Abstract:
A well water level sensing apparatus using a pressurized air column in contact with the water at its distal end to derive a correlated value dependent upon the length of the air column which is converted for retrieving stored water levels from memory and displaying the retrieved water levels on a visual display. The water level sensing apparatus may be manually initiated or programmatically controlled for continual monitoring.

Description:
CROSS-REFERENCE TO DISCLOSURE DOCUMENT 
     This application references Disclosure Document No. 478,776 filed Aug. 21, 2000. 
     BACKGROUND OF THE INVENTION 
     The invention generally resides in the field of instruments for measuring and displaying the level of a liquid in a containment vessel or a drilled well. A unique sensor system is employed to monitor, obtain depth (height) of the liquid (water) and transmit for display the determined depth (height) information to the user. 
     Over years varying types of instrumentation have been used to gauge the water level and available pressure in drilled wells so as to be able to determine water flow rate and capacity. The present invention enables the instrumentation and the apparatus needed to make such measurements. 
     Earlier devices for measuring water flow rate and well capacity were complicated and cumbersome to install and to maintain. One such device is that described in U. S. Pat. No. 5,105,662 [Marsh, et al.] which is suited for measuring the liquid level in a fixed dimension containment vessel, i.e. a fuel tank. Marsh, et al. discloses a system for measuring the level of a liquid material by direct pressure of the subject liquid against a pressure sensor balanced against a reference pressure in an air column. The reference pressure is based upon the static air pressure in the containment vessel holding the liquid as registered by the compression of the air column. 
     A second patent, U. S. Pat. No. 5,207,251 [Cooks], describes an automatic fill control for a liquid holding tank which uses a pressurized sensor to determine both flow rate and liquid level height. This is accomplished utilizing a gas bubble (column) as the correlating measurement device. Cooks describes a gas column as containing Nitrogen (N 2 ) which uses the gravimetric pressure of the liquid whose height (depth) is to be measured by being exerted against a second (pressure conducting) fluid. The second fluid, in turn, exerts pressure against a sensor. In this manner the primary pressure conducting fluid has its level of compression controlled by the pressure exerted against it by the fluid in the containment vessel which is used as a threshold for controlling a dispensing valve to add fluid to the vessel. 
     Finally, U. S. Pat. No. 5,901,603 [Fiedler] describes a hydrostatic pressure sensing device for measuring the height (depth) of a liquid in a containment vessel. The particular apparatus utilized comprises a pump for supplying pressurized air to a supply tank which is maintained at a 1.5 psi differential above the detected liquid pressure. Exiting the supply tank is an air supply line which is applied to one side of the hydrostatic pressure sensor. A temperature compensated solid state pressure transducer bleeds off or increases pressure by way of a manifold to maintain the appropriate pressure in the air supply. The reference side of the pressure sensor vents to the outside (ambient) air. The pressurized air supply line and the air reference ports are tied together through the manifold, also referred to as a drift compensation valve, so that the differential pressure transducer prevent drift by automatic correction and correlation of the pressures between the ambient (outside) air and the pressurized air column in the air supply line as applied to the pressure sensor which is submerged below the fluid level in the containment vessel. 
     In all of the foregoing devices, the complexity of the balancing of reference pressures against the variant pressures of the contained liquid require intermediate elements to counteract or to convey the pressure in order to obtain accurate results. The present invention creates a unique and simple series of elements for accurately determining the height of the water level in a drilled well and to instantaneously display, or continually record, that level for immediate of later use by the water user. 
     It is an object of the present invention to provide a simple system for measuring well water depth (height) utilizing a control circuit for determining the depth of the water by measuring the pressure of the water in a selectably dimensioned column and display such result instantaneously to the user. 
     It is also an object of the present invention to have the capacity to measure more than one well water level and to provide output control signals for communication with multi-purpose computers or to water flow rate controllers to regulate flow against demand. 
     It is a further object of the present invention to provide useful information to the display in the form of water flow rate (usage) in gallons, liters or feet per time segment, and to provide this information on a single inquiry or continuing inquiry basis. 
