, even if the flow rate supplied from the supply port into the flow cell body is 100 ml / min, the dissolved oxygen sensor should be measured with a dissolved oxygen throttle hole with a sensor sensitivity equivalent to that when the flow rate is about 380 ml / min. Is possible.

<Effect of this embodiment>
According to the water quality analyzer 100 according to the present embodiment configured as described above, the measurement target liquid supplied from the supply port P1 can be increased in flow rate by the dissolved oxygen throttle hole 321, and the dissolved oxygen sensor throttle. The liquid to be measured flowing from the hole 321 toward the dissolved oxygen sensor 5 flows substantially perpendicularly to the sensor surface, so that the replacement speed of the liquid to be measured near the sensor surface can be increased, and the dissolved oxygen sensor 5 The liquid to be measured can be measured in a region where the sensor sensitivity is constant. Therefore, the solution to be measured can be accurately measured by the dissolved oxygen sensor 5.

<Other modified embodiments>
The present invention is not limited to the above embodiment. In the following description, the same reference numerals are given to members corresponding to the above-described embodiment.

  For example, the sensor body can be used by immersing it alone without attaching the flow cell 3. At this time, a protective cover may be attached to protect the measurement sensor.

  In the embodiment, the dissolved oxygen sensor throttle hole, the conductivity sensor throttle hole, and the turbidity sensor throttle hole are formed. However, only the dissolved oxygen sensor throttle hole may be formed. In addition, a throttle hole may be formed for other sensors.

  Further, the dissolved oxygen sensor throttle hole of the above embodiment is formed so as to flow substantially perpendicular to the sensor surface of the dissolved oxygen sensor 5, but in addition, if the liquid to be measured directly hits the sensor surface, The installation location is not particularly limited.

  Further, in the embodiment, in order to simplify the configuration by effectively utilizing the existing flow cell 3 and reduce the manufacturing cost, the diaphragm structure is configured by adding the partition plate 32 to the configuration of the existing flow cell. However, the liquid to be measured supplied from the supply port P1 may be supplied to the dissolved oxygen sensor through the opening formed in the upper surface of the bottom surface portion from the internal channel formed in the bottom surface portion of the flow cell body. good. At this time, the opening is formed to face the dissolved oxygen sensor.

  In addition, although the partition plate of the above embodiment has a flat plate shape, the height of the sensor tip with respect to the bottom of the flow cell body is different, so that the throttle hole is positioned according to each sensor tip. In addition, it may be uneven with a stepped portion.

  In addition, some or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. .

The typical sectional view showing the composition of the water quality analyzer concerning this embodiment. The typical sectional view of the flow cell of the embodiment. The figure which shows the comparison result of the sensor sensitivity with the case where the flow cell of the embodiment is used, and the case where the conventional flow cell is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Water quality analyzer 2 ... Sensor main body 3 ... Flow cell 31 ... Flow cell main body P1 ... Supply port P2 ... Discharge port 32 ... Partition plate (throttle structure)
321... Restricted hole for dissolved oxygen sensor 322 ... Restricted hole for conductivity sensor 323 ... Restricted hole for turbidity sensor 5 ... Dissolved oxygen sensor (liquid sensor)
51 ... Sensor surface 6 ... Turbidity sensor 7 ... Conductivity sensor 8 ... Fixed positioning mechanism

Claims (6)

A liquid sensor flow cell for supplying a liquid to be measured to a liquid sensor,
A flow cell body containing the liquid sensor and having a supply port for supplying the liquid to be measured therein;
A flow cell for a liquid sensor, comprising: a throttle structure provided in the flow cell body, forming an opening facing the liquid sensor, and communicating with the supply port.   The flow cell for a liquid sensor according to claim 1, wherein the throttle structure is formed from a partition plate provided in the flow cell body and having a throttle hole facing the liquid sensor.   The flow cell for a liquid sensor according to claim 1 or 2, wherein the liquid sensor is a dissolved oxygen sensor. A water quality analyzer comprising: a sensor main body having a dissolved oxygen sensor; and a flow cell provided in the sensor main body for supplying a measurement target liquid to the dissolved oxygen sensor,
The flow cell is
A flow cell body attached to the sensor body to accommodate the dissolved oxygen sensor, and having a supply port for supplying the measurement target liquid and a discharge port for discharging the measurement target liquid;
A water quality analyzer comprising: a partition plate provided in the flow cell main body, partitioning the supply port and the discharge port, and having a throttle hole facing the dissolved oxygen sensor.   The water quality analyzer according to claim 4, wherein the flow cell is attached to the sensor body, and in the attached state, the water cell is provided with a fixed positioning mechanism that positions the dissolved oxygen sensor and the throttle hole. The sensor body further includes at least a conductivity sensor or a turbidity sensor,
The water quality analyzer according to claim 4 or 5, wherein the partition plate has a conductivity sensor throttle hole facing the conductivity sensor and a turbidity sensor throttle hole facing the turbidity sensor.