NL2024750B1 - Device for measuring the drainage flow rate of a plant growing substrate, method for the same and plant transpiration measurement device - Google Patents
Device for measuring the drainage flow rate of a plant growing substrate, method for the same and plant transpiration measurement device Download PDFInfo
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- NL2024750B1 NL2024750B1 NL2024750A NL2024750A NL2024750B1 NL 2024750 B1 NL2024750 B1 NL 2024750B1 NL 2024750 A NL2024750 A NL 2024750A NL 2024750 A NL2024750 A NL 2024750A NL 2024750 B1 NL2024750 B1 NL 2024750B1
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
- A01G31/00—Soilless cultivation, e.g. hydroponics
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Abstract
The invention relates to a method and a device for measuring the drainage flow rate of a plant growing substrate. The device comprises an inlet, an outlet, a reservoir Which is connected to the 5 inlet for receiving liquid from the inlet, a flow restrictor having a first end connected to the at least one reservoir and a second end connected to the outlet, a level sensor for sensing a liquid level in the reservoir and providing a corresponding signal at the output, and a processing unit, Wherein the second end communicates With a part of the reservoir for equalizing a gas pressure in the reservoir to a gas pressure at the second end, and the processing unit is configured to determine a value 10 corresponding to the drainage flow rate of the plant growing substrate based on the signal. The invention also relates to a plant transpiration measurement device.
Description
MEASUREMENT DEVICE The invention relates to a device for measuring the drainage flow rate of a plant growing substrate. Devices for measuring the drainage flow rate of plant growing substrate exist, and are used in plant growing environments. One such known device is known as a tipping bucket, which has a receiving space for collecting drainage liquid. As the receiving space fills beyond a determined amount, it tips about an axis to empty. A restoring force pushes the receiving space back. By counting the amount of times the receiving space tips, a flow rate can be determined.
These devices have a few drawbacks associated with them. Firstly, tipping buckets have a relatively coarse resolution determined by the capacity of the receiving space. Moreover, as the flow rate changes, there is a delay in the measurement as the receiving space fills. Further, in the case of relatively large flows, the receiving space may overflow and therefore register inaccurate measurements. Finally, the tipping bucket involves moving parts which can easily damage or wear.
ltis therefore an object of the invention to provide a device for measuring the drainage flow rate of a plant growing substrate which overcomes or reduces one or more of these drawbacks.
The object of the invention is achieved by a device for measuring the drainage flow rate of a plant growing substrate, said device comprising: - an inlet for receiving liquid drained from the plant growing substrate; - an outlet for discharging liquid from the device; - at least one reservoir which is connected to the inlet for receiving liquid from the inlet; - at least one flow restrictor having a first end connected to the at least one reservoir and a second end connected to the outlet for discharging liquid from the at least one reservoir; - a level sensor arranged to sense a liquid level in the at least one reservoir and having an output for providing a signal corresponding to the liquid level at the output; and - a processing unit connected to the output for receiving the signal, wherein: - the second end communicates with the at least one reservoir for equalizing a gas pressure in the at least one reservoir to a gas pressure at the second end; and - the processing unit is configured to determine a value corresponding to the drainage flow rate of the plant growing substrate based on the signal.
The device works by collecting liquid via the inlet in the at least one reservoir. Using the level sensor the liquid level in the at least one reservoir can be determined. Liquid exits the at least one reservoir via the flow restrictor. Since the flow out of the at least one reservoir is restricted by the flow restrictor, the flow rate out of the at least one reservoir depends on the liquid level in the at least one reservoir via a predetermined relation. Using the predetermined relation, the processing unit can therefore determine the flow rate of liquid coming into the at least one reservoir using the liquid level measurement. The equalization of gas pressure between the second end and the at least one reservoir aids in maintaining the predetermined relation, as pressure differences due to external factors are alleviated thereby.
The predetermined relation can be in the form of a look-up table, a formula, or any other suitable form.
In particular, the device may be capable of measuring a flow rate of a so called dripping flow, which is characterized by a non-continues flow of droplets. Such flows can not be measured using traditional flow meters, as they require a pressurized inlet. As such, the device according to the invention can be used for instance to measure the flow rate of liquid draining from a plant growing substrate. The device can however also be used to measure liquid from irrigation drippers of an irrigation system, for instance in order to provide feedback on the performance of the irrigation system.
