Patent Publication Number: US-2022221322-A1

Title: Through the Wall Tank Level Measurement with Telemetry and Millimeter Wave Radar

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application for patent claims the benefit of priority to U.S. Provisional Application No. 63/142,890, entitled “Through the Wall Tank Level Measurement with Telemetry and Millimeter Wave Radar,” filed Jan. 28, 2021, and is a continuation-in-part of U.S. Non-Provisional application Ser. No. 16/382,019, entitled “Tank Multi-Level Measurement Using through the Air Millimeter Wave Radar,” filed Apr. 11, 2019, which claims the benefit of priority to U.S. Provisional Application No. 62/656,032, entitled “Tank Multi-Level Measurement Using Through the Air Millimeter Wave Radar,” filed Apr. 11, 2018, and U.S. Provisional Application No. 62/691,139, entitled “Tank Multi-Level Measurement Using Through the Air Millimeter Wave Radar,” filed Jun. 28, 2018, all of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the invention relate generally to the use of radar to measure levels of fluids and other materials in a storage tank and, more specifically, to a self-contained, easy to install, tank level monitor with integrated display, keypad, radar, GPS, and cellular and satellite transmission capabilities for sending the data off-site for further analysis. 
     BACKGROUND 
     Storage tanks are used to store many types of liquids, such as oil, water, liquid fuels, liquid chemicals, and the like. It is important in many applications to be able to accurately measure the level of such fluids in a storage tank, for example, to detect loss due to leakage and/or theft, for automatic customer billing based on usage, and also to ensure a sufficient quantity of such fluids is available. From the fluid level, the volume of fluid in the tank can be determined using techniques known in the art (e.g., tank area times fluid level for a circular tank). Measuring a storage tank&#39;s fluid levels typically requires matching the liquid being stored with a particular sensing technology in order to accurately determine fluid level. Chemical attributes, viscosity, pressure, temperature, environment, cost constraints, power-on time, power requirements, accuracy requirements, and other considerations may dictate what type of sensor can be used for a given liquid. This is made even more difficult when the tank contains multiple types of fluids with different attributes. 
     Tank fluid levels are typically read using a mechanical float on a magneto restrictive rod, or using ultrasonics, hydrostatic pressure, guided wave radar and pulse radar. These sensors report data to a remote telemetry modem where the data is sent, for example, to a web site or other end user. However, creating a narrow beam width with limited power to pass FCC requirements and still accurately measure tank levels remains a challenge. 
     Accordingly, advancements are continually needed in the art of measuring storage tank levels. 
     SUMMARY OF THE DISCLOSED EMBODIMENTS 
     Embodiments of the invention relate to a fluid level monitor that use a millimeter wave (mmWave) radar system to measure levels of fluids and other materials in a storage tank. The mmWave radar system emits a chirp signal that reflects off objects and fluids and a return signal that is received by a receiving antenna. The received signal is mixed with the outgoing signal to generate a signal having an intermediate frequency which is directly proportional to the distance to one or more levels of fluid in the tank or obstructions. The fluid level monitor filters out signals resulting from extraneous obstructions and false signals by ignoring some resulting distances and lower power signals to determine the desired distance. 
     Advanced algorithms and filters are used to better determine the true tank level resulting from the monitor&#39;s operation. Once accurately determined, the tank levels and volume are displayed locally to the user on a display. In addition, wireless telemetry is used to send the resulting tank levels to remote web sites where further GPS location, charts, graphs, Key Performance Indicators, alerts, auto billing, emails, and text messages can be generated for the end users. In addition to the data being available on the web, Bluetooth is used to transmit data to a local display or smartphone. A smartphone can be used to wake and remotely read any tank&#39;s attributes and even program and configure the tank monitor. The tank monitor is adaptable to plastic tanks but can also be installed on metal tanks using an adapter. Since the monitor is totally enclosed, there is no contact with the fluid and the radar based monitor works on virtually any kind of chemical. 
     In general, in one aspect, embodiments of the present disclosure relate to a tank level monitor for measuring a distance from near a top of a tank to one or more fluids in the tank. The tank level monitor comprises, among other things, a chirp generator operable to generate a millimeter wave chirp that ramps linearly from a starting frequency to a predefined higher frequency within a specified time span. The tank level monitor also comprises an antenna and quadrature hybrid circuit configured to transmit the chirp generated by the chirp generator into the tank and to receive one or more chirp reflections from the tank. The tank level monitor further comprises a Luneburg lens coupled to the antenna and quadrature hybrid circuit, the antenna and quadrature hybrid circuit configured to transmit the chirp and receive the chirp reflections through the Luneburg lens. The tank level monitor still further comprises a mixer operable to mix the chirp with the chirp reflections to generate one or more intermediate frequency signals, and a processor operable to process the one or more intermediate frequency signals and derive signal strengths and distances from the one or more intermediate frequency signals, each distance indicative of the distance from near a top of the tank to one of the one or more fluids in the tank or an obstruction in the tank. The tank level monitor yet further comprises a controller operable to automatically select intermediate frequency signals having signal strengths above a predefined minimum or distances within a predefined distance window for further processing and ignore other intermediate frequency signals and distances. 
     In some embodiments, the controller is programmed to automatically select an intermediate frequency signal for further processing, the intermediate frequency signal representing the best returned signal for further processing. 
     In some embodiments, the controller is programmed to automatically further process the selected intermediate frequency signal by adding the selected intermediate frequency signal to a ballot, the ballot including previously selected intermediate frequency signals, the controller further programmed to automatically vote on the intermediate frequency signals on the ballot. 
     In some embodiments, the controller is programmed to automatically use distance windows to ignore distances indicative of obstructions in the tank. 
     In some embodiments, the controller is programmed to automatically focus on specific distance windows indicative of fluids in the tank. 
     In some embodiments, the processor is operable to process the one or more intermediate frequency signals using zoom Fourier transform. 
     In some embodiments, the tank level monitor further comprises a telemetry unit operable to transmit distance readings to an off-site location. In some embodiments, the telemetry unit is configured to use one of the following wireless telemetry technologies: cellular, satellite, Bluetooth, Wi-Fi, Z-Wave, ZigBee, WiMax, Sigbox, LoRa, Ingenu. 
     In some embodiments, the chirp generator generates a chirp according to a preselected chirp configuration profile, and wherein the chirp generator is operable to use three chirp profiles for a given tank level and volume reading. 
     In some embodiments, the tank level monitor further comprises a wake button that allows a user to wake the tank level monitor, the tank level monitor configured to obtain a tank level and volume reading and to present the reading upon being woken. 
     In some embodiments, the tank level monitor automatically wakes as needed to obtain a GPS location, obtain a tank level reading, and send data representing the GPS location and the tank level reading wirelessly to an off-site location. 
