Abstract:
The invention relates generally to a system and method for testing fuel evaporative systems, and more particularly to a stand-alone tank tester system (and method) for testing vehicle fuel tank integrity. Furthermore, a self-contained calibration tank with switchable leak sizes for calibrating the tank tester to multiple leak sizes is provided. Constant flow and vacuum methods for testing fuel tank integrity are also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Application is a divisional of U.S. patent application Ser. No. 11/965,113, filed Dec. 27, 2007 (currently pending), which is a divisional of U.S. patent application Ser. No. 11/546,300, filed Oct. 12, 2006 (now U.S. Pat. No. 7,409,852 B2, issued Aug. 12, 2008), which is a divisional of U.S. patent application Ser. No. 10/974,677, filed Oct. 28, 2004 (now U.S. Pat. No. 7,168,297 B2, issued Jan. 30, 2007), which claims priority to U.S. Provisional Patent Application Ser. No. 60/514,745, filed Oct. 28, 2003, each of which are hereby incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to a system and method for testing fuel evaporative systems, and more particularly to a stand-alone tank tester system (and method) for testing vehicle fuel tank integrity. 
       BACKGROUND OF THE INVENTION 
       [0003]    The loss of fuel from a vehicle fuel tank (and associated piping) through evaporation to the atmosphere may result in, among other things, undesirable hydrocarbon pollution. 
         [0004]    Accordingly, many systems and methods have been developed to test the tank integrity of vehicle fuel systems, and to identify vehicles that fail to comply with promulgated regulations and mandated guidelines (regardless of whether they are on the federal, state, or local level). 
         [0005]    Unfortunately, many existing fuel tank integrity testing systems can be expensive, cumbersome, and inconsistent. These and other drawbacks exist. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention solving these and other problems relates to a stand-alone tank tester system (and method) for testing vehicle fuel tank (or fuel system) integrity. 
         [0007]    According to an embodiment of the invention, a system is provided for a tank tester. The tank tester may perform various processes for testing fuel tank integrity, measurement of fuel tank volume, measurement of fuel volume, measurement of vapor space, measurement of fuel temperature, or other tests. The tank tester may include a computer-implemented component (“computer component”), a testing component, a housing, a calibration tank, and/or other elements. In some embodiments, the tank tester may perform various calibration and self-test procedures which may be necessary for efficient and accurate execution of fuel tank tests. 
         [0008]    Computer Component 
         [0009]    In one embodiment of the invention, the tank tester may include a computer component. The computer component may include various software elements and computer hardware such as, for example, a processor board. The processor board may include a processor which may be or include, for instance, any of the Intel x86 PC/AT microprocessors or compatible processors such as those available from Cyrix or AMD. The processor board may also include one or more analog inputs with A/D converters that interface with various sensors, one or more digital outputs to interface with one or more solenoids, and other elements. The processor board may also include one or more serial ports that may interface with additional equipment such as, for example, Emissions Inspection Systems (EIS) equipment, a modem, a real time clock, or other devices or elements. The processor board may also include one or more memory devices. The one or more memory devices may include flash erasable programmable read-only-memory (FEPROM), a hard disk, or other data suitable memory for data storage. 
         [0010]    The computer component may also include a signal conditioning board operatively connected to the processor board. The signal conditioning board may, among other things, condition electrical signals into and out from any sensors. The signal conditioning board may include a DC/DC power supply. The signal conditioning board may also include a pressure switch control for releasing pressure from the testing component (described in detail below) upon the existence of a predetermined pressure within the testing component. The signal conditioning board may further include one or more solenoid drivers for operating one or more solenoids throughout the tank tester. One or more solenoids may be utilized to operate various elements of the testing component including switches, valves, or other elements. 
         [0011]    The computer component may also include one or more sensors operatively connected to the processor board and/or the signal conditioning board. The one or more sensors may include pressure transducers, temperature sensors, or other sensors for operation of the tank tester. 
         [0012]    The computer component may also include external memory operatively connected to the processor board. The external memory may include flash memory, a hard disk, or other suitable memory for storing run-time programs, vehicle databases, testing lookup tables, recent test results, or other data. 
         [0013]    In one embodiment, the computer component may include or host an operating application. The operating application may include one or more software modules enabling the operation of, and user interaction with, the tank tester. The operating application may be based on any one of many computer programming languages such as, for example, C, C++, or other programming language. 
         [0014]    The operating application may include software for fuel tank testing, inspection test procedures and criteria, security measures, utilities, ancillary modules, or other software. The features enabled may include, among other things, integrated calibration and self test procedures, outside ambient temperature measurement, internal tank tester pressure measurements, fuel tank pressure measurements, evaporative tests, constant flow determination of a tank leak, vapor space compensation, temperature compensation, Reid Vapor Pressure (RVP) compensation, vacuum tank integrity testing, hydrocarbon detection, constant pressure tank integrity testing, use of vapor temperature for determination of liquid fuel temperature, interface with an Emissions Inspections System (EIS), or other features. One or more of the modules comprising the operating application may be combined. For some purposes, not all modules may be necessary. 
         [0015]    In one embodiment, the operating application may also include, or have access to, data look-up tables, and may use table calls for fuel tank vapor space calculations, pass/fail decisions, and/or other calculations and decisions. These tables may compensate for temperature and RVP when making the vapor space calculations, pass/fail determinations, or other calculations or decisions. In addition, the operating application may write test results and calibration test results to a record (“test record”). 
         [0016]    In one embodiment, the computer component may include an interface that enables one or more users to interact with the operating application. The interface may comprise a graphical user interface (GUI) presented to a user on a display device. A user may interact with the operating application and the GUI via a user input device. 
         [0017]    The computer component may also include other elements for the operation of the tank tester. As would be apparent to one skilled in the art, other configurations for the computer component may exist. 
         [0018]    Testing Component 
         [0019]    In one embodiment of the invention, the tank tester may include a testing component. The testing component may include a pressurized gas source, various pressure transducers, pressure regulators, valves, orifices, pneumatic pluming elements, or other elements for performing the operations of the tank tester described herein. 
         [0020]    In one embodiment, the pressurized gas source may contain or produce pressurized gas for use in the tank tester. The pressurized gas may comprise nitrogen, compressed air, or another gas. If the tank tester uses nitrogen as a pressurizing gas, then the nitrogen may be 98% pure. Other concentrations may be used. If the tank tester uses compressed air as a pressurizing gas, an air filter capable of removing harmful contaminants and moisture from the compressed air may be included. This filter may ensure that no contaminants enter the tank tester that could physically block any orifice, or chemically contaminate the internal components of the tester. The filter may be configured to filter down to 5-micron size particles. 
         [0021]    The pressurized gas source may be pneumatically connected to the various pressure transducers, pressure regulators, valves, orifices, or other elements included in the testing component of the tank tester. 
         [0022]    The testing element may also include an outlet hose. The outlet hose may interface with a tank adaptor at one of its ends. The tank adaptor may include any of a set of fuel filler neck adaptors (“tank adaptors”) that provide connectivity to various vehicles. 
         [0023]    According to an embodiment of the invention, the tank adaptor, outlet hose, and any pneumatic conduit or gasket materials may be comprised of material which may be pliable and impermeable to some or all gasoline constituents including, for instance, Methyl Tertiary Butyl Ether (MTBE), ethanol, and methanol. Material exhibiting these properties is known in the art. Furthermore, the tank adaptor, the outlet hose, and other elements within testing component may be fitted with quick disconnect couplers that facilitate easy and rapid connection and disconnection from the vehicle. 
         [0024]    Housing and Calibration Tank 
         [0025]    In some embodiments of the invention, the tank tester may include a housing that may enclose one or more components of the tank tester. In other embodiments of the invention, the housing may support one or more components of the tank tester. These components may be supported either internally within the housing, externally to the housing, or partially internal and partially external to the housing. In another embodiment, the housing may comprise a custom impact-resistant plastic enclosure with a carrying strap and/or handle. 
         [0026]    In one embodiment of the invention, a calibration tank may be included with the tank tester. The calibration tank may form a predetermined volume that may be pressurized. In some embodiments, the calibration tank may be supported internally within the housing. In some embodiments, the housing itself (or part of the housing) may form the calibration tank. In one embodiment, the calibration tank may include a bladder (not otherwise illustrated). In some embodiments, the bladder may conform itself within the housing. In another embodiment, the housing and/or the calibration tank may include a blow-molded case (not otherwise illustrated) with a volume that may be pressurized. As discussed above, the case may be formed, machined, or molded to have any predetermined volume. 
         [0027]    The volume of the calibration tank may comprise one gallon, two gallons, five gallons, ten gallons, or any other predetermined volume. In some embodiments, this volume may be adjustable. The calibration tank may serve as a component for performing various calibration procedures (described in detail below) enabling efficient and accurate operation of the tank tester. 
         [0028]    Calibration 
         [0029]    According to an embodiment of the invention, the tank tester may include a calibration module. The calibration module may enable calibration of the various elements of the tank tester. Calibration may include one or more of the following processes: self-test of inlet pressure, self-test of transducers, self-test of temperature sensors, sensor check/zero with pressure disconnected, sensor check/zero with pressure connected, system leak/decay check with no tank, tank volume check with no leak, passing tank calibration, failing tank calibration, or other process. 
         [0030]    As mentioned above, the calibration module may utilize a calibration tank that contains a known, predetermined volume (or vapor space). In one embodiment, the calibration tank may include switchable calibrated leak standards. For example, the calibration tank may contain purposefully designed leaks of varying sizes, one or more of which may be used to simulate fuel tank leaks of differing degrees. 
         [0031]    According to one embodiment, the calibration module may utilize an internal clock to determine when calibration is due. As an example, the calibration module may automatically lock out test procedures on the tank tester every 72 hours pending a successful completion of one or more calibration procedures. Other time intervals may be used. 
         [0032]    According to an embodiment, the calibration module may perform a system test for the tank tester&#39;s overpressure function. This system test monitors the tank tester&#39;s ability to disable the tank tester in the event that over pressurization of a calibration tank or fuel tank occurs. The tank tester may be capable of resuming normal operation after the overpressure condition has been eliminated and the tank tester successfully completes the calibration procedure. For a failed overpressure test, the tank tester may prevent further testing for a predetermined period of time, but may allow subsequent attempts to successfully complete calibration procedures, self-tests, or system tests. 
         [0033]    Upon successful completion of a calibration procedure, the calibration module may write the results to a calibration record with the date and time. The calibration module may then start a clock to time-out the next calibration due date and time according to a predetermined time period. The new record may be recorded to the calibration record. The data recorded in the calibration record (regardless of failure or passage) may include Station ID (facility conducting test), Tester ID (person conducting test), Calibration ID (the specific calibration iteration), Date/Time of Calibration, Software Version, Pressure Decay Results, Vapor Space Results, Simulated Test Results, Overall Calibration Result, Calibration Error, Date/Time of Next Calibration Due, or other data. To calculate the next time due, the software may add the predetermined time period to the current calibration date and time. Once calibration has been successfully completed, the calibration module may allow testing to occur. 
         [0034]    If the tank tester fails any portion of a calibration test, a user may be prompted to perform subsequent calibration procedures or contact a designated service provider for repairs. According to one embodiment, when service of the tank tester is required, the tank tester may not allow further tank testing or manual mode pressurization to be performed until full function has been restored by an authorized or designated service representative. 
         [0035]    Testing 
         [0036]    Fuel Evaporative Test 
         [0037]    According to an embodiment of the invention, the tank tester may include a test module. The test module may be utilized to conduct various fuel tank tests such as, for example, a fuel evaporative test. A fuel evaporative test may be performed to determine or calculate of the size of a hole in a fuel tank of unknown volume. 
         [0038]    During a fuel evaporative test, the tank tester may pressurize a fuel tank. During pressurization, the tank tester may determine if the maximum allowable fill time has been exceeded. If the fuel tank cannot be pressurized to a predetermined pressure in a predetermined amount of time, a gross leak may be present. If the fuel tank passes the fill-time portion of the test (indicating no gross leak), the test module may determine whether an otherwise unacceptable leak exists in the fuel tank (i.e., pass or fail). In accordance with this test, the tank tester may calculate the vapor space within the fuel tank being tested. 
         [0039]    Flow Method 
         [0040]    In another embodiment of the invention, the test module of the tank tester may perform a fuel evaporative test using a “flow method.” In this embodiment, the testing component of the tank tester may have two filling paths: Fast Fill Flow and Slow Fill Flow. 
         [0041]    Using the Fast Fill Flow path, a fuel tank may be pressurized to a predetermined pressure level such as, for example, 14″ H 2 O at a rate of approximately 8.5 standard liters per minute (SLPM). Once the desired pressure is achieved, the tank tester may switch to the Slow Fill Flow path. The Slow Fill Flow path may have an orifice and a precision pressure regulator set to a predetermined pressure level such as, for example, 14″ H 2 O. The precision pressure regulator attempts to maintain a constant pressure in the tank. If the tank has no leak, there will be no flow. If the tank has a leak, the flow rate of gas required to keep a constant pressure in the tank should be the flow rate of the leak. Based on this flow rate and the pressure in the tank, the size of the hole in the tank may be calculated and compared to a calibration standard. 
