Calibration module and measurement system

Abstract

To provide a calibration module having a configuration as simple as possible.SOLUTION: A calibration module comprising: a tank that holds a liquid; an introduction path that is connected to an introduction port of a sensor unit including a sensor and introduces the liquid supplied from the tank into the sensor unit; and a lead-out path that is connected to a lead-out port of the sensor unit and leads out the liquid from the sensor, wherein the introduction path introduces the liquid into the sensor unit by a water head pressure between the tank and the introduction port.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a calibration module and a measurement system. [Background technology]

[0002] In a measurement system that uses a sensor to circulate a liquid through a flow path and detect the characteristics of the liquid flowing through the flow path, the flow rate of the liquid flowing through the flow path is controlled using an electric pump, valve, etc. to ensure a stable flow of the liquid through the flow path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. H4-89566 Summary of the Invention [Problem to be solved by the invention]

[0004] Such conventional measurement systems require a power source not only for measurement but also for sensor calibration, which poses the problem that measurement and calibration cannot be performed in places where a power source cannot be secured.

[0005] The present invention has been made in view of the above-mentioned problems, and has as its main object to provide a calibration module with a very simple configuration that does not require a power source. [Means for solving the problem]

[0006] That is, the calibration module according to the present invention comprises: a tank for holding a liquid; an introduction path connected to an introduction port of a sensor unit having a sensor, for introducing the liquid supplied from the tank into the sensor unit; an outlet path connected to the outlet port of the sensor unit to discharge a liquid from within the sensor, The inlet passage introduces the liquid into the sensor unit by means of head pressure between the tank and the inlet port, where head pressure is the energy generated between two liquid levels at different heights.

[0007] The calibration module configured in this manner makes it possible to calibrate the sensor with a very simple configuration that does not require a flow control mechanism driven by electricity, such as an electric pump or an electric valve.

[0008] It is preferable to further provide an atmospheric vent provided on the outlet path, and to position the atmospheric vent at a higher position than the connection between the outlet path and the inlet port, since this allows the liquid introduced into the sensor unit to be discharged from the inlet port by hydraulic head pressure.

[0009] In a specific aspect of the present invention, a supply path for supplying a liquid from the tank to the introduction path; The supply path and the introduction path are connected to each other, so that the liquid is supplied to the sensor unit.

[0010] The liquid supply device further includes a discharge path connected to the discharge path for discharging the liquid discharged from the sensor unit to the outside. It is preferable that the supply path connected to the inlet path is switched to the outlet path, and the end of the inlet path on the tank side is sealed, so that any liquid remaining in the supply path can be discharged.

[0011] Furthermore, it is preferable that the inlet channel and the outlet channel are connected to each other so that liquid is discharged from the sensor unit.

[0012] It is preferable to provide a switching mechanism for switching between the supply path and the inlet path, between the inlet path and the outlet path, and between the supply path and the outlet path.

[0013] For a simpler configuration, the switching mechanism is preferably configured as a manually operable three-way valve.

[0014] The present invention includes not only the calibration module as described above, but also a measurement system including a sensor unit and the calibration module. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a calibration module that can calibrate a sensor with as simple a configuration as possible. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of a multi-sensor system including a sensor unit attached to a calibration module according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram of a multi-sensor system including a sensor unit attached to a calibration module according to an embodiment of the present invention; [Figure 3] FIG. 2 is a schematic diagram of a calibration module according to the embodiment. [Figure 4] FIG. 2 is a development view of a flow path of the calibration module according to the embodiment. [Figure 5] FIG. 4 is a schematic diagram showing a connection portion between a calibration module and a sensor unit according to the embodiment. [Figure 6] FIG. 4 is a schematic diagram showing a connection portion between a calibration module and a sensor unit according to the embodiment. [Figure 7] FIG. 10 is an exploded view of a flow path of a calibration module according to another embodiment of the present invention. [Figure 8] FIG. 10 is an exploded view of a flow path of a calibration module according to another embodiment of the present invention. [Figure 9] FIG. 10 is an exploded view of a flow path of a calibration module according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] A calibration module 100 and a measurement system 200 according to one embodiment of the present invention will be described below with reference to the drawings. In this specification, the up-down direction means the vertical direction, and unless otherwise specified, a high position means a position on the upper side in the vertical direction, and a low position means a position on the lower side in the vertical direction.

[0018] The calibration module 100 according to this embodiment is used, for example, when an individual sensor unit S incorporated in a multi-sensor system M as shown below is removed from the multi-sensor system and calibrated.