     It is a still further object of the present invention to provide a programmatically controlled water level measurement device which is capable of communicating with other computing devices as well as controlling and monitoring a plurality of measurements of for each of a plurality of wells. 
     Other objects will appear hereinafter. 
     SUMMARY OF THE INVENTION 
     A well water level sensing apparatus using a pressurized air column in contact with the water at its distal end to derive a correlated value dependent upon the length of the air column which is converted for retrieving stored water levels from memory and displaying the retrieved water levels on a visual display. The water level sensing apparatus may be manually initiated or programmatically controlled for continual monitoring. 
     The program control can be described as follows. Measuring the level of water in a well utilizing pressurized air comprises the steps of initializing a means for controlling the sensing and monitoring of the water level measurement which first reduces pressure in an air column inserted into a well to existing ambient pressure by closing a first valving means located between a pressure sensor and the air column to exhaust and isolate the air column. A second valving means located between a pump and an air tank of substantially equal volume as the air column is opened and the pump to charge the air tank to a predetermined measurement pressure is started. The second valving means is closed to isolate the air tank as the measurement pressure is detected by the pressure sensor. The first valving means is opened equalizing the measurement pressure between the air tank and the air column to obtain a direct pressure of the well water against the distal end of the air column. The pressure of the well water exerted against the air column is detected by the pressure sensor and the water level is calculated from the resultant sensed pressure. The calculated water level is then displayed on a visual display for viewing by a user. This method may further comprise continually sensing and monitoring the pressure of the well water exerted against the air column by repeating the sequence at preset periodic times. 
     The means for controlling the sensing and monitoring of the water level measurement may include a programmable computing device for controlling the sequence for measuring the well water depth using pressurized air. The controller may receive instructions over a communications channel from a multi-purpose computer to perform the well water depth measurements and providing well water depth measurements to said computer over said communications channel. The method may also include selectively sensing and monitoring the well water depth of a plurality of wells by repeating the measurement sequence for each well water depth measurement for each one of the plurality of wells. 
     The measurement may be accomplished by a number of elements for measuring well water depth using pressurized air which include a means for controlling the sensing and monitoring of water level measurements subject to program control for sequencing the order of operation of a first and a second valving means, an air tank, an air column, a pressure sensor, and a visual display. The first valving means is operatively connected between the pressure sensor and the air column, having its distal end inserted into a well, to reduce pressure in the air column to existing ambient pressure by exhausting said air and isolating the air column. The second valving means is operatively connected to a pump and an air tank of substantially equal volume as the air column, and to the pressure sensor, to couple the air tank to the air column upon the sensing of a predetermined measurement pressure being detected in the air tank by the pressure sensor. The pump is capable of charging the air tank to the predetermined measurement pressure. As above, the pressure sensor is capable of directly sensing the pressure of the well water exerted against the distal end of the air column, following the equalizing of the predetermined measurement pressure between the air tank and the air column, and to provide the sensed pressure to the controller for calculating the water level in the well from the sensed pressure. The controller will then display the calculated water level on the visual display. 
     The apparatus may be programmed for the controller to continually sense and monitor the pressure of the well water exerted against the distal end air column by repeating the sequence of operation at preset periodic times. The controller may also receive instructions over a communications channel from a multi-purpose computer to perform the well water depth measurements and provide well water depth measurements to said computer over said communications channel. The controller may also selectively sense and monitor the well water depth of a plurality of wells by repeating the sequence of operation for each well water depth measurement for each one of the plurality of wells. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For the purpose of illustrating the invention, there is shown in the drawings forms which are presently preferred; it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
     FIG. 1 is a schematic diagram of the well water level measuring apparatus of the present invention. 
     FIG. 2 is a block diagram of the various components housed within or connected to the well water level measuring apparatus of the present invention. 
     FIG. 3 is a diagrammatic scheme of the control program for the well water level measuring apparatus of the present invention. 
