- Email: [email protected]
well-depth meter
Measurement 152 (2020) 107326
Contents lists available at ScienceDirect
Measurement journal homepage: www.elsevier.com/locate/measurement
Dual-function water-level/well-depth meter Mohamed Rashed Water Research Center, King Abdulaziz University, Jeddah 80200, Saudi Arabia
a r t i c l e
i n f o
Article history: Received 12 August 2019 Received in revised form 29 September 2019 Accepted 25 November 2019 Available online 27 November 2019 Keywords: Groundwater Water table Indicator Sounder Design
a b s t r a c t Depth to water table and depth to well bottom are crucial measurements for hydrological and hydrogeological investigations. Available water level meters, commonly called well sounders, measure only depth to water table. For depth to well bottom, hydrogeologists hustle to sense when the sounder tip touches the well bottom to get a rough estimation of the depth to well bottom. This introduces significant amount of error and is extremely hard to apply in deep wells. Some recently introduced sounders have a special probe for measuring well bottom depth. However, those sounders are tedious to use and lack the required durability because of the need to roll up the entire cable and to swap probes for every measurement. Water-Level/Well-Depth (WL/WD) meter is novel dual-function well sounder that is capable of measuring both water table level and depth to well bottom using a single probe easily and precisely. The sounder probe is designed in a way that allows sensing both water table and depth to well bottom efficiently. The reel, cable and electronic circuit are also modified in a way that allows for switching between water level and well bottom depth measurements with a push of a button. Field tests conducted on the new WL/WB meter clearly show its efficiency, precision and durability. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction Depth to water and total depth to well bottom are two of the most essential field measurements for hydrologists and hydrogeologists. Depth to water level is important to calculate water table for unconfined aquifers and piezometric head for confined ones. These are vital parameters for monitoring groundwater and estimating important parameters such as flow directions and rates, transmissivity, sources of groundwater recharge, and hydraulic conductivity of aquifers. Total depth to well bottom is important in conducting pumping tests and calculating water volume in aquifers. It is also important for groundwater management and calculating vital well parameters such as safe yield. Today, a large variety of commercial water level meters are available (Fig. 1). All these meters adopt the same operation principle. The water level meter consists of a stainless-steel probe attached to a graduated tape or cable (Fig. 2). The cable is winded around a reel that contains an electronic circuit inside its central housing and covered with a front switch panel. The terminals of the electronic circuit are a couple of switches, a lamp, a battery housing and a small speaker; attached to the front panel at one side of the reel (Fig. 2). The operation mechanism of these water level meters is quite simple. The probe is inserted into the well and lowered gradually until the probe touches the water surface,
E-mail address: [email protected] https://doi.org/10.1016/j.measurement.2019.107326 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved.
connecting the 2 ends of the probe. This closes the circuit causing the lamp to flash and the speaker to peep. The major problem with all available water level meters, however, is that they measure only the depth to water level. The depth to the well bottom is roughly conducted by sensing the weight of the meter’s probe as it touches the well bottom or through feeling the weight difference, by the operator, as the probe lies flat on the well bottom [1]. Because of tape buoyancy and weight effects encountered in deep wells with long water columns, it is very difficult to determine when the probe is touching the bottom of the well. Soft sediments in the bottom of some wells make such a task even harder to achieve. Accordingly, this mechanism induces significant errors in well bottom measurements and can be difficult and tricky [2]. Moreover, this method is impossible to apply when the total well depth is more than few tens of meters because of the increasing effect of the cable’s or tape’s weight. Some recent sounders are equipped with special mechanisms for measuring total well depth. One of these mechanisms is to have 2 different probes, one to measure depth to water and the other to measure the total well depth. These meters, however, require pulling up the entire cable or tape, clean and dry the used probe, switch probes, and then lower down the new probe to make the second measurement. Obviously, this is tedious and requires more time and effort to be spent in field. Moreover, switching the probes is a delicate process and would eventually lead to reducing the lifespan of the entire meter. Switching probes can damage either
2
M. Rashed / Measurement 152 (2020) 107326
well bottom. These meters, however, are proven inefficient for several reasons. First, the user has to bear with the annoying beeping sound while lowering the probe for the entire length of the water column. Second, the user has only one shot at detecting the total depth accurately while lowering the probe, which is almost impossible. Users usually tweak the cable up and down several times to reach an accurate measurement. Last but most important, practical use of this kind of probes indicates that the sealing process is not always accurate, which is a source of great frustration in field. This article presents full details of designing, manufacturing, and testing a new dual-function meter that measures both depth to water table and total well depth, using a single fixed probe. The article also discusses the advantages of the new meter over available water level meters.