[0019] (Multi-sensor system) The above-described multi-sensor system M measures a fluid, for example, as shown in Figure 1 or 2. Note that the fluid is not particularly limited and includes, for example, not only liquids but also gases, mixtures of liquids and gases, mixtures of liquids and solids, etc.

[0020] A multi-sensor system M includes, for example, a plurality of sensor units S for measuring fluid, and a main body B to which each of the sensor units S is detachably attached. Although the system is referred to as a multi-sensor system M here for convenience, the number of sensor units S to be installed is not particularly limited, and may be, for example, one or more.

[0021] 3, the multi-sensor system M includes, for example, an inlet portion into which a fluid such as a liquid to be measured flows, an outlet portion from which the fluid flows, and a flow path R through which the fluid flows from the inlet portion to the outlet portion, as in this embodiment. For example, the sensor unit S may include a measurement flow path Ra through which the fluid flows, and the main body B may include a main body flow path Rb through which the fluid flows, and the sensor unit S may be attached to the main body B, thereby connecting the measurement flow path Ra and the main body flow path Rb to form the flow path R.

[0022] For example, if the multi-sensor system M described above measures values ​​related to water, each sensor unit S may be, for example, a turbidity meter, a color meter, a pH meter, a residual chlorine concentration meter, a conductivity meter, a flow meter, a water thermometer, etc. As the multiple sensor units S, the multi-sensor system M may be provided with multiple sensor units S that measure the same value related to the fluid, or may be provided with sensor units S that measure different values ​​from each other.

[0023] (sensor unit) As shown in Figure 3(a), the sensor unit S comprises a measurement flow path Ra, a cell C provided on the measurement flow path Ra, a sensor A placed in the cell C, and a housing H that houses these elements.

[0024] The measurement flow path Ra is formed, for example, between an inlet port P1 and an outlet port P2 provided at the bottom end of the housing H, and the cell C is provided above the inlet port P1 and the outlet port P2 of this measurement flow path Ra. Specifically, the inlet port P1 and the outlet port P2 are each openings formed in the bottom surface of the housing H.

[0025] In this embodiment, the measurement flow path Ra is formed within a resin block that forms the housing H, and it is preferable that the parts other than the inlet port P1 and the outlet port P2 are hermetically sealed.

[0026] The cell C accommodates the sensor A so that a fluid such as a liquid to be measured or a calibration liquid can be filled inside the cell C to enable the sensor A to measure a characteristic value of the fluid. The cell C is made of, but is not limited to, glass, acrylic resin, fluorine-based resin, silicone resin, etc., and is, for example, cylindrical with its axis extending vertically. The outer diameter of the cell C is, for example, 34 mm or more and 36 mm or less.

[0027] The upper end surface Ca of the cell C may be formed, for example, by the inner surface of the housing H, and it is preferable that the upper end of the cell C has an overflow outlet P3 formed therein through which fluid filled up to a position above the position where the sensor A is located in the cell C overflows toward the outlet port P2.

[0028] The sensor unit S preferably includes wireless communication means such as Wi-Fi or wireless LAN, or wired communication means such as a communication cable or wired LAN. The sensor unit S may be connectable to a communication device such as a mobile terminal (e.g., a smart device, a tablet computer, a notebook computer, etc.) via this communication means.

[0029] (Calibration module) Therefore, as shown in Figures 3 and 4, the calibration module 100 of this embodiment comprises a tank 1 that contains a liquid such as a calibration liquid to be supplied to the sensor unit S, a calibration flow path 2 for circulating the liquid, a connection part 6 for connecting the sensor unit S, and a base 4 that supports the sensor unit S.

[0030] The tank 1 can contain liquids such as calibration liquid and cleaning liquid required for calibrating and cleaning the sensor unit S. In this embodiment, the tank 1 is a recess formed from the top end toward the inside of a rectangular resin block. The tank 1 is positioned higher than the inlet port P1 of the sensor unit S so that the liquid level of the liquid contained therein is higher than the inlet port P1 of the sensor unit S. Furthermore, the tank 1 is positioned higher than the inlet port P1 of the sensor unit S so that the liquid level of the liquid contained therein is positioned vertically upward. In order to sufficiently fill the cell C of the sensor unit S with liquid, it is preferable that the bottom surface 1a of the tank 1 be positioned higher than the inlet port P1, and it is more preferable that the bottom surface 1a of the tank 1 be positioned higher than the sensor A disposed in the cell C. By positioning the bottom surface 1a of the tank 1 higher than the sensor A, the calibration liquid supplied from the tank 1 by hydraulic head pressure can be reliably raised to the height at which the sensor A is disposed.