         [0042]    Once a hole size is determined by the constant flow method, the tank may be allowed to leak down over a predetermine period. Based on the pressure drop in the tank versus time, the volume of the tank may be calculated. If the tank does not have any leaks, the volume may be calculated based on the Fast Fill Flow time and Fast Fill Flow rate. 
         [0043]    Constant Flow Test 
         [0044]    In another embodiment of the invention, the test module may perform a constant flow test. The constant flow test may operate by applying a constant flow of air to the fuel tank which may result in a increasing pressure. By measuring the rate at which a pressure corresponding to the pressure in the fuel tank increases, a determination may be made as to the integrity of the fuel tank (or fuel system). The pressure inside an un-compromised fuel tank would increase at a greater rate than that inside a compromised fuel tank. In some embodiments, the degree to which the fuel tank is compromised may be determined by the rate at which the pressure inside the fuel tank increases. 
         [0045]    Leak Down 
         [0046]    According to embodiment, the test module may test the integrity of a fuel tank using a leak down test. In performing the leak down test, the tank tester may pressurize the fuel tank to a predetermined pressure. Once the predetermined pressure is reached, a time interval elapses, and the pressure in the fuel tank is measured. Successive time intervals and pressure measurements may occur. If the pressure in the fuel tank remains approximately at the predetermined pressure, the fuel tank (or fuel system) may not be compromised (e.g., no leaks, or leaks within an accepted tolerance). If the pressure in the fuel tank decreases, the fuel tank (or fuel system) is most likely comprised (e.g., has a leak). The tank tester may then perform calculations to determine the size of the leak and whether the leak is acceptable (e.g., pass/fail). 
         [0047]    Vacuum Testing 
         [0048]    According to an embodiment of the invention, the test module may determine the integrity of a fuel tank (or fuel system) using vacuum testing. In one embodiment, vacuum testing may comprise reducing pressure in a fuel tank to a predetermined pressure below ambient pressure. Such a predetermined pressure may be achieved by applying a vacuum to the fuel tank. Once the predetermined pressure is reached, a pressure corresponding to the pressure in the fuel tank is measured. If the pressure in the fuel tank remains approximately at the predetermined pressure, the fuel tank (or fuel system) may not be compromised (e.g., no leaks, or leaks within an accepted tolerance). If the pressure in the fuel tank increases, the fuel tank (or fuel system) may be comprised (e.g., has a leak). The tank tester may then perform calculations to determine the size of the leak and whether the leak is acceptable (e.g., pass/fail). 
         [0049]    In another embodiment of the invention, vacuum testing may include applying a continuous vacuum to a fuel tank which results in a decreasing pressure inside the fuel tank. By measuring the rate at which a pressure corresponding to the pressure in the fuel tank decreases, a determination may be made as to the integrity of the fuel tank (or fuel system). The pressure inside an uncompromised fuel tank would decrease at a greater rate than that inside a compromised fuel tank. In some embodiments, the degree to which the fuel tank is compromised may be determined by the rate at which the pressure inside the fuel tank decreases. 
         [0050]    Mechanical Pressure 
         [0051]    According to one aspect of the invention, the test module of the tank tester may determine the integrity of the fuel tank (or fuel system) by applying a constant, predetermined pressure to the fuel tank via a mechanical device, such as a piston and cylinder. A force may be applied to the piston commensurate with the desired predetermined pressure to be applied to the fuel tank. Once a predetermined pressure has been reached in the tank, the force applied to the piston and the force corresponding to the pressure in the fuel tank should be equal and opposite. If the fuel system is uncompromised (e.g., no leaks), the piston should remain stationary (or nearly so). If the fuel system is compromised (e.g., leaks), the piston should move. The degree to which the piston moves is related to the degree to which the fuel system leaks. The movement of the piston in the cylinder may be measured via various well known mechanisms. 
         [0052]    Manual Mode 
         [0053]    In one embodiment of the invention, the tank tester may include a manual-test module. The manual-test module may perform a manual test sequence. In performing the manual test sequence a user may first select the manual test mode, connect the tank tester to a fuel tank, and initiate a manual test. The tank tester may then pressurize the fuel tank to a predetermined pressure level such as, for example, 14″ H 2 O. The tank tester may maintain that pressure for a predetermined time period. During pressurization, a user may take readings from the various sensors and transducers of the tank tester for use in determining the various qualities of a fuel tank being tested. At the end of the predetermined time period, the tester may vent any remaining tank pressure. 
         [0054]    Multiple Standards 
         [0055]    The test module may utilize different predefined standards for fuel tank tests. In one embodiment, a standard may be defined as a leak that exceeds an equivalent size gap. For example, the test module may base a pass/fail determination on a standard of a 0.020″ gap. Where a fuel evaporative system leak is less than or equal to a 0.020″ diameter gap the test module may return a pass determination. Accordingly, the test module may fail the fuel evaporative system where the leak exceeds a 0.020″ diameter gap. 
         [0056]    Under a different standard such as, for instance, a 0.040″ diameter gap standard, the test module may pass a vehicle where the fuel evaporative system leak is less than or equal to a 0.040″ diameter gap, and fail the fuel evaporative system where the leak exceeds a 0.040″ diameter gap. The false pass error rate may be less than ±5% and the false fail error rate may be less than ±1%. Other pass/fail standards and error rates may be used. All data pertinent to test standards may be stored in a file. This file may contain any and all data and/or algorithms required to make the Pass/Fail decision in the tank tester. 
         [0057]    Calculations and Compensation 
         [0058]    According to one aspect of the invention, the tank tester may further comprise a data analysis module. The data analysis module may, among other things, measure vapor space, temperature, and Reid Vapor Pressure (RVP) within a fuel tank being tested, and may compensate for these factors when making test calculations. 
         [0059]    Temperature measurements may be taken by one or more temperature sensors included in the tank tester. The temperature sensors may be placed in various locations within the testing component, and may be connected to a sensor or other element of the computer component of the tank tester. Additionally, various hardware and/or software components associated with the tank tester may be used to determine liquid fuel temperature based on measured vapor temperature. These temperature readings may be used in the calculations made during the various tests performed by the tank tester. 
         [0060]    The tank tester may also include a barometric pressure sensor that may enable measurement of the barometric pressure of the testing environment in which the tank tester is being used. The testing component may also include an ambient temperature sensor that may enable measurement of the ambient temperature of the testing environment. These measurements may also be used in the calculations performed by the tank tester. 
         [0061]    Reid Vapor Pressure (RVP) measurements may also be taken for the fuel in a fuel tank. RVP corresponds to the pressure induced in a closed volume (fuel tank) as a result of the liquid (fuel) in the closed volume evaporating. To improve the accuracy of the tank tester, the data analysis module may compensate for the RVP. In order to compute RVP, the data analysis module may obtain the following measurements or quantities: the volume of the fuel tank, the volume of the liquid in the tank, a measure of the liquid&#39;s tendency to evaporate, and the ambient temperature. With these variables, the amount of pressure induced by the evaporative effects of the fuel may determined. 
         [0062]    In some embodiments of the invention, the RVP may be measured directly by, for instance, releasing the pressure in the fuel tank, resealing the fuel tank, allowing the closed system to reach a steady state condition, and measuring the RVP at steady state. Once the RVP is determined, the data analysis module may compensate for RVP in its pressure measurements as would be apparent. 
         [0063]    In some embodiments, certain other measurements such as, for example the volume of the fuel tank, the volume of fuel in a fuel tank, the volume of vapor in the fuel tank, or other measurements, may be used by the tank tester in making calculations. In some embodiments, the volume of the fuel tank may be provided by the manufacturer of the fuel tank or integrator of the fuel system (e.g., an automobile manufacturer). In other embodiments, the volume of the fuel tank may be measured. In some embodiments, the volume of fuel may be measured. In other embodiments, the fuel tank may be drained and a known volume of fuel may be dispensed into the fuel tank. In some embodiments, the volume of the fuel tank and the volume of the liquid (fuel) may be used to determine the volume of vapor within the fuel tank. In other embodiments, the volume of the vapor may be measured directly without obtaining the volume of the fuel tank and/or the volume of the fuel. 
         [0064]    Safety Measures 
         [0065]    According to an embodiment of the invention, the tank tester may be configured to determine an overpressure condition for either an incoming supply pressure or a regulated test pressure. If at anytime during a procedure (for example, a fuel evaporative test or manual mode test) the tester inlet pressure from the air pressure regulator exceeds 35 psi (or other predetermined value), the tank tester may cease any test or procedure in progress. Tank tester software may prevent the tank tester from performing a pressurization of the fuel tank until any overpressure condition has been corrected. 
         [0066]    Additionally, if at anytime during a procedure, the fuel tank pressure exceeds 28″ H 2 O gauge (or other predetermined emergency pressure level), as measured by the tank tester, the tank tester may open one or more valves and vent any remaining pressure in the fuel tank. The tank tester may also prevent pressurization of the fuel tank for any procedure until the problem has been corrected. In some embodiments, a pressure switch may enable the release of pressure from the testing component upon the detection of the predetermined emergency pressure level. The pressure switch may act as a back-up in the event that a pressure transducer (or other element of the testing component) fails. According to one embodiment, the pressure switch may be wired in series with one or more valves within the testing component and may manipulate said valves to prevent over-pressurization as a fail-safe measure. 
         [0067]    At anytime during any test sequence, the test may be aborted by the activation of an abort button operatively connected to the computer component of the tank tester. The abort button may cause the tester to immediately open a system relief valve, write the “Tech. Abort” code to the Error field of the Test Record (or otherwise record the aborted test), and subsequently return to a main menu (discussed in detail below). 
         [0068]    Software Updates 
         [0069]    The tank tester may include a software update module. The software update module may enable the software associated with the tank tester (including the operating application and various software modules) to be updated in a number of ways. Software associated with the tank tester may be updated by a modem. For example, a built-in modem may dial a 1-800 number, allow a query of the tank tester for the software version, and update software modules and databases as required. In another embodiment, the tank tester may be connected to a phone line and a host may call the tank tester to commence an update process. 
         [0070]    In yet another embodiment, software may be updated using a compact flash card or other memory storage device within the tank tester, which may be removed from the tank tester, sent to a service provider for reprogramming, and reintroduced into the tank tester with updated software. Alternatively, memory storage devices containing updated software may be sent to tank tester users as replacements for older devices. 
         [0071]    In another embodiment, software may be updated by connecting the tank tester to a personal computer (or other computer). A user may then connect to the Internet or other designated network and link to a provider web page to download software updates. These updates may then be communicated to and stored within the tank tester. Alternatively, the tank tester may contain sufficient computer hardware and/or software to connect to the Internet or other network without the aid of an additional computer. 
         [0072]    Menus 
         [0073]    In one embodiment, the tank tester may include a main menu. Any one or more of the following menu options may be displayed in the main menu (or other menus) and may be facilitated by the tank tester&#39;s software and/or hardware: (1) Fuel Evaporative Test, (2) Diagnostic Manual Mode testing, (3) Calibration, (4) Self-test, (4) Status Mode, (5) Software update, (6) Service mode, (7) QA State Menu, or other options. 
         [0074]    In one embodiment a Status Mode may display the following information: testing station&#39;s license number (or other testing station identification); next test record number; tester number; date/time; loaded software version number; update software version number; and tester lock out reason. 
         [0075]    In one embodiment, a QA State Menu may provide access to certain data stored on the tank tester. The QA State Menu may be accessed via the tank tester&#39;s display device and user input device, a separate computer (such as a laptop), or other device. The QA State Menu may include a menu comprising one or more of the following options: update config. tables, load software update, download test records, download calibration records, lock-out tester, or other options. The QA State Menu may be password protected via a password protection module of the tank tester. The password protection module may also be used to provide password protection to any menu or feature of the invention described herein. 
         [0076]    System Communications 
         [0077]    According to an embodiment, the tank tester may include a communications module. The communications module may enable standard RS232 communications protocols that may be used for communication between an EIS and the tank tester. In addition, a laptop computer (or other suitable device) using RS232 communications may be used for software and table updates for the tank tester. Communications protocols as used herein may enable users to perform one or more various functions including, for example: updating operating software as deemed necessary; updating tables for pass/fail standards; downloading test data from records stored in the tank tester; downloading tank tester calibration records stored in the tank tester; outputting pass/fail results to the EIS; or communicating with other computers or a network of computers. Furthermore, the communications module may perform updates and other communications using a modem incorporated into the tank tester. Protocols other than RS232 may be used. 