     FIGS. 4A, B and C is a diagrammatic chart of the overall program control of the well water level measuring apparatus of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description is of the best presently contemplated mode of carrying out the invention. The description is not intended in a limiting sense, and is made solely for the purpose of illustrating the general principles of the invention. The various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings. 
     Referring now to the drawings in detail, where like numerals refer to like parts or elements, there is shown in FIG. 1 the well water measuring apparatus  10  of the present invention. The measuring apparatus  10  is comprised of a number of interrelated elements which can be described as follows. The heart of the measuring apparatus  10  is the controller  12  which monitors peripheral apparatus status, sends commands and information, and receives information for use in calculation and display. The controller establishes a reference pressure in the air tank  14  by sending a command signal to the pump  16  through line  16   a  to turn the pump  16  on to increase the air pressure in air tank  14  and off when the required pressure is present in the air tank. The air tank  14  is pressurized by turning on pump  16  and allowing air to flow through the valve  18  which is opened and monitored by the controller  12  through lines  18   a, b.  Valve  18  allows air from pump  16  to flow through the interconnecting piping system to the air tank  14 . The air pressure is variable depending upon the depth of the well which will be described more fully hereinafter. 
     When the air tank  14  is being pressurized, the valve  20  is closed so as to separate the air column  22  (to the well) from the remainder of the piping system. The valve  20  is closed and monitored by the controller  12  through lines  20   a, b.  Valve  20 , in its closed position, prohibits air flow into and down the well water air column tube  22  so that the air tank  14  can be pressurized to the desired pressure. A pressure transducer  24  is located proximate to the controller  12  so that the pressure in the piping system can be monitored at all times, or as necessary. Thus, with valve  20  closed and valve  18  open, the air tank  14  can be pressurized to the desired pressure by engaging pump  16 . The pressure transducer  24  senses the increase in pressure and as the desired pressure is achieved the controller  12 , which monitors the pressure transducer  24 , turns off the pump  16  in response to the desired pressure being achieved. 
     The pressure to which the air tank  14  is charged varies directly according to the approximate depth of the well. For wells up to 200 feet in depth the pressure is set at 4 psi. For wells having depths greater than 200 feet but not greater than 400 feet the pressure is set at 8 psi. For wells having a depth greater than 400 feet but not greater than 600 feet the pressure is set at 12 psi. And for wells having a depth greater than 600 feet but not greater than 800 feet the pressure is set at 16 psi. The ratio of pressure to volume will remain substantially the same as well depth increases. The measurement pressure is derived from the volume of the air column  22  which is increased in length, but not diameter, for each greater depth well. Additionally, the air tank  14  is required to have the same volume as the air column  22  which will be explained in greater detail below in connection with the method of operation of the apparatus. 
     When the desired measurement pressure in the air tank  14  is achieved, the controller  12 , having already disengaged the pump  16 , closes valve  18  to isolate the pump  16  from the remainder of the piping system. Once this is accomplished, the well water level measurement can begin. 
     To initiate the well water level measurement, a start switch  26 , indicated as a push button switch in FIG. 1, is engaged which begins a series of steps in the controller  12 . These steps will be described in greater detail below, but for an overview, the valve  20  is opened allowing the pressurized air in the air tank  14  to flow into the tubing  22  to its distal end located near the bottom of the well creating a dynamic pressure within the tubing or air column  22 . Since the tubing or air column  22  has been positioned within the well to a known depth (height), the compression of the pressurized air in the air column  22  against the transducer  24  provides a pressure differential which can be utilized to calculate the height or level of the water within the well. Once calculated the height or level of the water in the well is displayed in analog fashion as shown in FIG. 1 by the depth meter  28 , or by any other means of display, e.g. digital display. When the sensing of the water level is completed and no additional monitoring is requested, an exhaust line  30  in valve  20  is utilized to return the air pressure in the piping system to ambient levels. 
     With reference to FIG. 2, there is shown a number of elements which are housed in, or connected to the controller  12 . The central element of the controller  12  is a microprocessor which is programmed to perform the required functions of the water level measurement to be described more fully below. The microprocessor receives a measurement initiation signal from either the push button switch  26  or from a remote control through the remote control port. The remote control initialization signal mat originate with a multi-purpose computer over a communications channel, i.e. the RS232 port. 