     In some embodiments, the controller is operable to wake upon receiving a wake command from a smartphone or a remote display via Bluetooth, obtain a tank level reading, and send data representing the tank level reading wirelessly to an off-site location. 
     In some embodiments, the chirp generator generates more than 30 chirps per frame sample. 
     In some embodiments, the processor is further operable to apply one or more of the following filters to the intermediate frequency signals: OS-CFAR filter, and Blackman filter. 
     In some embodiments, the controller is further operable to transmit tank level and volume readings to an external display using Bluetooth. 
     In some embodiments, the controller is further operable to transmit tank level and volume readings to a smartphone using Bluetooth 
     In some embodiments, the controller is further operable to receive commands and tank parameters from a smartphone via Bluetooth. In some embodiments, the tank level monitor can receive a tank template from the smartphone, the tank template containing setup and configuration parameters for a specific type of tank. 
     In some embodiments, the controller is further operable to wake up upon receiving a wake-up sequence from a smartphone over Bluetooth, the wake up sequence initiated on the smartphone by a user touching any monitor serial number via a smartphone app running thereon, the controller further operable to obtain and send tank level and other tank data to the user via the smartphone. 
     In general, in another aspect, embodiments of the present disclosure relate to a method of monitoring tank level for measuring a distance from near a top of a tank to one or more fluids in the tank. The method comprises, among other things, generating, at a chirp generator, a millimeter wave chirp that ramps linearly from a starting frequency to a predefined higher frequency within a specified time span, and transmitting, through a quadrature hybrid circuit to an antenna, then through a Luneburg lens, the chirp generated by the chirp generator into the tank. The method also comprises receiving, through the Luneburg lens coupled to the antenna and through the quadrature hybrid circuit, one or more chirp reflections from the tank, and mixing, at a mixer, the chirp with the chirp reflections to generate one or more intermediate frequency signals. The method further comprises processing, at a processor, the one or more intermediate frequency signals and derive strengths and distances from the one or more intermediate frequency signals, each distance indicative of a distance from near a top of the tank to one of the one or more fluids in the tank or an obstruction in the tank. The method still further comprises automatically selecting, at a controller, intermediate frequency signals having signal strengths above a predefined minimum or distances within a predefined distance window for further processing and ignoring other intermediate frequency signals and distances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
       The foregoing and other advantages of the disclosed embodiments will become apparent upon reading the following detailed description and upon reference to the drawings, wherein: 
         FIG. 1  is an external view showing an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIG. 2  is an interior view of an exemplary a tank level monitor according to an embodiment of this disclosure; 
         FIG. 3  is a schematic diagram for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 4A-4C  are flow diagrams for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 5A-5B  are interior views showing a radar board for an exemplary a tank level monitor according to an embodiment of this disclosure; 
         FIGS. 6A-6C  are schematic diagrams for a Luneburg lens used in an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 7A-7D  are interior views showing a radar assembly for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 8A-8B  are views showing a radar assembly housing for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIG. 9  is a bottom view of the radar assembly housing for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIG. 10  shows front and back views of a radar board for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 11A-11C  are schematic diagrams showing a quadrature hybrid circuit for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 12A-12B  are circuit diagrams showing operation a quadrature hybrid circuit for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 13A-13B  show exemplary chirp profiles for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 14A-14D  are graphs of exemplary chirp profiles for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIG. 15  shows exemplary status and error messages for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIG. 16  shows an exemplary keypad and commands for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 17A-17C  are exterior views showing an exemplary tank level monitor mounted on a tank according to an embodiment of this disclosure; 
         FIGS. 18A-18E  are additional exterior views showing an exemplary tank level monitor mounted on tanks according to an embodiment of this disclosure; 
         FIGS. 19A-19D  are still additional exterior views showing an exemplary tank level monitor mounted on tanks according to an embodiment of this disclosure; 
         FIG. 20  is an exterior view showing an overhead display for an exemplary tank level monitor mounted on tanks according to an embodiment of this disclosure; 
         FIGS. 21A-21B  show a remote display and an iPhone display for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 22A-22C  are exemplary smartphone screens for tracking the location of an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIGS. 23A-23B  are exemplary smartphone screens for monitoring multiple exemplary tank level monitors according to an embodiment of this disclosure; 
         FIGS. 24A-24B  are exemplary smartphone screens for reviewing past tank level volume readings for an exemplary tank level monitor according to an embodiment of this disclosure; 
         FIG. 25  is an exemplary smartphone screen for issuing simple text commands to an exemplary tank level monitor according to an embodiment of this disclosure; and 
         FIG. 26  show exemplary requests that can be made via a smartphone app to an exemplary tank level monitor according to an embodiment of this disclosure. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     As an initial matter, it will be appreciated that the development of an actual, real commercial application incorporating aspects of the disclosed embodiments will require many implementation specific decisions to achieve a commercial embodiment. Such implementation specific decisions may include, and likely are not limited to, compliance with system related, business related, government related and other constraints, which may vary by specific implementation, location and from time to time. While a developer&#39;s efforts might be considered complex and time consuming, such efforts would nevertheless be a routine undertaking for those of skill in this art having the benefit of this disclosure. 
     It should also be understood that the embodiments disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. Thus, the use of a singular term, such as, but not limited to, “a” and the like, is not intended as limiting of the number of items. Similarly, any relational terms, such as, but not limited to, “top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,” “side,” and the like, used in the written description are for clarity in specific reference to the drawings and are not intended to limit the scope of the invention. 
     This disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following descriptions or illustrated by the drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of descriptions and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations herein, are meant to be open-ended, i.e., “including but not limited to.” 
     Embodiments of the fluid level monitor herein employ a single-chip sensor having mmWave measurement capability, such as one of the family of mmWave sensors from Texas Instruments (TI). The sensor preferably uses Frequency-Modulated Continuous Wave (FMCW) radar operating in the 76-81 GHz band with a 4 GHz chirp. An ARM processor is used for the receivers to control and calibrate the signals. A built-in Digital Signal Processor (DSP) is used to perform radar math and run Fast Fourier transforms, such as Zoom Fast Fourier transform, on the signals to directly determine distances to fluids. One or more embodiments use a single receive and transmit antenna and a Luneburg lens configuration to focus the radar beam. Radar circuits such as the TI mmWave family of integrated circuits provide compact methods of processing the necessary signals to determine distance. 
     The variations among the TI mmWave family (AWR1443, AWR1642, IWR1642, IW1843) have different attributes depending upon needs, but the technology used is the same. One or more embodiments use the IWR1642 or AWR1642 sensors from TI. The “A” indicates automotive use, typically for driverless cars, and the “I” indicates industrial use, but the functionality is otherwise identical. Examples of fluid level monitors that use one of the AWR1642 sensors in a manner similar to the embodiments described herein are available from Lasso Technologies LLC, of Dallas, Tex. 