         [0078]    According to an embodiment of the invention, the tank tester may include a serial mode module for serial mode operation. Serial mode operation may be two-fold. A first serial mode operation may be for checkout and testing of production line tank testers and repair of returned tank testers. A second serial mode operation may be for integrating communication to EIS equipment. The configuration of the serial port may, for instance, have a baud rate fixed at 9600 baud. Other signaling rates may be used. 
         [0079]    According to an embodiment, with the tank tester connected to and communicating with an EIS, the tank tester may be powered by a 12 VDC source limited to 0.5 amps supplied by the RS 232 communications port. Other configurations may be implemented. Alternatively, the tank tester may be integrated with an EIS. 
         [0080]    According to an embodiment, a development/service mode may also be provided. The development/service mode may run an evaporative test and show current pressure, temperature and flow readings during the test and show results after the test is finished. The development/service mode may also run a manual service and test mode while displaying sensor readings solenoid or valve status. Furthermore, the development mode may allow the update of software, databases and tables in conjunction with or apart from other features described herein. 
         [0081]    Interlocking Tank Adaptor Safety Mechanism 
         [0082]    In one embodiment, the tank adaptor of the tank tester (which interfaces with and seals the tank tester to the fuel system) may provide a closed system between the fuel system and the tank tester. In some embodiments of the invention, the tank adaptor may allow the tank tester to pressurize the fuel system, among other things. 
         [0083]    One drawback associated with pressurizing a fuel system may arise when a fuel tank is full, or nearly full, of fuel. If the pressure is not properly released, some fuel may spill or splash out of the tank. According to one aspect of the invention, the tank tester may include an interlock that prevents fuel from spilling, splashing, or otherwise being released from the fuel system when it is depressurized. This may be accomplished either at (or proximate to) the tank adaptor alone, or in combination with various functionality incorporated into the tank tester. 
         [0084]    In some embodiments, the tank adaptor may be unable to be physically removed from the fuel neck until pressure inside the fuel tank returns to ambient pressure. For example, the tank adaptor may incorporate or otherwise operate with an interlock that prevents the tank adaptor from being removed from the fuel neck until pressure inside the tank returns to ambient pressure. 
         [0085]    In some embodiments, the tank adaptor may include a valve (e.g., bleed valve, etc.) that releases the pressure in the fuel system. In some embodiments, the valve may include an automated valve that controls the return of ambient pressure to the fuel tank. 
         [0086]    Hydrocarbon Detector 
         [0087]    In one embodiment, the tank tester may contain various mechanical components, hardware components, and/or software components (or modules, such as a hydrocarbon detection module) that may enable the tank tester to detect fuel vapor that escapes from the fuel system. To facilitate fuel vapor detection, a small amount of pressure above ambient pressure may be applied to the fuel system. This pressure may force any fuel vapor out of a compromised fuel system. Such fuel vapor may be detected by a detector incorporated into the tank tester such as, for example, a gas analyzer or other detector capable of detecting hydrocarbons. In addition to detecting whether fuel vapor may be leaking from the fuel system, the detector may also be used to determine the approximate location of the leak by, for example, using a probe from the detector to identify areas with increased levels of hydrocarbons. Devices suitable for hydrocarbon detection are known to those skilled in the art. 
         [0088]    Integrated Fuel Cap and Fuel Tank Testing 
         [0089]    Currently, tank integrity and fuel cap tests may be performed separately. According to one aspect of the invention, the tank tester may be modified to contain sufficient devices, as well as computer hardware and/or software to enable simultaneous measurement of fuel cap leakage and fuel tank integrity. 
         [0090]    These and other objects, features, and advantages of the invention will be apparent through the detailed description of the preferred embodiments and the drawings attached hereto. It is also to be understood that both the foregoing general description and the following detailed description are exemplary and not restrictive of the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0091]      FIG. 1  is a schematic diagram of a tank tester system, according to an embodiment of the invention. 
           [0092]      FIG. 2  is an exemplary illustration of various components which may be utilized by a tank tester system, according to an embodiment of the invention. 
           [0093]      FIG. 3  is an exemplary illustration of various components which may be utilized by a tank tester system, according to an embodiment of the invention. 
           [0094]      FIG. 4  is an exemplary illustration of various sensors and plumbing components for use with a tank tester system, according to an embodiment of the invention. 
           [0095]      FIG. 5  is an exemplary illustration of various sensors and plumbing components for use with a tank tester system, according to an embodiment of the invention. 
           [0096]      FIG. 6  is an exemplary flow chart of a calibration process, according to an embodiment of the invention. 
           [0097]      FIG. 7  is an exemplary flow chart of a calibration process, according to an embodiment of the invention. 
           [0098]      FIG. 8  is an exemplary flow chart of a calibration process, according to an embodiment of the invention. 
           [0099]      FIG. 9  is an exemplary flow chart of a self-test process, according to an embodiment of the invention. 
           [0100]      FIG. 10  is an exemplary flow chart of a fuel tank test process, according to an embodiment of the invention. 
           [0101]      FIG. 11  is a schematic diagram of a tank tester system, according to an embodiment of the invention. 
           [0102]      FIG. 12  is an exemplary flow chart of a manual mode test process, according to an embodiment of the invention. 
           [0103]      FIG. 13  is an exemplary flow chart of a password protection process, according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0104]    According to an embodiment illustrated in  FIG. 1 , a system  100  is provided for a tank tester  101 . Tank tester  101  may be used to test the integrity of a fuel system  150 , as described in greater detail below. Fuel system  150  may include a fuel tank  140 , a fuel tank neck  143 , fuel  145 , and/or other elements. Fuel system  150  may by a fuel system for a car, motorcycle, light-duty truck, heavy-duty truck, or other motor vehicle. Tank tester  101  may include a computer-implemented component  103  (“computer component  103 ”), a testing component  117 , a housing  130 , a calibration tank  135 , and/or other elements. 
         [0105]    Computer Component 
         [0106]    In one embodiment, computer component  103  may include various computer hardware and software elements such as, for example, a processor  105 . Processor  105  may be or include, for instance, any of the Intel x86 PC/AT microprocessors or compatible processors such as those available from Cyrix or AMD. 
         [0107]    Computer component  103  may include an operating application  107 . Operating application  107  may include one or more software modules  109   a - 109   n  enabling the operation of, and user interaction with, tank tester  101 . Operating application  107  may be based on any one of many computer programming languages such as, for example, C, C++, or other programming language. 
         [0108]    In particular, operating application  107  may include a data analysis module, a test module, a calibration module, a self-test module, a manual test module, a communications module, a serial mode module, a software update module, a password protection module, a hydrocarbon detection module, and/or other modules. The features enabled may include, among other things, fuel tank temperature measurement, fuel tank pressure measurements, tank tester calibration procedures, fuel tank integrity tests, vapor space compensation, temperature compensation, Reid Vapor Pressure (RVP) compensation, hydrocarbon detection, interface with an Emissions Inspections System (EIS), and other features. One or more of the modules comprising operating application  107  may be combined. For some purposes, not all modules may be necessary. 
         [0109]    In one embodiment, operating application  107  may also include, or have access to, data look-up tables, and may use table calls for fuel tank vapor space calculations, pass/fail decisions, and/or other calculations and decisions. These tables may compensate for temperature and RVP when making the vapor space calculations, pass/fail determinations, or other calculations or decisions. In addition, operating application  107  may write test results and calibration test results to a record (“test record”). 
         [0110]    Computer component  103  may include one or more memory devices  108 . Memory device  108  may include, for instance, flash erasable programmable read only memory (FEPROM), hard disk, or other suitable memory for data storage. Memory device  108  may enable the storage of test records or other results or error files. Memory device  108  may also enable the storage of any data necessary to perform the functions of tank tester  101  described herein. 
         [0111]    According to an embodiment of the invention, one or more users may access tank tester  101  and operating application  107  through an interface. The interface may comprise a graphical user interface (GUI)  110  presented to a user on a display device  111 . The user may interact with operating application  107  and GUI  110  via a user input device  113 . Display device  111  may be or include, for instance, a display screen such as a 20″ by 4″ LCD screen. In some embodiments, display device  111  may include other types of known display screens. 
         [0112]    In one embodiment, user input device  113  may be or include, for instance, a 4 by 4 digital keypad with various keys. In another embodiment, user input device  113  may include a combination of four buttons to accommodate one or more of the following functions for scrolling through and selecting items from menus displayed via graphical user interface  110 : (1) scroll up; (2) scroll down; (3) select (or start); and (4) abort. Alternately, a rocker type switch may be substituted to accommodate the scroll up and down function thereby reducing the number of buttons to three. Other configurations are possible. In some embodiments, user input device  113  may include other types of known input devices or keyboards. 
         [0113]    In one embodiment, display device  111  may enable interaction with GUI  110  via various menus, with which a user may interact, using user input device  113 . Both display device  111  and user input device  113  may be operatively connected to processor  105 . 
         [0114]    It should be understood that various software modules  109   a - 109   n  utilized to accomplish the functionalities described herein may be maintained on one or more of processor  105 , control application  107 , memory device  108 , or other components of the system. In other embodiments, as would be appreciated, the functionalities described herein may be implemented in various combinations of hardware and/or firmware, in addition to, or instead of, software. 
         [0115]    In one embodiment, tank tester  101  may also include an outlet hose  121 . Outlet hose  121  may include a section of pneumatic conduit that may enable pneumatic connection between tank tester  101  and fuel system  150 . One end of outlet hose  121  may terminate in a tank adaptor  123 . Tank adaptor  123  may be one of a set of fuel tank filler neck adaptors that may interface with fuel neck  143 , regardless of the make or model of the vehicle of which fuel system  150  is a part. 
         [0116]    In an embodiment of the invention illustrated in  FIG. 2 , an exemplary configuration of computer component  103  may be provided in a system  200 . System  200  may include a processor board  201 . Processor board  201  may include a processor  203 . Processor board  201  may also include, for instance, one or more analog inputs  205   a - 205   n  with A/D converters for interface with various sensors, one or more digital outputs  207   a - 207   n  to interface with one or more solenoids or other elements. Processor board  201  may also include one or more serial ports  213   a - 213   n  which may interface with additional equipment such as, for example, Emissions Inspection Systems (EIS) equipment, a modem  216 , a real time clock  215 , or other elements. Processor board  201  may also include one or more memory devices  217 . One or more memory devices  217  may include FEPROM, a hard disk, or other suitable memory for storing data. 
         [0117]    System  200  may also include a signal conditioning board  219  operatively connected to processor board  201 . Signal conditioning board  219  may, among other things, condition electrical signals into and out from any sensors. Such signal conditioning may be accomplished as would be apparent to one skilled in the art. Signal conditioning board  219  may include a DC/DC power supply  223 . Power supply  223  may include a 12 volt 0.5 amp power supply, although other voltages and amperages may be used. Signal conditioning board  219  may also include a pressure switch control  225  which may release pressure from testing component  117  ( FIG. 1 ) when a predetermined pressure is reached within testing component  117 . Signal conditioning board  219  may also include one or more solenoid drivers  227   a - 227   n  for operating one or more solenoids throughout tank tester  101 . One or more solenoids may be useful for the operation of various elements of testing component  117  such as, for example, switches, valves, or other elements. 
         [0118]    System  200  may include tamper switch  229  operatively connected to processor board  201  and/or signal conditioning board  219 . 
         [0119]    System  200  may include one or more sensors  231   a - 231   n  operatively connected to processor board  201  and/or signal conditioning board  219 . One or more sensors  231   a - 231   n  may include pressure transducers, temperature sensors, or other sensors for the operation of tank tester  101 . 
         [0120]    System  200  may also include external memory  233  operatively connected to processor board  201 . External memory  233  may include flash memory, a hard disk, or other suitable memory for storing run time programs, vehicle databases, testing lookup tables, recent test results, or other data. 
         [0121]    Furthermore, computer component  103  may include a display device  235  and a user input device  237  operatively connected to processor board  201 . Display device  235  and user input device  237  may be the same as, or similar to, display device  111  and user input device  113  described above with reference to  FIG. 1 . 
         [0122]    In an embodiment of the invention illustrated in  FIG. 3 , an alternative configuration of computer component  103  may be provided in a system  300 . System  300  may include a processor board  301 . Processor board  301  may include a processor  303 . Processor board  301  may also include, for instance, 50 pin compact flash memory  305 , 512 kb (or other memory size) flash ROM  307 , 512 kb (or other memory size) SRAM  309 , a battery  311 , a real time clock  313 , one or more serial ports  315   a - 315   n , a DB9 (or other format) connector  317 , a plug in modem card  319  which may include an RJ11 or similar connector, a power input  321  and other elements. 
