|Publication number||USRE42386 E1|
|Application number||US 12/775,076|
|Publication date||May 24, 2011|
|Filing date||May 6, 2010|
|Priority date||Sep 30, 2003|
|Also published as||CA2475912A1, US7030768, US7369055, US20050068186, US20060176185|
|Publication number||12775076, 775076, US RE42386 E1, US RE42386E1, US-E1-RE42386, USRE42386 E1, USRE42386E1|
|Inventors||Andrew J. Wanie|
|Original Assignee||Wanie Andrew J|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (36), Referenced by (1), Classifications (11), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a Continuation-in-part of U.S. Ser. No. 10/675,641 filed on Sep. 30, 2003 now U.S. Pat. No. 7,030,768.
The present invention relates generally to water softener salt tanks, and more specifically to a system which continuously monitors the level of the salt contained within and activates an alarm when an unacceptably low level of salt is reached within the tank.
Water softeners are used to soften hard water prior to the water being utilized by an individual. The water softener includes a salt tank through which water and salt form a brine solution.
During operation of the water softener, the salt contained in the water softener salt tank is used up over time, such that the salt needs to be replenished in order to maintain the effectiveness of the water softener. However, due to the normal placement of water softeners within a home, i.e., often in a basement in the well pump room, and the opaque materials utilized to form the tanks in which the salt is contained, many times the salt in the water softener salt tank is unknowingly completely exhausted, such that it can no longer form a brine solution and that water used thereafter by an individual is “hard.”
Running out a brine tank of salt causes hard water to pass through the hot water heater causing build up of sediment in the tank, along with causing unwanted characteristics in the water such as hardness on the skin, and poor lathering and cleaning of soaps and detergents. Most users of water softeners have let their brine tanks run out of salt due to the poor visual signs of low salt in the tank, and due to the fact that the tanks are usually placed in a location that is infrequently seen or visited such as the basement or closet.
To remedy this problem, a number of different monitoring devices for water softener salt tanks have been developed. The majority of these mechanisms involve a number of interacting parts which, when the salt reaches a predetermined lower limit in the tank, operate to provide some type of indication to a user that the salt in the water softener tank needs to be replenished.
While the majority of these devices are generally effective in providing an indication to an individual when salt in a water softener tank needs to be replenished, the costs for assembly and/or maintenance of these prior art monitoring devices are often high due to the large number of interacting or interconnected components of the devices which do not hold up well under the harsh conditions formed by the salt water present in the water softener tank. The devices are also cumbersome to install for the average user.
Therefore, it is desirable to develop a monitoring system for a water softener salt tank that is not constructed from a large number of parts, and that is capable of accurately determining the amount of salt remaining in the water softener salt tank, and is more easily installed outside the harsh environment of the tank. It is also desirable to develop a monitoring system which can be adapted for use with a variety of water softener tanks without requiring significant modifications.
What is therefore needed is a system that is easily installed, preferably attaches to the outside of the tank without the need for the drilling of any holes, and is configured to conform to various shapes and sizes of the tank. What is needed is a system that preferably includes smart software that can be easily programmable. What also is needed is a system that has a remote alarm that can be placed up to 100 feet away from the salt tank and is preferably battery operated with many years of life. What is needed is a system that is rugged and reliable and is also low-cost and preferably has different sensitivity depending on variables within the home and the tank itself. What is needed is a system that is self-calibrating and/or can be calibrated by the user and can be adjusted on a trial and error basis.
While there have been many means developed to sense substances inside containers, this invention relates to sensing salt, water, brine, and the combinations of each along with the unique problems involved in sensing these substances inside the environment of the brine tank of a water softener. This invention also includes a device that is preferably on the outside of the brine tank without making any major modifications to the container, and with a means for sensing into the container preferably through the wall. This invention further includes an alert signaler located in a frequented area of the house so it will be noticed when it alarms.
According to one aspect of the present invention, a water softener salt tank monitoring system is provided in which the system includes a sensing unit capable of sensing the presence of the solution inside the container or brine tank through the use of means for sensing that includes capacitive elements. This capacitive sensing unit is connected to a monitoring device that processes the data from the sensing unit. The sensing unit and monitoring device are contained within a housing preferably adapted to be positioned on the exterior of the water softener salt tank. The system notifies a user of a low salt condition through an alarm that can be mounted on the brine tank or elsewhere in the home.