     The measurement initiation signal begins the pressurization process of opening and closing valves  18  and  20 , respectively, and engaging the pump  16 . As the pressure is increasing, such pressure increase is monitored by the controller  12  through the pressure sensor  24  by the sensor differential amplifier. The output of the sensor differential amplifier is applied to a span scale and offset amplifier which scales the value received from the sensor  24  and which is processed into a digital value in the analog-to-digital converter and received by the microprocessor on one of its data inputs. When the desired pressure is sensed, the microprocessor begins to instruct the valves and pump in accordance with stored instructions. Pump  16  is disengaged, valve  18  is closed and valve  20  is opened to initiate the water level sensing through the air column  22  applied against the pressure transducing sensor  24 . 
     With the desired pressure in the air column  22 , the pressure transducing sensor  24  is displaced a distance proportionate to the pressure caused by the air column  22  which is directly exposed to the well water at its distal end located within the well. The sensor differential amplifier again sends its signal indicative of the sensor displacement to the span scale and offset amplifier which scales the value. This value is converted into a digital value in the A/D converter and applied to the same data input of the microprocessor. A calculation ensues in the microprocessor based upon data entered previously which is particular to the well being monitored and a value is determined. The resultant value is applied to a digital-to-analog converter and applied to an analog display instrument or gauge  28  for viewing by the user. The gauge  28  displays the depth of the well water which may be expressed in feet, gallons or liters. 
     The microprocessor also is capable of providing a digital readout through an LCD display controllable by the microprocessor. The controller  12  can communicate with other digital devices, e.g. multi-purpose computers, through an RS232 communications port on a bi-directional data link with the microprocessor. An LED port or output from the microprocessor gives an indication of sensing or monitoring ON, with the LED remaining on throughout the monitoring operation. Of course, the entire controller  12  and its various peripherals are powered by a standard AC power source which provides both line voltage and transformed DC voltage of +5, −5 and +12 volts to the various internal components of the controller  12 . 
     Additionally, the microprocessor is connected to a tester port for providing a test data output from the D/A converter for checking the functions of the microprocessor. The input amplifier network, i.e. the sensor differential and the span scale and offset amplifiers, has an offset voltage applied for establishing a zero adjustment for the scaling function of the pressure differential value. The A/D converter has a reference voltage applied to accurately effect the conversion. 
     The controller  12  is calibrated in accordance with the following procedure. A check of the applied DC voltages is performed on the power supply outputs. An air pressure of 2 psi is applied to the pressure sensing transducer  24  looking for “0” volts at the output of the span scale and offset amplifier. If any value other than zero, the offset voltage control is adjusted to achieve a “0” voltage reading. Once this is accomplished, an air pressure (in the case of a 200 foot depth) of 4 psi is applied to the pressure sensing transducer  24  looking for “5” volts at the output of the span scale and offset amplifier. This optimizes the span scale and offset amplifier and completes the calibration of the input amplifiers. The next step is to calibrate the A/D converter by applying no pressure to the pressure sensing transducer  24  looking for “0” level on the display  28 . Once this is accomplished, an air pressure of 4 psi is applied to the pressure sensing transducer  24  and the display  28  is adjusted for its maximum reading. This calibrates the analog display to read and display the values presented from the resultant calculations of the differential pressure detected by the pressure sensing transducer  24 . In this manner the controller  12  is calibrated to produce accurate readings based upon its sensors and internal circuits. 