The flow restrictor provides resistance to the flow of liquid. Specifically, the flow restrictor provides a predetermined resistance for a predetermined pressure of liquid. In particular, the flow restrictor may restrict flow with respect to other components of the device, such as the inlet and outlet, that is, the flow restrictor may provide a higher resistance than said other components.
The part of the at least one reservoir may for instance be an upper part of the at least one reservoir, a part of the at least one reservoir at the inlet side thereof, or any other part above a maximum liquid level of the at least one reservoir.
In an embodiment of the device the second end and said part of the at least one reservoir both communicate with an external environment, to equalize their gas pressures to that of the environment.
Communicating both the second end and said part of the at least one reservoir with the external environment allows to equalize the pressure therebetween. In yet another embodiment of the device according to the invention, the flow restrictor extends into the at least one reservoir, so that the first end is displaced away from an inner wall of the at least ONE reservoir.
The effect of the inner wall on the liquid is mitigated in this embodiment, so that the predetermined relation may be easier to model. The flow restrictor may comprise a substantially cylindrical body. The cylindrical body can be used to extend the flow restrictor through an opening in a wall of the at least one reservoir. The opening may for instance be a T-junction, in particular when the at least one reservoir is a tube. The maximum liquid level may be a liquid level of the at least one reservoir which corresponds to a height of the at least one reservoir at which no more liquid fits the at least one reservoir. Therefore, the maximum liquid level can be defined as the highest height in the at least one reservoir to which, during use, the liquid level can reach. The maximum liquid level may therefore be defined at the top of the at least one reservoir, or at the vertical position of an overflow of the at least one reservoir.
A minimum liquid level may be a liquid level of the at least one reservoir which corresponds to a height of the at least one reservoir at which liquid no longer flows out of the at least one reservoir. Therefore, the minimum liquid level can be defined as the lowest height in the at least one reservoir to which, during use, the liquid level can reach. The minimum liquid level may be defined at the lowest position of the at least one flow restrictor.
In yet another embodiment of the device according to the invention, the level sensor comprises a pressure sensor with a first pressure inlet communicated with the at least one reservoir to sense a hydrostatic pressure of liquid in the at least one reservoir.
By sensing the hydrostatic pressure, a measure for the liquid level can be obtained, because the liquid level and the hydrostatic pressure are related via the density of the measured liquid. Since the density of the measured liquid may be known rather accurately, a rather accurate measurement of the liquid level can be made via the hydrostatic pressure.
In particular the pressure sensor may comprise a second pressure inlet, which communicates to the second end, and wherein the pressure sensor is configured to measure a pressure difference between the first pressure inlet and the second pressure inlet. Such a pressure sensor is sometimes referred to as a differential pressure sensor.
By communicating the second end with the second pressure inlet, a differential pressure across the second end and the hydrostatic pressure is measured by the pressure sensor. This differential pressure is related to the pressure difference across the at least one flow restrictor, so that a relatively accurate pressure measurement can be obtained. Via the relatively accurate pressure reading, a relatively accurate level measurement and thereby a relatively accurate flow rate measurement can be obtained. Even more in particular, the second pressure inlet communicates to the external environment. In this way, the second pressure inlet is equalized to the pressure of the external environment.
Accordingly, the pressure at the second pressure inlet can be equalized easily to other components, by also communicating them to the external environment. This is especially useful if the second end also communicates to the external environment, so that the second end and the second pressure inlet are both equalized to the pressure of the external environment.
In yet another embodiment of the device according to the invention the at least one flow restrictor comprises a channel connecting the first end to the second end, through which channel liquid can flow.
The channel can provide an accurately predictable flow resistance, so that the predetermined relation can be modelled relatively accurately. Additionally or alternatively, the channel may make the flow restrictor relatively robust to for instance pressure vibrations in the at least one reservoir.
In particular, the channel has a cross sectional dimension, such as a diameter, and a length, wherein the cross sectional dimension is smaller than the length, wherein preferably at least 5 times as small, more preferably at least 10 times as small, most preferably at least 20 times as small. In this embodiment, the channel is longitudinal in shape, which aids in providing predictable flow resistance and/or resisting disturbances.