         [0123]    System  300  may also include a signal conditioning board  323  operatively connected to processor board  301 . System  300  may include one or more solenoid drivers  325   a - 325   n  operatively connected to processor boards  301  and/or signal conditioning board  323  which may enable the operation of one or more solenoids throughout tank tester  101 . System  300  may include a pressure switch  327  operatively connected to processor board  301  and/or signal conditioning board  323 , which may enable the release of pressure from testing component  117  ( FIG. 1 ) upon the existence of a predetermined pressure within testing component  117 . 
         [0124]    System  300  may also include one or more sensors  329   a - 329   n  operatively connected to processor board  301  and/or signal conditioning board  323 . One or more sensors may include, for instance, a inlet pressure sensor  329   a , a flow pressure sensor  329   b , a manifold pressure sensor  329   c , a absolute pressure sensor  329   d , a temperature sensor  329   e , a solenoid power sensor  329 , or other sensors  329   n.    
         [0125]    Furthermore, system  300  may include a display device  331  and a user input device  333  operatively connected to processor board  301 . Display device  331  and user input device  333  may be the same as, or similar to, display device  111  and user input device  113  described above with reference to  FIG. 1 . 
         [0126]    Those having skill in the art will appreciate that the aforementioned systems may work with various configurations. Accordingly, more or less of the aforementioned system components may be used and/or combined in various embodiments. 
         [0127]    According to one embodiment, the power consumption by tank tester  101  may be slightly less than 12 Volts, 0.5 Amps (6 Watts). Other configurations may be implemented. In some embodiments, a 110 VAC wall pack transformer and connector to tank tester  101  may also be provided. 
         [0128]    Testing Component 
         [0129]    According to an embodiment of the invention, tank tester  101  may include a testing component  117 . Testing component  117  may include various electronic sensor elements, electronic control elements, and pneumatic pluming elements for performing the operations of tank tester  101  described herein. 
         [0130]    In an embodiment of the invention illustrated in  FIG. 4 , an exemplary configuration of testing component  117  may be provided in a system  400 . System  400  may include a pressurized gas source  401 . Pressurized gas source  401  may contain and/or produce pressurized gas for use in tank tester  101 . Pressurized gas may include nitrogen, compressed air, or other gas. If tank tester  101  uses nitrogen as a pressurizing gas, the nitrogen may be 98% pure. Other concentrations may be used. If tank tester  101  uses compressed air as a pressurizing gas, an air filter capable of removing harmful contaminants and moisture from the compressed air source may be included. This filter may ensure that no contaminants enter tank tester  101  that could physically block any orifice, or chemically contaminate the internal components of tank tester  101 . The filter may comprise material known to one of skill in the art and may be configured to filter down to 5-micron size particles. 
         [0131]    Pressurized gas source  401  may reside outside a testing component housing  403 . In alternative embodiments, pressurized gas source  401  may reside inside a testing component housing (or other housing) or enclosures associated with tank tester  101 . 
         [0132]    Pressurized gas source  401  may be pneumatically connected to an input filter  404 . Input filter  404  may enable filtering of particulates or contaminates from pressurized gas flowing from pressurized gas source  401 . Furthermore, a high pressure regulator  402  may be pneumatically connected to pressurized gas source  401  to enable regulation of pressure into testing component  117 . According to an embodiment of the invention, pressure regulator  402  (and other pressure regulators described herein) may enable a controlled flow rate of between two and four liters per minute (LPM). Other flow rates or ranges of flow rates may be achieved. 
         [0133]    Pressurized gas source  401  may be pneumatically connected to an inlet pressure transducer  405 . Pneumatic connection may be accomplished by pneumatic conduit which may comprise material known to one skilled in the art, suitable to perform the various functions and processes described herein. Inlet pressure transducer  405  may include an electronic sensor enabling the measurement and communication of pressure levels to computer component  103 . In one embodiment, inlet pressure transducer  405  may sense pressure ranges from 0-50 pounds per square inch (psi). Other pressure ranges may be used. Inlet pressure transducer  405  may monitor the inlet pressure levels of testing component  117  and communicate those pressure levels to computer component  103 . Computer component  103  may then take appropriate action. For example, if inlet pressure levels exceed a predetermined level such as, for instance, 35 psi, valves or other elements within testing component  117  may be activated to correct the situation. According to an embodiment of the invention, tank tester  101  may be configured to measure inlet pressures of 0-35 psi within ±10% of point, and internal tank tester pressures of 0″-28″ H 2 O ±5% of range. Other ranges may be used. 
         [0134]    Pressurized gas source  401  may also be pneumatically connected to a first valve  406 . First valve  406  may enable partial or complete obstruction of gas flow through testing component  117 . First valve  406  may have a first end and a second end. In one embodiment, an input filter  404  may be pneumatically connected between pressurized gas source  401  and first valve  406 . In some embodiments, first valve  406  may be, include, or be controlled by, a mechanism such as, for example, a solenoid driver or other mechanism. 
         [0135]    The second end of first valve  406  may be pneumatically connected to pressure regulator  407 . Pressure regulator  407  may enable a specific flow rate of gas through testing component  117 . Pressure regulator  407  may be pneumatically connected to a second valve  409 . Second valve  409  may enable partial or complete obstruction of gas flow through testing component  117 . Second valve  409  may have a first end and a second end. In one embodiment, the first end of second valve may be pneumatically connected to pressure regulator  407 . In some embodiments, second valve  409  may be, include, or be controlled by a mechanism such as, for example, a solenoid driver or other mechanism. 
         [0136]    The second end of second valve  409  may be pneumatically connected to an orifice  410 . Orifice  410  may include a section of pneumatic conduit of predetermined inner diameter through which gas may flow. When open, orifice  410  may include an inner diameter of 0.023 centimeters. Other diameters may be used for orifice  410 . Orifice  410  may enable the controlled flow of gas through testing component  117  and may be controlled by an electronic switch. 
         [0137]    Orifice  410  may be pneumatically connected to air reservoir  411 . Air reservoir  411  may include an enclosure in which gas may be stored and/or through which gas may flow. In one embodiment, air reservoir  411  may hold up to 0.34 liters of gas. In other embodiments other volumes of gas may be held in air reservoir  411 . 
         [0138]    An outlet hose  413  may be pneumatically connected to air reservoir  411 . In alternative embodiments outlet hose  413  may be connected directly to orifice  410 , the second end of second valve  409  or other element of testing component  117 . Outlet hose  413  may have first and second ends. The first end of outlet hose  413  may be pneumatically connected to air reservoir or other element of testing component  117 . The second end of outlet hose  413  may end in tank adaptor  415 . Tank adaptor  415  may include a set of fuel filler neck adaptors that provide connectivity to various vehicles. 
         [0139]    According to an embodiment of the invention, tank adaptor  415 , outlet hose  413 , and any pneumatic conduit or gasket materials may be pliable and impermeable to some or all gasoline constituents including, for instance, Methyl Tertiary Butyl Ether (MTBE), ethanol, and methanol. Furthermore, tank adaptor  415 , outlet hose  413 , and other elements within testing component  117  may be fitted with quick disconnect couplers that facilitate easy and rapid connection and disconnection from the vehicle. 
         [0140]    A differential transducer  417  may be pneumatically connected between the second end of second valve  409  and orifice  410 . Differential transducer  417  may also be pneumatically connected to air reservoir  411 . Differential transducer  417  may include an electronic sensor enabling the measurement and communication of pressure levels to computer component  103 . In one embodiment, differential transducer  417  may sense pressure ranges from 0-14.5 psi. Other pressure ranges may be used. Differential transducer  417  may measure the pressure differential between a section of pneumatic conduit prior to orifice  410  and air reservoir  411 . 
         [0141]    A reservoir pressure transducer  419  may be pneumatically connected to air reservoir  411 . Reservoir pressure transducer  419  may include an electronic sensor enabling the measurement and communication of pressure levels in air reservoir  411  to computer component  103 . In one embodiment, reservoir pressure transducer  419  may sense pressure ranges from 0-40″ H 2 O. Other pressure ranges may be used. 
         [0142]    A third valve  421  may be pneumatically connected to air reservoir  411 . Third valve  421  may enable partial or complete obstruction of gas flow through testing component  117 . Third valve  421  may have a first end and a second end. In one embodiment, the first end of third valve may be pneumatically connected to air reservoir  411 . In some embodiments, third valve  421  may be, include, or be controlled by a mechanism such as, for example, a solenoid driver or other mechanism. 
         [0143]    The second end of third valve  421  may be pneumatically connected to a vent outlet  423 . Vent outlet  423  may enable the outlet of gas from testing component  117 . In some embodiments vent outlet  423  may be pneumatically connected to a filter and/or an outlet canister. For example, at the conclusion of a test, compressed fuel tank fumes may vent through vent outlet  423  into a charcoal canister. The remaining fuel tank fumes may be vented back though tank tester  101 &#39;s valves to an alternate outlet. Testing component  117 &#39;s alternate outlet may be routed out of a test facility (e.g., a building or other environment) or into another area/container. According to one embodiment, tank tester  101  may be fully vented to a separate container such as, for instance, a charcoal canister, that may be purged on a next (or other subsequent) test cycle. 
         [0144]    A check valve  425  may be pneumatically connected to air reservoir  411 . Check valve  425  may enable the release of gas to prevent over-pressurization. Check valve  425  may operate to allow such release upon a occurrence of a predetermined pressure level within testing component  117  such as, for instance, 1 psi or other predetermined pressure level (“cracking pressure”). Check valve  425  may have a first end and a second end. In one embodiment, the first end of check valve  425  may be pneumatically connected to air reservoir  411 . In some embodiments, check valve  425  may be, include, or be controlled by a mechanism such as, for example, a solenoid driver or other mechanism. The second end of check valve  425  may be pneumatically connected to vent outlet  423 . 
         [0145]    A pressure switch  427  may be connected to testing component  117 . Pressure switch  427  may include an electronic and/or mechanical switch that may open one or more valves to release pressure from testing component  117  upon the detection of a predetermined pressure within tank tester  101  or a fuel system being tested. A pressure switch  427  may act as a back-up in the event that a pressure transducer (or other element of testing component  117 ) fails. According to one embodiment, pressure switch  427  may be wired in series with one or more valves within testing component  117 , and may manipulate the valves to prevent over-pressurization as a fail-safe measure. 
         [0146]    A temperature sensor  429  may also be included in testing component  117 . Temperature sensor  429  may determine the temperature of gas within testing unit  117  or a connected fuel system. Temperature sensor  429  may be placed in various locations within testing component  117  and may be connected to computer component  103 . Testing component  117  may also include a barometric pressure sensor  431  for detecting the barometric pressure of a testing environment in which tank tester  101  is being used. 
         [0147]    In an embodiment of the invention illustrated in  FIG. 5 , an alternative configuration of testing component  117  may be provided in a system  500 . System  500  may include a pressurized gas source  501 . Pressurized gas source  501  may contain and/or produce pressurized gas for use in tank tester  101 . Pressurized gas source  501  may be pneumatically connected to input filter  504 . Input filter  504  may enable filtering of particulates or contaminates from pressurized gas flowing from pressurized gas source  501 . Furthermore, a high pressure regulator  502  may be pneumatically connected to pressurized gas source  501  to enable regulation of pressure into testing component  117 . 
         [0148]    Pressurized gas source  501  may be pneumatically connected to an inlet pressure transducer  505 . Inlet pressure transducer  505  may include an electronic sensor for measuring and communicating pressure levels to computer component  103 . In one embodiment, inlet pressure transducer  505  may sense pressure ranges from 0-100 psi. Other pressure ranges may be used. 
         [0149]    Pressurized gas source  501  may also be pneumatically connected to a first valve  507 . First valve  507  may enable partial or complete obstruction of gas flow through testing component  117 . First valve  507  may have a first end and a second end. In one embodiment, the first end of first valve  507  may be pneumatically connected to input filter  504  and/or pressurized gas source  501 . A temperature sensor  506  may be connected to a section of pneumatic conduit between input filter  504 , or pressurized gas source  501 , and first valve  507 . Temperature sensor  506  may also be placed in other areas of testing component  117 . Temperature sensor  506  may measure and communicate gas temperature to computer component  103 . In some embodiments, tank tester  101  may include an ambient temperature sensor for measuring the temperature of a surrounding testing environment. 
         [0150]    The second end of first valve  507  may be pneumatically connected to a first orifice  509 . First orifice  509  may include a section of pneumatic conduit of predetermined inner diameter through which gas may flow. When open, first orifice  509  may include an inner diameter of 0.024 centimeters. Other diameters may be used. First orifice  509  may enable controlled flow of gas through testing component  117  and may be controlled by an electronic switch connected to computer component  103 . 
         [0151]    First orifice  509  may be pneumatically connected to manifold transducer  511 . Manifold transducer  511  may include an electronic sensor for measuring and communicating pressure levels to computer component  103 . In one embodiment, manifold transducer  511  may sense pressure ranges from 0-1.45 psi. Other pressure ranges may be used. 
