Abstract:
Fuel flow information is generated in an engine compartment and transmitted for display on the fuel page(s) of a GPS signal receiver located in view of a vehicle operator. A fuel transducer coupled to a pre-programmed micro-controller are provided as an integrated single unit in the engine compartment of the vehicle (e.g., an aircraft). The integrated transducer/micro-controller unit outputs RS232 fuel flow signals to the GPS signal receiver without requiring any extra panel space. Since the transducer/micro-controller is already pre-programmed to compensate for the proportionality or “K” factor, no further calibration or compensation programming is needed at installation time (or when one composite transducer/computer unit is substituted for another). Separate transducer/micro-controller power supply and grounding connections suppress common mode noise. A blinking LED power/fuel flow visual display on the unit in the engine compartment helps trouble shoot power and/or transducer problems.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to apparatus and method for generating vehicular engine fuel flow data suitable for supply to a GPS-receiver for display to a vehicle operator (e.g., the pilot or co-pilot of an aircraft).  
         BACKGROUND OF THE INVENTION  
         [0002]    The following prior art issued U.S. patents are examples of prior art fuel flow measuring systems for various types of vehicles:  
           [0003]    U.S. Pat. No. 6,275,231—Obradovich (2001)  
           [0004]    U.S. Pat. No. 6,195,604—Moore et al (2001)  
           [0005]    U.S. Pat. No. 6,151,549—Andrews et al (2000)  
           [0006]    U.S. Pat. No. 4,400,779—Kosuge et al (1983)  
           [0007]    U.S. Pat. No. 4,296,472—Sarkis (1981)  
           [0008]    U.S. Pat. No. 4,218,744—Pratt et al (1980)  
           [0009]    U.S. Pat. No. 4,050,295—Harvey (1977)  
           [0010]    U.S. Pat. No. 3,908,451—Walker et al (1975)  
           [0011]    Walker et al, Harvey, Pratt et al, Sarkis and Kosuge et at are representative of prior art dealing with various fuel flow measuring systems. None of these patents discloses a system that interfaces with a vehicle GPS signal receiver, although the Pratt et al patent uses a Flow Scan model 201 transducer.  
           [0012]    Andrews et al, Moore et al and Obradovich disclose systems that utilize both fuel transducers/sensors and GPS signal receivers. Andrews et al discloses a truck fuel control system that adjusts fuel flow on the basis of the truck&#39;s elevation, as determined by the GPS signal receiver. Moore et al discloses a tractor monitoring system, which incorporates a GPS signal receiver for plotting a yield map showing the amount of grain harvested in a given area. Obradovich discloses a management system for an automobile, which includes a GPS signal receiver for an associated navigation system.  
           [0013]    There are also fuel flow monitoring systems for aircraft that generate fuel flow data for input to an existing GPS “fuel page” display. For example, fuel flow computer and display systems are available from Insight Instrument Corporation, from JP Instruments, Inc. and from Shadin, Inc. However such prior systems include a transducer mounted in the engine compartment and a separate cabin panel mounted computer and display. The separately installed computer/display requires programming upon installation to accommodate the proportionality or “K” factor of the particular installed transducer and, of course, requires its own panel space—even though the same fuel flow data may be passed on to the GPS receiver for display there as well.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention is directed to a simplified, less expensive, fuel flow data generating method/apparatus for use in conjunction with a GPS signal receiver. The exemplary simplified fuel flow system includes a micro-controller and fuel flow transducer co-located in a common installation housing in the engine compartment. The micro-controller is disposed in the engine compartment (between the flow transducer and the cabin panel mounted GPS signal receiver) to perform fuel flow calculations, including pre-programmed “K” factor compensation for the particular transducer co-packaged therewith. The resulting fuel flow data is displayed on the “fuel flow” page(s) of the GPS signal receiver—without requiring any extra panel space.  
           [0015]    In operation, a user need only turn on the GPS receiver and enter the total fuel on board on the fuel page (if not previously entered), which is the typical procedure associated with many aircraft GPS signal receivers. Nearly instantly, fuel flow information will be produced and displayed on the fuel pages of the GPS signal receiver display. More particularly, the fuel flow transducer inputs raw incremental fuel flow measurement pulses to a co-located factory-programmed micro-controller that calculates calibrated fuel flow rate (and perhaps total fuel used or other fuel-related parameters). The calculated fuel flow data is then formatted and transmitted through the firewall to a serial data interface on the GPS receiver for display.  