     Referring now to  FIG. 1 , a tank level monitor is shown generally at  100  according to some embodiments. The tank level monitor  100  is designed to use a mmWave radar that meets FCC requirements. By way of context, any RF power transmitted in the United States requires FCC approval and licenses. Different sections of the FCC code must be passed to be legally used for a particular application and frequency. The main section dealing with the use of radar on storage tanks is FCC 15.256 Level Probing Radar 75-85 GHz. The key FCC 15.256 requirements are set out below.
         Fundamental emission limits EIRP 1 MHz and 50 MHz bandwidth   On tank, pointing down   Stationary use   Peak EIRP (Equivalent Isotropic Radiated Power) 34 dBm   Azimuth beam width −3 dB beam width&lt;8 degrees   Antenna side lobe gain relative to main beam −38 dB       

     The tank level monitor  100  disclosed herein can pass the above FCC 15.256 requirements. In addition, the tank level monitor  100  can be used on smaller tanks  101 , such as IBC (Intermediate Bulk Containers), as well as on virtually any plastic tank or metal tank when an adapter is used. The tank level monitor  100  has an advantage of very fast and easy installation, such as by using tape or adhesive between the radar  102  and the plastic tank wall  105 . No holes need to be drilled in the tank and embodiments of the tank level monitor  100  can be installed in a few minutes. The customer can screw or strap the enclosure to the tank if preferred over 3M tape. 
     Embodiments of the tank level monitor  100  can be placed almost anywhere on top of the tank  101 . Packaging the tank level monitor  100  in an appropriate plastic enclosure allows the tank level monitor  100  to be used through the access ports on larger metal tanks, such as an ISO tank. In contrast, alternative technologies require that a sensor be installed through the tank wall, which has the disadvantage of needing modifications to the tank, thus risking damage, direct contact with the fluid, increased installation time, and potential sensor cleaning issues. The tank level monitor  100  is also low profile so that the tanks can be stacked using a forklift, which is not practical with other tank level measurement methods with higher profile. Display  103  allows the user to see level and volume in the tank. Embodiments of the tank level monitor  100  is fully self-contained with integrated measurement, power, display, and telemetry with no external antennas, for a clean, easy to install superior solution. 
       FIG. 2  shows the tank level monitor  100  with the top cover removed. As can be seen, the tank level monitor  100  is comprised of a main control board  202 , on which a controller resides that controls a display, programming keys, telemetry, and transmission and reception of radar to read tank levels. Housing  201  contains the radar board and lens which is connected to the main control board  202  through a power and signal cable  208 . Display  205  provides the user with system status, programmability, errors, level, and number of gallons. Power section  210  provides power to different sections of the control board  202  as needed. Programming buttons  204  allow the adjustment of many radar and telemetry parameters. On/Off switch  207  or magnetic switch  211  can be used to turn the tank level monitor  100  on using an external magnet to wake main control board  202 . Pushbutton  206  allows a user to wake the tank level monitor  100  anytime to take a radar tank reading and display number of gallons and depth on display  205  so the user can know the tank level. Main control board  202  supervises the coordination of the various components of the tank level monitor  100 . Satellite modem  203  sends data off-site, for example, to web sites where further data analysis is performed and data is conveyed to remote users. In place of satellite modem  203 , a cellular modem can be used, or any wireless communication method to send the data. GPS antenna  209  is used to provide location data so that the location of the tank level monitor  100  can be embedded with the tank level information. 
       FIG. 3  shows a functional block diagram  300  for the tank level monitor  100 . The functional block diagram  300  contains controller  302  which pulls data from radar module  309  and controls other functions of the tank level monitor  100 . Controller  302  also is responsible for controlling the power supplied to radar module  309 . Radar module  309  automatically boots up and runs one or more configuration profiles to determine multiple distances to the fluid and associated signal strengths. Power is provided using any suitable non-rechargeable battery  312 , or a rechargeable battery can be used with battery charger  311 , or solar panel  310 . Power supply  315  is managed by controller  302  and turned on and off as needed to each major section of the monitor  100  to save battery life. 
     Controller  302  wakes at intermediate intervals and communicates with other parts of the tank level monitor  100  to take level measurements and send them to the user. After taking measurements, controller  302  puts the tank level monitor  100  in a low power sleep mode to save battery life. Controller  302  will then wake as needed and turn on relevant onboard circuits to repeat the measurement and reporting cycle. Telemetry to off-site locations, such as external web servers, is provided using a cellular module  306  or satellite telemetry module  307 . Other wireless technologies such as Bluetooth, Wi-Fi, Z-Wave, ZigBee, WiMax, Sigbox, LoRa, and Ingenu could be implemented for the telemetry module  307  to send data to an end user. In some embodiments, the tank level monitor  100  has a LoRa module  325  to allow data to be sent to a local wireless mesh network near the tank. A LoRa antenna  326  can gather data from similar tank level monitors  100  installed on other nearby tanks and send the data over wired ground networks or cellular or other wireless means to web sites, the user, and other locations. 
     The geographical location of the monitor  100  can be determined using a GPS module  308 . In some embodiments, an external PLC  316  may be used to read data through Modbus circuit  305 . Alternatively, a 4-20 mA transmitter  304  can be used to generate a 4-20 mA signal to PLC  316 . Other communication methods to external ports, such as HART, could also be implemented. Wake early pushbutton  324  wakes the monitor  100  to take a reading and show the results on display  318 . Bluetooth module  303  is used to communicate wirelessly with a separate local display  320 . A user can press a button  321  on the local display  320  to read the level and gallons readings  323  for the tank  352 . Bluetooth Low Energy (BLE) is used so that Bluetooth module  303  can be available when button  321  is pressed. This is done by using BLE module  303  to wake controller  302  and radar module  309  so that the gallon and level readings  323  are shown to the user. Smartphone  322  and a monitoring app running thereon can also be used to allow the Bluetooth module  303  to be used to program setup parameters for the radar module  309  and see real time updates of the level and volume in the tank, with interactive charts and graphs, and also to see alarms. In addition, a smartphone can be used to wake a sleeping monitor  100  by simply touching any one of the customer&#39;s listed devices on their smartphone. Display  318  or smartphone  322  allows the user to see the status of the tank level monitor  100 , the level, and the gallons (see  FIG. 15 ), and the programming (see  FIG. 16 ). Keypad  319  allows the user to change the operation of tank level monitor  100 , as described in  FIG. 16 . 