[0031] The calibration flow path 2 comprises, for example, an inlet path 21 connected to the inlet port P1 of the sensor unit S to introduce the liquid supplied from the tank 1 into the measurement flow path Ra of the sensor unit S, an outlet path 22 connected to the outlet port P2 of the sensor unit S to discharge excess liquid from the measurement flow path Ra of the sensor unit S to the outlet, a supply path 23 that supplies liquid from the tank 1 to the inlet path 21, and an outlet path 24 that discharges the liquid stored in the sensor unit S to the outside.

[0032] In this embodiment, the inlet path 21 and the outlet path 22 are formed, for example, inside a resin block attached to a base 4 on which the sensor unit S can be placed. Also, the supply path 23, the discharge path 24, and a part of the outlet path 22 are formed inside the same resin block in which the tank 1 is formed. Note that these resin blocks are configured, for example, to be detachable from the base 4, and after being removed from the base 4, can be divided into several resin blocks, stored inside the base 4, and carried, and then reassembled when in use.

[0033] The supply path 23 is formed, for example, to connect the bottom surface 1a of the tank 1 and the inlet path 21. The supply path 23 is also formed to connect with the outlet path 24. The outlet path 24 is formed to connect not only with the supply path 23 but also with the inlet path 21. At the junction of these supply path 23, outlet path 24, and inlet path 21, a switching mechanism 5 is provided to switch the connection destinations between these paths.

[0034] In this embodiment, the calibration flow path 2 is configured as described above by arranging a resin block having the supply path 23 and the discharge path 24 formed therein next to a resin block having the inlet path 21 and the outlet path 22 formed therein, so that the inlet path 21 and the supply path 23, and the inlet path 21 and the discharge path 24 are connected to each other.

[0035] The outlet path 22 has a high-position portion 22a that is located higher than the lower end of the discharge path 24, preferably higher than the connection point X between the inlet path 21 and the discharge path 24, and more preferably higher than the upper end surface Ca of the cell C of the sensor unit S, and this high-position portion 22a is preferably formed inside the same resin block as the tank 1. Note that, in order to reliably fill the measurement flow path Ra of the sensor unit S with liquid from the tank 1, it is preferable that the highest part of the high-position portion 22a is located lower than the bottom surface 1a of the tank 1 and higher than the upper end surface Ca of the cell (the highest position of the measurement flow path Ra).

[0036] Furthermore, it is preferable that the high portion 22a of the outlet path 22 is provided with an air-opening portion 22b, for example, drilled from the side wall of the resin block toward the high portion 22a. The air-opening portion 22b is preferably provided at a position higher than the connection point between the inlet path 21 and the outlet path 24, more preferably at a position higher than the upper end surface Ca of the cell C of the sensor unit S, and preferably at a position higher than the highest position of the high portion 22a.

[0037] It is preferable that the downstream side of the higher portion 22a of the discharge path 22 is connected to an outlet 22c disposed below the atmosphere opening portion 22b. The outlet 22c is for discharging to the outside any excess liquid that flows through the discharge path 22 and overflows the highest point of the higher portion 22a. Furthermore, it is preferable that the inner diameter of the discharge path 22 is larger on the side closer to the outlet 22c than on the side closer to the discharge port P2, and more specifically, it is preferable that the inner diameter of the discharge path 22 at the rear stage is larger than the inner diameter of the discharge path 22 at the front stage at the position where the discharge path 22 is connected to the atmospheric opening portion 22b.

[0038] In order to position the lower end of the discharge path 24 as low as possible, it is preferable that the base 4 has a space below it for accommodating a container U for receiving waste liquid.

[0039] The switching mechanism 5 may be configured with a plurality of valve bodies, etc., but for a simpler configuration, it is preferable that the switching mechanism 5 is configured with a single three-way valve. An example of such a switching mechanism 5 is a three-way valve that has a knob for easy manual operation and that can change the connection destinations of each flow path by rotating the knob, for example, in 90° increments.

[0040] (Connection description) As described above, the calibration module 100 according to this embodiment includes the connection part 6 that connects the measurement flow path Ra of the sensor unit S and the calibration flow path 2.

[0041] The connection section 6 may, for example, as shown in Figures 5 and 6, include two connecting pipes 61 that are straight pipes extending in a straight line and through which a fluid flows, a first elastic body 62 that seals between these connecting pipes 61 and the sensor unit S, and a second elastic body 63 that seals between the connecting pipes 61 and the calibration module 100.