The system for monitoring can alternatively use another type of indirect means for sensing such as an inductance-based, infrared wave-based or electromagnetic wave-based system. The inductance-based system preferably utilizes an inductive coil to sense the presence of the solution inside the brine tank. The infrared wave-based system preferably emits an infrared wave or beam that is either reflected back by the solution or is sensed on the other side of the container by a receiver. The electromagnetic wave-based system emits low frequency radio waves that are reflected back to the sensing unit. The reflecting waves' intensity and return time are used to calculate a level of salt in the brine tank. Each of these sensing units is connected to a monitoring device that monitors the tank and actuates an alarm mechanism as needed.
According to another aspect of the present invention, the unit housing is attached to the outside of the brine tank through a variety of techniques. This includes the use of an adhesive, tabs having double sided tape, hook and loop fasteners (e.g., Velcro), tabs having a male and female connection and a rod fastened to the tank upon which the housing may be slid up and down.
According to still another aspect of the present invention, a capacitance-based monitoring system includes a computer comprised of a processor and memory, for example, on a chip. Software running on the processor tracks the variations in capacitance values and cycle times to aid in detecting the salt level. Other software permits various other aspects of the present invention. One such aspect includes the processor determining a proper threshold for setting an alarm point. Another aspect includes the processor operating without determining a threshold by analyzing high and low capacitance values. Still another aspect permits a user to vary the sensitivity setting of the detection mechanism. A further aspect measures capacitance high points, low points, and the time between them to enable the detection mechanism to go into a sleep mode, thereby increasing battery life. Yet another aspect tracks the time between high and low points to determine if the tank has a build-up of substance on the inside of the tank.
According to yet another aspect of the present invention, an induction-based detection mechanism is located in a housing that is mounted on a shaft fastened to the tank. The device housing slides up and down on the shaft until the inductance of the solution is sensed. The housing can then be fixed in place to monitor the substance in the tank.
According to another aspect of the present invention, an infrared-based monitoring system is used. An infrared wave or beam is generated that may be reflected back by the substance in the tank. If the level of the substance is below the infrared wave, the infrared wave is sensed by a sensing unit on the opposite side of the tank.
According to still another aspect of the invention, the monitoring device, detection mechanism and sensing unit are preferably housed in an airtight and watertight enclosure made of plastic material that is as close as possible in proximity to a container surface of regular or irregular shape. The enclosure is easily installed by a person of normal abilities in a cost effective and efficient way. The enclosure has the ability to conform to the irregular shapes through inventive flexible mounting pads. The pads can be permanently attached to the enclosure or permanently attached to the surface with the ability to remove and replace the enclosure on the surface for maintenance issues.
These, and other aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.
A clear conception of the advantages and features constituting the present invention, and of the construction and operation of typical mechanisms provided with the present invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings accompanying and forming a part of this specification, wherein like reference numerals designate the same elements in the several views, and in which:
In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word “connected,” “attached” or terms similar thereto are often used. They are not limited to direct connection or attachment but include connection or attachment through other elements where such is recognized as being equivalent by those skilled in the art.
The present invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments described in detail in the following description.
With reference now to the drawing figures,
Referring now to
Looking now at
The central member 56 is adaptable for use with containers 30 having various sizes due to the construction of the central member 56 from a number of modular segments 58. As best shown in
The recess 64 is shaped to be matingly engageable with the attachment 62, such that the recess 64 includes an inner tapered end 70, a cylindrical bore 71 and a peripheral notch 72 spaced from the tapered end 70. Consequently, when an attachment 62 on one body portion 60 is inserted into a recess 64 on an adjacent body portion 60, the respective body portions 60 are engaged with one another as best shown in
As one end of each segment 58 has a recess 64, in order to enable one of the lower member 52 or the upper member 54 to be secured to the central member 56, an end segment 78, best shown in
Referring now to
The housing 80 also includes a removable panel 91 having a pair of tabs 92 at one end and a biased lock 93 with a handle 93a at the opposite end. Tabs 92 are engageable with opposed ends of an opening 94 in the housing 80 to selectably expose the power source receptacle 84 in order to enable a replaceable power source, such as a battery (not shown), to be connected to the sensor 44 in any conventional manner and positioned and retained within the receptacle 84. The housing 80, base 82, and circuit plate 88 also each include a central aperture 94a, 94b and 94c, respectively, that are aligned with one another to form the opening 48 through which the central member 56 of the detection mechanism 46 extends. The aperture 94a in the housing 80 can also include a flexible skirt 95 extending into the aperture 94a around the central member 56 to prevent material from passing through the opening 48 and around the central member 56 into the tank 30. The skirt 95 may also act as a humidity seal.