         [0152]    First orifice  509  may be pneumatically connected to a pressure switch  513 . Pressure switch  513  may include an electronic and/or mechanical switch that may enable the release of pressure from testing component  117  via one or more valves upon the detection of a predetermined pressure such as, for instance, 25″ H 2 O or other pressure level. 
         [0153]    First orifice  509  may be pneumatically connected to outlet filter  515 . Outlet filter  515  may include an activated charcoal filter or other filter for removing particulates and impurities from gas traveling into an outlet hose  517 . Outlet hose  517  may have first and second ends. The first end of outlet hose  517  may be pneumatically connected to outlet filter  515 . In alternative embodiments, the first end of outlet hose  517  may not be connected to outlet filter  515 , but may rather be connected to first orifice  509 , to the second end of first valve  507 , or to another element of testing component  117 . The second end of outlet hose  517  may terminate in tank adaptor  519 . 
         [0154]    Pressurized gas source  501  may also be pneumatically connected to a second valve  521 . Second valve  521  may enable partial or complete obstruction of gas flow through testing component  117 . Second valve  521  may have a first end and a second end. In one embodiment, the first end of second valve  521  may be pneumatically connected to input filter  504  and/or pressurized gas source  501 . In some embodiments, second valve  521  may be, include, or be controlled by a mechanism such as, for example, a solenoid driver or other mechanism. 
         [0155]    The second end of second valve  521  may be pneumatically connected to a second orifice  523 . Second orifice  523  may include a section of pneumatic conduit of predetermined inner diameter through which gas may flow. When open, second orifice  523  may include an inner diameter of 0.022 centimeters. Other diameters may be used. Second orifice  523  may enable the controlled flow of gas through testing component  117 , and may be controlled by an electronic switch connected to computer component  103 . 
         [0156]    Second orifice  523  may be pneumatically connected to a pressure regulator  525 . Pressure regulator  525  may enable the controlled flow of gas through testing component  117 . Pressure regulator may be pneumatically connected to a section of pneumatic conduit between first orifice  509  and outlet filter  515 , or may be otherwise pneumatically connected to outlet hose  517 . 
         [0157]    A differential transducer  527  may be pneumatically connected to a section of pneumatic conduit located between the second end of second valve  521  and second orifice  523 . Differential transducer  527  may also be pneumatically connected to a section of pneumatic conduit located between second orifice  523  and pressure regulator  525 . Differential transducer  527  may include an electronic sensor for measuring and communicating pressure levels to computer component  103 . In one embodiment, differential transducer  527  may sense pressure ranges from 0-14.5 pounds per square inch (PSI). Other pressure ranges may be used. Differential transducer  527  may measure the pressure differential between a section of pneumatic conduit on either side of second orifice  523 . 
         [0158]    A vent outlet  529  may be pneumatically connected to a section of pneumatic conduit located between first valve  507  and outlet hose  517 . Vent outlet  529  may enable the outlet of pressure and gas from testing component  117 . In some embodiments vent outlet may be pneumatically connected to a filter and/or an outlet tank. 
         [0159]    A check valve  531  may be pneumatically connected to testing component  117 . Check valve  531  may enable the release of pressure from testing component  117  to prevent over-pressurization. Check valve may operate to allow such a release upon reaching a predetermined pressure level within testing component  117  such as, for instance, 1 psi or other predetermined pressure level (“cracking pressure”). In some embodiments, check valve  531  may be, include, or be controlled by a mechanism such as, for example, a solenoid driver or other mechanism. 
         [0160]    A relief valve  533  having first and second ends may be pneumatically connected to testing component  117 . The first end of relief valve  533  may be pneumatically connected to a portion of pneumatic conduit located between first valve  507  and outlet hose  517 . The second end of relief valve  533  may be pneumatically connected to vent outlet  529 . Relief valve  533  may enable partial or complete obstruction of gas flow through testing component  117 . 
         [0161]    Housing and Calibration Tank 
         [0162]    According to an embodiment of the invention illustrated in  FIG. 1 , tank tester  101  may include a housing  130 . In one embodiment of the invention, housing  130  may enclose one or more components (e.g.,  103 ,  117 ) of tank tester  101 . In another embodiment of the invention, housing  130  may support one or more components of tank tester  101 . These components may be supported either internally within housing  130 , externally to housing  130 , or partially internal and partially external to housing  130 . In another embodiment, housing  130  may comprise a custom impact-resistant plastic enclosure with a carrying strap and/or handle. 
         [0163]    In one embodiment of the invention, a calibration tank  135  may be included in tank tester  101 . Calibration tank  135  may form a volume that may be pressurized. In some embodiments, housing  130  itself (or a portion thereof) may form calibration tank  135 . In these embodiments, housing  130  may be manufactured and assembled so as to form a compartment having a predetermined volume that may be pressurized. In various embodiments, the volume of calibration tank  135  may comprise one gallon, two gallons, five gallons, ten gallons or any other predetermined volume. In some embodiments this volume may be adjustable. Calibration tank  135  may also be constructed to withstand an internal pressure of at least 20″ H 2 O. Other pressure tolerances may be used. Furthermore, calibration tank  135  may be resistant to shock or other normal conditions present in an automotive repair shop or other environment with no more than 1% (or other percentage) deformation. 
         [0164]    In one embodiment, calibration tank  135  may include a bladder (not otherwise illustrated). In some embodiments, the bladder may conform itself within housing  130 . As discussed above, the bladder may comprise any predetermined volume that may also be pressurized. 
         [0165]    In another embodiment, housing  130  and/or calibration tank  135  may include a blow-molded case (not otherwise illustrated) having a predetermined volume that may be pressurized. 
         [0166]    As discussed above, the case may be formed, machined, or molded to have any predetermined volume. 
         [0167]    Calibration 
         [0168]    According to an embodiment of the invention, tank tester  101  may include a calibration module. The calibration module may be utilized to calibrate various elements of tank tester  101 . Calibration may be used to adjust and confirm the consistency and accuracy of tank tester  101 &#39;s vapor space calculations, for various test pass/fail determinations, or for other calculations. Calibration may include, for example, pressurization of tank tester  101 &#39;s internal components to check for leaks, calculation of a known calibration tank volume, testing of a calibration tank configured to pass, testing of a calibration tank configured to fail, or other procedures. Calibration may also include various self-tests of the tank tester  101 &#39;s transducers, temperature sensors, or other components. 
         [0169]    According to one embodiment, the calibration module may utilize an internal clock (e.g., real time clock  215  of  FIG. 2 ) to determine when calibration is due. As an example, the calibration module may automatically lock out test procedures on tank tester  101  every 72 hours pending a successful completion of one or more calibration procedures. Other time intervals may be used. 
         [0170]      FIG. 6  illustrates an exemplary process  600 , wherein the calibration module of tank tester  101  may test the internal integrity of testing component  117 . This may be referred to herein as “phase one” of tank tester  101 &#39;s calibration procedure. In an operation  601 , an event may occur wherein automated calibration of tank tester  101  is initiated. This event may include, the passage of a predetermined amount of time, the completion of a predetermined number of tests, user selection of a calibration mode, or other event. In an operation  603 , the display device  111  ( FIG. 1 ) of tank tester  101  may display a prompt such as, for example: “INSTALL CAL. ADAPTOR. PRESS START.” As used herein, “prompt” may include any message displayed to a user conveying information regarding tank tester  101 . In an operation  605 , a user may install a calibration adaptor to plug outlet hose  121  ( FIG. 1 ) of tank tester  101  thus enabling internal pressurization. Also, in an operation  605 , the calibration procedure may be commenced by a user, for example, by the user pressing a start button that is operatively connected to computer component  103  ( FIG. 1 ) of tank tester  101 . After the calibration procedure is commenced in operation  605 , an operation  607  may occur, in which tank tester  101  may display the following prompt: “CALIBRATION SEQUENCE IN PROGRESS.” Other prompts conveying a similar message may be used. In an operation  609 , tank tester  101  may pressurize its internal plumbing and external hose to 14″ H 2 O. Other pressure thresholds may be used. In an operation  611 , the pressurized gas source may be turned off and one or more internal pressure sensors (transducers) may monitor the internal pressure decay. 
         [0171]    If, in an operation  613 , the system pressure decay exceeds a predetermined decay threshold such as, for example, 1″ H 2 O in 60 seconds, tank tester  101  may fail phase one of the calibration test. In an operation  615 , tank tester  101  may display a prompt such as, for example: “PHASE ONE CAL FAILED.” Other pressure decay levels may be used to determine the failure of phase one calibration. In an operation  617 , tank tester  101  may vent any remaining pressure in tank tester  101  to the atmosphere. In operation  617  the calibration module may also lock out tank tester  101  and prevent it from performing other procedures until the calibration procedure has been successfully completed. In an operation  619 , the calibration module may write “F” in a Pressure Decay-Phase One Result field of a Calibration Record or otherwise record the failure of phase one of the calibration procedure. In an operation  621 , tank tester  101  may display the following prompt: “REMOVE CAL ADAPTOR” and return to the main menu of tank tester  101  (described in detail below). Other prompts conveying similar messages may be used. If, in operation  613 , tank tester  101  does not exceed the predetermined pressure decay threshold, and thus successfully completes phase one of the calibration procedure, tank tester  101  may, in an operation  623 , indicate passage of phase one by displaying a prompt conveying such a message. In some embodiments, the calibration module may then proceed to phase two of the calibration procedure. 
         [0172]      FIG. 7  illustrates exemplary process  700 , in which the calibration module of tank tester  101  may test and/or calibrate tank tester  101 &#39;s ability to determine the volume of a tank. This may be referred to herein as “phase two” of tank tester  101 &#39;s calibration procedure and may be triggered by the successful completion of phase one or other event. 
         [0173]    In an operation  701 , tank tester  101  may display a prompt such as, for example: “CONNECT THE CAL TANK TO THE TESTER. TURN CAL. LEAK SWITCH TO OFF.” In an operation  703 , a user may connect a calibration tank to tank tester  101 . In an operation  705 , while compensating for temperature, tank tester  101  may pressurize the calibration tank to a predetermined pressure level such as, for instance, 14″ H 2 O or other pressure level. Having the exact volume of the calibration tank stored in memory, tank tester  101  may then, in an operation  707 , calculate the volume of the calibration tank. In an operation  709 , tank tester  101  may then compare the calculated volume of the calibration tank with the calibration tank volume stored in memory. If, in an operation  711 , the calculated volume differs from the stored volume exceeding a level of ±10% or other benchmark, tank tester  101  may fail phase two of calibration, and in an operation  713 , may display a prompt such as, for example: “PHASE TWO CAL FAILED. DISCONNECT TESTER FROM CAL TANK.” In an operation  715 , tank tester  101  may vent any remaining pressure to the atmosphere and the calibration module may lock out tank tester  101  to prevent further procedures until tank tester  101  successfully passes the calibration procedure. In an operation  717 , the calibration module may write “F” in the Vapor Space Calculation—Phase Two Result field of the Calibration Record or otherwise record the failure of phase two calibration. In an operation  719 , tank tester  101  may return to the main menu. 
         [0174]    If, in an operation  711 , the calculated volume the calibration tank does not differ from the stored volume of the calibration tank exceeding exceed a level of +10% or other benchmark, and thus successfully completes phase two of the calibration procedure, tank tester  101  may, in an operation  721 , indicate passage of phase two by displaying a prompt conveying such a message. In some embodiments, the calibration module may then proceed to phase three of the calibration procedure. 
         [0175]      FIG. 8  illustrates exemplary process  800 , in which the calibration module of tank tester  101  may test and/or calibrate tank tester  101 &#39;s ability to pass and fail tanks according to a particular test. This may be known as “phase three” of tank tester  101 &#39;s calibration procedure and may be triggered by the successful completion of phase two or other event. In an operation  801 , tank tester  101  may display a prompt such as, for example: “SELECT PASS. PRESS START.” In an operation  803 , a user may select “pass” from a menu and may commence calibration by, for example pressing a start button that is operatively connected to computer component  103  ( FIG. 1 ). In an operation  805 , tank tester  101  may undergo a testing procedure such as, for example, a vapor leak test or other testing procedure, using a calibration tank with the goal of simulating a passing test. The integrity of the calibration tank may be such that the calibration tank should pass the test. For example, if the test were a vapor leak test, the calibration tank may be configured such that no leaks (or insubstantial leaks) are present. If, in an operation  807 , tank tester  101  determines that the calibration tank passes the test, tank tester  101  may, in an operation  809 , proceed to simulate a failed test of the same type. In operation  809 , tank tester  101  may display a prompt such as, for example: “SELECT FAIL. PRESS START.” In an operation  811 , the user may select “fail” from a menu and press the start button or other button to begin the calibration. 
         [0176]    In an operation  813 , tank tester  101  may again utilize tank tester  101 &#39;s testing procedure, and tests the calibration tank. In this instance the calibration tank may be configured such that it should fail the test. If, in an operation  815 , tank tester  101  fails the test tank, thus passing phase three of the calibration procedure, tank tester  101  may display a prompt such as, for example: “CAL PASSED. DISCONNECT CAL. TANK” in an operation  817 . 