2. Design and manufacture
Fig. 1. Examples of commercially available water level meters.
Fig. 2. Water level meter (Modified after [3].
the probe’s connection with the cable or the waterproofing of the probe itself. Other dual meters use different mechanism. These have a plastic cover attached to the tip of the probe, that collapses and seals the probe, cutting the beeping sound when it touches the
The general shape of the WL/WD meter is almost identical to those of common water level meters. Fig. 3 shows different view angels of the WL/WD meter. The graduated 3-wires insulated cable is winded around an ordinary cable reel, made of galvanized steel and has the appropriate size to host a 100 m-long cable. The electronic circuit is inserted in the central hole of the reel and the circular front panel is made of 2 layers of black and yellow 2 mmthick acrylic sheets. A simple mechanism to hold the probe in addition to reel break mechanism are installed on the back of the reel’s base (Fig. 3). The core innovation of the WL/WD meter, however, is solely based on the novel design of the probe. The probe itself is made of a 190 mm-long stainless-steel tube (Fig. 4). The inner diameter of the tube is 12 mm and the outer diameter is 14 mm, with a wall thickness of 1 mm. An oval shape hole that is 28 mm-long is drilled on opposite sides of the tube and at 21 mm from its lower edge. A black 1 mm copper wire is soldered to the inner wall of the tube about 10 mm from its upper end. A stainless-steel pin, whose length is 27 mm and diameter is 2 mm, is mounted along the vertical axis of the tube and with 14 mm of its length hanging in the middle of the oval hole (Fig. 4). A red wire is connected to this pin and isolated from surrounding using heat-shrink insulator. A copper disc that fits snuggly in the tube is mounted below the lower end of the oval hole. The height of the copper disc is 2 mm and it has a 1 mm hole near its periphery to allow a path of the blue wire. The blue wire is soldered to a 12 mm long hollow cylindrical copper tube whose length is 12 mm and inner diameter is 4 mm. This tube is mounted inline with the vertical axis of the probe tube. The copper tube is surrounded by the fiber head that is 20 mm long and its outer diameter is 12 mm to snugly fit inside the stainlesssteel probe. A cone shape is engraved in the upper end of the fiber head, while its lower end is threaded (Fig. 4). The upper section of the fiber head has a 1 mm hole to make way for the blue wire to the copper tube. The copper tube is snugged and glued in the central cylindrical hole drilled in the center of the fiber head. A 28 mm long copper rod is inserted in the copper tube and its diameter is adjusted so it moves smoothly inside the tube (Fig. 4). The lower end of the copper rode is rounded and the entire mechanism is covered by the waterproof rubber cap that is screwed on the fiber head. The area of the oval hole is covered and completely sealed using high quality adhesive epoxy. Above the oval hole, the entire tube is filled by a 100 mm cylindrical lead mass. This lead mass has a 1.5 mm vertical hole as a path for the red wire and another engraved to its periphery for the blue wire. A cone shape fiber cap is used to cover the upper end of the probe, with a 4 mm hole in its center for the meter’s cable. The upper and lower sections of the probe are covered with high-quality thick adhesive heat-shrink insulators (Fig. 4).
M. Rashed / Measurement 152 (2020) 107326
Fig. 3. Dual-function WL/WD meter (a) front view, (b) side view, and (c) back view.
Fig. 4. Structure of WL/WD probe (a) real photograph, (b) cross-section, and (c) parts shapes, dimensions, and specifications.