     In the field, the controller  12 , containing all of the circuitry elements, and the mechanical elements, i.e. the pump  16 , the valves  18 ,  20 , and the air tank  14  will be mounted or positioned inside the well owner&#39;s residence or business location. A ¼ inch (internal dimension) plastic tube is connected between the controller  12  and a 4-way port  32 . From the 4-way port  32 , a ¼ inch (internal dimension) plastic tube is connected to the air tank  14  and separate ¼ inch plastic tubes are connected to valves  18  and  20 . From the other end of valve  18  a ¼ inch plastic tube is connected to pump  16 . Each of the valves  18  and  20  are connected by signal control wires to the controller  12 , with pump  16  connected in the same manner. One additional ¼ inch plastic tube is connected to the other end of valve  20 , which tube is cut to a length equal to the depth of the well and installed into the well alongside the well water pump piping so that its distal end is in proximity to the bottom of the well. This tube  22  creates the air column against which the pressure differential of the weight of the water in the well will be used to calculate the height (depth) of the water level from the bottom of the well. 
     There will be three differing installations of the air column tubing  22 : new wells, existing wells, and upon pump replacement on existing wells. For a new well the installation will require only the fastening of the air column tubing  22  onto the exterior of the water line at the same time the water line is being positioned in the well with the submersible pump. The air column tubing  22  is then run from the well with the water line into the building. Once inside the building, the air column tubing  22  is connected to the valve  20  and the calibration of the apparatus is performed through the foregoing checks. 
     An existing well installation will require the placing of a ½ inch (internal dimension) PVC pipe into the well to the depth of the submersible pump. This pipe acts as a conduit for the air column tubing  22  and requires the tubing  22  to be secured within the bottom opening of the pipe. Securing the tubing  22  can be done by drilling two angled holes slightly larger than the tubing  22  into the PVC pipe at distances approximately 8 and 12 inches from the bottom end of the pipe. The air column tubing  22  is inserted through the drilled holes and arranged to extend to within 4 inches of the bottom opening of the pipe. The distance inside the pipe is preferred to keep dirt and other sediment from clogging the end of the air column tubing  22 . The PVC pipe or conduit for carrying the air column tubing  22  to the bottom of the well can be assembled in sections of any desired length and glued together with the air column tubing  22  extending from the top of the final section which is secured to the well cap. The air column tubing  22  is passed through a pre-drilled hole in the well cap and is inserted into another series of ½ inch PVC pipe sections which are run into the building. The conduit should be insulated against moisture seepage and freezing, with the preferred method being to trench and bury the conduit. As before, the ¼ inch plastic tubing, i.e. the air column tubing  22 , is connected to the valve  20  and calibration of the apparatus is performed by following the foregoing checks. 
     When a submersible pump is being replaced and the well water level measuring apparatus of the present invention is desired to be added, the ¼ inch air column tubing  22  is attached to the water line as the replacement submersible pump is being lowered into the well. The air column tubing  22  is then connected to the well cap and run into the building as was done for an existing well water pump using the ½ inch PVC pipe sections to create a conduit for the air column tubing  22 . Once inside the building, the air column tubing  22  is connected to valve  20  and calibration is performed using the foregoing checks. In all cases extreme care should be taken to ensure that the air column tubing  22  is not crimped when fastening and bending which could produce false readings to the pressure sensing transducer  24 . 
     The overall programming of the well water level sensing apparatus of the present invention can be described with reference to FIG.  3 . An initializing sequence is begun on start-up which checks all inputs and outputs, closes all valves, and sets all values to zero. Once initialization is completed, the pump valve, valve  18 , is opened and pump  16  is started. This effects a pressurization of the air tank  14  which is monitored by the pressure sensing transducer  24  through the 4-way port  32 . The controller  12  makes a continuing inquiry checking whether the desired pressure (4 psi) has been achieved. Once the pressure sensing transducer  24  and the associated sensor differential amplifier, span scale and offset amplifier and A/D converter have performed their respective functions and transmitted the resultant value to the microprocessor indicating that the desired pressure (4 psi) has been achieved, the pump  16  is stopped and the valve  18  is closed. To make certain the instructed functions are achieved, a short delay is enabled. Following the short delay, the air column tubing valve  20  is opened and following another short delay to allow for equilibrium between the air pressure in the air tank  14  and in the air column tubing  22  values from the pressure sensing transducer  24  are accepted by the microprocessor. In all instances, the size of the air tank  14  and the volume of the air column tubing  22  are substantially identical. This requirement will cause the size of the air tank to vary in accordance with the volume of the air column  22  which increases in  20  length as the well gets deeper. 