         [0177]    If, in operation  807 , tank tester  101  fails the test or, in an operation  815 , tank tester  101  passes the test, and thus fails to properly identify the pass or fail conditions of the calibration procedure, then, in an operation  819  tank tester  101  may vent any remaining pressure to the atmosphere. In operation  819 , the calibration module may also lock out tank tester  101  and prevent it from performing procedures or tests until tank tester  101  successfully passes the calibration procedure. In an operation  821 , the calibration module may write “F” in the Vapor Space Calculation—Phase Two Result field of the Calibration Record or otherwise record the failure of phase three calibration. In an operation  823 , tank tester  101  may return to the main menu and display a prompt such as, for example: “PHASE 3 TESTER CAL FAILED.” 
         [0178]    In one embodiment, the calibration module may utilize switchable calibrated leak standards. To accomplish this, the calibration tank may contain gaps of different sizes for different standards. The use of these orifices may be controlled automatically upon selection of a particular leak standard. For example, if a 0.020″ standard is selected, a 0.016″ (pass) and 0.024″ (fail) gap may be used in conjunction with a calibration tank for the pass/fail calibration of tank tester  101 . If a 0.040″ standard is selected, a 0.035″ (pass) and 0.045″ (fail) gap may be used in conjunction with the calibration tank for the pass/fail calibration of tank tester  101 . Other leak standards may be used. Furthermore, if an “Off” position is selected, the calibration tank may be sealed to create a sealed test container. 
         [0179]    Upon successful completion of the calibration procedure, the calibration module may write the results to the calibration record with the date and time, and start a timer for the next calibration due date and time. The new record may be recorded to the calibration record. The data recorded in the calibration record regardless of failure or passage may include Station ID (facility conducting test), Tester ID (person conducting test), Calibration ID (the specific calibration iteration), Date/Time of Calibration, Software Version, Pressure Decay for Phase One, Vapor Space calculated for Phase Two, Result of Phase 3, Overall Calibration Result, Calibration Error, Date/Time of Next Calibration Due, or other data. To calculate the next time due, the software may add the predetermined time period to the current calibration date and time. 
         [0180]      FIG. 9  illustrates an exemplary process  900 , wherein a self-test module of tank tester  101  may perform a self-test. A self-test may occur with a pressurized gas source connected to tank tester  101 , and may also occur with applicable outlet vents of tank tester  101  open. 
         [0181]    In an operation  901 , a self-test may be initiated by, for example, user selection of a self-test, initiation of a substantive tank test, successful completion of other calibration procedures, or other event. In an operation  903 , tank tester  101  may display a prompt such as, for example: “SELF TEST—PLEASE WAIT” while the self-test module checks to verify that the calibration period has not expired. If, in an operation  905 , a predetermined calibration period has expired, the self-test module may, in an operation  907 , display a prompt such as, for example: “CALIBRATION REQUIRED” and return to the main menu. 
         [0182]    If, in an operation  905 , the predetermined calibration period has not expired, the self-test module may begin a self-test procedure in an operation  909 . In operation  909 , self-test module may test whether tank tester  101 &#39;s inlet pressure is within a predetermined range while a known pressure is applied to tank tester  101 . If, in an operation  911 , inlet pressure falls outside the predetermined range, tank tester  101  may proceed to an operation  913 . In operation  913 , tank tester  101  may determine the number of times (within the present self-test) that inlet pressure has been self-tested. If a predetermined number of inlet pressure self-tests has not been exceeded, then tank tester  101  may proceed to an operation  915 , wherein tank tester  101  may display a prompt such as, for example: “INLET PRESSURE ERROR—CHECK INLET SUPPLY LINE.” The self-test module may then return to operation  909  and reinitiate the inlet pressure test. The self test module may then proceed through operations  911  and  913 . If, in operation  913 , tank tester  101  fails the inlet pressure self-test a second time (or other predetermined number of times), tank tester  101  may, in an operation  917 , display a prompt such as, for example: “INLET PRESSURE ERROR, CALL SERVICE.” In an operation  919  the self-test module may return to the main menu without setting a lockout and may record the error. 
         [0183]    If, in an operation  911 , tank tester  101 &#39;s inlet pressure falls within the predetermined range, then the self-test module may, in an operation  921 , proceed to test whether tank tester  101 &#39;s pressure sensors (transducers) fall within a predetermined range. To make this determination, sensor readings are taken while a known pressure is applied to tank tester  101 . If, in an operation  923 , the sensors fall outside an expected range, then tank tester  101  may, in an operation  925 , display a prompt such as, for example: “SENSOR ERROR—CALL SERVICE.” Other prompts conveying similar messages may be used. In an operation,  927 , the self-test module may return to the main menu without setting a lockout and may write the error code Pressure Sensor Error to the test record in the Error Code field, or otherwise record the error. 
         [0184]    If, in an operation  923 , tank tester  101 &#39;s pressure sensors fall within the predetermined range, the self-test module may proceed, in an operation  929 , to test whether tank tester  101 &#39;s temperature sensors fall within a predetermined range. This determination may be made by taking temperature readings from the temperature sensors while a known temperature is applied to tank tester  101 . If, in an operation  931 , the temperature sensors fall outside the predetermined range, then tank tester  101  may, in an operation  933 , display a prompt such as, for example: “TEMPERATURE SENSOR ERROR—CALL SERVICE.” In an operation  935 , the self-testing module may return to the Main Menu without setting a lockout and may write the error code Temperature Sensor Error to the test record in the Error Code field or otherwise record the error. 
         [0185]    If, in operation  931 , temperature sensors fall within the predetermined range, the self-test module may, in an operation  937 , determine that the self test has been successfully completed and may display a prompt conveying such a message. 
         [0186]    According to an embodiment, the calibration module may perform a system-test for tank tester  101 &#39;s overpressure function. This system-test monitors for tank tester  101 &#39;s ability to disable tank tester  101  in the event that over pressurize of a calibration tank or fuel tank occurs. Tank tester  101  may be capable of resuming normal operation after the overpressure condition has been eliminated, and tank tester  101  successfully completes the calibration procedure successfully. Upon failing the system-test, tank tester  101  may prevent further testing with the device for a predetermined period of time, but may allow subsequent attempts to successfully complete calibration procedures, self tests or system tests. Once calibration has been successfully completed, the calibration module may allow testing to occur. 
         [0187]    If tank tester  101  fails any portion of a calibration test, a technician may be prompted to perform subsequent calibration procedures or contact a designated service provider for repairs. According to one embodiment, when service of tank tester  101  is required, tank tester  101  may not allow further tank testing or manual mode pressurization to be performed until full function has been restored by an authorized or designated service representative. 
         [0188]    Although the calibration procedures described above may have been described as occurring in a particular order (“phase one,” “phase two,” etc.), it should be understood that the aforementioned calibration procedures, self-test procedures, and system test procedures may be performed in any sequence. Any sequence of calibration procedures, self-test procedures, and system test procedures may be referred to as “calibration.” 
         [0189]    Testing 
         [0190]    Fuel Evaporative Test 
         [0191]    Once calibration have been performed, any number of tests, measurements, and/or calculations may be performed. According to an embodiment of the invention, tank tester  101  may include a test module. The test module may enable tank tester  101  to conduct various fuel tank tests such as, for example, a fuel evaporative test. A fuel evaporative test may enable calculation of the size of a leak in a fuel tank of unknown size. 
         [0192]      FIG. 10  illustrates an exemplary process  1000 , wherein a test module of tank tester  101  may perform a fuel evaporative test. In an operation  1001 , fuel evaporative test may be selected from the main menu or a fuel evaporative test may otherwise be initiated. In an operation  1003 , tank tester  101  may display a prompt such as, for example: “CONNECT TO TANK, SEAL EVAP SYSTEM, PRESS START.” In an operation  1005 , a user may then connect tank tester  101  to a fuel tank to be tested, seal or otherwise prepare all necessary systems, and commence the test. The user may commence the test by, for example, pressing a start button that is operatively connected to computer component  103  ( FIG. 1 ). 
         [0193]    In an operation  1007 , tank tester  101  may pressurize the fuel tank. During or after pressurization, tank tester  101  may determine if the maximum allowable fill time has been exceeded. For example, a gross leak may be indicated if the fuel tank cannot be pressurized to 5″ H 2 O in the first 60 seconds of fill time. If, in an operation  1009 , the fill time has been exceeded, tank tester  101  may proceed to an operation  1011 . In operation  1011 , the test module may determine how many times operation  1007  has been performed. If operation  1007  has not been performed more than a predetermined number of times, then tank tester  101  may, in an operation  1013 , display a prompt such as, for example: “GROSS LEAK DETECTED. CHECK ALL CONNECTIONS AND PRESS START.” The test module may then return to operation  1007  and reinitiate pressurization. 
         [0194]    The test module may then proceed through operations  1009  and  1011 . If, in operation  1011 , operation  1007  has been performed more than the predetermined number of times, the test module may, in an operation  1015 , display a prompt such as, for example: “TEST FAILED. TEST COMPLETE.” Other prompts conveying similar messages may be used. In an operation  1017 , the test module may write a “G” (for “gross leak”) to the “Test Result” field of the Test Record or otherwise record the failure and may then display a prompt such as, for example: “UNSEAL EVAP SYSTEM. DISCONNECT TESTER.” In an operation  1019 , tank tester  101  may monitor the fuel tank pressure for 30 seconds (or other time period) after which, tank tester  101  may vent any remaining pressure from tank tester  101  and may return to the main menu. 
         [0195]    If, in an operation  1009 , the fuel tank passes the fill-time portion of the test (indicating no gross leak), the test module may, in an operation  1021 , determine whether an otherwise unacceptable leak exists in the fuel tank (e.g., pass or fail) and make vapor space calculations. In making such calculations, the test module may compensate for temperature, Reid Vapor Pressure (RVP), and vapor space (described in detail below). Temperature, RVP, and vapor space compensation may be used to ensure accuracy of pressure, volume, and leak measurements. 
         [0196]    In operation  1021 , the test module may write the ambient temperature to the “Ambient Temp” field of the test record or otherwise record the ambient temperature during the test. In operation  1021 , the test module may also write the calculated vapor space results to the “Vapor Space” field of the test record or otherwise record the vapor space results. If the fuel tank passes the test, then, in operation  1021 , the test module may write a “P” to the Test Result field of the Test Record or otherwise record passage of the test. In an operation  1023 , tank tester  101  may display a prompt such as, for example: “TEST PASSED. PRESS START TO CONTINUE.” Similar steps may be taken in the event of fuel tank failure. In an operation  1025  the user may press the start button or otherwise indicate readiness to disengage tank tester  101  from the tested fuel system. In an operation  1027 , tank tester  101  may display a prompt such as, for example: “UNSEAL EVAP SYSTEM. DISCONNECT TESTER.” If tank tester  101  senses any pressure in the fuel tank 10 seconds (or other predetermined amount of time) after the last prompt, tank tester  101  may automatically vent the remaining pressure from the tank and testing component  117  ( FIG. 1 ) to the atmosphere or other area. In an operation  1027 , tank tester  101  may turn to the main menu. 
         [0197]    Flow Method 
         [0198]    In one embodiment of the invention, the test module of tank tester  101  may perform a fuel evaporative test designed to calculate the size of a hole in a subject tank using a “flow method.” In this embodiment, testing component  117  of tank tester  101  may have a “Fast Fill Flow” and “Slow Fill Flow” filling path. Using the Fast Fill Flow path, the subject tank may be pressurized to a predetermined pressure level such as, for example 14″ H 2 O at a rate of approximately 8.5 standard liters per minute (SLPM). Once the desired pressure is realized, tank tester  101  may switch to the Slow Fill Flow path. The Slow Fill Flow path may have an orifice and precision pressure regulator set to a predetermined pressure level such as, for example, 14″ H 2 O. The pressure regulator attempts to maintain a constant pressure in the subject tank. If the subject tank has no leak, there will be no flow. If the subject tank has a leak, the flow rate of gas required to keep a constant pressure in the subject tank should be the flow rate of the leak. Based on this flow rate, and the pressure in the subject tank, the size of the hole in the subject tank may be calculated and compared to a calibrated standard. 
         [0199]    Once a hole size is determined by the flow method, the tank may be allowed to leak down over a certain period of time. Based on the pressure drop in the tank versus time, the volume of the tank may be calculated. If the tank does not have any leaks, the volume may be calculated based on the Fast Fill Flow time and Fast Fill Flow rate. 