In the embodiment shown, the power source within the receptacle 84 is connected via the circuit plate 88 to a limit switch 96 fixed to the circuit plate 88 and extending outwardly through a first slot 97 in the housing 80. The switch 96 includes a base 98 secured by prongs 99 to the circuit plate 88 and a biased arm 100 extending outwardly from the base 98 through the slot 97 and supporting a stop 101 opposite the base 98. The housing 80 also includes a second slot 102 that is spaced from the first slot 97 in which is disposed an operating switch 104 connected to the plate 88 and used to selectively change the operating mode of the sensor 44, i.e., to select light only (L), alarm only (A), or both (B), shown collectively as L, A, B positions. The housing 80 also preferably includes additional openings 105 for a reset button 106, an indicator lamp 108, and an audible alarm device 110 (e.g., a speaker) which are all connected to the plate 88 and allow the sensor 44 to provide visible and/or audible signals when a signal from the limit switch 96 is received by the sensor 44. Note: power is always on as long as a battery is installed, like a smoke alarm. However, the alarm may also sound when battery power is low.
More specifically, in operation, once an amount of salt 202 has been placed within the body 32 of the tank 30, the cover 40 and monitoring device 42 are positioned over the body 32. The lower member 52 of the detection mechanism 46 is positioned on the upper level 200 of the salt 202. As the water softening system operates, the upper level 200 of the salt 202 within the tank 30 is lowered, thereby allowing the lower member 52 and detection mechanism 46 to slide downwardly with respect to the sensor 44. When the upper salt level 200 has reached a predetermined lower limit based on the length of the central member 56, the detection mechanism 46 is positioned with respect to the tank 30 such that the upper member 54 contacts and depresses the stop 101 and the arm 100 of the limit switch 96. The depressing of the arm 100 sends a signal from the switch 97 to the plate 88 that serves to operate the sensor 44 to emit a visual signal using the indicator lamp 108 and/or an audible signal using the speaker 110 to alert an individual to the low level of salt present within the tank 30. As will be more fully described below, the alarm indicator may be located at a position closer to the individual's living area but remote from the location of the sensor and the softener, for example, in the basement.
Referring now to
However, the monitoring device 112 does not include a direct detection mechanism 46 as in the previous embodiment, but performs the monitoring function utilizing an indirect detection mechanism (not shown). The detection mechanism utilized by the device 112 is a mechanism that is constructed and functions similarly to that shown in Heger U.S. Pat. No. 6,023,159, which is herein incorporated by reference. Specifically, in this mechanism, the sensor 113 includes a means for sensing, e.g., a capacitor plate (not shown) and a ground plate (not shown) disposed on or adjacent the base 116 near the sidewall 36 of the tank 30. The plate senses the capacitance of the material within the tank 30 immediately adjacent the device 112 and compares this capacitance value to a reference value stored within the device 112. The reference value is a value corresponding to a condition where the upper level 200 of salt 202 within the tank or container 30 has reached a lower limit approximately just beneath the level of the device 112. The reference value is determined and stored in any suitable manner (e.g., on a computer chip) within the device 112 by positioning the device 112 against the tank 30 either prior to the addition of salt to the tank 30 or above the upper level 200 of the salt 202 within the tank 30 and sensing the capacitance of the tank 30 without any salt 202 adjacent the device 112 by depressing a calibrate button 136 disposed on the housing 114 in an opening 124e. The device 112 can also effectively monitor the upper level 200 of the salt 202 within the tank 30 at preselected intervals utilizing a timer (not shown) located within the device 112 and connected to the indirect detection mechanism to selectively operate the detection mechanism at the end of each interval measured by the timer.