In yet another embodiment of the device according to the invention, the at least one flow restrictor connects to the at least one reservoir at a predetermined non-zero height above a lowest point of the at least one reservoir.
This embodiment the flow restrictor may be relatively resistant against clogging or at least partial obstruction by debris, by allowing the debris to settle at the bottom of the at least one reservoir.
Once settled, the debris may not or no longer clog or obstruct the flow restrictor. Throughout this application, height, lowest, bottom, top etc. are defined as directions during normal use. Alternatively, the directions may be defined with respect to the positions of the inlet and outlet, as the inlet is positioned higher than the outlet during use. In particular, the level sensor can be placed below the at least one flow restrictor and above a bottom of the at least one reservoir.
In this embodiment, the sensor may be able to measure the liquid level relatively accurately because it is placed above the bottom of the at least one reservoir, as influence by debris collecting at the bottom of the at least one reservoir may be avoided. Moreover, placing the level sensor below the at least one flow restrictor enables the level sensor to be disposed below a liquid level of 5 aliquid exiting through the at least one flow restrictor, so that the level sensor is completely submerged in said liquid. The level sensor may provide a more accurate level reading accordingly. In yet another embodiment of the device according to the invention, the at least one flow restrictor comprises two flow restrictors arranged at different heights as measured from the bottom of the at least one reservoir.
i0 By providing flow restrictors at different heights, the flow rate of liquid out of the at least one reservoir increases as the liquid level increases and reaches another flow restrictor. As an example, at a relatively low flow rate of liquid entering the at least one reservoir there will be a relatively low liquid level. At that low liquid level, liquid may exit the at least one reservoir via one flow restrictor. As the flow rate of liquid entering the at least one reservoir increases, the liquid level increases. As the liquid level increases it eventually reaches another flow restrictor, through which additional liquid can flow out of the at least one reservoir. Accordingly, the liquid flowing out of the at least one reservoir increases as liquid flow rate into the at least one reservoir increases, 50 that the device in this embodiment is suitable for relatively large flow rates as well as for relatively low flow rates.
In yet another embodiment of the device according to the invention, the at least one reservoir comprises multiple reservoirs, such as two, three or more reservoirs, arranged in parallel to each other, each being connected to the inlet, and each being connected to the outlet via at feast one respective flow restrictor.
By providing multiple reservoirs with respective flow restrictors, the device may be able to measure relatively large flows. Moreover, if the multiple reservoirs are arranged side by side, the device may have a relatively small height. Such a device is especially suitable for use ine.g. a greenhouse, as there is often limited height available for installation of such a device.
Obviously, each single reservoir may comprise multiple flow restrictors independently of the other reservoirs. The flow restrictors may optionally be arranged at different heights.
In yet another embodiment of the device according to the invention, the at least one reservoir comprising a resealable opening, preferably positioned at a or the bottom of the at least one reservoir.
Using the resealable opening, the at least one reservoir may be opened temporarily for maintenance. For instance, debris may be removed through the opening. It is especially advantageous if the opening is positioned at the bottom of the at least one reservoir, because debris is likely to collect there. The resealable opening may for instance be a screw cap.
In yet another embodiment of the device according to the invention, the device further comprises a filter between the inlet and the at least one reservoir. The filter may filter liquid flowing into the at least one reservoir, thereby reducing the amount of debris in the at least one reservoir. Debris may at least partially block the at least one flow restrictor, thereby changing the relation between the liquid level and the flow through the flow restrictor. Accordingly, the debris may make the flow rate measurement inaccurate or incorrect. Therefore, providing a filter aids in achieving accurate and/or correct measurement results. In yet another embodiment of the device according to the invention, the device further comprises a bypass which bypasses the flow restrictor, and thereby allows liquid flow from the inlet to the outlet in case the flow restrictor is blocked. In particular, the bypass may be an overflow for the at least one reservoir which leads to the outlet. The bypass ensures that even if the flow restrictor is blocked, liquid can be discharged via the device. The same is advantageous if the inflow rate is larger than the rate at which liquid can flow out of the device through the at least one flow restrictor. Accordingly, the device in this embodiment helps to avoid leaks and floods. The bypass may connect to the top of the at least one reservoir. In the case the device comprises multiple reservoirs, a second reservoir may connect to the inlet via the overflow of a first reservoir. Accordingly, when the flow of liquid is too large for a single reservoir with its respective at least one flow restrictor, the second reservoir is automatically filled as the first reservoir overflows. A chain of two, three or more reservoirs can in this way be made by connecting consecutive reservoirs to the overflow of preceding reservoirs. The invention also relates to a plant transpiration measurement device, comprising a device for measuring drainage flow rate of a plant growing substrate according to any one of claims 1 — 13, wherein the processing unit of said device is further configured to: - receive a plant weight value corresponding to a weight of one or more plants; - receive a substrate weight value corresponding to a weight of the plant growing substrate;
- receive an irrigation flow value corresponding to a flow rate of an irrigation supply to the plant growing substrate; and - determine, based on the plant weight value, the substrate weight value, the irrigation flow value and the value corresponding to the drainage flow rate of the plant growing substrate, a transpiration value corresponding to transpiration from one or more plants.