           [0016]    The transducer can be a conventional commercially available fuel sensor such as, for example, a Flowscan 201B fuel sensor. A commercially available GPS signal receiver can be used such as, for example, the Garmin 430/530.  
           [0017]    By utilizing the fuel page(s) display of a suitable GPS signal receiver already located in a vehicle (e.g., the cockpit of an airplane), no additional display device or space need be provided to add clutter to the instrument panel.  
           [0018]    The transducer and co-located micro-controller assembly in the vehicle engine compartment preferably includes an LED (light emitting diode) which indicates power supply while also flashing at a rate related to that of fuel flow output pulses from the transducer thus facilitating trouble shooting processes.  
           [0019]    Simplified installation is facilitated by the single transducer/computer unit (e.g., on the engine, serially within an engine compartment fuel supply line and electrically to an RS232 data input of an existing GPS unit).  
           [0020]    Separate power supply and grounding connections to the transducer and micro-controller, in conjunction with an isolating opto-coupler therebetween, also help suppress common mode noise and/or other “ground problems”. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 depicts an exemplary embodiment of an integrated transducer/micro-controller engine-mounted assembly in accordance with this invention;  
         [0022]    [0022]FIG. 2 is a block diagram of the assembly depicted in FIG. 1;  
         [0023]    [0023]FIG. 3 is an exemplary hardware/software/firmware process flowchart for the micro-controller of FIG. 2;  
         [0024]    [0024]FIGS. 4 and 5 show the fuel page display of an exemplary GPS signal receiver in accordance with an exemplary embodiment of the invention; and  
         [0025]    [0025]FIGS. 6 and 7 depict exemplary modifications of the exemplary embodiment for installation on multi-engine vehicles. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0026]    An exemplary integrated transducer/micro-controller engine mounted assembly  10  is shown in FIG. 1. A stainless steel housing  12  is affixed to and supported on engine mounting bracket  14 . For example, such bracket may be adapted to mate with engine the juxtaposed engine casing flanges on top of a typical horizontal reciprocating piston aircraft engine (e.g., near the center of the engine where an injection fuel flow distributor is typically mounted). When so mounted, it will be relatively convenient to direct the total engine injection fuel flow into and out of housing  10  as shown (e.g., standard fuel line connectors  13 ). As also depicted, a shielded multi-conductor electrical cable connection  16  projects from the back side of housing  10  so that it can be conveniently routed to and through the firewall, into the cabin and connected to a conventional RS232 data input port of an existing GPS unit (and to the GPS or other suitable power source if electrical power is not available on a pin of the data port connector).  
         [0027]    As shown in FIG. 1, LED  28  is visible to maintenance personnel when the engine cowling is opened. If the LED is lit, then it is known that the unit  10  is being supplied with electrical power (e.g., via the shield and a conductor of cable connection  16 ). The LED  28  is also configured to flash on and off at a rate related to fuel flow signals (e.g., incremental fuel flow pulses) output from the fuel flow transducer inside housing  10 . Thus by causing fuel to flow (e.g., by activating a fuel pump and/or by starting the engine), the operator and/or maintenance personnel can tell whether the fuel flow transducer/computer is functioning.  
         [0028]    [0028]FIG. 2 shows in block diagram the transducer/micro-controller assembly components of the FIG. 1 exemplary embodiment. As shown in FIG. 2, fuel flow transducer  20  senses incremental amounts of fuel flow to a vehicle engine, (i.e., an airplane engine), and outputs a corresponding number of electrical signal pulses. Although transducer  20  may have its own internal opto-coupler, output pulses from transducer  20  are preferably connected through yet another isolating opto-coupler  22  to micro-controller  24 . Micro-controller  24  outputs processed data signals through a voltage level changing interface  26  to the conventional serial data input port of GPS signal receiver  40 , and to LED  28 . A power supply  29 / 29 ′ supplies separate operating power connections to (a) transducer  20 , and (b) opto-coupler  22 , micro-controller  24  and interface  26 .  