When the device 112 determines the salt level in the tank 30, the capacitance of the material within the tank 30 is measured by the detection mechanism, and this actual capacitance value is compared with the calibration or reference value stored in the device 112. If the actual capacitance value is a predetermined percentage above the reference value, the device 112 can retest for the actual capacitance value to provide an assurance factor in the accuracy of actual value obtained by the device 112, and/or can initiate the timer to countdown another interval prior to a subsequent test. However, if the actual capacitance value determined is equal to or above the reference value, the device or indicator 112 can initiate an audible and/or visual alarm or alert utilizing the speaker 134 and lamp 132 on the housing 114.
For example, two formulas are instructive for illustrating at least this embodiment and method. The first formula is for calibrating the device 112 at the point it is attached with the substance at the point of attachment. In terms of determining the level of substance in a container, i.e., salt in the tank 30, one method preferably uses, e.g., software or a chip within the device 112 to look at the difference between a reference value and an actual value. The reference value is determined by the previously described calibration, at the point where the device is attached, with the tank filled, or at least with salt above the level at where the device is attached. That value is stored in the device. If the actual value is a predetermined percentage, (e.g. 10%) greater than the reference value, the device will notify the user of the low salt condition. Thus, the formula for this operation can be represented as follows:
Notify If: Actual Value>(Reference Value+(Reference Value×10%))
The second formula can be for calibrating the device 112 over an empty spot on the tank 30 or when the salt is below the level that the device is attached. The device can also be configured to be calibrated over an empty tank. In this method, if the actual value is less than a predetermined percentage, (e.g. 10%) greater than the reference value, the device will notify the user of the low salt condition. Thus, the formula for this operation can be represented as follows:
Notify If: Actual Value<(Reference Value+(Reference Value×10%))
In an alternative construction to the embodiment of the device 112 shown in
As shown in
With regard to each of the aforementioned embodiments of the invention, in addition to the incorporation of the lamps 108 and 132 and speakers 110 and 134 on the respective housings 80 and 114, the monitoring devices 42 and 112 can utilize a salt level indicator, e.g., a remote alarm 142, best shown in
Another embodiment of the inventive system 10 is shown in
Standard residential water softeners regenerate (i.e., use salt) on a repetitive schedule, the length of the cycle is dependent on the amount of water that is used in the residence. This interval varies in increments of days (longer or shorter depending on water use). The monitoring device 112 only needs to test for the absence of salt media at the level where the device 112 is attached at an interval that is less than or equal to twice the interval that it regenerates. Therefore, the unit has the capability through the use of programming or a switch (not shown) for the user to select the intervals that they want the device or unit to check for the absence of salt media. This setup dramatically increases the life of the battery that runs the sensor/sending unit 113. Based on the selection of interval, the monitoring device 112 tests for capacitance change, e.g., the absence of salt media at a certain level, using only the sensing unit 113 with the stored capacitance value discussed above. Alternatively, the monitoring device 112 may compare the capacitance level at the secondary sensing unit 138 to that at the primary sensing unit 113. If the device 112 detects the presence of salt media, it will perform multiple additional tests, and if the results are the same, the device 112 will not send an alert signal to the low salt indicator. If the device 112 detects the absence of salt media at the level at where it is attached, it will again perform multiple tests. If those test results are the same, the device will trigger an alert signal as described above.
The monitoring device 112 is capable of giving a warning, e.g., an audible alert (A) at the tank only, visual alert (L) at the tank only, both an audible and visual alert (B) at the tank, and or a combination of the same through a remote receiving unit 142. (See, e.g., instructional indicia L, A, B near switch 128 in
The audible warning or alert (A) at the monitoring device 112 or receiving unit 142 are heard through preferably a miniature speaker 152 or piazzo buzzer and the visual alert is done through preferably the use of light (L), e.g., LEDs. The alert type is selectable, e.g., by switch 128, by the user at the monitoring device 112 and the receiving unit 142. Not only does this allow the user to select options they may prefer, it also gives options for those that are hearing or seeing impaired. This option also gives the manufacturer the ability to sell a monitoring device 112 that only works at the brine tank or selling one that adds on as an option the remote receiving unit 142.