3
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M. Rashed / Measurement 152 (2020) 107326
The basic circuit of conventional groundwater level indicator is quite simple. The circuit is powered by a 9-volt battery connected in series to a buzzer and a LED. The circuit is open, and one end is connected to the outer body of the probe and the other end is connected to the pin in the hole inside the probe. When the probe touches the water inside a well, the circuit is closed allowing the current to flow igniting the audible and visual alarms. Additional resistors, capacitors and diodes are connected to the circuit for regulating and amplifying the signal. The sensitivity switch is a potentiometer that allows using the water level indicator for waters with different conductivities. These indicators also have an on/off switch that disconnects the battery from the circuit to prolong the battery life. The circuit of the dual WL/WD meter is similar to that of an ordinary water level indicator except for few modifications. In the modified circuit of the WL/WD meter, instead of the on/off switch, a 3-way switch is added to the circuit and mounted on the front panel of the meter. The common wire (black) is connected directly to the body of the probe (outer 14 mm stainless-steel tube). This wire is soldered to the inner wall of the tube. The negative power wire coming out of the circuit, is connected to the middle point of the 3-way switch. The 2 wires coming from the probe (red and blue), are connected to the other 2 ends of the 3-way switch. With this arrangement, when the switch is in the middle position, the device is off and no current passes to the circuit. When switch is in the left position, the open circuit is connected to the stainless pin in the middle of the oval hole. In this position, when the probe touches the water surface, it closes the circuit causes the buzzer to beep and the indicator lamb to light. When the switch is turned to the opposite position, the stainless pin is excluded from the circuit causing the sound to stop and the light to turn off. However, in this position, the open circuit is connected to the copper cylindrical tube near the tip of the probe and hence to the copper rod inside it. Consequently, when the rubber cap is pressed as the probe reaches the bottom of the well, it pushes the copper rod upward causing it to touch the copper disc above, that is connected to the body of the probe, causing the buzzer and the light to ignite. In conclusion, the same circuit of an ordinary water level indicator can be modified in a way that allows measuring both depth to water level and total well depth in a single measurement and using a fixed rugged probe. Fig. 5 shows the circuit diagram of the dual WL/WD meter, and the front panel. The new 3-way switch can be inserted in the preferable spot in the front panel. In this case, it is located near the right periphery of the panel and the 3 positions are indicated on the panel.
3. Tests and advantages The dual WL/WD meter was subjected to several tests and experiments in order to test its efficiency and durability. Several measurements of depth to water level and to well bottom were conducted in open wells and in cased wells. Even in open wells with soft sediments in the well bottom, the WL/WD meter provides easy and accurate measurements. The length and diameter of the central copper rod (part no. 2) are fine-tuned so that the rod moves smoothly, while always in contact, inside the copper cylinder (part no. 3) and the smallest touch of the rubber cap (part no. 1) closes the circuit of the meter. Precision in designing and manufacturing this section of the probe is the key for accurate and successful measurement of the depth to well bottom. In order to test the waterproofing of the probe and its durability, the probe was submersed in a water for 48 h with no signs of water leakage into the probe. Additionally, the probe was also
Fig. 5. Schematic sketch of the electric circuit (top) and the front panel (bottom) of the WL/WD meter.
submersed into a well at depth of 35 m below water surface for 30 min with no leakage. The major advantage of the dual WL/WD meter is its cost; it is almost equivalent to that of an ordinary water level indicator. The capability to take both measurements of the depth to water and total depth of well with no need to roll up the cable and to swap probes is another advantage. It reduces the time and effort spent to collect field data and prolongs the lifespan of the meter. Another advantage is the capability to modify ordinary water level indicators and convert them into dual function meters. With basic knowledge of electronics, the circuit of an ordinary water level meter can be easily modified for dual function. Manufacturing the probe itself may need a little effort, but it can be easily done using the detailed description and specifications explained in the previous section. The only disadvantage is that, for well total depth measurements, 4.5 cm must be to the graduated cable reading in order to compensate for the distance between the 2 sensors in the probe.