         [0029]    Transducer  20  may be of the type that causes fuel to turn an impeller mounted on jewel bearings. The impeller interrupts the infrared light beam of an internal slotted opto-coupler. The opto-coupler signal is then amplified to produce an open-collector output current pulse. Transducer  20  typically produces a pulse stream having a number of pulses linearly related to increments of fuel flow for flow rates down to 0.3 gallons per hour—without causing any appreciable pressure drop in fuel flow to the engine.  
         [0030]    Alternatively, the fuel transducer may be based on other flow related phenomena (e.g., a pressure drop through an orifice, an ultrasonic-based transducer using Doppler effects, a heated probe induced temperature gradient, or any other known flow measurement technique) and/or output an analog signal related to sensed fuel flow. A conventional A/D converter could be used to provide corresponding digital signals related to measured flow.  
         [0031]    By coupling the electrical output from transducer  20  into micro-controller  24  through yet another opto-coupler  22  (i.e., external to the flow transducer) and separating the electrical return paths (e.g., engine ground for transducer  20  and GPS ground for other circuits) and effectively using separate power supplies, the potentially deleterious effects of common-mode noise voltages can be reduced or virtually eliminated while also enhancing safety of the installation.  
         [0032]    For example, common mode noise may appear superimposed on ground connections because of alternator problems or higher than normal ground wire resistances. Two current regulator/limiting diodes D 1 , D 2  (e.g., gate-shorted FET&#39;s) respectively supply current limited regulated electrical power to transducer  20  (including its internal opto-coupler) and the remainder of the circuits. They regulate the current for the open-collector outputs of the opto-couplers. As shown, the electrical return path (i.e., “ground”) of the transducer in assembly  10  is the engine/airframe and therefore common-mode noise (i.e., alternator return path currents) present on the airframe may appear as offsets added to the output pulse of transducer  20 . Such offsets, if not alleviated, may reduce the signal-to-noise ratio of the transducer output pulses proportionally.  
         [0033]    However, in the preferred exemplary embodiment, the transducer output pulses are filtered through an additional opto-coupler  22  with its transistor output side powered from the separate power supply  29 ′ (which also powers the micro-controller  24  and interface chip  26 ). Preferably the power supplies  29 ,  29 ′ also provide over-voltage and over-current protection (as well as reverse-polarity protection) as an added bonus. As a result, the fuel flow transducer/computer assembly  10  is relatively immune to common mode noise voltages and has a relatively high signal-to-noise ratio.  
         [0034]    The current-limiting by power supplies  29 ,  29 ′ and separated power supply/ground return for circuit components mounted near fuel sources is also desired for safety reasons. For example, if the flexible conductive ground strap between the engine and airframe develops some appreciable resistance (e.g., it becomes loosely attached, corrosion occurs, etc.), then a relatively small gauge ground wire associated with some other circuit may effectively become a lower resistance ground return path for unexpectedly large current. Such has been known to effectively burn up a small wire and start a fire. Thus there is more than one reason to desire the use of separate, current limited, power supply/return circuits in the exemplary embodiment.  
         [0035]    Factory-programmed micro-controller  24  reads (i.e., detects and counts) raw incremental fuel flow pulses, received from transducer  20  through opto-coupler  22  (e.g., during interrupts), compensates for the appropriate pre-determined K factor (i.e., a customized proportionality calibration factor), calculates fuel flow rate, converts calculated fuel flow rate into a serial stream of RS232 digital data acceptable to GPS signal receiver  40 , and outputs the serial stream of data to a suitable voltage level adapter interface  26 .  
         [0036]    Micro-controller  24 , in the preferred exemplary embodiment, also drives LED  28 , using flow rate dependent pulse modulation which, upon opening the cowling, indicates to the operator or service person: (a) the presence of power to the fuel flow assembly  10  and (b) the operability of the transducer/micro-computer by blinking of the LED. For higher fuel flow rates LED  28  may blink more rapidly and conversely for lower fuel flow rates LED  28  may blink less rapidly. For example, at engine idle LED  28  may blink about once per second, and as the engine revs up it may blink proportionately more rapidly.  
         [0037]    LED  28  is preferably disposed on housing  12  of assembly  10  in the engine compartment where it can be best viewed while the vehicle is at rest, although the engine can be revved to observe changes in fuel flow rates. Alternatively, even with the engine off, one can engage a fuel pump to pressurize the fuel injection system and thus temporarily cause sufficient fuel flow to cause blinking of LED  28  and thus confirm operation of at least transducer  20 , opto-coupler  22  and micro-controller  28 . This simple troubleshooting capability can be quite advantageous out in the field.  