The transpiration rate of a plant is an indicator for plant status, because the transpiration rate of a plant is higher when its stomata are open and the plant is able to absorb carbon dioxide, which is essential for growing. Thus, the transpiration rate of a plant can be used to determine if its growing conditions are suitable or optimal.
Using the irrigation flow value and the measured drainage flow rate, the processing unit can determine how much fluid, e.g. water, is absorbed by a plant or a group of plants and the substrate together. Then, by using the weight value for the plant and the substrate, the processing unit can determine how much liquid has exited the plant via transpiration. Thus, the processing unit determines the transpiration value based on a mass balance of the system and the plant and/or group of plants.
The device for measuring the drainage flow rate may have any of the above described features, alone or in any suitable combination, and offer the corresponding advantages.
The invention also relates to a method of measuring a drainage flow rate of a plant growing substrate, the method comprising the steps, to be conducted in any suitable order, of: a) receiving liquid drained from the substrate; b) collecting the received liquid in a reservoir; c) allowing restricted flow from the at least one reservoir; d) measuring a liquid level in the at least one reservoir; and €) determining a value corresponding to the drainage flow rate of the plant growing substrate based on the measured liquid level. Via the restricted flow, a predetermined relation is made via the liquid level and the in and outflow rates of liquid into and from the at least one reservoir. Thus, by measuring the liquid level, the drainage flow of the plant growing substrate can be determined using the predetermined relation. The method may be performed by a device as described above, with any of the above described features, alone or in combination.
The invention will be further elucidated with reference to the appended drawings, in which: Figure 1 shows schematically a cross-sectional view of a device in an embodiment according to the invention; Figure 2 shows a side view of the device of figure 1; Figure 3 shows a detail of the flow restrictor of the device of figures 1 and 2 in cross- sectional view; Figure 4 shows using a flow chart the steps to be performed by a processing unit of a plant transpiration measurement device; Figure 5 shows using a flow chart an embodiment of the method according to the invention; Figure 6 shows schematically a cross-sectional view of a device in a second embodiment of the device according to the invention; and Figure 7 shows schematically a perspective view of a device in a third embodiment of the device according to the invention.
Inthe figures, like elements are referred to using like reference numerals. Like elements of different embodiments are referred to using like reference numerals increased by 100 (one hundred).
Figures | and 2 show a device 1 for measuring the drainage flow rate of plant growing substrate. The device has an inlet 2 and an outlet 3. Liquid drained from the plant growing substrate can be received in the inlet 2. Liquid can be discharged via the outlet 3. A reservoir 4 is connected to the inlet 2 for receiving liquid therefrom. The reservoir 4 has a resealable opening, in this example at its bottom 42. Specifically, the resealable opening can be sealed and opened using a screw cap 43. The device 1 further has a flow restrictor 3, which is shown in detail in figure 3, with a first end 51 and a second end 52. The first end is connected to the reservoir 4, and the second end is connected tothe outlet 3. Accordingly, liquid can be discharged from the reservoir 4 via the flow restrictor 5 to the outlet. In this example, the inlet 2 is connected to the reservoir 4 via a filter 8. The filter 8 filters liquid from the inlet 2, so that filtered liquid enters the reservoir 4. In this embodiment, as an example, the inlet 2, outlet 3 and reservoir 4 are constructed of tubes, such as PVC or metal tubes. The reservoir 4 in this example is a substantially upright or vertical tube, closed at its bottom 42.