     The radar module  309  is an AWR1642 radar chip from Texas Instruments in some embodiments. The AWR1642 is a single chip that includes a radar sensor in the 76-81 GHz band with multiple transmit and receive antennas and built-in phase locked loops (PLL) and A/D converters. The AWR1642 chip  309  has one cortex R4F core and one DSP C674x core available for user programming and are referred to as MSS/R4F  337  and DSS/C674X  336 , respectively. Basically, the MSS processor  337  controls transmission of the radar signal and the DSS processor  336  processes the received radar signal using advanced mathematics. Ramp generator  332  works with synthesizer  333  to generate the chirps, which may be customized via processor  337 . Ramp generator  332  generates a millimeter wave chirp that ramps linearly from a starting frequency to a predefined higher frequency within a set time period. In some embodiments, ramp generator  332  generates more than 30 chirps per frame sample. 
     The tank level monitor  100  configures the chirp generator to send 64 chirps in some embodiments instead of the more common 10 chirps used in the art. These 64 chirps are averaged, which minimizes much of the noise and also improves the accuracy of the final tank level and volume readings. The quadrature hybrid circuit  340  allows the transmit signal from power amplifier  331  to reach antenna  341  with no feedback to damage the low noise amplifiers (LNA)  330 . The Luneburg lens  342  creates a focused RF signal, indicated at  353 , from antenna  341  towards fluid  351  in tank  352 . The echoed response signal  353  feeds back through the lens  342 , and quadrature hybrid circuit  340  to the receive LNAs  330 . Only one transmit and receive antenna is used on the AWR1642. Mixers  334  receive and multiply the signal being transmitted with the signal being received that instant from the low noise amplifiers  330  and antenna  341 . The product of the mixers  334  creates the intermediate frequency (IF) signal  335  which is sent to the analog to digital converters  336 . The digital front end  338  receives the signals and digitizes and stores these values in analog buffers for use by the DSP  336 . The DSP  336  performs the signal processing of the received signals and runs a Fast Fourier transform (e.g., Zoom), OS-CFAR, and Blackman routines on each peak of the IF signal to determine distances to fluid. 
     Processor  337  works with memory  339  to coordinate the various functions on the radar module  309 . A single tank level and volume reading can be determined within the DSP  336  and used as the correct distance reading, or the 10 strongest distance readings in terms of signal power can be sent over serial port  345  to controller  302  for further analysis. It should of course be understood that fewer or more than 10 strongest distance readings may be sent for further analysis by controller  302 . Satellite telemetry module  306  and cellular telemetry module  307  can be used to transmit data off-site as scheduled or needed. GPS location data is captured using GPS circuit  308 . 
       FIG. 4A  shows a flowchart  400  outlining the basic steps for processing a radar echo in the tank level monitor  100  in some embodiments, while  FIG. 4C  shows exemplary signal peaks A, B, C, D, E, F, G, H, I, J generated from an actual radar echo. For most embodiments, 10 data points will be analyzed corresponding to the 10 strongest peaks resulting from the 64 chirps. Any of these 10 peaks could represent the correct fluid level, since multiple echoes are usually returned for each chirp due to reflections within the tank and inherent noise in the radar circuit. 
     The flowchart  400  generally begins at  401 , where the tank level monitor  100 , or more specifically the radar module  309  therein, sets the current/next radar chirp configuration profile. At  402 , the radar module  309  generates 64 chirps that are transmitted into the tank. Experience has found that increasing the chirp width greatly improves the accuracy of the resulting fluid level readings. Intuitively, increasing the transmitted power would seem to yield better results, but increasing the transmitted power actually increases noise and reflections and can produce erroneous results. Likewise, increasing the received amplification can degrade performance if over-amplification of noisy echoes produces bad level readings. Increasing the chirp loops can improve performance accuracy. Multiple chirp profiles with different transmitted and received power, chirps, chirp widths, and chirp loops are used while determining a valid level. 
     At  403 , the radar module  309  collects data from the return echoes of the current chirp configuration profile. Three chirp configuration profiles are contemplated, although fewer or more than three profiles may certainly be used. The data collected is the signal strength or power for various reflections or echoes resulting from the chirp, along with the corresponding range or distance to the fluid for the reflections based on the signal strength or power. 
     At  404 , the radar module  309  makes an initial determination of the 10 best (strongest) peaks based on the signal strength of the reflections or echoes, along with their range or distance to the fluid. Exemplary peaks A, B, C, D, E, F, G, H, I, J are shown in  FIG. 4C . At  405 , the radar module  309  runs a Zoom Fast Fourier Transform (FFT) on each of the 10 best (strongest) peaks, or rather the digitized representations of their waveforms. The Zoom FFT determines the spectral components of the peaks in order to determine the distances to the fluid, since distance is directly related to the intermediate frequency (IF). To improve resolution, the radar module  309  uses a Zoom FFT processing technique that enhances the 10 strongest return signals. This is a processing technique that is added as an enhancement to the existing chip software in the DSP  336 . Zoom FFT processing of the 10 strongest return signals allows analysis of the fine spectral resolution of each peak of the returned data at high “Zoom” resolution. In some embodiments, the radar module  309  applies the Zoom FFT to each of the 10 peaks (using the DSP  336 ) as follows:
         Frequency translation to shift the frequency range to 0 Hz.   Low-pass filter to prevent aliasing.   Re-sample at a lower rate.   Perform Zoom FFT on the re-sampled data (the resulting spectrum will now have a much higher resolution bandwidth, which results in better distance accuracy).       

     The above Zoom FFT process is repeated on each of the 10 example peaks A, B, C, D, E, F, G, H, I, J shown in  FIG. 4C , resulting in a precise IF for each peak that can be translated into a distance or range to fluid. The result is a set of 10 ranges corresponding to the 10 peaks, each range having a corresponding signal power or strength value, for a given chirp profile, as follows: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th]. 
     At  406 , the radar module  309  applies a filter to the data from  404  to eliminate false range or distance readings for each of the 10 values. This is to account for real-world tanks that often produce spurious reflections and echoes, potentially resulting in false distance readings, making detecting the correct distance challenging. In some embodiments, the filter applied by the radar module  309  is a mathematical algorithm, such as the well-known Order Sorted-Constant False Alarm Rate (OS-CFAR) algorithm, to minimize false readings. Background noise and false reflections can cause noise problems, so setting an accurate signal strength threshold for the returned signal is challenging. Setting a frequency threshold level for all distance readings does not work since the noise floor varies for different distance readings. The OS-CFAR algorithm uses a varying threshold based upon the present noise level, which is independent of the surrounding noise power for the underlying noise model, as determined by evaluating neighboring frequencies using a sliding window to inspect all frequencies. A changing threshold is calculated from the signal-to-noise ratio of the fluid echo return by estimating the noise floor near the frequency of interest and calculating the average power level. A frequency and thus distance is valid if it exceeds this threshold. 