         [0038]    The RS232 interface chip  26  receives lower level (e.g., 3-5 volt) logic level RS232 signals, namely, the serial stream of data output from micro-controller  24 . It generates its own higher level (e.g., 7-10 volt) drive voltages and relays the higher level RS232 signals onward to GPS signal receiver  40  at an acceptable voltage level for typical GPS receivers.  
         [0039]    The system  10  does not require user calibration (i.e., at installation or any other time), because the assembly of transducer  20 , opto-coupler  22 , micro-controller  24 , etc. is pre-calibrated at the factory (e.g., by pre-programming mico-controller  24  to match the K factor value for the particular transducer  20  included therewith). Although-this means that the transducer alone cannot be easily swapped out in the field, the overall unit assembly  10  can be easily changed out together as a unit in the field. Thus, different fuel flow assemblies  10  are interchangeable—even though there is no need to change out or re-program GPS signal receiver  40  when a particular fuel flow system  10  is substituted for a different one. The K factor of transducer  20  is accounted for by micro-controller  24  in that micro-controller  24  is factory-programmed to take into account the specific K factor of its associated transducer  20 .  
         [0040]    [0040]FIG. 3 depicts a simplified hardware/software/process flowchart for micro-controller  24 . For example, flow rate counter  30  and fuel used counter  31  receive pulse data from opto-coupler  22 . Data from these counters are used for calculating calibrated (i.e., compensated for K factor) fuel flow and, if desired, fuel used. An 8 MHz clock  37  drives flow rate timer  38  and bit rate timer  35 . The calculated digital result is passed to output formatter  34  and to an output pulse width/frequency modulator  33  which drives LED  28 . Transmit section 36 receives formatted data from process  34  and from bit rate timer  35  and transmits a (low level) RS232 signal at 9600 baud to interface  26 .  
         [0041]    In operation, the total fuel used is computed using continuous accumulation of pulses coming from transducer  20  through opto-coupler  22 . The fuel flow rate is measured by periodically averaging the fuel quantity represented by 100 pulses (nominal fuel flow rate of 17 gallons/hour produces 30,000 pulses per gallon) per unit time (e.g., once every three-quarters of a second). Micro-controller  24  starts flow rate timer  38 , flow rate counter  30  and fuel used counter  31  on the first input pulse from opto-coupler  22 , waits about half a second and then stops flow rate counter  30  and flow rate timer  3 S on the next pulse received. It then calculates the fuel flow rate using the number of pulses accumulated into flow rate counter  30  and the number of seconds accumulated into flow rate timer  38 . Such operations are repeated cyclically to provide a sequence of calculated flow rate values. Conventional averaging techniques may be used to smooth out the calculated fuel flow rate over a moving time window.  
         [0042]    In many cases, the GPS unit itself will calculate and display cumulative fuel used based on input fuel flow data. However, it may be desirable (or necessary) to generate and supply such cumulative fuel use data to the GPS unit and thus the preferred exemplary embodiment includes this capability. The value in total fuel used counter  31  is compared against a look-up table and if the fuel used counter value is bigger, then the fuel used counter  31  is reset and the amount of fuel represented by that predetermined value is added to an ongoing accumulation of total fuel used (e.g., as maintained in another memory register counter). The addition is preferably done in a way that eliminates floating-point underflow errors. The accuracy of the fuel flow rate and total fuel used calculations can be around 0.0001% through the use of such floating-point arithmetic. However, the overall accuracy of the exemplary fuel flow system  10  is limited by the accuracy of typical transducers  20  to about 1%.  
         [0043]    After the fuel flow rate and total fuel used have been calculated, micro-controller  24  arranges the data into the proper format via an output formatter module  34 , and times the data output to interface  26  at 9600 baud via bit rate timer  35  and transmit module  36 . The transmission may typically occur every second as requested by GPS signal receiver  40 . The 9600 baud rate is typical for most commercially available GPS signal receivers, but the exemplary fuel flow system  10  can support baud rates up to 19200.  