[0042] As described above, the sensor unit S has an inlet port P1 and an outlet port P2 formed at the ends of the measurement flow path Ra, and the two connecting tubes 61 each have a first end portion provided with a first intubation section 64 that is inserted into the inlet port P1 or the outlet port P2. The first elastic body 62 is formed in an annular shape and is disposed between the outer periphery of the first intubation section 64 and the inner periphery of the inlet port P1 or the outlet port P2.

[0043] With this configuration, the first elastic body 62 elastically deforms uniformly over the entire circumference, and therefore the gap between the outer periphery of the first intubation section 64 and the inner periphery of the introduction port P1 or the outlet port P2 is sealed by the first elastic body 62. The configuration of the first elastic body 62 is not particularly limited, but the first elastic body 62 may be configured to be elastically deformable in the radial direction, and may be, for example, an O-ring.

[0044] The inlet path 21 and outlet path 22 of the calibration module 100 each have a connection port at the end connected to the measurement flow path Ra of the sensor unit S, and the connecting tube 61 has a second intubation section 65 at its second end that is inserted into the connection port. The second elastic body 63 is formed in an annular shape and is disposed between the outer periphery of the second intubation section 65 and the inner periphery of the connection port.

[0045] With this configuration, the second elastic body 63 elastically deforms evenly around the entire circumference, and therefore the gap between the outer periphery of the second intubation section 65 and the inner periphery of the connection port of the calibration module 100 is sealed by the second elastic body 63. The configuration of the second elastic body 63 is not particularly limited, but the second elastic body 63 may be configured to be elastically deformable in the radial direction, and may be, for example, an O-ring.

[0046] (Method for calibrating the sensor unit using the calibration module) First, the sensor unit S is attached to the calibration module 100 via the connection portion, and a calibration solution for calibrating the sensor unit S is poured into the tank 1.

[0047] At this time, the end of the supply path 23 connected to the introduction path 21 may be sealed by a three-way valve constituting the switching mechanism 5, but in this embodiment, the three-way valve is set to the initial position (first position) and the liquid is poured into the tank 1 with the supply path 23 and the introduction path 21 connected. Due to the difference in vertical height between the liquid surface of the liquid and the introduction port P1 of the sensor unit S, the liquid in the tank 1 is introduced into the cell C of the sensor unit S from the introduction port P1 via the supply path 23 and the introduction path 21 by hydraulic head pressure. Whether the liquid supplied from tank 1 has reached the position of sensor A can be confirmed by checking the level of the liquid remaining in tank 1 or supply path 23. When the level of the liquid flowing from tank 1 through supply path 23 into sensor unit S reaches the same level as the level of the liquid flowing into sensor unit S from introduction port P1 provided on the underside of sensor unit S, the head pressure is balanced and the flow of the liquid stops, and the level of the liquid in tank 1 or supply path 23 when the flow stops represents the level of the liquid in sensor unit S.

[0048] The excess of the calibration liquid that has been introduced into the cell C of the sensor unit S and filled the inside of the cell C flows from the outlet port P2 into the outlet path 22, liquid-tightly filling the inside of the cell C and the outlet path 22. At this time, the calibration liquid needs to fill the sensor unit S from the introduction port P1 to the outlet port P2, but it is preferable that the calibration liquid fills the sensor unit S from the introduction port P1 to the upper portion 22a of the outlet path 22, and more preferably fills the sensor unit S from the introduction port P1 to the highest position of the upper portion 22a.

[0049] Next, by rotating the three-way valve, for example, by 90° and setting it to a second position where the end of the inlet passage 21 on the tank 1 side is sealed and the supply passage 23 and the discharge passage 24 are connected, the connection destination of the supply passage 23, which was connected to the inlet passage 21, is switched to the discharge passage 24, and the tank side end of the inlet passage 21 is sealed. At this time, the liquid level of the calibration solution remaining in the supply passage 23 is positioned above the lower end of the discharge passage 24, so that the calibration solution remaining in the supply passage 23 is discharged to the outside from the discharge passage 24 by hydraulic head pressure.

[0050] In this way, the introduction path 21 and the measurement flow path Ra in the cell C of the sensor unit S are filled liquid-tightly, and the sensor A included in the sensor unit S is calibrated in a state where the flow of liquid has stopped. The calibration work may be performed by connecting the sensor unit S to a terminal such as a smartphone using the above-mentioned communication means.