M. Rashed / Measurement 152 (2020) 107326
This, however, is negligible effort compared to the extra cost, time, and effort that have to be spent when using multi-probe indicators that appeared recently. 4. Conclusions Dual-function WL/WD meter is a new device that is capable of measuring both depth to water level and total depth of well, using a single fixed probe. The main advantage of the WL/WD meter is that it allows the user to measure both parameters in a single round. With the WL/WD meter, the user lowers the probe inside a well, measures the depth to water surface (WL), shifts the function switch to total well depth (WD), and continues lowering the probe to measure the total depth of the well bottom. This saves the time and effort required to pull up the entire cable length back to the surface, clean and dry the probe, and replace the probes. Moreover, it obviously increases and longevity and durability of the meter. It is common knowledge, among groundwater professionals, that rolling up and down the cable and switching probes are the 2 major factors of wear and tear to water level meters. Accordingly, the durability of the new WL/WD meter, is expected to be double that of ordinary water level meters. The WL/WD, with its dual-function capability in a single fixed probe, simplifies the measurement process, reduces the required time and effort needed to conduct both measurements, and lowers the size, weight and cost of the meter itself. The electric circuit schematic and probe design and dimensions of the dual-function WL/WD are explained in detail to allow
5
anyone, with basic engineering skills and with minimal manufacturing facilities, to replicate it. Finally, it is worth mentioning that the WL/WD meter costs less than half of the commercial price of some ordinary water level meters. This cost is expected to be even less in mass production of the WL/WD meter. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was supported by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, Saudi Arabia under grant no. (D-191-123-1440). The author, therefore, gratefully acknowledge the DSR technical and financial support. References [1] C. Taylor, W. Alley. Ground water level monitoring and the importance of longterm water level data collection. U.S. Geological Survey, Circular 1217, 2001. [2] B. Striggow. Operating procedures: Groundwater level and well depth measurements. US Environmental protection Agency, Science and Ecosystem Support Division, Athens, Georgia. No. SESDPROC-105-R2, 9p, 2013. [3] Solinst. Model 101 P7 Water Level Meter Operating Instructions. https:// www.solinst.com/products/level-measurement-devices/101-water-levelmeter/operating-instructions/101-water-level-meter.php. Last accessed: August 2nd, 2019, 2014.
Contents lists available at ScienceDirect
Measurement journal homepage: www.elsevier.com/locate/measurement
Dual-function water-level/well-depth meter Mohamed Rashed Water Research Center, King Abdulaziz University, Jeddah 80200, Saudi Arabia
a r t i c l e
i n f o
Article history: Received 12 August 2019 Received in revised form 29 September 2019 Accepted 25 November 2019 Available online 27 November 2019 Keywords: Groundwater Water table Indicator Sounder Design
a b s t r a c t Depth to water table and depth to well bottom are crucial measurements for hydrological and hydrogeological investigations. Available water level meters, commonly called well sounders, measure only depth to water table. For depth to well bottom, hydrogeologists hustle to sense when the sounder tip touches the well bottom to get a rough estimation of the depth to well bottom. This introduces significant amount of error and is extremely hard to apply in deep wells. Some recently introduced sounders have a special probe for measuring well bottom depth. However, those sounders are tedious to use and lack the required durability because of the need to roll up the entire cable and to swap probes for every measurement. Water-Level/Well-Depth (WL/WD) meter is novel dual-function well sounder that is capable of measuring both water table level and depth to well bottom using a single probe easily and precisely. The sounder probe is designed in a way that allows sensing both water table and depth to well bottom efficiently. The reel, cable and electronic circuit are also modified in a way that allows for switching between water level and well bottom depth measurements with a push of a button. Field tests conducted on the new WL/WB meter clearly show its efficiency, precision and durability. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction Depth to water and total depth to well bottom are two of the most essential field measurements for hydrologists and hydrogeologists. Depth to water level is important to calculate water table for unconfined aquifers and piezometric head for confined ones. These are vital parameters for monitoring groundwater and estimating important parameters such as flow directions and rates, transmissivity, sources of groundwater recharge, and hydraulic conductivity of aquifers. Total depth to well bottom is important in conducting pumping tests and calculating water volume in aquifers. It is also important for groundwater management and calculating vital well parameters such as safe yield. Today, a large variety of commercial water level meters are available (Fig. 1). All these meters adopt the same operation principle. The water level meter consists of a stainless-steel probe attached to a graduated tape or cable (Fig. 2). The cable is winded around a reel that contains an electronic circuit inside its central housing and covered with a front switch panel. The terminals of the electronic circuit are a couple of switches, a lamp, a battery housing and a small speaker; attached to the front panel at one side of the reel (Fig. 2). The operation mechanism of these water level meters is quite simple. The probe is inserted into the well and lowered gradually until the probe touches the water surface,
E-mail address: [email protected] https://doi.org/10.1016/j.measurement.2019.107326 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved.