         [0044]    During computation and transmission, fuel flow pulses are still always being counted and accumulated (by separate counters  30 ,  31 ) so no fuel pulses are lost. The next computation cycle is very similar to the first one. For flow rate calculation, fuel flow counter  30  is reset and new pulse accumulation begins. However, fuel used counter  31  is not necessarily periodically reset (e.g., when its content exceeds some pre-determined total) but may be large enough to just keep adding pulses between re-fueling operations and thus directly provide a cumulative measure of fuel used. Storing all the information in floating-point registers that cannot possibly overflow during a flight eliminates the possibility of integer overflow. Moreover, the typically-required output data format will cause overflow well before the fuel used register would, because in most GPS data formats a 5 digit integer number (99999) is the maximum value that can be transmitted.  
         [0045]    The self-contained transducer/computer module  10  provide the user with a simple and efficient way of providing fuel information directly to GPS fuel pages. It does so by eliminating tedious installation and set-up procedures that are required for other fuel flow computers. Just mount module  10  on top of the engine (in series with the engine fuel flow) and electrically connect it to the GPS input power, RS232 input and ground. There is no programmable K factor to set-up, no switches to turn, no jumpers to remove or add.  
         [0046]    LED  28  preferably is mounted on a printed circuit board (together with the data processing circuits) contained inside the stainless steel case  12  that contains the Flowscan  201  fuel flow transducer. A proper sized hole is drilled in the case and the LED is pushed half way outside the case so it can easily be viewed from outside. The LED is of high-brightness and wide viewing angle type to make it visible from a couple of feet away. To see the LED, a person should open the cowling and look on top of the engine where the module  10  can typically be mounted.  
         [0047]    The GPS typically has the capability to calculate fuel usage per distance traveled, remaining fuel to the next waypoint, etc. The fuel information will show on the fuel pages of the GPS. The GPS has to be setup by the installer (not the manufacturer) to receive the input serial stream. Major GPS manufacturers accept the “format Z” serial communication protocol described below. For example, for a GARMIN 430/530, the GPS should be setup to receive “SHADIN FADC” on serial port 1.  
         [0048]    Since even LED  28  is located on case  12 , the unit  10  literally takes no panel space. The module  10  does not need user calibration because it contains its own Flowscan  201  transducer and is calibrated (by programming micro-controller  24 ) at the factory where module  10  is manufactured/assembled. The internal Flowscan  201  transducer cannot be replaced in the field. However, units  10  are interchangeable in the field. The software for each micro-controller  24  changes with the K factor of the Flowscan transducer  20  used in that particular unit  10 .  
         [0049]    In the presently preferred exemplary embodiment, a different software object code is available for each K factor. When it is time for the software to be loaded, a technician researches the Flowscan K factor for the particular transducer being used in that particular module  10  and loads the appropriate object code into the micro-controller  24  (part of the object code file name may be the K factor; for example for a K factor of 2995 the object code file name could be TF2995.OBJ). The programming is done with the micro-controller on-board so there are no mix-ups. After programming, a computerized test is done to verify that the fuel flow and fuel used is computed correctly. From that point on, the unit is sealed and ready for shipping.  
         [0050]    Manufacturers of other fuel flow computers require additional boxes to be installed between the Flowscan transducer (mounted on top of the engine) and the display unit (mounted on the panel, inside the cockpit). However, the present self-contained module  10  is mounted on the engine, the fuel lines connect directly with it, there are no additional boxes required. It is literally: fuel in, digital fuel flow data out.  
         [0051]    As noted, “ground problems” are eliminated through the use of separate power supplies, ground connection points and the additional opto-coupler.  
         [0052]    Prior fuel flow computers require the installation of a transducer (e.g., the Flowscan  201 ) on top of the engine connected serially in the fuel supply line and a panel-mount instrument. However, the present module  10  has the Flowscan  201  transducer built-in and connects directly to the GPS. If the power is taken from the GPS connector (and not from the aircraft power bus) then the only electrical connection is with the GPS.  
         [0053]    The following is an example of the “computer sentence” RS232 (transmission data format) that is accepted (once every second) by Garmin  400  series GPS signal receivers. This format is referred to as a “Z” format, because it transmits a “Z” character in front of every recognized data value. This format is a fixed sequence bounded by start (STX) and end (ETX) transmission characters. This or similar data transmission formats are used by other GPS manufacturers.  