[0051] After the calibration is completed, the three-way valve is rotated, for example, by another 90° to set it to the third position where the inlet path 21 and the outlet path 24 are connected, thereby connecting the inlet path 21 and the outlet path 24, and the calibration liquid flows back from the sensor unit S through the inlet path 21 and is discharged to the outside through the outlet path 24.

[0052] In this case, an atmospheric opening section 22b is provided on the outlet path 22, for example, by drilling from the side wall of the resin block toward the outlet path 22, and the atmospheric opening section 22b is provided at a position higher than the connection point X between the inlet path 21 and the outlet path 24, so that the liquid introduced into the sensor unit S can be discharged from the outlet path 24 via the inlet port P1 by hydraulic head pressure.

[0053] <Effects of the Calibration Module and Calibration Method According to the Present Embodiment> Since the calibration liquid is introduced into and discharged from the liquid-tightly connected sensor unit S using hydraulic head pressure, the sensor unit S can be calibrated with as simple a configuration as possible, without using a flow control mechanism driven by a power source as in the conventional case.

[0054] By using a calibration module 100 with such a simple configuration, calibration work can be performed without any problems even in places where it is difficult to install a power source, for example.

[0055] Furthermore, compared to injecting calibration liquid using a syringe or the like, it is possible to adjust the flow rate to a constant value by adjusting the position of the tank 1, the amount, etc., and it is possible to easily achieve a flow rate that is less likely to trap air bubbles regardless of the skill of the operator and allows for as accurate a calibration as possible.

[0056] The tank 1 and calibration flow path 2 are formed inside the resin block, and these resin blocks can be removed and replaced, so it is easy to change the inner diameter and length of the flow path depending on the sensor unit S to be calibrated.

[0057] Since calibration is performed by stopping the flow when a certain amount of calibration solution has accumulated in cell C, the amount of calibration solution used can be minimized, and the costs and environmental impact of the calibration work can be kept as low as possible.

[0058] Since the liquid remaining inside the supply path 23 is discharged before the liquid inside the cell C is discharged, it is possible to minimize the amount of liquid remaining inside the supply path 23 and to prevent the liquid newly introduced from the tank 1 through the supply path 23 into the sensor unit S from mixing with another type of liquid that had previously flowed through the supply path 23, thereby minimizing the amount of liquid used to wash the inside of the flow path or to replace the liquid inside the flow path.

[0059] The measurement flow path Ra is connected to the calibration flow path 2 by the connection part 6 as described above, the first elastic body 62 seals the gap between the connection tube 61 and the sensor unit, and the second elastic body 63 seals the gap between the connection tube 61 and the calibration module, so that, for example, the sensor unit S and the calibration module 100 can be securely connected without fluid leaking from the flow path.

[0060] <Modification> The present invention is not limited to the above-described embodiment. For example, the above-mentioned calibration module can be used not only as a calibration module, but also as a measurement system 200 in which the liquid to be measured is poured into a tank, the liquid to be measured is filled into the sensor unit by hydraulic head pressure, and the properties of the liquid to be measured are measured by the sensor provided in the sensor unit when the above-mentioned inlet path and measurement flow path are filled liquid-tight with the liquid to be measured.

[0061] In the above embodiment, the sensor unit is detachable from the calibration module, but the present invention is not limited to this, and the calibration system or measurement system may be an inseparable integral unit of the calibration unit and the sensor unit.

[0062] In the above-described embodiment, a switching mechanism is provided at the connection point between the supply channel, the inlet channel, and the outlet channel. However, this is not limiting, and a simpler configuration may be used in which no switching mechanism is provided at all, as shown in Fig. 7 or 8. In this case, for example, a flow control mechanism such as a manually openable valve that controls the flow rate of fluid may be provided only on the outlet channel, as shown in Fig. 7, or flow control mechanisms such as manually openable valves may be provided on the outlet channel and the inlet channel, as shown in Fig. 8. In this case, too, it is preferable that the connection point between the supply channel, the inlet channel, and the outlet channel is located at a lower position than the higher portion of the outlet channel, and it is preferable that the position of the fluid control mechanism provided in the outlet channel is located at a lower position than the higher portion of the outlet channel. In the above-described embodiment, the atmosphere open portion 22b is provided at a position higher than the high-level portion 22a of the outlet path 22, but for example, the atmosphere open portion 22b may be provided at a position lower than the high-level portion 22a as shown in Fig. 9. In this case, it is preferable that a part of the atmosphere open flow path 22d connecting the high-level portion 22a and the atmosphere open portion 22b has a portion higher than the high-level portion 22a. Furthermore, the supply path, discharge path, inlet path and outlet path do not have to be formed within the resin block as described above, and each may be formed by appropriate piping.