connecting the 2 ends of the probe. This closes the circuit causing the lamp to flash and the speaker to peep. The major problem with all available water level meters, however, is that they measure only the depth to water level. The depth to the well bottom is roughly conducted by sensing the weight of the meter’s probe as it touches the well bottom or through feeling the weight difference, by the operator, as the probe lies flat on the well bottom [1]. Because of tape buoyancy and weight effects encountered in deep wells with long water columns, it is very difficult to determine when the probe is touching the bottom of the well. Soft sediments in the bottom of some wells make such a task even harder to achieve. Accordingly, this mechanism induces significant errors in well bottom measurements and can be difficult and tricky [2]. Moreover, this method is impossible to apply when the total well depth is more than few tens of meters because of the increasing effect of the cable’s or tape’s weight. Some recent sounders are equipped with special mechanisms for measuring total well depth. One of these mechanisms is to have 2 different probes, one to measure depth to water and the other to measure the total well depth. These meters, however, require pulling up the entire cable or tape, clean and dry the used probe, switch probes, and then lower down the new probe to make the second measurement. Obviously, this is tedious and requires more time and effort to be spent in field. Moreover, switching the probes is a delicate process and would eventually lead to reducing the lifespan of the entire meter. Switching probes can damage either
2
M. Rashed / Measurement 152 (2020) 107326
well bottom. These meters, however, are proven inefficient for several reasons. First, the user has to bear with the annoying beeping sound while lowering the probe for the entire length of the water column. Second, the user has only one shot at detecting the total depth accurately while lowering the probe, which is almost impossible. Users usually tweak the cable up and down several times to reach an accurate measurement. Last but most important, practical use of this kind of probes indicates that the sealing process is not always accurate, which is a source of great frustration in field. This article presents full details of designing, manufacturing, and testing a new dual-function meter that measures both depth to water table and total well depth, using a single fixed probe. The article also discusses the advantages of the new meter over available water level meters.
2. Design and manufacture
Fig. 1. Examples of commercially available water level meters.
Fig. 2. Water level meter (Modified after [3].
the probe’s connection with the cable or the waterproofing of the probe itself. Other dual meters use different mechanism. These have a plastic cover attached to the tip of the probe, that collapses and seals the probe, cutting the beeping sound when it touches the
The general shape of the WL/WD meter is almost identical to those of common water level meters. Fig. 3 shows different view angels of the WL/WD meter. The graduated 3-wires insulated cable is winded around an ordinary cable reel, made of galvanized steel and has the appropriate size to host a 100 m-long cable. The electronic circuit is inserted in the central hole of the reel and the circular front panel is made of 2 layers of black and yellow 2 mmthick acrylic sheets. A simple mechanism to hold the probe in addition to reel break mechanism are installed on the back of the reel’s base (Fig. 3). The core innovation of the WL/WD meter, however, is solely based on the novel design of the probe. The probe itself is made of a 190 mm-long stainless-steel tube (Fig. 4). The inner diameter of the tube is 12 mm and the outer diameter is 14 mm, with a wall thickness of 1 mm. An oval shape hole that is 28 mm-long is drilled on opposite sides of the tube and at 21 mm from its lower edge. A black 1 mm copper wire is soldered to the inner wall of the tube about 10 mm from its upper end. A stainless-steel pin, whose length is 27 mm and diameter is 2 mm, is mounted along the vertical axis of the tube and with 14 mm of its length hanging in the middle of the oval hole (Fig. 4). A red wire is connected to this pin and isolated from surrounding using heat-shrink insulator. A copper disc that fits snuggly in the tube is mounted below the lower end of the oval hole. The height of the copper disc is 2 mm and it has a 1 mm hole near its periphery to allow a path of the blue wire. The blue wire is soldered to a 12 mm long hollow