     At  407 , the radar module  309  runs additional filtering, for example, by applying a Blackman filter routine, to the data from  404  to smooth the data. The well-known Blackman filter is effective for pulling out very small signal levels which are superimposed on larger signals. 
     At  408 , the radar module  309  checks whether Zoom FFT, OC-CFAR, and the Blackman routines have been run on all 10 peaks. If not, then the radar module  309  continues until all 10 data points are processed. The resulting 10 ranges and corresponding signal strengths are then stored for that chirp profile. An exemplary set of samples or data for a given chirp profile may resemble the following: [210.9, 60.6] [334.3, 138.7] [459.7, 17.3] [658.8, 1.0] [824.5, 0.4] [914.2, 0.3] [1007.8, 0.2] [1102.4, 0.2] [1680.4, 0.2] [1748.4, 0.2] where range is in millimeters (mm) and power is in decibels (dB), respectively. 
     At  409 , the radar module  309  checks whether three chirp configuration profiles have been run as described above, with 10 ranges and corresponding signal strengths stored for each of the three chirp profiles. This results in three sets of samples or data, one set for each chirp configuration profile, each set containing 10 range-power pairs per profile. Each set of data is sometimes referred to herein as the “response” resulting from a given chirp profile. 
     At  410 , each of the three responses are evaluated and the two responses that have the most similar ranges/distances to one another are selected. In some embodiments, the evaluation involves comparing the ranges/distances of the three responses to determine which two responses line up most closely with one another (i.e., have the smallest variations). Several ways exist for performing the comparison, including comparing individual ranges/distances within one response to another, averaging the ranges/distances and comparing the average for one response to another, and the like. Three exemplary responses are shown below, Res 1, Res 2, and Res 3: 
     Res 1: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th].
 
Res 2: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th].
 
Res 3: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th].
 
     Of these three responses, assume that Res 2 and Res 3 have ranges/distances that are most similar to one another. In that scenario, Res 2 and Res 3 are selected while the first response, Res 1, is discarded or otherwise not used. The radar module  309  then averages the range values and the power values for these two responses, Res 2 and Res 3, to produce a single set of 10 range-power pairs. This approach has been found to consistently produce the most accurate results. 
     At  411 , the radar module  309  sends the data for further analysis by the controller  302 . The controller  302  attempts to select the best range-power pair from among the 10 range-power pairs. The selected range-power pair is then placed on a “ballot” along with other (previously selected) range-power pair candidates and put to a “vote” to determine the best candidate thus far. This process helps to weed out bad readings that sometimes get repeated. 
     In some embodiments, the controller  302  selects the best range-power pair from among the 10 range-power pairs by ignoring distances that are too close to the top of the tank (i.e., signal strength above a certain decibel level) or too large such that they extend beyond the bottom of the tank. This may be done by setting appropriate signal strength or distance thresholds or windows (i.e., minimum and maximum acceptable signal strength level and distance level). For example, the signal strength threshold may be a decibel level representing 10 inches from the fluid to the top of the tank (i.e., too close to the top), or three inches of fluid remaining in the tank, or some other decibel level indicating that the tank is effectively empty. The controller  302  then selects the remaining range-power pair having the strongest signal as the best candidate. 
     If no strong signal is found, the controller  302  then checks whether there is a signal with a distance near the bottom of tank, but still greater than a first threshold representing a depth near the bottom of the tank (i.e., signal&gt;threshold 1 (roughly 10 dB)). If yes, then the range-power pair for that signal is selected as the best candidate from the 10 pairs. If still no strong signal is found, then the controller  302  checks whether the signal is very weak, less than a second threshold representing an effectively empty tank (i.e., signal&lt;threshold 2 (roughly 3 dB)). In that case, the controller  302  puts a range-power pair that represents an empty tank on the ballot. The thresholds and windows can be set automatically by the monitor  302  for a given tank, or they can be set manually by users and revised from time to time as needed. 
     The above process allows signals that have a reasonable strength level, but are not necessarily the strongest signal, to still be considered in determining a correct distance measurement. Using a signal strength threshold for echoes that are more distant means that the echoes with the strongest power value will not necessarily be used, but this is likely to produce the correct distance to the fluid. This is because, for example, data for peak A may indicate a strong echo, but that echo may be due to an obstruction near the top of the tank and does not represent the correct distance to the fluid. On the other hand, data for peak B may represent the correct distance measurement, even though it has only 80 percent of the maximum signal strength shown by peak A. The approach taken at  412  thus allows distances that most likely represent the correct distance to be used instead of using incorrect distances based on the strongest peaks. The final most likely depth value candidate is then “voted,” as continued in  FIG. 4B . 
     Referring to  FIG. 4B , even though special filtering, advanced math and other techniques are used to determine the correct distance to the fluid, spurious random incorrect distances sometimes are returned by the radar module  309 . Additional measures can be implemented to prevent incorrect readings from being presented to customers. To this end, a list of the candidate distances determined by the controller  302  are maintained at  420  during the time period that the radar module  309  is on (e.g., 5 seconds). During this radar on-time, the radar module  309  runs the three chirp configurations twice per second, resulting in 10 runs. The controller  302  thus produces 10 best range-power pair candidates per each 5-second run of the radar module  309 . Each of these 10 range-power pair is potentially a candidate to be voted on as the correct fluid depth. 
     At  421 , the controller  302  determines, from the 10 fluid depths returned by the radar module  309 , whether the fluid depth with the highest signal strength is within a predetermined variation, such as 0.5 inches or a certain percentage, of the prior depths. If yes, then that depth (i.e., one with the highest signal strength) is considered to be already included on the current list or “ballot” of depths. The flowchart  400  then proceeds to  423  and a “vote” is cast for that existing best depth. If no, then the depth is considered to be a new best depth, and the new best depth is added to the “ballot” at  422 . A vote is again cast for the best depth at  423 . The radar module  309  typically stays on for 5 seconds and reads around 15 depth/distance measurements during that time. At the end of the 5 seconds, the controller  302  looks for the depth/distance with the most votes at  424 , and that depth is presented to the user as the “correct” depth/distance at  425 . At  426 , the controller  302  checks whether the radar module  309  On-time is done. If not, then the flowchart  400  returns to  FIG. 4A  and continues the process. If yes, then at  427 , the controller  302  presents the depth/distance with the most votes the user via the displays and/or the telemetry module. 
     Thus, by using multiple chirp configuration profiles, filtering, and voting as described above, the tank level monitor  100  provides a depth detection method that is extremely reliable and accurate. 
       FIGS. 5A-5B  show an exemplary embodiment of the tank level monitor  100  partially disassembled. As can be seen, the tank level monitor  100  comprises an enclosure  500 , a battery  502  or rechargeable battery  503 , main control board  501 , display  505 , and programming buttons  506 . The battery can take on many forms, such as a sealed lead acid battery  502  or Lithium Thionyl Chloride battery  503 . A radar assembly  504  is also shown that sends the distance measurements to the main control. 