[0063] In the above-described embodiment, the measurement flow path and the calibration flow path were airtightly connected, and therefore the atmospheric vent was provided on the outlet path. However, the atmospheric vent does not necessarily have to be provided on the outlet path, and may be provided, for example, downstream of the cell in the measurement flow path provided in the sensor unit, and above the connection between the inlet path and the outlet path. It goes without saying that various other modifications and combinations are possible within the scope of the present invention. [Explanation of symbols]

[0064] 200... Measurement System 100···Calibration Module 1 Tank 21...Introduction route 22 Derivation path 22a...Higher part 22b: Open to atmosphere 23...supply route 24...Exhaust channel 5. Switching mechanism S Sensor unit Ra Measurement flow path A Sensor P1: Introduction port P2: Outlet port

Claims

1. a tank for holding a liquid; an introduction path connected to an introduction port of a sensor unit having a sensor, for introducing the liquid supplied from the tank into the sensor unit; an outlet path connected to the outlet port of the sensor unit to discharge a liquid from within the sensor, A calibration module, wherein the inlet path introduces liquid into the sensor unit by means of a hydraulic head pressure between the tank and the inlet port.

2. 2. The calibration module according to claim 1, further comprising an atmosphere vent provided on the outlet path, the atmosphere vent being provided at a position higher than a connection between the outlet path and the outlet port.

3. a discharge path connected to the inlet path for discharging the liquid led out of the sensor unit to the outside; 3. The calibration module according to claim 1, wherein the outlet passage has a higher portion located at a position higher than a connection point between the inlet passage and the outlet passage.

4. 4. The calibration module of claim 3, wherein the elevated portion is located below a bottom surface of the tank.

5. 5. The calibration module according to claim 3, wherein the elevated portion is provided at a position higher than the highest portion of the measurement flow path formed in the sensor unit.

6. The calibration module according to any one of claims 3 to 5, which cites claim 2, wherein the atmospheric opening portion is provided at a position higher than the highest part of the elevated portion.

7. a supply path for supplying liquid from the tank to the introduction path; 7. The calibration module according to claim 1, wherein the supply path and the introduction path are connected to each other so that a liquid is supplied to the sensor unit.

8. A calibration module as described in any one of claims 1 to 7, configured so that the connection destination of the supply path connected to the inlet path is switched to the outlet path and the end of the inlet path on the tank side is sealed, thereby enabling the liquid remaining in the supply path to be discharged.

9. 9. The calibration module according to claim 8, wherein the inlet path and the outlet path are connected to each other so that the liquid is discharged from the sensor unit.

10. A calibration module as described in claim 8 or claim 9, which relies on claim 7, and which is provided with a switching mechanism that switchably connects the supply path and the inlet path, the supply path and the outlet path, and the inlet path and the outlet path, respectively.

11. 11. The calibration module of claim 10, wherein the switching mechanism is a manually operable three-way valve.

12. a tank for holding a liquid; a sensor unit including a sensor for measuring the liquid; an introduction path connected to an introduction port of the sensor unit to introduce the liquid supplied from the tank into the sensor unit; an outlet path connected to the outlet port of the sensor unit to discharge a liquid from within the sensor, A measurement system, wherein the introduction path introduces liquid into the sensor unit by hydraulic head pressure between the tank and the introduction port.

13. The measurement system according to claim 12 , wherein the sensor unit is one of a turbidity meter, a color meter, a pH meter, a residual chlorine concentration meter, a conductivity meter, a flow meter, and a water temperature meter.

14. A method for calibrating a sensor, comprising: introducing a liquid contained in a tank into a sensor unit having a sensor through an introduction path connected to an introduction port of the sensor unit; introducing a liquid into the sensor unit by a head pressure between the tank and the introduction port; a sensor calibration method for calibrating the sensor in a state where the introduction channel and the measurement channel are filled with the liquid;

15. A measurement method in which a liquid contained in a tank is introduced into a sensor unit having a sensor through an introduction path connected to an introduction port of the sensor unit, introducing a liquid into the sensor unit by a head pressure between the tank and the introduction port; a measuring method in which the sensor is calibrated in a state in which the introduction channel and the measurement channel are filled with the liquid.

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