cylindrical copper tube whose length is 12 mm and inner diameter is 4 mm. This tube is mounted inline with the vertical axis of the probe tube. The copper tube is surrounded by the fiber head that is 20 mm long and its outer diameter is 12 mm to snugly fit inside the stainlesssteel probe. A cone shape is engraved in the upper end of the fiber head, while its lower end is threaded (Fig. 4). The upper section of the fiber head has a 1 mm hole to make way for the blue wire to the copper tube. The copper tube is snugged and glued in the central cylindrical hole drilled in the center of the fiber head. A 28 mm long copper rod is inserted in the copper tube and its diameter is adjusted so it moves smoothly inside the tube (Fig. 4). The lower end of the copper rode is rounded and the entire mechanism is covered by the waterproof rubber cap that is screwed on the fiber head. The area of the oval hole is covered and completely sealed using high quality adhesive epoxy. Above the oval hole, the entire tube is filled by a 100 mm cylindrical lead mass. This lead mass has a 1.5 mm vertical hole as a path for the red wire and another engraved to its periphery for the blue wire. A cone shape fiber cap is used to cover the upper end of the probe, with a 4 mm hole in its center for the meter’s cable. The upper and lower sections of the probe are covered with high-quality thick adhesive heat-shrink insulators (Fig. 4).
M. Rashed / Measurement 152 (2020) 107326
Fig. 3. Dual-function WL/WD meter (a) front view, (b) side view, and (c) back view.
Fig. 4. Structure of WL/WD probe (a) real photograph, (b) cross-section, and (c) parts shapes, dimensions, and specifications.
3
4
M. Rashed / Measurement 152 (2020) 107326
The basic circuit of conventional groundwater level indicator is quite simple. The circuit is powered by a 9-volt battery connected in series to a buzzer and a LED. The circuit is open, and one end is connected to the outer body of the probe and the other end is connected to the pin in the hole inside the probe. When the probe touches the water inside a well, the circuit is closed allowing the current to flow igniting the audible and visual alarms. Additional resistors, capacitors and diodes are connected to the circuit for regulating and amplifying the signal. The sensitivity switch is a potentiometer that allows using the water level indicator for waters with different conductivities. These indicators also have an on/off switch that disconnects the battery from the circuit to prolong the battery life. The circuit of the dual WL/WD meter is similar to that of an ordinary water level indicator except for few modifications. In the modified circuit of the WL/WD meter, instead of the on/off switch, a 3-way switch is added to the circuit and mounted on the front panel of the meter. The common wire (black) is connected directly to the body of the probe (outer 14 mm stainless-steel tube). This wire is soldered to the inner wall of the tube. The negative power wire coming out of the circuit, is connected to the middle point of the 3-way switch. The 2 wires coming from the probe (red and blue), are connected to the other 2 ends of the 3-way switch. With this arrangement, when the switch is in the middle position, the device is off and no current passes to the circuit. When switch is in the left position, the open circuit is connected to the stainless pin in the middle of the oval hole. In this position, when the probe touches the water surface, it closes the circuit causes the buzzer to beep and the indicator lamb to light. When the switch is turned to the opposite position, the stainless pin is excluded from the circuit causing the sound to stop and the light to turn off. However, in this position, the open circuit is connected to the copper cylindrical tube near the tip of the probe and hence to the copper rod inside it. Consequently, when the rubber cap is pressed as the probe reaches the bottom of the well, it pushes the copper rod upward causing it to touch the copper disc above, that is connected to the body of the probe, causing the buzzer and the light to ignite. In conclusion, the same circuit of an ordinary water level indicator can be modified in a way that allows measuring both depth to water level and total well depth in a single measurement and using a fixed rugged probe. Fig. 5 shows the circuit diagram of the dual WL/WD meter, and the front panel. The new 3-way switch can be inserted in the preferable spot in the front panel. In this case, it is located near the right periphery of the panel and the 3 positions are indicated on the panel.