                                       STX           ZA012CRLF   (“012” represents indicated air speed - knots)       ZB345CRLF   (“345” represents true air speed - knots)       ZC678CRLF   (“678” represents Mach speed - thousandths)       ZD + 1234CRLF   (“sign1234” represents pressure altitude - tens of feet)       ZE + 5678CRLF   (“sign5678” represents density altitude - tens of feet)       ZF + 12CRLF   (“sign12” represents outside air temperature - Celsius)       ZG + 34CRLF   (“sign34” represents true air temperature - Celsius)       ZH567CRLF   (“567” represents wind direction - degrees from North)       ZI123CRLF   (“123” represents wind speed - knots)       ZJ + 45CRLF   (“sign45” represents rate of return - degrees per           second)       ZK + 678CRLF   (“sign678” represents vertical speed - tens of feet/           minute)       ZL123CRLF   (“123” represents heading - degrees from North)       ZM4567CRLF   (“4567” represents fuel flow, right - tenths of gallons/           hour)       ZN1234CRLF   (“1234” represents fuel used, right - tenths of gallons)       ZO5678CRLF   (“5678” represents fuel flow, left - tenths of gallons/           hour)       ZP1234CRLF   (“1234” represents fuel used, left - tenths of gallons)       ZQ567CRLF   (“567” represents error log/reason indicator)       ZR890CRLF   (“890” represents checksum)       ETX                                                          
 
         [0054]    [0054]FIGS. 4 and 5 show the fuel flow display pages for the exemplary Garman 430 GPS signal receiver  40  that may be utilized with the exemplary fuel flow system  10 . To operate the installed fuel flow computer system on, for example, an aircraft, the pilot turns on GPS signal receiver  40  and then conventionally enters the total fuel on board (FOB) as shown in FIG. 5 (e.g., typically at start-up after a re-fueling operation when a known starting fuel amount is readily available). Immediately thereafter GPS signal receiver  40  will display the fuel flow rate and total fuel used as described above and as shown in FIG. 5 where the display reveals:  
                                                           Fuel on board (FOB) =   86   gallons           Fuel flow (FLOW) =   16.0   gallons/hour           Fuel Required (REQ) =   56.4   gallons           (to go from present position to CYSN)           Left Fuel on Board (LFOB) =   29.2   gallons           Left Reserve Flight Time (LRES) =   1:50   hours:minutes           Fuel Efficiency (EFF) =   9.6   gallons/nm           Range (RNG) =   819   nm           Endurance (ENDUR) =   5:21   hours:minutes                      
 
         [0055]    The system  10  described above is intended for a single engine powered vehicle. If a multi-engine vehicle (e.g., a twin engine airplane having engines on both the left and right side) is involved, then some modifications will be required to properly display vehicle fuel usage on the GPS receiver.  
         [0056]    For example, one may provide micro-controller  24  with an RS232 data input and appropriate software/firmware to add input “Z” format fuel data to the otherwise locally calculated fuel flow data (and possibly cumulative fuel flow if present) before outputting composite RS232 “Z” formatted fuel data. Such a modified fuel flow measuring assembly  10 ′ is depicted in FIG. 6 as receiving data from an unmodified fuel flow measuring assembly  10  so as to produce composite “Z” format fuel data to GPS receiver  40 . Of course, any desired plurality N of modified units  10 ′ could be connected together in a daisy-chain fashion to accommodate a corresponding number N of engines.  
         [0057]    Alternatively, as depicted in FIG. 7, a plurality of unmodified units  10  could have their Z—format fuel data accumulated in an intermediate data combiner  11  before input to a common GPS unit  40 . Two such units are depicted in FIG. 7 although, as will be appreciated, any desired number N of such units could be similarly accommodated if the combiner  11  (e.g., a suitably programmed micro-processor) is provided with appropriate connectors and the like.  
         [0058]    While the invention has been described in connection with what is presently considered to be preferred exemplary embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover all modifications and equivalent arrangements included within the spirit and scope of the appended claims. It will be understood, for example, that the computing circuits may be implemented entirely in hardware or partly in hardware (micro-processor, micro-controller, hardwired arithmetic and/or gate circuits, etc.) firmware, software, DSP chips, programmed gate arrays, and the like.