The inlet 2 connects to the at least one reservoir 4 on an upper part thereof, in this example at the top of the reservoir 4.
As liquid enters the inlet 2, it is filtered by the filter 8 and then enters the reservoir 4. In the shown example, the flow restrictor 5 is placed a predetermined non-zero height above the bottom 42 of the reservoir 4. Accordingly, liquid in the reservoir 4 accumulates and a liquid level rises at least until it reaches the height of the flow restrictor 5. Then, since the flow restrictor 5 restricts the flow of liquid out of the reservoir 4, the liquid level may rise further. Due to the predetermined shape and size of the flow restrictor 5, the rate at which fluid exits through flow restrictor 5 depends on the pressure difference across the flow restrictor 3, i.e. the pressure difference between pressures at the first and second end 51, 52 respectively. The pressure difference is in part determined by the liquid level due to the hydrostatic pressure of the liquid. Thus, the outflow rate through the flow IO restrictor 5 is related to the liquid level. Therefore, via a predetermined relation, the liquid level is depended on the inflow of liquid via the inlet 2. The invention makes use of this principle by using a level sensor 6 to sense the liquid level in the at least one reservoir 4. The level sensor 6 is disposed below the flow restrictor 5 and above a bottom 42 of the reservoir 4. The sensor 6 has an output 61 for providing a signal corresponding to the liquid level. The device further comprises a processing unit 7 connected to the output 61 which receives the signal. The processing unit 7 is configured to determine a value corresponding to the drainage flow rate of the plant growing substrate based on the signal. To this end, the processing unit 7 makes us of the predetermined relation, for instance via a lookup table or a formula, both of which may be calibrated before use.
As can best be seen in figure 1, a tube having a widened portion 31 is connected to the outlet 3 and to the second end 52. The second end 52 is connected to the external environment via the tube with the widened portion 31. The device further has a bypass 9 which bypasses the flow restrictor 5. The bypass 9 is connected on one end 91 to the reservoir 4, in this example to its top, and on the other end 92 to the widened portion 31. Since the widened portion 31 has a larger cross section than the bypass 9, the reservoir 4 communicates with the external environment via the bypass 9. The second end 52 of the flow restrictor 5 thus communicates with the same external environment as the top of the reservoir 4, so that their pressure is substantially equalized. Hydrostatic pressure due to air in the environment is herein neglected. The shown level sensor 6 is a pressure sensor 6. The pressure sensor 6 comprises a first pressure inlet 62 communicated with the reservoir 4 to sense a hydrostatic pressure of liquid in the at least one reservoir. Further, the pressure sensor 6 has a second pressure inlet 63, which communicates to the external environment. The pressure 6 measures the difference in pressure between the two inlets 62, 63, i.e. the pressure between the external environment and the hydrostatic pressure of the liquid in the reservoir 4.
As can be seen best in figure 3, the flow restrictor 5 extends into the reservoir 4, so that its first end 51 is displaced away from an inner wall 41 of the reservoir 4. In this example, a T-junction is placed in the reservoir 4. The T-junction has an opening through which the flow restrictor 5 extends. The flow restrictor 5 has a cylindrical body 53 which seals against the T-junction of the reservoir 4. The flow restrictor 5 further has a channel 54 which connects the first end 51 to the second end 52. Liquid can flow from one end 51 to the other 52 through the channel 54. The channel 54 is longitudinal in shape. Preferably. the channel has a constant cross sectional shape, preferably a circular shape. As liquid flows through the channel 54, walls of the channel provide flow resistance to the liquid, which accounts for the restriction of flow. In the shown example, a length L of the channel 54 is about 20 times larger than its diameter d. Figure 4 shows how a plant measurement device determines a plant transpiration value. The plant measurement device comprises the device 1 of figure | — 3. The processing unit 7 thereof is further configured to, in a first step S1, receive a plant weight value corresponding to a weight of one or more plant, to in a second step S2, receive a substrate weight value corresponding to a weight of the plant growing substrate and to, in a third step S3, receive an irrigation flow value corresponding to a flow rate of an irrigation supply to the plant growing substrate. Finally, the processing unit is configured to, in a fourth step S4, determine, based on the plant weight value, the substrate weight value, the irrigation flow value and the value corresponding to the drainage flow rate of the plant growing substrate, a transpiration value corresponding to transpiration from one or more plants. The steps described in relation to figure 4 may be conducted in any suitable order. Figure 5 shows an embodiment of the method according to the invention, comprising step T1 of receiving liquid drained from the substrate, step T2 of collecting the received liquid in at least one reservoir, step T3 of allowing restricted flow [rom the at least one reservoir, step T4 of measuring a liquid level in the at least one reservoir and step T5 of determining a value corresponding to the drainage flow rate of the plant growing substrate based on the measured liquid level. Figure 6 shows a device 101 which is similar to the device 1 of figures 1 and 2. Accordingly, only the mutual differences are described herein. The device 101 includes a single reservoir 104 but has two flow restrictors 105-1, 105-2 connected thereto. The two flow restrictors 105-1, 105-2 connect to the reservoir at different heights, 1.e. at different distances from the bottom of the reservoir 104.