     An internal calculation based upon predetermined values is initiated by the microprocessor which provides a water depth based upon the sensed pressure differential from stored values in a table. The retrieved value from the table indicative of water depth is then displayed on whichever human readable device has been selected, i.e. an analog display gauge or a digital readout. Each complete sequence may be manually started or be continually monitored at preset times for later retrieval for viewing. 
     A more in depth program sequence is set out in FIGS. 4A, B and C. The microprocessor in the controller  12  is programmed to perform the following tasks in the described sequenced. At start-up, the variables are defined and the ports are initialized. This includes commands to close all valves and set “0” conditions on all ports. Particularly, the signal processing data port is also initialized. On entering the main routine, the microprocessor is waiting for a signal that the manual start has been requested by depressing the push button  26 . Once the microprocessor detects that the push button  26  has been depressed, a series of instructions are given. The valve  20 , the tubing valve, is instructed to close. The valve  18 , the pump valve, is instructed to open. The pump  16  is instructed to start. An inquiry is set to detect the desired pressure (4 psi) by the pressure sensing transducer  24  which continually provides pressure differential values until the desired pressure is sensed and the information is passed through the input amplifiers and provided (in digital format) to the microprocessor. 
     Once the desired pressure (4 psi) is detected, and referring to FIG. 4B, the pump valve  18  is instructed to close which is followed by a short delay. After the delay, the pump  16  is instructed to stop. This is followed by an instruction to the microprocessor to read the water level detection routine which requires the issuing of new instructions. The microprocessor instructs the tubing valve  20  to open followed by a short delay allowing for equilibrium to occur between the air column tube  22  and the air tank  14 . Following the delay, a first reading is made of the A/D converter which produces a digital value from the input amplifiers linked to the pressure sensing transducer  24 . The transducer  24  provides a differential pressure from the equalized pressure in the air column  22  and the air tank  14 , which is directly exposed to the water pressure at the bottom of the well, to the input amplifiers which scale the value for the A/D converter. The output of the A/D converter is then read by the microprocessor and the value is shifted to create a unique address for the predetermined conversion table. The table conversion routine is called and the table is read based upon the shifted value received from the A/D converter. Another short delay provides for the stored value in the table to be retrieved and applied to the output conversion routine. 
     Referring to FIG. 4C, the D/A conversion is called and the retrieved stored value is sent to the selected display for viewing by the user. The analog display gauge  28  then displays the water level by displacing the arrow marker over the appropriate arc length showing the water level indication along the associated scale. This step is followed by another short delay before the microprocessor begins looking for another start request from the manual push button  26 . The display will continue to retain the indicated value until cleared by the microprocessor by either program control or by manual request. 
     In the explanation of the programmatic sequences and in the explanation of the various arrangement and interaction of the physical elements of the invention, 4 psi is utilized as a sample desired pressure. However, it should be understood that other pressures to which the air tank  14  and the air column  22  can be charged will work similarly as the well depth increases. The important requirement is that the volume of the air tank  14  varies as the internal volume of the air column tubing  22 . So that the longer the air column  22  to accommodate a deeper well the size of the air tank  14  increases to remain at the same volume. 
     The foregoing are examples of single well water level measurement. The present invention has the capacity to the well water depth of a plurality of wells by repeating the described sequence of well water depth measurement for each one of the plurality of wells. The present invention may also continually sense and monitor the pressure of the well water exerted against the air column by repeating the sequence at preset periodic times. This can be displayed on the visual display, or the resultant calculated water level can be communicated to the multi-purpose computing device over the communications channel for sequential storage in memory for later retrieval and viewing. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, the described embodiments are to be considered in all respects as being illustrative and not restrictive, with the scope of the invention being indicated by the appended claims, rather than the foregoing detailed description, as indicating the scope of the invention as well as all modifications which may fall within a range of equivalency which are also intended to be embraced therein.