       FIGS. 6A-6C  show an exemplary horn  600  that may be used in some embodiments to focus the radar energy on the fluid. As this cut-away view shows, the horn  600  includes a lens  601  and antenna arrangement that is used to focus the radar energy on the fluid. The lens is a Luneburg lens  601 , which is a spherically symmetric (ball shaped) gradient-index lens that can transform the spherical wave of a point source placed on its surface into plane waves on the opposite side of the lens. A Luneburg lens&#39; dielectric constant ideally is 2 at the center  604  and gradually decreases to 1 on the outer surface  603  to match the dielectric of air. Ideally, the lens will start from a focal point on one side and parallel radiation on the opposite side with a focal point of infinity and plane waves. Within the lens, the paths of the rays are arcs  605 . On the surface, no reflection or bending occurs creating parallel rays  612 . Many variations of a Luneburg lens have been developed over the years. This tank level monitor  100  uses a solid Teflon ball  601  as a lens which has low tangent losses, and a dielectric constant of about 2.2, which results in a performance similar to an ideal Luneburg lens at much less cost. Other radar compatible plastics such as Rexolite, Preperm, or Polyethylene can also be used instead of Teflon. The RF signal is emitted from antenna  606  through the waveguide  607  and into the lens  601 . Plastic screws  609  support the ball using drilled dimples. The wave planes pass through cavity  608  and through the enclosure wall  610 . The lens focuses the beam into a tight pattern  620  with minimal side lobes which can pass FCC requirements for tank level measurement. Several other antennas tried do not come near this performance. 
       FIGS. 7A-7D  show different views of the radar assembly  700 . The radar assembly  700  is comprised of a housing  702 , the Luneburg lens cement tree and a radar board  704  which contains the radar, quadrature hybrid circuit, radar computer, and antenna. Housing  702  contains the radar circuit board  704  and mates with assembly cover  707 . Assembly cover  707  may be lined with radar absorbing rubber  708  to help meet FCC radiation requirements. Header  705  is used for programming and connection to the main control board  302 . Luneburg lens  703  is suspended in the center of the assembly cover  707  using plastic screws  706  in some embodiments. 
       FIGS. 8A-8B  show the exemplary radar housing in more detail. The radar housing or enclosure  800  is generally made of two halves, and upper half  802  and a lower half  804 . Radar absorbing material  806 , such as ARC SB-1006, lines the inside of the upper half  802  to decreases RF side lobes. Plastic screws  808  suspend the Luneburg lens  803  to provide separation from the housing so the RF power is not altered, and also holds the two halves together. Waveguide  805  directs the RF energy from the patch antenna (i.e., the metal trace antenna pattern in the circuit board (see  FIG. 7A  at  704 ) to the Luneburg lens. Threaded holes  807  are provided to screws and secure the radar board in place. Mounting holes  809  are used to fasten the upper half to the bottom half of the enclosure  800 . 
       FIG. 9  shows a further view of the radar assembly at  900 . The radar housing  901  contains the Luneburg lens and the radar board. Radar chip  907  is one of the mmWave products from TI, in this case the AWR1642. This powerful radar chip handles the RF signals necessary to determine distance. Antenna contact  903  feeds the signals from the patch antennas into waveguide  904 . Alignment posts  906  mate with radar board  902 . Pocket  905  provides clearance for the radar chip  907 . Circuit board  902  is the radar board and has six trace layers and special plating to maximize performance. 
       FIG. 10  shows the radar board  1000  in more detail. The radar board  1000  has a power section  1007 , debug-programming connector or header  1006 , and can interface directly to controller  302 . Quadrature hybrid circuit  1008  with dual antenna feeds is diagrammatically shown but the actual traces are on an internal layer within the board. Antenna contact  1001  feeds the Luneburg lens discussed earlier. Screws-in holes  1002  allow the board to be anchored to the radar housing. The mmWave radar AWR1642 can be seen at  1004  and is also represented elsewhere herein by reference  309 . 
       FIG. 11A  shows the circular polarization of the RF energy, which is the ideal waveform desired to improve the likelihood that a signal will be reflected. In a circularly polarized antenna, the plane of polarization rotates in a corkscrew pattern making one complete revolution during each wavelength. Since circular polarized antennas send and receive in all planes, the signal strength stays strong as the signal transfers to a different plane. 
       FIG. 11B  shows a schematic diagram of a quadrature hybrid circuit  1100 . The quadrature hybrid circuit  1100  allows the use of a Luneburg lens with high gain, narrow beam width and a single antenna used for both the transmitter and receiver. As seen in  FIG. 11C , the quadrature hybrid circuit  1100  is basically a power splitter that divides an input signal  1101  into two outputs  1103  and  1104  having a 90° phase shift therebetween. The transmit power from the radar chip  1113  (AWR1642) has a 90° phase difference after passing through the quadrature hybrid circuit  1100 , which is connected to the two axes  1103  and  1104  of a waveguide feeding antenna  1115  to emit circularly polarized waves. The power of the input signal  1101  is split equally between the coupled through-ports  1103  and  1104  with a 90° phase difference. Signal power reflection is prevented from damaging the Receive (RX) input  1112  of the radar chip  1113  because the coupled ports are isolated by a resistor on line  1102  from the output ports  1103  and  1104  and due to the nature of a quadrature hybrid circuit. The RF energy reflected by the tank fluid enters antenna  1115  and feeds into axes  1103 ,  1104  and back through the quadrature hybrid  1100 . Phase shifts in the quadrature hybrid direct the energy back over the line  1102  into the receive signal  1112 . No power goes back to the Transmit (TX 1 ) pin  1101  since this is now the isolated port on the quadrature hybrid. Ground  1110  surrounds the antenna to maintain 50 ohms impedance matching. The physical dimensions of the rectangular aperture  1108  in the quadrature hybrid circuit  1100  are λ/4, or about 1 mm by 1 mm at 80 GHz. The impedance of the quadrature hybrid  1105  Zo is 50 ohms. 