Both of the flow restrictors 105-1, 105-2 connect to the outlet 103. The flow restrictors 105-1, 105- 2 are thus connected in parallel to each other. The device may comprise more than one reservoir
104. Figure 7 shows a device 201 which is similar to the device 1 of figures 1 and 2. Accordingly, only the mutual differences are described herein. The device 201 includes three separate reservoirs 204-
il 1, 204-2, 204-3, The reservoirs 204-1, 204-2, 204-3 are each connected to the inlet 202 for receiving liquid therefrom. Each reservoir 204-1, 204-2, 204-3 has is corresponding flow restrictor 205-1, 205-2, 205-3 which connects the reservoir 204-1, 204-2, 204-3 to the outlet 203. The reservoirs 204-1, 204-2, 204-3 are thus connected in parallel to each other. Moreover, the reservoirs 204-1, 204-2, 204-3 are placed side by side, in this case at substantially the same height.
Accordingly, the total height of the device 201 is relatively small. As can be seen in figure 7, each flow restrictor 205-1, 205-2, 205-3 communicates to the environment via open tube section 232 to ensure equal pressure at the second end of each flow restrictor 205-1, 205-2, 205-3. Although the invention has been described hereabove with reference to a number of specific examples and embodiments, the invention is not limited thereto. Instead, the invention also covers the subject matter defined by the claims, which now follow.
Claims (17)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2024750A NL2024750B1 (en) | 2020-01-24 | 2020-01-24 | Device for measuring the drainage flow rate of a plant growing substrate, method for the same and plant transpiration measurement device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2024750A NL2024750B1 (en) | 2020-01-24 | 2020-01-24 | Device for measuring the drainage flow rate of a plant growing substrate, method for the same and plant transpiration measurement device |
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| Publication Number | Publication Date |
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| NL2024750B1 true NL2024750B1 (en) | 2021-09-09 |
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| Application Number | Title | Priority Date | Filing Date |
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| NL2024750A NL2024750B1 (en) | 2020-01-24 | 2020-01-24 | Device for measuring the drainage flow rate of a plant growing substrate, method for the same and plant transpiration measurement device |
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| NL (1) | NL2024750B1 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0299828A (en) * | 1988-10-06 | 1990-04-11 | Iseki & Co Ltd | Flow measuring device |
| CN2092089U (en) * | 1991-03-07 | 1992-01-01 | 机械电子工业部天津工程机械研究所 | Liquid flowmeter |
| KR20170114009A (en) * | 2016-03-31 | 2017-10-13 | (주) 이레아이에스 | Apparatus for managing nutriculture |
-
2020
- 2020-01-24 NL NL2024750A patent/NL2024750B1/en not_active IP Right Cessation
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0299828A (en) * | 1988-10-06 | 1990-04-11 | Iseki & Co Ltd | Flow measuring device |
| CN2092089U (en) * | 1991-03-07 | 1992-01-01 | 机械电子工业部天津工程机械研究所 | Liquid flowmeter |
| KR20170114009A (en) * | 2016-03-31 | 2017-10-13 | (주) 이레아이에스 | Apparatus for managing nutriculture |
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