If the audible alert only type signal is chosen, the alert can be silenced by pressing and holding the reset button 156, on the receiving unit 142 and then button 130 on the monitoring device 112 (see, e.g.,
The monitoring device 112 is also capable of giving off a separate distinguishable audible and visual alert notifying the user of a low battery condition. In one embodiment, the device 112 will also transmit a separate signal to the receiving unit 142 to give off the same low battery alert. The alert may be cancelled by the same procedure as canceling the low salt alerts. If the condition is not corrected by replacing the battery, the unit will also preferably resend to the remote receiving unit 142 the “low battery” condition signal, at the same intervals that it tests for low salt conditions.
Referring now to
Different softener cycles contribute to unique problems in sensing with capacitance. The capacitive values may change dramatically during the different cycles due to factors other than the level of the salt decreasing. For example, when producing brine, the tank may contain solid salt or other solid material or media, brine solution, aqueous material like fresh water turning into brine, very little water or brine, salinic humidity, gases and salt build up that make it difficult to accurately and repeatedly sense the level of salt in the tank. The capacitive values can go up by simply removing the cover from the tank and releasing gases and/or humidity from the tank. The values can go up while salt or other media is added to the tank and then go down. This causes difficulties when trying to set calibration points for determining alarm thresholds for capacitive sensing devices or finding the proper time to catch the changes in capacitance. See, e.g., the initial increase after the calibration sequence was started as shown in
In one embodiment shown, the monitoring device 312 includes software 370 that determines the proper threshold 372 for setting the alarm point in dealing with the increasing and decreasing values of capacitance. The capacitive values are monitored during calibration and the software waits until the value peaks and/or goes down after the initial reading to prevent getting a false threshold. The threshold 372 can be a percentage increase over the calibration threshold determined via a calibration mechanism 373. This is done through the formula or software program shown below.
Another embodiment includes software 370 that permits a user to place the monitoring device 312 on the tank without the need to set a threshold 372 for the device 312. During the normal cycles of the water softener making, using and re-making brine, the capacitive values within the tank will go through peaks and valleys. The device 312 has software 370 on a chip or PC board 311 that makes use of this and either looks for peaks to be less than or equal to the previous peak during the brining cycle. One example of the steps taken by the software 370 is seen in the flowchart shown at
The software 370 could also be written to learn the differences between initial calibration values and peak values to optimize alarm points.
Another embodiment preferably includes software 370 to solve the problem of proper placement of the monitoring device 312 on the tank. The peaks and valleys of the capacitive values mentioned above are time and position dependant. If the device 312 is placed very low on the tank in the brine solution, the time between peaks and valley can be shorter and the percentage changes in capacitance can be smaller. If the device 312 is placed higher on the tank and/or out of the brine solution, the time between peaks and valleys can be longer and the capacitance changes can be larger. The problem is if the time between checks of capacitive values is too long, and or the percentage increase or decrease that is looked for in the software 370, the actual change in capacitance can be missed. This often causes the system to fail to alarm. This is solved by giving the user the use of a variable-sensitivity setting. This is done through the use of timers 371 preferably in the software 370, and with different values associated with percentage increases or decreases associated with each timer value. The user can choose from multiple sensitivities which in turn may change the amount of time between sensing episodes and or the amount of increase or decrease in capacitance relative to alarm threshold settings. This allows for increased life of the power source, e.g., battery 310, if lower sensitivity settings are chosen. It also allows for detecting smaller changes in capacitance on varying locations on the tank. An example of the sensitivities and the percentage increase or decrease is shown below:
Another embodiment includes software 370 that has the ability to measure the time between peaks and valleys of the capacitive values. This is useful in that it would allow the unit to learn and set the optimum time between sensing to increase battery life and to make the need to setting sensitivity unnecessary as the device will learn the proper interval. This would also allow for the monitoring device 312 to determine and average the preferred amount of time between regeneration cycles and also learn on average how often the container needs to be filled with salt or other media. Once the device 312 has this information, it can go into a sleep mode for longer periods of time, and decrease energy use. This can also be used as a secondary means of determining and/or tracking time between tank regenerations. The flowchart on
Another embodiment includes software 370 to notify the user of a “dirty” tank condition or failure of the softener to regenerate. In such instances, a “dirty” tank condition includes salt or other media buildup on the inside of the salt tank that may render the sensing unit 313 useless. In other instances, the water softener may stop working and/or not regenerate at the appropriate intervals. In using the software 370 mentioned above, one can set a maximum time that the system has to see at least one peak or valley change in capacitive values. If one is not seen during this period of time, the monitoring device 312 notifies the user via an alarm of a dirty tank condition and/or faulty water softener. It should be noted that the above software functions could be accomplished thru other means such as electrical circuitry and/or mechanical means.