         [0200]    Constant Flow Test 
         [0201]    In another embodiment of the invention, the test module of tank tester  101  may perform a constant flow test. The constant flow test may operate by applying a constant flow of gas to fuel tank  140  which results in a increasing pressure. By measuring the rate at which a pressure corresponding to the pressure in fuel tank  140  increases, a determination is made as to the integrity of fuel tank  140  (or fuel system  150 ). The pressure inside an un-compromised fuel tank would increase at a greater rate than that of a compromised fuel tank. In some embodiments, the degree to which the fuel tank is compromised may be determined by the rate at which the pressure inside the fuel tank increases. 
         [0202]    Leak Down 
         [0203]    According one embodiment, the test module may determine the integrity of a fuel tank using a leak down test. In performing a leak down test, tank tester  101  may pressurize fuel tank  140  to a predetermined pressure. Once the predetermined pressure is reached, a time interval may elapse and a pressure corresponding to the pressure in fuel tank  140  is measured. Successive time intervals and pressure measurements may occur. If the pressure in fuel tank  140  remains approximately at the predetermined pressure, fuel tank  140  (or fuel system  150 ) may not be compromised (e.g., no leaks, or leaks within an accepted tolerance). If the pressure in fuel tank  140  decreases, fuel tank  140  (or fuel system  150 ) may be comprised (e.g., has a leak). Tank tester  101  may then perform calculations to determine the size of the leak and whether the leak is acceptable (e.g., pass/fail). 
         [0204]    Vacuum Testing 
         [0205]    In one embodiment, the test module of tank tester  101  may determine the integrity of a fuel tank (or fuel system) using vacuum testing. In one embodiment, vacuum testing may operate by reducing pressure in fuel tank  140  to a predetermined pressure below ambient pressure. Such a predetermined pressure may be achieved by applying a vacuum to fuel system  150 . The vacuum may be applied by a suitable device such as, for example, a vacuum pump, or other device known to one skilled in the art. Once the predetermined pressure is reached, a pressure corresponding to the pressure in fuel tank  140  is measured. If the pressure in fuel tank  140  remains at approximately the predetermined pressure, fuel tank  140  (or fuel system  150 ) may not be compromised (e.g., no leaks, or leaks within an accepted tolerance). If the pressure in fuel tank  140  increases, fuel tank  140  (or fuel system  150 ) may be comprised (e.g., has a leak). Tank tester  101  may then perform calculations to determine the size of the leak and whether the leak is acceptable (e.g., pass/fail). 
         [0206]    In another embodiment, vacuum testing may operate by applying a continuous vacuum to fuel tank  140  which results in a decreasing pressure inside fuel tank  140 . By measuring the rate at which a pressure corresponding to the pressure in fuel tank  140  decreases, a determination may be made as to the integrity of fuel tank  140  (or fuel system  150 ). The pressure inside an uncompromised fuel tank would decrease at a greater rate than that inside a compromised fuel tank. In some embodiments, the degree to which the fuel tank is compromised may be determined by the rate at which the pressure inside the fuel tank decreases. 
         [0207]    Mechanical Pressure 
         [0208]    According to one aspect of the invention illustrated in  FIG. 11 , the test module of a system  1100  may determine the integrity of the fuel tank  140  (or fuel system  150 ) by applying a constant, predetermined pressure to fuel tank  140  via a mechanical device, such as a piston  162  and cylinder  160 . A force may be applied to piston  162  commensurate with the desired predetermined pressure to be applied to fuel tank  150 . The force may be applied to piston  162  by an electric or fuel based motor, by a hydraulic device, or by another suitable device known to one skilled in the art. Once the predetermined pressure is reached in the tank, the force applied to piston  162  and the force corresponding to the pressure in fuel tank  140  should be equal and opposite. If fuel system  150  is uncompromised (e.g., no leaks), piston  162  should remain stationary (or nearly so). If fuel system  150  is compromised (e.g., leaks), piston  162  should move. The degree to which piston  162  moves may be related to the degree to which fuel system  150  leaks. The movement of piston  162  in cylinder  160  may be measured via various well known mechanisms. 
         [0209]    Manual Mode 
         [0210]    In one embodiment of the invention, tank tester  101  may include a manual-test module.  FIG. 12  illustrates an exemplary process  1200 , wherein a manual-test module of tank tester  101  may perform manual test sequence. In an operation  1201 , manual test mode of tank tester  101  may be initiated. Initiation may occur upon selection by a user or by other event. In an operation  1203 , tank tester  101  may display a prompt such as, for example: “PRESS START TO BEGIN TEST.” In an operation  1205 , a user may commence the test by, for example, pressing a start button that is operatively connected to computer component  103  ( FIG. 1 ). In an operation  1207  tank tester  101  may display a prompt such as, for example: “SEAL EVAP SYSTEM. CONNECT TO TANK. PRESS START.” In an operation  1209 , a user may connect tank tester  101  to a fuel tank, prepare the system, and continue the test by, for example, pressing the start button. In an operation  1211 , tank tester  101  may pressurize the fuel tank to 14″ of H 2 O (or other predetermined pressure level) and maintain that pressure for no more than 10 minutes or other predetermined amount of time. While in the Manual Mode operation, tank tester  101  may display the following prompt: “MANUAL MODE. TIME REMAINING: XX.” The “XX” may represent the time remaining on the predetermined amount of time and may count down as the timer elapses. If the user re-initiates the test cycle by, for example, pressing the start button prior to the expiration of the predetermined time limit, tank tester  101  may restart the timer and continue to pressurize the fuel evaporative system. This process may be repeated until either the timer expires or the user aborts the test by, for example, pressing an abort button that is operatively connected to computer component  103 . During pressurization, a user may take readings from the various sensors and transducers of tank tester  101  for use in determining the various qualities of a fuel tank being tested. At the end of the predetermined time period, in an operation  1213 , tank tester  101  may vent any remaining tank pressure and display a prompt such as, for example: “TEST COMPLETE. UNSEAL EVAP SYSTEM. DISCONNECT TESTER.” In an operation  1215 , the manual-test module may return to the main menu. 
         [0211]    If at anytime during the manual mode sequence the testing pressure applied to the fuel tank exceeds 28″ H 2 O (or other predetermined pressure level), tank tester  101  may automatically abort the manual operation, open the pressure vent, and display a prompt such as, for example: “SYSTEM OVERPRESSURE. TEST ABORTED. UNSEAL EVAP SYSTEM. DISCONNECT TESTER.” Tank tester  101  may subsequently lock out the fuel evaporative test and manual mode operation until a successful calibration has been completed and return to a main menu. 
         [0212]    Additional Components 
         [0213]    In some embodiments, tank tester  101  may also include one or more devices (e.g., pliers/clamps) capable of pinching an outlet hose or other pneumatic conduit to completely block vapor flow. These devices may be used during various testing or calibration procedures to block gas flow through tank tester  101 . The devices may apply sufficient pressure to substantially completely block any flow while also leaving the conduit undamaged and serviceable. In addition, the devices may be self-locking and capable of performing approximately 5,000 clamping cycles. 
         [0214]    In one embodiment, tank tester  101  may also include tapered hose plugs that may plug vapor hose openings in the event that the aforementioned pinching devices are incompatible with the vehicle being tested. These hose plugs may be configured to fit ⅛ to ½ inch inner diameter hose in ⅛-inch increments. Other configurations may be used. In lieu of specially designed plugs, a set of plugs manufactured by Thexton, Part Number 312, or equivalent may be substituted. 
         [0215]    In one embodiment, tank tester  101  may also include a calibration adaptor designed to plug the end of tank tester  101 &#39;s hose (that normally connects to a tank adaptor). This adaptor may be used to plug tank tester  101 &#39;s hose end during certain calibration procedures as described above. 
         [0216]    Multiple Standards 
         [0217]    In one embodiment, the test module may enable the use of different predefined standards for fuel tank tests. For example, the test module may base a pass/fail determination on a standard on a 0.020″ gap. Where a fuel evaporative system leak is less than or equal to a 0.020″ diameter gap, the test module may return a pass determination. Accordingly, the test module may fail the fuel evaporative system where the leak exceeds a 0.020″ diameter gap. 
         [0218]    Under a different standard such as, for instance, a 0.040″ diameter orifice standard, the test module may pass a vehicle where the fuel evaporative system leak is less than or equal to a 0.040″ diameter gap, and fail the fuel evaporative system where the leak exceeds a 0.040″ diameter gap. The false pass error rate may be less than ±5% and the false fail error rate may be less than ±1%. Other pass/fail standards and error rates may be used. All data pertinent to test standards may be stored in a file. This file may include any or all data and/or algorithms required to make the Pass/Fail decision in tank tester  101 . 
         [0219]    Calculations and Compensation 
         [0220]    According to one aspect of the invention, tank tester  101  may contain a data analysis module. The data analysis module may, among other things, measure vapor space, temperature, and Reid Vapor Pressure (RVP) within a fuel tank being tested and may compensate for these factors when making test calculations. 
         [0221]    Temperature measurements may be taken by one or more temperature sensors included in tank tester  101 . The temperature sensors may be placed in various places within the testing component and may be connected to a sensor or other element of computer component  103 . Additionally, various hardware and software components associated with tank tester  101  may be used to determine liquid fuel temperature based on measured vapor temperature. These temperature readings may be used in the calculations made during the various tests performed by tank tester  101 . 
         [0222]    Tank tester  101  may include a barometric pressure sensor for measuring the barometric pressure of the testing environment in which tank tester  101  is being used. Tank tester  101  may also include an ambient temperature sensor for measuring the ambient temperature of the testing environment. These measurements may also be used in the calculations performed by tank tester  101 . 
         [0223]    Referring back to  FIG. 1 , Reid Vapor Pressure (RVP) measurements may be taken for a volume of fuel  145  in fuel tank  140 . RVP corresponds to the pressure induced in a closed volume (fuel tank  140 ) as a result of the evaporation of liquid (fuel  145 ) in the closed volume. To improve the accuracy of tank tester  101 , the data analysis module may compensate for RVP. In order to compute RVP, the data analysis module may obtain the following measurements or quantities: the volume of fuel tank  140 , the volume of the liquid (fuel  145 ) in fuel tank  140 , a measure of the liquid&#39;s tendency to evaporate, and the ambient temperature of the surrounding environment. With one or more of these variables, the amount of pressure induced by the evaporative effects of the fuel  145  may be determined. 
         [0224]    In some embodiments of the invention, RVP may be measured directly by, for instance, releasing the pressure in fuel tank  140 , resealing fuel tank  140 , allowing the closed system to reach a steady state condition, and measuring RVP at steady state. Once RVP is determined, the data analysis module may compensate for RVP in pressure measurements as would be apparent. 
         [0225]    In some embodiments, certain other measurements such as, for example the volume of fuel tank  140 , the volume of fuel  145  in fuel tank  140 , the volume of vapor in fuel tank  140 , or other measurements may be used by tank tester  101  in making calculations. In some embodiments, the volume of fuel tank  140  may be provided by the manufacturer of fuel tank  140  or integrator of fuel system  150  (e.g., automobile manufacturer). In other embodiments of the invention, the volume of fuel tank  140  may be measured. In some embodiments of the invention, the volume of fuel  145  in a fuel tank  140  may be measured. In other embodiments, fuel tank  140  may be drained and a known volume of fuel  145  may be dispensed into fuel tank  140 . In some embodiments, the volume of fuel tank  140  and the volume of fuel  145  may be used to determine the volume of vapor within fuel tank  140 . In other embodiments, the volume of the vapor may be measured directly without obtaining the volume of fuel tank  140  and/or the volume of the fuel  145 . 
         [0226]    Safety Measures 
         [0227]    According to an embodiment of the invention, tank tester  101  may be configured to determine an overpressure condition for either an incoming supply pressure or a regulated test pressure. If at anytime during a procedure (for example, a fuel evaporative test or manual mode test) the tester inlet pressure from the air pressure regulator exceeds 35 psi (or other predetermined value), tank tester  101  may cease any test or procedure in progress. Tank tester software may prevent tank tester  101  from performing a pressurization of the fuel tank until any overpressure condition has been corrected. 
         [0228]    Additionally, if at anytime during a procedure the fuel tank pressure exceeds 28″ H 2 O (or other predetermined pressure level) as measured by tank tester  101 , tank tester  101  may open one or more valves and vent any remaining pressure in the fuel tank. Tank tester  101  may also prevent pressurization of the fuel tank for any procedure until the problem has been corrected. 
         [0229]    At anytime during a test sequence, the test may be aborted by the activation of an abort button that is operatively connected to computer component  103  ( FIG. 1 ). The abort button may cause tank tester  101  to immediately open a system relief valve, write the “Tech. Abort” code to the Error field of the Test Record (or otherwise record the aborted test), and subsequently return tank tester  101  to the main menu. 
         [0230]    Software Updates 
         [0231]    A tank tester  101  may include a software update module. The software update module may enable software associated with tank tester  101  (including the operating application and various software modules) to be updated in a number of ways. 