       FIGS. 12A-12B  graphically illustrates two signals that are 90 degrees apart as applied to two inputs on a patch antenna in the radar board  1200 . This will create a circularly polarized radar signal. The quadrature hybrid circuit described above, and the patch antenna are etched onto the radar circuit board  1200 . When the radar chip  1201  transmits, it sends a chirp, indicated that 1203, with a transmit power and phase angle of zero. The quadrature hybrid circuit  1210  splits this incoming power in half into two signals  1204  and  1205  at 90 degrees and 180 degrees apart from the incoming phase. The signals combine in antenna  1208  to create a circular polarized radar signal. The RF signal from antenna  1208  passes through Luneburg lens  1207 , through the air in the tank  1219  and is reflected by the fluid  1220  therein. When the RF signal is reflected by the fluid, the signal passes through the Luneburg lens  1207  into antenna  1208  and again the signal is split into two half power signals  1213  and  1214  which are 90 degrees apart. They pass through the quadrature hybrid  1210 . Due to the nature of the quadrature hybrid, no power is returned to the Transmit (TX) port and all power goes to the Receive (RX 1 ) port. The Transmit (TX) port becomes the isolation port for the quadrature hybrid circuit. Reflections from mismatches sent back to the output ports are cancelled by the radar chip  1201 . The processor and the telemetry module, both generally indicated  1221 , direct the generation of chirps, data gathering, and determination of the depth level as described previously. 
       FIG. 13A  show an example of the radar chirp signal at  1301 . The radar generates this exemplary chirp signal to determine fluid level in the tank. Measuring fluid level in a tank using mmWave is challenging because there are many reflections and multiple paths of the signal between the tank walls. Reflections and excess noise due to high amplification can cause erroneous readings of the fluid level. Embodiments of the tank level monitor  100  uses various methods to improve the accuracy of the tank level and volume readings. 
       FIG. 13B  shows a list of different configuration profile parameters used by the mmWave radar module  309 , specifically the AWR1642 radar chip. These parameters are stored in nonvolatile memory in the AWR1642 chip and include the gain, number of chirps, timers, number of samples, and chirp frequencies. The high and low pass filters can be changed by the user within the AWR1642 radar chip. In most instances, there is no single set of operational parameters that suits all fluids and fluid levels. Accordingly, in some embodiments, an approach of using three or more profiles  1304  to generate chirps in rapid succession and selecting the best outcome provided an excellent method of obtaining good measurement results. Some of the chirp parameters that can be changed are shown at  1303 . The software in the AWR1642 radar chip can automatically generate chirps using three configuration profiles in very rapid succession and collects data on each resulting response. Data is analyzed automatically as described previously in  FIG. 4  to return the correct fluid level to the user. 
       FIGS. 14A-14D  show performance data associated with different chirp configuration profiles. The data shows the performance of the radar module as used to measure fluid level while draining a tank a few inches. The tank depth readings in these figures show that, although not required, it is beneficial to run multiple different chirp profiles. Three different chirp configuration profiles I, II, and III were used in this example, as shown in graphs  1401 ,  1402 ,  1403  in  FIGS. 14A-14C . Each chirp configuration profile resulted in sporadic high and low spikes  1410  in the measurements. These sporadic spikes  1410  are due to multi-path reflections and noise in the radar system that result in large measurement errors. As can be seen in graphs  1401 ,  1402 ,  1403 , the radar module  309  produced different measurement curves using the three different configuration profiles. This demonstrates that a single chirp configuration profile will not produce good measurement results given an unknown fluid level. Running different configuration profiles and selecting the best results as described herein provides a more accurate way to determine the correct fluid level. Radar module  309  can automatically use three different profile-configurations using processor  337  and can gather the resulting tank level measurements. Three responses are obtained, each representing a different configuration profile, and each containing 10 sets of distances and signal strength measurements: 
     Res 1: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th]
 
Res 2: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th]
 
Res 3: [RANGE 1st, POWER 1st] [RANGE 2nd, POWER 2nd] . . . [RANGE 10th, POWER 10th]
 
     Then, two of the three responses from above that have the strongest signal strengths are then averaged to create a set of 10 best distance and signal readings, as shown at  1404  in  FIG. 14D . As mentioned earlier, this may include, for example, [RANGE 1st, POWER 1st] from profiles 1 and 2, [RANGE 2nd, POWER 2nd] from profiles 2 and 3, [RANGE 10th, POWER 10th] from profiles 1 and 3, and so on. As this figure show, merging the chirp responses (by ignoring depth level readings that vary greatly from their counterparts) shows that running multiple chirp profiles can produce highly accurate results. 
     In general, individual configuration profiles typically have an error of about 5-10%. The three-configuration profile approach herein can produce results with an accuracy of within 0.5 percent, as seen in graph  1404 . And the radar module  309  can perform all of this in about 0.5 seconds. The set of range/distance and signal power readings is then sent to controller  302  to determine the most likely correct level using the process described with respect to  FIGS. 4A-14C . A single fluid depth and gallons are then sent to the user on display  318  and telemetry modules  306  or  307 . 
       FIG. 15  shows exemplary messages that may be displayed to the user on display  318  or sent off-site via the telemetry modules  306  or  307 . These messages include system status messages, examples of which are listed at  1501 , as well as system error messages, examples of which are listed at  1502 . These messages provide users with useful information about the tank level monitor  100 . Those having ordinary skill in the art will understand that other status and error messages besides the ones shown here may also be used. 
       FIG. 16  shows an exemplary keypad  1601  (also see  FIG. 3  at  319 ) that may be used in some embodiments to program operation of the tank level monitor  100 . The programmability of the tank level monitor  100  allows it to be used in many diverse situations on different chemicals. An exemplary list of programming messages is shown at  1602  (along with information about the parameters). These messages  1602  may be displayed to the user via the display  103  to assist the user in programming the tank level monitor  100 . 
       FIGS. 17A-17B  show different views of the tank level monitor  100  in isolation and  FIG. 17C  shows a view of the tank level monitor  100  as installed on top of a tank. As discussed previously, the tank level monitor  100  can used on virtually any type of tank. The typical installation is where the monitor  100  is placed on top of a plastic tank  101  and the radar signals can “see” through the plastic tank wall. Installation on metal tanks is also possible by using a special adapter to mount to one of the tank flanges, as shown in  FIGS. 17A and 17B . An ISO tank with a typical 2-inch NPT fitting is shown at  1700  in  FIG. 17C . In  FIGS. 17A and 17B , a nipple  1703  screws into a tank flange  1705 . Teflon plate  1702  screws onto nipple  1703  and the tank level monitor  100  is attached to the plate  1702  so that the radar beam is centered over the 2-inch nipple. The Teflon plate has a low dielectric constant, so the radar beam easily passes through it while it inherently protects the radar from the caustic fluid and seals the tank. Shut-off valve  1704  keeps fluid from leaking in case there is a major accident and the tank rolls over during transportation and breaks plate  1702  from nipple  1703 . Many other mounting techniques are available within the scope of the disclosed embodiments. 
       FIG. 18A-18E  are views of the tank level monitor  100  mounted on several different types of tanks. The tank level monitor  100 , with its adaptive algorithms and sophisticated filtering and depth discernment, can be adapted to many types of tanks. Adapter  1702  from the previous figures can be used for mounting and to access fluid on larger tanks. Smaller ISO tanks  1803 , as well as larger poly tanks  1801 , metal ISO Tanks  1802 , ISO tanks  1804 , tanks  1805  of the type used in tank farms. 