3. Tests and advantages The dual WL/WD meter was subjected to several tests and experiments in order to test its efficiency and durability. Several measurements of depth to water level and to well bottom were conducted in open wells and in cased wells. Even in open wells with soft sediments in the well bottom, the WL/WD meter provides easy and accurate measurements. The length and diameter of the central copper rod (part no. 2) are fine-tuned so that the rod moves smoothly, while always in contact, inside the copper cylinder (part no. 3) and the smallest touch of the rubber cap (part no. 1) closes the circuit of the meter. Precision in designing and manufacturing this section of the probe is the key for accurate and successful measurement of the depth to well bottom. In order to test the waterproofing of the probe and its durability, the probe was submersed in a water for 48 h with no signs of water leakage into the probe. Additionally, the probe was also
Fig. 5. Schematic sketch of the electric circuit (top) and the front panel (bottom) of the WL/WD meter.
submersed into a well at depth of 35 m below water surface for 30 min with no leakage. The major advantage of the dual WL/WD meter is its cost; it is almost equivalent to that of an ordinary water level indicator. The capability to take both measurements of the depth to water and total depth of well with no need to roll up the cable and to swap probes is another advantage. It reduces the time and effort spent to collect field data and prolongs the lifespan of the meter. Another advantage is the capability to modify ordinary water level indicators and convert them into dual function meters. With basic knowledge of electronics, the circuit of an ordinary water level meter can be easily modified for dual function. Manufacturing the probe itself may need a little effort, but it can be easily done using the detailed description and specifications explained in the previous section. The only disadvantage is that, for well total depth measurements, 4.5 cm must be to the graduated cable reading in order to compensate for the distance between the 2 sensors in the probe.
M. Rashed / Measurement 152 (2020) 107326
This, however, is negligible effort compared to the extra cost, time, and effort that have to be spent when using multi-probe indicators that appeared recently. 4. Conclusions Dual-function WL/WD meter is a new device that is capable of measuring both depth to water level and total depth of well, using a single fixed probe. The main advantage of the WL/WD meter is that it allows the user to measure both parameters in a single round. With the WL/WD meter, the user lowers the probe inside a well, measures the depth to water surface (WL), shifts the function switch to total well depth (WD), and continues lowering the probe to measure the total depth of the well bottom. This saves the time and effort required to pull up the entire cable length back to the surface, clean and dry the probe, and replace the probes. Moreover, it obviously increases and longevity and durability of the meter. It is common knowledge, among groundwater professionals, that rolling up and down the cable and switching probes are the 2 major factors of wear and tear to water level meters. Accordingly, the durability of the new WL/WD meter, is expected to be double that of ordinary water level meters. The WL/WD, with its dual-function capability in a single fixed probe, simplifies the measurement process, reduces the required time and effort needed to conduct both measurements, and lowers the size, weight and cost of the meter itself. The electric circuit schematic and probe design and dimensions of the dual-function WL/WD are explained in detail to allow
5
anyone, with basic engineering skills and with minimal manufacturing facilities, to replicate it. Finally, it is worth mentioning that the WL/WD meter costs less than half of the commercial price of some ordinary water level meters. This cost is expected to be even less in mass production of the WL/WD meter. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was supported by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, Saudi Arabia under grant no. (D-191-123-1440). The author, therefore, gratefully acknowledge the DSR technical and financial support. References [1] C. Taylor, W. Alley. Ground water level monitoring and the importance of longterm water level data collection. U.S. Geological Survey, Circular 1217, 2001. [2] B. Striggow. Operating procedures: Groundwater level and well depth measurements. US Environmental protection Agency, Science and Ecosystem Support Division, Athens, Georgia. No. SESDPROC-105-R2, 9p, 2013. [3] Solinst. Model 101 P7 Water Level Meter Operating Instructions. https:// www.solinst.com/products/level-measurement-devices/101-water-levelmeter/operating-instructions/101-water-level-meter.php. Last accessed: August 2nd, 2019, 2014.