         [0232]    Software associated with tank tester  101  may be updated by a modem. For example, a built-in modem may dial a 1-800 number, allow a query of tank tester  101  for the software version, and update software modules and databases as required. In another embodiment, tank tester  101  may be connected to a phone line and a host may call tank tester  101  to commence an update process. 
         [0233]    In yet another embodiment, software may be updated using a compact flash card or other memory storage device within tank tester  101 . Such a device may be removed from tank tester  101 , sent to a service provider for reprogramming, and reintroduced into tank tester  101  with updated software. Alternatively, memory storage devices containing updated software may be sent to tank tester users as replacements for older devices. 
         [0234]    In another embodiment, software may be updated by connecting tank tester  101  to a personal computer (or other computer). A user may then connect to the Internet (or other designated network) and link to a provider web page to download software updates. These updates may then be communicated to (and/or stored within) tank tester  101 . Alternatively, tank tester  101  may contain sufficient computer hardware and/or software to connect to the Internet or other network without the aid of an additional computer. 
         [0235]    Menus 
         [0236]    In one embodiment, tank tester  101  may include a main menu. In various embodiments, any one or more of the following menu options may be displayed in the main menu or other menus and may be facilitated by tank tester  101 &#39;s software and/or hardware: (1) Fuel Evaporative Test, (2) Diagnostic Manual Mode testing, (3) Calibration, (4) Self-test, (4) Status Mode, (5) Software update, (6) Service mode, (7) QA State Menu, or other options. 
         [0237]    In one embodiment, a Status Mode may display the following information: testing station&#39;s license number (or other testing station identification); next test record number; tester number; date/time; loaded software version number; update software version number; and tester lock out reason. 
         [0238]    The testing station license number of an entity using tank tester  101  may include a license number issued by a state automotive authority or other authority. Other station identification may be used. Station identification may be entered into tank tester  101  during initial operation or startup. In one embodiment, station identification may consist of eight characters. In one embodiment, the first two characters of the identification number may be alphas followed by six digits. Other identification number formats may be used. 
         [0239]    Tank tester  101  may assign each test a consecutive number (test record number). The number may be written in a Test Record Number field of the test record or otherwise recorded. In one embodiment, this field may be numeric and have a length of six digits. Furthermore, each tank tester  101  may have a unique serial number which may be recorded in the test record. 
         [0240]    Using an internal clock, tank tester  101  may assign a date/time stamp to each valid test. A valid test may, in certain embodiments, consist of a completed fuel evaporative test with a pass/fail result recorded to the test record. The time may also change to coincide with changes from standard time in a particular time zone to daylight savings time. In addition, tank tester  101  may compensate for leap year. In one embodiment, the date and time may be formatted as follows: mmddyyyy_hhmm. The hour stamp may use the 24-hour clock format. The date/time may be written to the Test Date/Time field of the test record or otherwise recorded. 
         [0241]    The loaded software version number may contain the version number in current use by tank tester  101 . The loaded software version number may be written to the Loaded Software Version Number field of the test record or otherwise recorded. This field may be populated in the test record for every valid test. 
         [0242]    The update software version number may contain the version number of update software that is currently loaded but not being used by tank tester  101 . The update software version number may be recorded into a field of the test record. This field of the test record may be populated if tank tester  101  has update software loaded. At a predetermined date, the software of tank tester  101  may be updated, and the old software may be discarded. After the update software version turns into the loaded software version, the update software version number field may be blank. 
         [0243]    If tank tester  101  has been locked out, then one of the following reasons (or other reasons) may be displayed on the status page: clock failure, sensor failure, QA/State tester lockout, or calibration failure. 
         [0244]    In one embodiment, a QA State Menu may provide access to certain data stored on tank tester  101 . The QA State Menu may be accessed via tank tester  101 &#39;s display device and user input device, a separate computer (such as a laptop), or other device. The QA State Menu may require a password. In one embodiment, the password may consist of a six character, case sensitive alphanumeric and may change daily. The access code algorithm may be supplied by a service provider or system administrator. Other configurations may be implemented. 
         [0245]    The QA State Menu may consist of a menu including one or more of the following options: update config. tables, load software update, download test records, download calibration records, lock-out tester, or other options. 
         [0246]      FIG. 13  illustrates an exemplary process  1300 , wherein the QA State Menu (or other password protected area) of tank tester  101  may be accessed. In an operation  1301 , the QA State Menu may be selected. In an operation  1303 , tank tester  101  may display a prompt such as, for example: “ENTER PASSWORD.” In an operation  1305 , a user may enter a password. While entering the password, tank tester  101 &#39;s display device may display only X&#39;s or other indicators on the screen. In an operation  1307 , a password protection module may verify the password. If, in an operation  1309 , the password is incorrect, the software may proceed to an operation  1311 . In an operation  1311 , the password protection module may determine if the number of times a password has been entered (“password try”) exceeds a predetermined allowable number. If, in an operation  1311 , the number of password tries does not exceed the allowable number, tank tester  101  may, in an operation  1313  display a prompt such as, for example: “PASSWORD INCORRECT. REENTER PASSWORD.” The password protection module may then return to operation  1305  wherein the user may enter a password. The password protection module may proceed through operations  1307 ,  1309 , and  1311 . If, in an operation  1311 , the number of password tries exceed the allowable number, the password protection module may, in an operation  1315 , return to the main menu and record a password error to the test record or otherwise record the error. In operation  1315  the password protection module may also record the date and time of the error to the test record. 
         [0247]    If, in operation  1309 , the password is correct, then the password protection module may (in an operation  1317 ) display the QA State Menu which may contain one or more of the following options: update config. tables, load software update, download test records, download calibration records, lock-out tester, or other option. In some embodiments, the QA State Menu, or other menu, may enable update of tank tester  101 &#39;s internal clock. 
         [0248]    The password protection module is described above for use in conjunction with the QA State Menu. The password protection module may, however, be used to provide password protection to any menu or feature of the invention described herein. 
         [0249]    If the update config. tables option is selected form the QA State Menu, the software update module may enable the update of the testing parameter in a Config. Table (or other location) as necessary to improve accuracy or compliance with mandated guidelines. If the load software update option is selected, a connected computer may communicate with tank tester  101  to load an updated software version into tank tester  101 &#39;s memory for activation at a later date. If the download test records option is selected, a user may access test records and download some or all records to a connected computer. The download may be stored in a unique file on the connected computer identified by Tester ID and Station ID. The process may not delete any records from tank tester  101 . If the download calibration records option is selected, a user may access a calibration record and download all records to a connected computer. The download may be stored in a unique file on the connected computer identified by Tester ID and Station ID. The process may not delete any records from tank tester  101 . If the lockout tester option is selected, a user may send a lock out code to tank tester  101  that prevents tank tester  101  from performing tests or other procedures. In one embodiment, calibration and or self-tests may not be locked out by selection of the tester lockout option. 
         [0250]    Test Record 
         [0251]    According to an embodiment, tank tester  101  may record test results and related data to a test record. The test record may include multiple fields containing various types of test data such as, for example test start year, test start month, test start day, test start hour, test start minute, test start second, vehicle year, vehicle make, vehicle model, head space, ambient temp, pressure increase/decrease, test result (pass, fail, abort, etc), abort code, date of last calibration, software version number, and/or other data. 
         [0252]    According to an embodiment, a test record may be read from tank tester  101  by sending a command with four data bytes in the range of 0000 to 9999 (or other range). Tank tester  101  may respond with the data for the selected tank test results as follows: 
         [0000]                                        &lt;STX&gt;&lt;echoed command&gt;&lt;command data (status bytes)           XXXXrr...rr&gt;&lt;chesksum&gt;&lt;ETX&gt;            → where XXXX is the record number (as requested)            → rr...rr is the test record data (see above) or all zeros if no such            record has been collected                    
Other processing alternatives may be implemented.
 
         [0253]    System Communications 
         [0254]    According to an embodiment, tank tester  101  may include a communications module. The communications module may enable standard RS232 communications protocols that may be used for communication between an EIS and tank tester  101 . In addition, a laptop computer (or other suitable device) using RS232 communications may be used for software and table updates for tank tester  101 . Communications protocols as used herein may enable users to perform one or more various functions including, for example: updating operating software as deemed necessary; updating tables for pass/fail standards; downloading test data from records stored in tank tester  101 ; downloading tester calibration records stored in tank tester  101 ; outputting pass/fail results to the EIS; communication with other computers or a network; or other function. Furthermore, the communications module may perform updates and other communications using a modem incorporated into tank tester  101 . Protocols other than RS232 may be used. 
         [0255]    According to an embodiment, tank tester  101  may include a serial mode module for serial mode operation. Serial mode operation may be two-fold. A first serial mode operation may be for checkout and testing of production line tank testers and repair of returned tank testers. A second serial mode operation may be for integrating communication to EIS equipment. The configuration of the serial port may, for instance, have a baud rate fixed at 9600 baud. Other signaling rates may be used. 
         [0256]    According to an embodiment, when connected to and communicating with an EIS, tank tester  101  may be powered by a 12 VDC source limited to 0.5 amps supplied by the RS 232 communications port. Other configurations may be implemented. Alternatively, tank tester  101  may be integrated with an EIS. 
         [0257]    According to an embodiment, a service mode may also be provided. The development/service mode may run an evaporative test and show current pressure, temperature and flow readings during the test and show results after the test is finished. The service mode may also run a manual service and test mode while displaying sensor readings solenoid or valve status. Furthermore, the development mode may allow the update of software, databases and tables in conjunction with or apart from other features described herein. 
         [0258]    Interlocking Tank Adaptor Safety Mechanism. 
         [0259]    According to embodiment, the tank adaptor of tank tester  101  (e.g., tank adaptor  415  in  FIG. 4  or tank adaptor  519  of  FIG. 5 ) may provide a closed system between fuel system  150  and tank tester  101 . In some embodiments of the invention, tank adaptor  121  may enable tank tester  101  to pressurize fuel system  150 , among other things. 
         [0260]    One drawback associated with pressurizing fuel system  150  may arise in the event that fuel tank  140  is full, or nearly so, of fuel  145 . If the pressure is not properly released, some fuel  145  may spill or splash out of the tank. According to one aspect of the invention, tank tester  101  may include an interlock that prevents fuel from spilling, splashing or other being released from fuel system  150  when it is depressurized. This may be accomplished either at or proximate to tank adaptor  121  alone or in conjunction with various functionality incorporated into tank tester  101 . 
         [0261]    In some embodiments of the invention, tank adaptor  121  may be unable to be physically removed from fuel neck  143  until pressure inside fuel tank  140  returns to ambient pressure. In some embodiments, tank adaptor  121  may incorporate or otherwise operate with an interlock that prevents tank adaptor  121  from being removed from fuel neck  143  until the pressure returns to ambient pressure (i.e., the pressure of the testing environment). 
         [0262]    In some embodiments, tank adaptor  121  may include a valve (e.g., bleed valve, etc.) that releases the pressure in fuel system  150 . In some embodiments, tank tester  101  may include the valve (such as the relief valves described in  FIGS. 4 and 5 ). Other embodiments may incorporate the valve elsewhere as would be apparent. In some embodiments, tank tester  101  may include an automated valve that controls the return of ambient pressure to fuel tank  140 . 
         [0263]    In one embodiment, a kit containing various tank adaptors may be provided with tank tester  101 . These adaptors may be designed to fit a majority of vehicles&#39; fuel tank filler necks. In case none of the adaptors fit, a universal tank adaptor may be provided. These adaptors may be made using materials that may be pliable and impermeable to all gasoline constituents. These adaptors may also be made using non-conductive material to prevent sparks. 
         [0264]    Hydrocarbon Detector 
         [0265]    According to one aspect of the invention, tank tester  101  may contain various mechanical components, hardware components, and/or software components (or modules, such as a hydrocarbon detection module) that may enable tank tester  101  to detect fuel vapor that escapes from fuel system  150 . To facilitate fuel vapor detection, a small amount of pressure above ambient pressure may be applied to fuel system  150 . This pressure may tend to force any fuel vapor out of a compromised fuel system  150 . Such fuel vapor may be detected by a detector incorporated into tank tester  101  such as, for example, a gas analyzer or other detector capable of detecting hydrocarbons. In addition to detecting whether fuel vapor may be leaking from fuel system  150 , the detector may also be used to determine the approximate location of the leak by, for example, using a probe from the detector to identify areas with increased levels of hydrocarbons. Devices suitable for hydrocarbon detection are known to those skilled in the art. 
         [0266]    Integrated Fuel Cap and Fuel Tank Testing 
         [0267]    Currently, tank integrity and fuel cap tests may be performed separately. According to one aspect of the invention, tank tester  101  may be modified to contain sufficient devices, as well as computer hardware and/or software to enable simultaneous measurement of fuel cap leakage and fuel tank integrity. 
         [0268]    Other embodiments, uses and advantages of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification should be considered exemplary only, and the scope of the invention is accordingly intended to be limited only by the following claims.