These preferred embodiments are configured to be connected to an irregular surface such as a cylindrical water softener tank via container attachment means 330 as shown in
In the embodiment shown, tabs 322, 323 are mounted directly to the bottom housing piece 316 and in another embodiment not shown, they are removable. Tabs 322, 323 are offset from the bottom 317 of the enclosure 314 by the thickness of double side adhesive 362a, b to allow for the bottom enclosure piece 316 to contact the surface of the container. Mounting brackets 360, 361 are thin and flexible enough to conform to irregular shapes, while still allowing circuitry 311 within the enclosure 314 to maintain it natural shape, that being flat.
In an embodiment where the enclosure 314 is removable such as shown, a round male member or tab 323 is mounted on one end of the enclosure 314 and a rectangular protruding male member or tab 322 is mounted on the opposite end. The flexible mounting bracket 361 for the round tab 323 is designed to allow the round tab 323 to snap into a generally circular receiving female member or slot 321. The flexible mounting bracket 360 for the rectangular tab 322 is designed to allow the tab 322 to slide into a rectangular slot 320 in the flexible mounting bracket. The combination of the two tabs 322, 323 permits the easy removal and reattachment of the monitoring device 312 from the surface of the tank. Attaching the enclosure 314 requires sliding the rectangular tab 322 into the slot 320 of the corresponding flexible mounting bracket 360, and then snapping the round tab 323 into slot 321 of the corresponding bracket 361. The reverse sequence will remove the enclosure 314. When engaged, the rectangular shape of tab 322 and slot 320 prevent rotation of the enclosure 314 on the mounting surface. It is important to prevent any rotation of the enclosure 314 to ensure optimum and repeatable measurement by the monitoring device 312.
Another means of attaching the enclosure to an irregular surface is by the means of a hook and loop fastener (also known as Velcro). Indentations in the bottom 317 of the enclosure 314 are provided to compensate for the thickness of the combined hook and loop pieces (not shown) such that the housing or enclosure 314 is mounted flush with the surface. This allows for the enclosure 314 to be in close contact with the surface of the tank. The hook and loop pieces are preferably flexible enough to allow for connection to irregular surfaces.
Referring now to
Referring now to
In a final embodiment not shown, the monitoring system can utilize an emitter as disclosed in McEwan U.S. Pat. No. 5,512,834, which is herein incorporated by reference. Specifically, the beam source or emitter sends out waves of low frequency electromagnetic radiation (radio waves) into a tank, which bounce off of the salt within the tank for reflection back to a wave detector in a monitoring device. The angle of reflection of the waves to the device, and the duration of time for the waves to be emitted and reflected back to the device can be used by the detector to determine the amount of salt within the tank. If the amount or level is below a lower limit, the device can activate an audible or visible alarm, as described previously. The sensing unit can be positioned anywhere on the tank or cover, so long as the device is properly calibrated for the position it is in, in a known manner.
While the preferred embodiments and best modes of utilizing the present invention have been disclosed above, other variations are also possible. For example, instead of a water softener salt tank, the system 10 may include any type of storage container used to hold an amount of material within the container. Further, while the structural components of each device in the system 10 are preferably formed of a non-corrosive, sealable, insulating plastic material for use with water softeners, any other suitable rigid material, such as a metal, could be used. Also, while the calibration device and alarm are shown as being single units used with a single device, these items can be configured to transmit or receive signals to and from multiple units and devices in order to monitor several containers or tanks simultaneously.
Various alternatives are contemplated as being within the scope of the following claims which particularly point out and distinctly claim the subject matter regarded as the invention.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8869612||Oct 5, 2011||Oct 28, 2014||Baxter International Inc.||Non-invasive radio frequency liquid level and volume detection system using phase shift|
|U.S. Classification||340/618, 73/304.00C, 200/61.21, 340/612|
|International Classification||H01H35/00, G08B21/00, G01F23/26, G01F23/00, G01F23/60|