       FIG. 19A-19D  are views of the tank level monitor  100  mounted on taller chemical tanks  1901  where the tank level monitor  100  can sit unseen at the top of the tank and transmit level readings by satellite, smartphone or locally to the monitor&#39;s remote display. The tank level monitor  100  can also be mounted on the taller poly tanks  1902 ,  1903 , as well as frac tanks  1904 . 
       FIG. 20  shows an embodiment where the tank level monitor  100  (not expressly seen) is used to send fluid level readings for a tank  2000  to an overhead display  2001 . A close-up view of the overhead display is shown at  2002 . Looking at an overhead display  2002  is faster than accessing data online or via a smartphone and is particularly helpful when taking tank level inventories from a moving vehicle, such as a pickup truck, or when an operator is walking through the tank yard. The tank level monitor  100  sits on top of the tank  2000  and takes measurements of the fluid level, then transmits data to an overhead display  2002 , such as an LCD display. The LCD display  2002  is preferably a type that continually displays the data sent to the display and is only updated when new data is received from the tank level monitor  100 . Back lighting turns on so the LCD display  2002  can be seen at night. The LCD uses very low current for battery power. In some embodiments, a separate remote display  2003  can be used to get the current level detailed readings in the tank. 
       FIGS. 21A-21B  show examples of the tank level monitor  100  communicating with a remote display  2101  or a smartphone  2111  using Bluetooth. Remote display  2101  is positioned at the base of a tall tank, such as the one shown at  2000  ( FIG. 20 ). The operator can then press button  2102  on the remote display  2101  to get the current level within seconds. When the button is pressed, a BLE low power Bluetooth module on the remote display  2101  communicates with and wakes up the tank level monitor  100 . Having a Bluetooth module in the tank level monitor  100  creates a private wireless serial connection with the smartphone  2111  or remote display  2101  when a device requests a connection. When sleeping, the monitor  100  advertises its identity using BLE to interrogate whether a smartphone or remote display wants to communicate. Monitor  100  takes readings and updates local display  2104  as well as sends data to the user at the base of the tank on display  2101 . Alternatively, smartphone  2111  can display the current tank status as well as be used to program the tank level monitor  100 . A suitable smartphone app can use the Bluetooth capability of each monitor  100  to allow the user to select a specific monitor  100  and create a private communication link to that monitor  100 . Any one of many monitor  100  nearby (within Bluetooth range) can be accessed using a smartphone. This same Bluetooth capability allows the remote display or smartphone to access data and wake the monitor from sleep without touching the monitor  100 . 
       FIGS. 22A-22C  show examples of screens that may be displayed on an iPhone or Android app for the tank level monitor  100 . The exemplary smartphone screen  2201  in  FIG. 22A  shows all the various monitors  100  that belong to a particular login or customer. The exemplary smartphone screen  2202  in  FIG. 22B  shows the location of all monitors  100  on a map. The exemplary smartphone screen  2203  in  FIG. 22C  shows driving instructions that can guide the user to the site. The screens leverage the existing GPS location and navigation capability equipped in most Smartphones 
       FIGS. 23A-23B  show examples of screens that may be displayed on a smartphone to allow a user to select which of several monitors to evaluate. An additional feature is the ability for the user to touch any of the serial numbers  2201  on the smartphone to initiate a wake-up sequence for that particular monitor  100  over Bluetooth. Within seconds of doing so, the monitor  100  wakes (if sleeping) and accepts a private connection (i.e., via a handshake) between the smartphone and that monitor, a tank reading is taken, and the monitor  100  sends data to the smartphone showing tank level, battery level, any error messages, distance to fluid, and signal strength data (see  FIG. 24A  at  2401 ). The exemplary smartphone screen  2301  in  FIG. 23A  shows all the various monitors  100  that belong to a particular login or customer account. Once the monitor is selected as shown in smartphone screen  2305  (e.g., by using drop down menu  2307 ), the user can select the date range of interest at fields  2308  and see all depth readings taken during the selected date range at  2309 . 
       FIGS. 24A-24B  show examples of screens that may be displayed on a smartphone to allow a user to directly communicate with a selected monitor  100 . The exemplary smartphone screen  2401  in  FIG. 24A  shows a smartphone app that uses Bluetooth to allow the user to directly communicate with a selected monitor  100  and see all current depth readings taken by the monitor  100 . The exemplary smartphone screen  2402  in  FIG. 24B  shows a smartphone app that allows the user to access and see any alarms that may have occurred at a selected monitor  100 . 
       FIG. 25  shows an example of a screen that may be displayed on a smartphone to allow the user to communicate with a selected monitor  100  using simple text messages. The exemplary smartphone screen  2501  in  FIG. 25  shows a smartphone app that uses Bluetooth to allow the user to send simple text messages to the selected monitor  100 . The controller  302  in the monitor  100  receives the text messages via the Bluetooth module  303  and extracts the text information therefrom. Programming within the monitor  100  processes the extracted text information and modifies the appropriate operational parameters stored in the controller  302  accordingly. To this end, the text information needs to be in a format that is understandable and recognizable by the controller  302 . Examples of text messages that may be sent to the monitor  100  are shown at  2502  and can include parameter values that can be directly downloaded into the monitor from the text messages. Commands may be sent to the monitor  100  from a smartphone via Bluetooth in a similar manner. 
       FIG. 26  shows examples of commands that a user may send to the monitor  100  via a smartphone to allow the user to control various operations. The exemplary commands, indicated at  2601 , allow the monitor  100  to be programmed using the smartphone. In some cases, the user can also use the smartphone to request a current tank parameter, indicated at  2602 , for a given tank. The monitor  100  also has tank templates  2603  saved therein for various types of tanks to allow the user to quickly configure the tank for customer&#39;s monitor. The tank templates include various attributes about the tanks that the user may fill in via the smartphone. These attributes may include a lookup strapping chart for the customer&#39;s tank, radar power needed for the tank, tuning settings for the tank, distance at top of tank (to ignore for reading purposes), tank height, other tank dimensions, time of day call-in times, GPS update times, and even GMT time offset in some cases. The tank and radar settings and other information may be stored on the smartphone in some embodiments, or the information may be stored on the monitor  100  in some embodiments, or a combination of both. In embodiments where the tank templates and information are already preloaded on the monitor  100  (which is normally the case), a customer may simply send a command like “T12” (see  2603 ) to automatically configure a particular tank. This speeds installation of the monitor  100  on the tank, particularly when all tanks in a large tank yard are identical, so manual tuning of the monitor is not required. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled.