Patent Publication Number: US-2012044068-A1

Title: Tanker Truck Monitoring System

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/251,887 filed Oct. 15, 2008 which is fully incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION  
     The present invention relates to a system to monitor trucks operable to carry fluids, and in particular flammable fluids such as petroleum products. 
     BACKGROUND OF THE INVENTION 
     Modern transportation of liquids generally expends a significant amount of time and money. Though some liquids, such as water, sewage, etc., are generally transported by a pipeline, other liquids are often too delicate or too dangerous to transport by pipeline and are typically transported by tanker truck. In particular, liquid fuels are expensive, hazardous, and prone to handling error and theft, and therefore transport by tanker trucks is common for motor transportation of liquid fuels to retail outlets. In particular, liquid fuels are typically transported by tanker trucks under the recommended practices specified by the American Petroleum Institute (API) and the National Fire Protection Association (NFPA). These organizations have standards that define how liquid fuels are to be loaded, unloaded and transported within the United States. These standards have typically become common practices in most regions of the world. 
     The API Recommended Practice 1004 defines the use of an overfill system on conventional DOT-406 and MC-306 tanker trucks. During fuel loading, the primary means to shut off the flow of fuel is typically through a metering system at a gantry controller that measures the amount of fuel being loaded. Once a specified amount has been loaded, the gantry controller typically shuts off fuel pumps. Conventional overfill systems, however, are secondary emergency shut off systems. Conventional overfill systems generally include one or more overfill sensors mounted inside the tank, and often include one overfill sensor for each compartment of the tank. Conventional overfill systems typically communicate a permissive signal to the gantry controller to indicate that the gantry controller may load the tanker truck. When an overfill sensor becomes wet, conventional overfill systems typically prohibit the permissive signal to prevent further fuel loading, often stopping the loading process midway. Thus, conventional overfill systems generally have the primary purpose to prevent a fuel spill should the metering system fail. 
     These conventional overfill systems are generally electronic devices coupled to electronic sensors that are designed detect an overfill condition. Conventional overfill systems often operate in harsh and varied environments, and generally experience extreme temperatures, jostling, rocking, stretching, swaying, bumps, noxious vapors, and electrical disturbances. In particular, conventional overfill systems are typically susceptible to vibration and environmental corrosion, as well as rough handling by operators. As such, conventional overfill systems are often prone to failure. For example, sensors and wires may experience wear and intermittently send signals that may erroneously indicate a fault, or overfill condition. Similarly, sensors and wires may experience wear and intermittently fail to send signals that indicate a fault, or overfill condition. These intermittent problems may prevent loading of the tanker truck. After being denied the ability to load, operators typically return to a maintenance bay to determine the cause of the problem, but these intermittent problems are often hard to reproduce. Thus, these problems are often either ignored (possibly leading to dangerous overfills, spills, improper loading, and/or improper unloading) or addressed through potentially unnecessary and costly repair or replacement (including repair or replacement of the sensors, wires, and/or monitoring system, or even replacement of a compartment or the entire tank). As such, conventional overfill systems are typically unable to quickly and easily allow technicians to diagnose problems that occur intermittently as they are often unable to track those problems and/or reproduce those problems in a timely and efficient manner. 
     Furthermore, operator error is often another source of loading problems. Operators may commit a number of errors resulting in overfill and/or loading rejections from the gantry controller. Moreover, operators often commit a number of errors that result in potentially hazardous conditions, including attempting to enter an amount of fluid in excess of a compartment&#39;s capacity, connecting a filling line to an inlet for the wrong compartment than intended, and/or attempting to load a compartment that has remaining fluid from a previous load. Other typical operator errors include failing to connect the tanker truck to ground before filling, failing to establish a vapor connection between the compartment being filled and the supply tank supplying the liquid to the compartment, failing to set brakes of the tanker truck, and/or failing to engage one or more safety interlocks of the tanker truck. Conventional overfill systems are typically unable to monitor these conditions and prevent loading problems that typically occur due to operator error. 
     Additionally, tanker trucks are often prone to theft. As the cost of fuel rises, theft of fuel from tanker trucks generally increases. To steal the fuel, operators typically drain the bottom piping of the tanker truck that leads from the inlet to a compartment. However, this theft is often difficult to detect, as the operators typically make an unauthorized stop at some remote location and drain the fuel from the piping for personal use or black market sale. Up to about forty gallons may be drained from the bottom piping without affecting the liquid level of the compartments of the tanker truck. Conventional overfill systems are also typically unable to monitor either the tanker truck piping or the tanker truck location to detect theft of the fuel. 
     Moreover, errors often occur when unloading the tanker truck. One error common includes delivering a load to the wrong location, which results in non-payment by the intended recipient as well as non-payment by the unintended recipient. Another error includes unintentionally mixing fluids in tanks, which results in additional expenditures associated with pumping out that mixed fluid and proper disposal. Conventional overfill systems are unable to monitor the unloading of the tanker truck to determine errors that may occur. 
     Consequently, there is a continuing need to overcome these deficiencies. 
     SUMMARY OF THE INVENTION 
     The invention provides for a system and method to monitor a tanker truck that includes at least one compartment to retain a fluid. The system includes a plurality of sensors, each of the plurality of sensors configured to detect an event. The system also includes a monitoring unit electrically coupled with the plurality of sensors to detect the event. The monitoring unit includes a processing unit, a time module, and a memory, and is operable to time stamp the sensed event with information from the time module and store the detected and time stamped event in the memory. The system further includes a handheld data terminal configured to communicate with the monitoring unit. The handheld data terminal is operable to retrieve and display the stored event, and includes a processing unit, a memory, a user interface, a time module, and a display. 
     These and other advantages will be apparent in light of the following figures and detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a perspective view of a tanker truck being loaded with fuel at a loading island consistent with embodiments of the invention; 
         FIG. 2  is an enlarged view of the circled area  2  of  FIG. 1  and illustrates a monitoring unit consistent with embodiments of the invention; 
         FIG. 3  is a block diagram of couplings of a plurality of sensors to a monitoring unit consistent with embodiments of the invention; 
         FIG. 4  is a diagrammatic illustration of a schematic of, and couplings to, one embodiment of the monitoring unit of  FIG. 2  consistent with embodiments of the invention; 
         FIG. 5  is a block diagram of one embodiment of a monitoring system to monitor the tanker truck of  FIG. 1  that includes the monitoring unit of  FIG. 2 , a handheld data terminal, and a computer consistent with embodiments of the invention; 
         FIG. 6  is a diagrammatic illustration of a schematic of one embodiment of the handheld data terminal of  FIG. 5  consistent with embodiments of the invention; 
         FIG. 7  is a block diagram of an alternative embodiment of a monitoring system to monitor the tanker truck of  FIG. 1  that includes a monitoring unit, a handheld data terminal, and the computer consistent with embodiments of the invention; 
         FIG. 8  is a diagrammatic illustration of a schematic of, and couplings to, one embodiment of the monitoring unit of  FIG. 7  consistent with embodiments of the invention; 
         FIG. 9  is a diagrammatic illustration of a schematic of one embodiment of the handheld data terminal of  FIG. 7  consistent with embodiments of the invention; 
         FIG. 10  is a flowchart illustrating a process of the monitoring unit of  FIG. 2  and/or  FIG. 7  to detect events and determine actions based on those events; 
         FIG. 11  is a flowchart illustrating a process of the handheld data terminal of  FIG. 5  and/or  FIG. 7  to retrieve event information from and/or transfer data to the monitoring unit of  FIG. 2  and/or  FIG. 7 , respectively, consistent with embodiments of the invention; 
         FIG. 12  is a flowchart illustrating a process to process data received from the handheld data terminal of FIG,  5  and/or  FIG. 7  in the monitoring unit of  FIG. 2  and/or  FIG. 7 , respectively, consistent with embodiments of the invention; and 
         FIG. 13  is a block diagram of one embodiment of an event screen displayed by the monitoring system of  FIG. 5  and/or  FIG. 7  to display event and/or monitoring unit information. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the sequence of operations as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes of various illustrated components, will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments may have been enlarged or distorted relative to others to facilitate visualization and clear understanding. 
     DETAILED DESCRIPTION 
     Embodiments of the invention include a method and monitoring system to monitor a tanker truck. In some embodiments, the tanker truck may include a tank with a plurality of compartments, and the monitoring system may include a monitoring unit, a handheld data terminal, and a computer. The monitoring unit monitors a plurality of sensors to detect an event. In some embodiments, these sensors may include an overfill sensor, a retain sensor, a brake sensor, a valve sensor, a vapor connection sensor, a ground sensor, a socket sensor, and a safety interlock sensor. Upon detecting an event, such as an overfill condition, a retain condition, the engagement or disengagement of a brake, the opening or closing of an American Petroleum Institute (API) valve, the establishment or loss of a vapor connection, the establishment or loss of a ground connection, the establishment or loss of an electrical connection to a gantry controller, and/or the engagement or disengagement of a safety interlock, monitoring unit may timestamp the event and store an indication of the event and the timestamp as event information in a memory. 
     The monitoring unit may communicate with the handheld data terminal, which may be used to download data, such as programming information, identification information, event information, or fluid information from the monitoring unit. The handheld data terminal may also be used to download data, such as programming information, identification information, or fluid information to the monitoring unit. The handheld data terminal may be further configured to display the event information. The handheld data terminal, in turn, may communicate with the computer, which may also display the event information through an event display application. Advantageously, it is believed that this allows intermittent or otherwise transient events to be viewed by users to diagnose errors. 
     In some embodiments, the monitoring unit may be coupled to a Global Positioning Satellite (GPS) receiver. Thus, the monitoring unit may determine the GPS location of the tanker truck in response to detecting the event. In alternative embodiments, the monitoring unit may determine the GPS location of the tanker truck at predetermined time intervals. Advantageously, it is believed that the monitoring system may detect theft of liquid from the tanker truck by determining when an API valve to a compartment is open, determine the time of this event, and determine the location of the tanker truck at about the time of the event. 
     In some embodiments, the monitoring unit may communicate with the handheld data terminal through a cable. Similarly, in some embodiments the handheld data terminal may communicate with the computer through a cable. In alternative embodiments, the monitoring unit may communicate with the handheld data terminal and/or computer through wireless communication. Similarly, in alternative embodiments the handheld data may communicate with the monitoring unit and/or computer through wireless communication. In particular embodiments, the monitoring unit may communicate with the handheld data terminal through low-power wireless communication and communicate with the computer through long range wireless communication. 
     Tanker Truck 
       FIG. 1  illustrates a tanker truck  10  having a tank  12  mounted on a trailer  13 . The tank  12  is configured with four compartments  14   a,    14   b,    14   c,  and  14   d  configured to retain a fluid and having respective covers  16   a,    16   b,    16   c,  and  16   d.  Although four compartments  14   a,    14   b,    14   c,  and  14   d  are illustrated in  FIG. 1  by dashed lines, these dashed lines are for illustration purposes only. As such, there may be any number of compartments in any location in the tank  12 . In some embodiments, the tank  12  may have one or up to about eight compartments. Below the tank  12  are a plurality of pipes  18   a,    18   b,    18   c,  and  18   d  in fluid communication with the respective compartments  14   a,    14   b,    14   c,  and  14   d.  Each of the pipes  18   a,    18   b,    18   c,  and  18   d  may have a valve assembly  20  located at the end thereof for loading fluid into the compartments and unloading fluid from the compartments in a manner known in the art. In specific embodiments, each valve assembly  20  may include an American Petroleum Institute (API) valve as is well known in the art. 
     Fluid, such as liquid fuel, is loaded into the compartments  14   a,    14   b,    14   c,  and  14   d  at a loading rack or island  22 . The loading rack  22  has at least one dispensing line  24  which draws fluid from a fluid supply  28  via a pump (not shown). The dispensing line  24  typically traverses a gantry (not shown) to the truck  10 , where the end of the dispensing line  24  is mechanically coupled to the valve assembly  20  via a coupler  26 . In specific embodiments, each coupler  26  may couple to the API valve as is well known in the art. Although one embodiment of loading rack  22  is illustrated and described, any number of different loading racks may be used in accordance with the present invention. 
     Although  FIG. 1  illustrates the fluid supply  28  being in the form of a holding tank located underneath the loading island  22 , the fluid supply  28  may assume other forms and may be remotely located from the loading island  22 . Similarly, although one dispensing line or hose  24  is illustrated being connected to pipe  18   a  to fill compartment  14   a,  any number of dispensing lines may be operational at the same time to fill multiple compartments simultaneously. In some embodiments, the compartments may be filled with different types of fuel drawn from different fuel supplies. 
     A vapor recovery fitting  30  forms part of the tank  12  and may be connected to a vapor recovery hose  32  which extends between the vapor recovery fitting  30  and the supply tank  28 , as is conventional in the art to prevent vapors from escaping to the atmosphere. The vapor recovery fitting  30  is in fluid communication with a vapor connection hose  34  that may be connected to at least one of the covers  16   a,    16   b,    16   c,  and/or  16   d  to remove vapor from the respective compartments  14   a,    14   b,    14   c,  and  14   d  as they are loaded with fluid. The dispensing line  24 , coupler  26 , hoses  24 ,  32 ,  34 , vapor recovery fitting  30  and fuel supply  28  are all conventional in the art. The invention of the present application is not intended to be limited by the number, configuration or operation of these items. 
     At the loading island  22  is a gantry controller  36  which has a cable  38  extending outwardly therefrom. The gantry controller  36  may control the pump to load the fluid to at least one compartment  14   a,    14   b,    14   c,  or  14   d.  In some embodiments, the gantry controller  36  may load the fluid in response to a permissive signal from the truck  10 .  FIG. 2  is an illustration of a monitoring unit  40  that may provide the permissive signal through at least one socket  42 ,  44  to a plug  46  secured to the end of cable  38 , and thus to the gantry controller  36 . The monitoring unit  40  is configured to detect and store events and provide or prohibit the permissive signal, among other tasks. As shown in  FIG. 2 , there are two sockets  42 ,  44 , each with a different configuration of contact points to communicate with different plugs and different gantry controllers. Socket  42  may be an “optic” type socket traditionally used to directly communicate with optic sensors disposed within the compartments  14   a,    14   b,    14   c,  and  14   d  of the truck  10 , while socket  44  may be a “thermistor” type socket traditionally used to directly communicate with thermistor sensors disposed within the compartments  14   a,    14   b,    14   c,  and  14   d  of the truck  10 . In some embodiments, the monitoring unit  40  communicates directly with the overfill sensors and provides the permissive signal to either, or both, of the sockets  42 ,  44 . Although socket  42  and  44  are shown in  FIG. 2 , one having ordinary skill in the art will appreciate that the truck  10  may include only one type of socket  42  or  44 , and thus the monitoring unit  40  may be connected to only that socket  42  or  44 . 
     To load a compartment  14   a,    14   b,    14   c,  or  14   d,  a permissive signal for that compartment  14   a,    14   b,    14   c,  or  14   d  must be supplied to the gantry controller  36 . When the permissive signal is absent, the gantry controller  36  may refuse to load the compartment  14   a,    14   b,    14   c,  or  14   d  that does not have a permissive signal, or may refuse to load all the compartments  14   a,    14   b,    14   c,  and  14   d.  The monitoring unit  40  may supply the permissive signal to the gantry controller  36  based upon analysis of a plurality of inputs from a plurality of sensors disposed throughout the truck  10  and/or tank  12 .  FIG. 3  is a block diagram  50  of a plurality of couplings between the plurality of sensors and the monitoring unit  40 . In some embodiments, the tank  12  includes at least one overfill sensor  52  and at least one retain sensor  54  within each compartment  14   a,    14   b,    14   c,  and  14   d.  Each overfill sensor  52  and retain sensor  54  may be electrically coupled to the monitoring unit  40 . Each overfill sensor  52  is configured to determine if that sensor is dry and functioning properly, and provide a signal indicating that determination to the monitoring unit  40 . If an overfill sensor  52  is wet and/or malfunctioning, the monitoring unit  40  may prevent the permissive signal for at least that compartment  14   a,    14   b,    14   c,  or  14   d  configured with that wet and/or malfunctioning overfill sensor  52 . Similarly, each retain sensor  54  is configured to determine if that sensor is dry and functioning properly, and provide a signal indicating that determination to the monitoring unit  40 . If a retain sensor  54  is wet and/or malfunctioning, the monitoring unit  40  may prevent the permissive signal for at least that compartment  14   a,    14   b,    14   c,  or  14   d  configured with that wet and/or malfunctioning retain sensor  54 . Additionally, when an overfill sensor  52  and/or retain sensor  54  becomes dry, wet, and/or malfunctions the monitoring unit  40  may record that event and store an indication of the time of that event. In some embodiments, each overfill sensor  52  may be an FT101, an FT151, or an FT202 series overfill sensor as distributed by DixonBayco of Chestertown, Md. In some embodiments, each retain sensor  54  may be an FT152 or an FT206 series retain sensor as distributed by DixonBayco. 
     In some embodiments, the tank  12  may also include at least one valve sensor  56  electrically coupled to the monitoring unit  40  to monitor at least one valve assembly  20 . Each valve sensor  56  is configured to provide a signal indicating whether an API valve of at least one compartment  14   a,    14   b,    14   c,  or  14   d  is open. When the valve sensor  56  indicates an open and/or closed API valve, the monitoring unit  40  may record that event and store an indication of the time of that event. In some embodiments, each valve sensor  56  may be disposed in a pipe  18   a,    18   b,    18   c,  or  18   d,  and may be a pressure sensor as is well known in the art. In alternative embodiments, each valve sensor  56  may be in mechanical communication with an API valve to determine when a poppet of each API valve is open. In further alternative embodiments, each valve sensor  56  may be configured to measure the fluid in and/or out of a compartment  14   a,    14   b,    14   c,  or  14   d  or pipe  18   a,    18   b,    18   c,  or  18   d.    
     In some embodiments, the tank  12  may further include at least one vapor connection sensor  58  electrically coupled to the monitoring unit  40  to determine whether a vapor connection has been established between the tank  12  and supply tank  28 . In specific embodiments, one vapor connection sensor  58  may be configured for each compartment  14   a,    14   b,    14   c,  or  14   d  to determine whether a vapor connection has been established between that compartment  14   a,    14   b,    14   c,  or  14   d  and a fluid supply. When the vapor connection sensor  58  indicates that a vapor connection has been established and/or eliminated between at the tank  12  and/or the compartment  14   a,    14   b,    14   c,  or  14   d,  the monitoring unit  40  may record that event and store an indication of the time of that event. In some embodiments, each vapor connection sensor  58  may be disposed in a cover  16   a,    16   b,    16   c,  or  16   d,  and may be a pressure sensor as is well known in the art. In alternative embodiments, each vapor connection sensor  58  may be in mechanical communication with the vapor connection hose  34  to determine when a fluid connection between the vapor connection hose  34  and the respective compartment  14   a,    14   b,    14   c,  or  14   d  is established. 
     In some embodiments, the tank  12  may additionally include at least one socket sensor  60  electrically coupled to the monitoring unit  40  to determine whether an electrical connection has been established with the gantry controller  36 . In specific embodiments, one socket sensor  60  is configured for each socket  42 ,  44  to determine whether an electrical connection has been established between that socket  42 ,  44  and the gantry controller  36 . When the socket sensor  60  indicates that an electrical connection to the gantry controller  36  has been established and/or eliminated, the monitoring unit  40  records that event and stores an indication of the time of that event. 
     In some embodiments, the truck  10  and/or the tank  12  may include at least one ground sensor  62  electrically coupled to the monitoring unit  40  to determine whether a connection to an electrical ground has been established. When a connection to the electrical ground has not been established, the monitoring unit  40  may prevent the permissive signal to the gantry controller  36 . As such, when the ground sensor  62  indicates that a connection to the electrical ground has been established and/or eliminated, the monitoring unit  40  may record that event and store an indication of the time of that event. 
     In some embodiments, the truck  10  and/or the tank  12  may also include at least one brake sensor  64  electrically coupled to the monitoring unit  40  to determine whether brakes of the truck  10  and/or the tank  12  have been engaged. When the brakes of the truck  10  and/or the tank  12  have not been set, the monitoring unit  40  may prevent the permissive signal to the gantry controller  36 . As such, when the brake sensor  64  indicates that the brakes have and/or have not been set, the monitoring unit  40  may record the event and store an indication of the time of that event. 
     In some embodiments, the truck  10  and/or the tank  12  may further include at least one safety interlock sensor  66  electrically coupled to the monitoring unit  40  to determine whether safety interlocks of the truck  10  and/or tank  12  have been engaged. In some embodiments, safety interlocks may include pressure controllers or pressure valves to prevent the inadvertent or deliberate venting of vapors from the tanks, electronic governors that prevent the truck  10  from being started as fluid is transferred from the supply tank  28  to the compartments  14   a,    14   b,    14   c,  and  14   d  of the tank  12 , electronic circuits such as relays that electronically isolate the truck  10  from the tank  12  as fluid is transferred from the supply tank  28  to the compartments  14   a,    14   b,    14   c,  and  14   d  of the tank  12 , a “dead man&#39;s” switch to prevent fluid loading when it is not activated by the operator, a safety interlock bar to prevent access to at least one valve assembly  20  and/or the vapor recovery fitting  30  of the tank  12  (e.g., a bar that, when lifted, allows access to at least one valve assembly  20  and/or the vapor recovery fitting  30  such that, when lifted, the brakes of the truck  10  are engaged), and/or other safety interlocks well known in the art. When the safety interlock sensor  66  indicates that the safety interlocks have been engaged and/or disengaged, the monitoring unit  40  may record the event and store an indication of the time of that event. Thus, as shown in  FIG. 3 , the truck  10  and/or tank  12  may include a plurality of sensors  52 - 66  electrically coupled to the monitoring unit  40  to indicate various events of the truck  10  and/or tank  12 . 
     Based on the inputs from one or more of the plurality of sensors  52 - 66 , the monitoring unit  40  may monitor the truck  10  and/or tank  12  for events, such as incorrect connections, incorrect operation, operator errors, error conditions, and/or inconsistencies in operation. In specific embodiments, events may include an overfill condition and/or cessation of an overfill condition of at least one compartment  14   a,    14   b,    14   c,  or  14   d  (as indicated by the at least one overfill sensor  52 ), a retain condition and/or cessation of a retain condition of at least one compartment  14   a,    14   b,    14   c,  or  14   d  (as indicated by the at least one retain sensor  54 ), an open and/or closed condition of the valve assembly  20  for at least one pipe  18   a,    18   b,    18   c,  or  18   d  of at least one respective compartment  14   a,    14   b,    14   c,  or  14   d  (as indicated by the at least one valve assembly sensor  56 ), an establishment of a vapor connection and/or loss of a vapor connection of at least one compartment  14   a,    14   b,    14   c,  or  14   d  (as indicated by the at least one vapor connection sensor  58 ), an establishment of an electrical connection and/or a loss of an electrical connection between a socket  42 ,  44  and the gantry controller  36  (as indicated by the at least one socket sensor  60 ), an establishment of an electrical connection to a ground and/or a loss of an electrical connection to a ground (as indicated by the at least one ground sensor  62 ), an engagement and/or disengagement of a brake (as indicated by the at least one brake sensor  64 ), and/or an establishment and/or release of at least one safety interlock (as indicated by the at least one safety interlock sensor  66 ), among others. Additional events will be apparent to one having skill in the art. 
     The monitoring unit  40  is configured to monitor the sensors  52 - 66  for events, timestamp each event, and store that event and its associated timestamp (collectively, “event information”). In some embodiments, the monitoring unit  40  also indicates connections of external devices, power outages of the truck, low power provided from the truck, the service history of the truck, and an identification of the tank  12 , and in particular the trailer that supports the tank  12 . The monitoring unit  40  is further configured to provide a permissive signal to the gantry controller  36  through at least one socket  42 ,  44  to load at least one compartment  14   a,    14   b,    14   c,  or  14   d.  In specific embodiments, the monitoring unit  40  will not provide the permissive signal for one or more of the compartments  14   a,    14   b,    14   c,  and  14   d  if an overfill condition is present (indicating that there is fluid in a compartment  14   a,    14   b,    14   c,  or  14   d  above a first predetermined level), a retain condition is present (indicating that there is fluid in a compartment  14   a,    14   b,    14   c,  or  14   d  above a second predetermined level), a brake is not engaged, an API valve to the compartment to be filled is not open, a vapor connection to the compartment to be filled is not open, the truck  10  is not connected to a ground, there is no electrical connection between the monitoring unit  40  and the gantry controller  36 , and/or a safety interlock of the truck  10  is not engaged. 
     One suitable monitoring unit  40  consistent with embodiments of the invention is a part no. FT208 series monitoring unit as manufactured by DixonBayco.  FIG. 4  is a diagrammatic illustration  70  of one embodiment of the monitoring unit  40  consistent with embodiments of the invention. As shown in  FIG. 4 , the monitoring unit  40  includes a processing unit  72 , memory  74 , and time module  76 . The processing unit  72  may receive signals from the sensors  52 - 66 , process the signals, and, upon detecting an event, timestamp the event with a time from the time module  76  and store the event information in the memory  74 . The processing unit  72 , in some embodiments, may be a processor, microprocessor, or microcontroller as is well known in the art. In specific embodiments, the processing unit  72  is a part no. PIC18F4685 microcontroller as distributed by Microchip Technology, Inc. (“Microchip”), of Chandler, Ariz. The memory  74 , in some embodiments, may be partially and/or fully comprised of electrically erasable programmable read-only memory (“EEPROM”), random access memory (“RAM”), dynamic random access memory (“DRAM”), static random access memory (“SRAM”), flash memory, memristors, hard disk drive, and/or another digital storage medium In specific embodiments, the memory  74  may be comprised of a plurality of part no. 24LC256 serial EEPROM memory chips as also distributed by Microchip. The time module  76 , meanwhile, in some embodiments may be an electronic chip operable to maintain a relatively stable time and communicate that time to the processing unit  72 , and in specific embodiments may be a part no. DS1307 real-time clock as distributed by Maxim Integrated Products of Sunnyvale, Calif. (“Maxim”). 
     In some embodiments, monitoring unit  40  may further include at least one shift register  78  to receive the signals from the sensors  52 - 66  and selectively provide the signals to the processing unit  72 . In alternative embodiments, the monitoring unit  40  may include at least one multiplexer (not shown) to receive the signals from the sensors  52 - 66  and selectively provide the signals to the processing unit  72 . The monitoring unit  40  may also be electrically connected to a timer reset module  80  that, in some embodiments, may be a pushbutton that, when activated, provides a timer reset signal to the processing unit  72 . In some embodiments, the timer reset signal is interpreted by the processing unit  72  as a command to ignore an event for a period of time. In specific embodiments, the timer reset signal may be interpreted by the processing unit  72  to ignore a retain condition for about forty minutes. In those embodiments, during loading of at least one compartment  14   a,    14   b,    14   c,  and  14   d,  the user may activate the timer reset module  80  to prevent a retain condition being declared while loading fluid, thereby maintaining the permissive signal and preventing erroneous cessation of the fluid loading. 
     The monitoring unit  40  may additionally include a communication interface  82 , a communications port  84 , LED drivers  86 , and an LED array  88  to communicate data about the truck  10  and/or tank  12 . The communication interface  82  may provide the ability for the monitoring unit  40  to communicate to an external device through a port  84 . In some embodiments, the communication interface  82  may be configured to communicate as specified by American national standard ANSI/TIA/EIA-422. In those embodiments, the communication interface  82  may include a model no. MAX490 full-duplex RS-485/RS-422 transceiver. In alternative embodiments, the communication interface  82  may be configured to communicate through the universal serial bus (USB) 2.0 standard as is well known in the art. As such, the serial port  84  may include connections for EIA-485 communication and/or a USB receptacle, both of which are well known in the art. The processing unit  72  may indicate an event, such as a retain and/or overfill condition of one or more of the compartments  14   a,    14   b,    14   c,  or  14   d  through an LED array  88  supplied power and signals from a plurality of LED drivers  86 . In some embodiments, LED array  88  includes about twenty-one LEDs, and in specific embodiments the twenty-one LEDs may include eight LEDs to indicate overfill conditions of up to about eight compartments, eight LEDs to indicate retain conditions of up to about eight compartments, one LED to indicate that the monitoring unit  40  is powered on, one LED to indicate whether the monitoring unit  40  is currently supplying the permissive signal, one each of LEDs to indicate the status of the signals to and from at least one sensor, and one LED to indicate a connection of the monitoring unit  40  to an external device. The monitoring unit  40  may include a battery (not shown). 
       FIG. 5  is block diagram of a monitoring system  90  for the tanker truck that includes the monitoring unit  40 , a handheld data terminal (hereinafter, “terminal”)  92  and a computer  94 . In some embodiments, the monitoring unit  40  is configured to communicate with the terminal  92 , which may be configured to download information from the monitoring unit  40  as well as upload information to the monitoring unit  40 . The terminal  92  may in turn be configured to communicate with the computer  94 . Computer  94  may include at least one central processing unit (“CPU”)  96  coupled to a memory  98 , which may represent the RAM devices comprising the main storage of computer  94 , as well as any supplemental levels of memory, e.g., cache memories, non-volatile or backup memories (e.g., programmable or flash memories), read-only memories, etc. In addition, memory  98  may be considered to include memory storage physically located elsewhere in computer  94 , e.g., any cache memory in a processor in CPU  96 , as well as any storage capacity used as a virtual memory, e.g., as stored on a mass storage device  100  or on another computer (not shown) coupled to computer  94 . 
     Computer  94  may communicate externally with a user through a user interface  102  that may be attached to one or more user input devices (e.g., a keyboard, a mouse, a trackball, a joystick, a touchpad, and/or a microphone, among others) and a display  103  (e.g., a CRT monitor, an LCD display panel, and/or a speaker, among others). The computer  94  may also communicate externally with another computer through a network (not shown) coupled to computer through a network interface  104 . In some embodiments, the network interface  104  may be a wireless network interface as is well known in the art. The computer  94  may communicate with the terminal  92  through a serial interface  106  as is well known in the art. In some embodiments, the computer  94  may communicate with the terminal  92  through a USB interface as is well known in the art. Thus, the computer  94  may download and process the event information from the terminal  92 . 
     Computer  94  operates under the control of an operating system  108 , and executes or otherwise relies upon various computer software applications, components, programs, objects, modules, data structures, etc. For example, an event display application  109  may be resident in memory  98  to display the event information received from the terminal  92 . 
       FIG. 6  is a diagrammatic illustration  110  of one embodiment of the terminal  92  consistent with embodiments of the invention to download and display event information from the monitoring unit  40 , as well as transfer that event information to the computer  94 . The principle components of the terminal  92  include a terminal processing unit  112  coupled to a terminal memory  114 . The terminal  92  is powered by an energy storage device  116 , such as a battery pack. The terminal processing unit  112 , in some embodiments, may be a processor, microprocessor, or microcontroller as is well known in the art. In specific embodiments, the terminal processing unit  112  is a part no. PIC18F4685 microcontroller as distributed by Microchip. The terminal memory  114 , in some embodiments, may be partially and/or fully comprised of EEPROM, RAM, DRAM, SRAM, flash memory, memristors, hard disk drive, and/or another digital storage medium. In specific embodiments, the terminal memory  114  may be comprised of a plurality of part no. 24LC1025 CMOS serial EEPROM memory chips as also distributed by Microchip. 
     The terminal  92  includes a liquid crystal display (“LCD”)  118  to display the event information, though one of ordinary skill in the art will recognize that other types of displays may also be used. Thus, after downloading the event information from the monitoring unit  40 , a user of the terminal  92  may interact with the keypad  120  to view, scroll through, and acknowledge event information displayed on the LCD display  118 , In addition, the user may also interact with the keypad  120  to input data to the terminal for transfer to the monitoring unit  40 , such as the type and amount of fluid being loaded to and/or unloaded from each compartment  14   a,    14   b,    14   c,  and  14   d,  or to verify the time of the monitoring unit  40  and/or terminal  82 . The user may further interact with the keypad  120  to view sensor event data. Thus, the monitoring unit  40  may determine whether it is appropriate to load and/or unload the fluid. In specific embodiments, the LCD display  118  is four-line, twenty-character per line, LCD display as is well known in the art. In some embodiments, the keypad  120  is an about five button keypad as is also well known in the art. The terminal  92  includes at least one communication interface  122  coupled to a port  124  to communicate with the monitoring unit  40 . In some embodiments, the communication interface  122  communicates with the monitoring unit through the ANSI/TIA/EIA-422 standard, and communicates with the computer  94  through the USB 2.0 standard. As such, the port  124  may include a port to communicate through the ANSI/TIA/EIA-422 standard and a USB port as is well known in the art. In those embodiments, the communication interface  122  may include both a model no. MAX490 full-duplex RS-485/RS-422 transceiver as distributed by Maxim and a model no. CP2102 USB bridge as distributed by Silicon Laboratories of Austin, Tex. Furthermore, the terminal  82  may include a terminal time module  126  to timestamp events of the terminal  82  (e.g., the time data was downloaded from a monitoring unit  40  or the time data was downloaded to a monitoring unit  40 ) as well as synchronize time with a monitoring unit  40  (e.g., for example, when first connecting with a monitoring unit  40  or otherwise configuring or setting up a monitoring unit  40 ). The time module  126 , in some embodiments may be an electronic chip operable to maintain a relatively stable time and communicate that time to the terminal processing unit  112 , and in specific embodiments may be a part no. DS1307 real-time clock as distributed by Maxim. 
     In operation, and with reference to  FIG. 5  and  FIG. 6 , the monitoring unit  40  may detect an event, store an indication of the event, and timestamp that indication. The stored and timestamped indication may be referred to as “event information.” When the monitoring unit  40  connects with the terminal  92 , the operator may be provided with the opportunity to download the event information from the monitoring unit  40  to the terminal  92 . The operator may also be provided with the opportunity to input data to the terminal  92  to transfer to the monitoring unit  40 , such as the current time or other programming data. When the operator downloads the event data, the operator may view and scroll through the event information using the terminal  92 . Thus, the operator may be able to troubleshoot events, errors, and other conditions of the truck  10  by viewing the event information on the terminal  92  display  118 . After downloading the event data (e.g., after one event data download from the monitoring unit  40 , after a plurality of event data downloads from the monitoring unit  40 , or after a plurality of event data downloads from a plurality of monitoring units  40 ), the operator may connect the terminal  92  to the computer  94  to transfer the event information from the terminal  92  to the computer  94 . The event information may be stored on the computer  94  as well as displayed on the display  103  of the computer  94 . 
     Although the monitoring system  40 , terminal  92 , and computer  94  have been described with various components, and have been described as communicating in particular manners, advantages and modifications may be incorporated without departing from the scope of the invention. For example,  FIG. 7  is a block diagram of an alternative embodiment of a monitoring system (“system”)  200  for a tanker truck  10  consistent with embodiments of the invention. In this embodiment, the system  200  includes a monitoring unit  202 , handheld data terminal (“terminal”)  204 , and computer  206  operable to communicate through at least one network  208 . In some embodiments, the computer  206  in  FIG. 7  is substantially similar to computer  94  illustrated in  FIG. 5 . 
     In some embodiments, the monitoring unit  202  may monitor a truck  10  and/or tank  12  for events, timestamp and store indications of each event, and determine and store the location of the truck  10 . The monitoring unit  202  may be configured to transfer the event, timestamp, and location information (“event information”) to the terminal  204  through the network  208  or through a first local connection  210 . The network  208  may be a long range wireless network, while the first local connection  210  may be a direct electrical connection between the monitoring unit  202  and the terminal  204  or a local low-power wireless connection. The terminal  204 , in turn, may be configured to display the event information and be interfaced by a user of the terminal  204  to view the event data and input information to the monitoring unit  202 . The terminal  204  may be further configured to transfer the event information to the computer  206  through the network  208  or through a second local connection  212 . The second local connection  212 , in a similar manner to the first local connection  210 , may be a direct electrical connection between the terminal  204  and the computer  206  or a local low-power wireless connection. Furthermore, the monitoring unit  202  may be configured to communicate directly to the computer  206  through network  208 . 
       FIG. 8  is a diagrammatic illustration  220  of an alternate embodiment of the monitoring unit  202  for the system  200  of  FIG. 7  consistent with embodiments of the invention. Returning to  FIG. 8 , the monitoring unit  202  may include a processing unit  222 , memory  224 , and a time module  226 . In a similar manner to the monitoring unit  40  of  FIGS. 2-5 , the monitoring unit  202  illustrated in  FIG. 8  may receive signals from the sensors  52 - 66 , process the signals, and, upon detecting an event, timestamp the event with a time from the time module and store the event and timestamp information (“event information”) in the memory  224 . The processing unit  222 , in some embodiments, may be a processor, microprocessor, or microcontroller as is well known in the art, while the memory  224  may be partially and/or fully comprised of EEPROM, RAM, DRAM, SRAM, flash memory, memristors, hard disk drive, and/or another digital storage medium. In a similar manner to the monitoring unit  40  of  FIGS. 2-5 , in specific embodiments the processing unit  222  may be a part no. PIC18F4685 microcontroller as distributed by Microchip, while the memory  224  may be comprised of a plurality of part no. 24LC256 serial EEPROM memory chips as also distributed by Microchip. The time module  226 , in some embodiments, may be an electronic chip operable to maintain a relatively stable time and communicate that time to the processing unit  222 , and in specific embodiments may be a part no. DS1307 real-time clock as distributed by Maxim. 
     In some embodiments, the monitoring unit  222  may further include at least one shift register  228  to receive the signals from the sensors  52 - 66  and selectively provide the signals to the processing unit  222 . In alternative embodiments, the monitoring unit may include at least one multiplexer (not shown) to receive the signals from the sensors  52 - 66  and selectively provide the signals to the processing unit  222 . The monitoring unit  202  may also be electrically connected to a timer reset module  230  that, in some embodiments, may be a pushbutton that, when activated, provides a timer reset signal to the processing unit  222 . In some embodiments, the timer reset signal is interpreted by the processing unit  222  as a command to ignore an event for a period of time. In specific embodiments, the timer reset signal may be interpreted by the processing unit  222  to ignore a retain condition for about forty minutes. In those embodiments, during loading of at least one compartment  14   a,    14   b,    14   c,  and  14   d,  the user may activate the timer reset module  230  to prevent a retain condition being declared while loading fluid, thereby maintaining the permissive signal and preventing erroneous cessation of the fluid loading. 
     The monitoring unit  202  may also receive a signal from a global positioning satellite (“GPS”) receiver  232  disposed on the truck  10  that indicates the current GPS position of the truck  10 . Thus, the processing unit  222  may receive an indication of its current location. In some embodiments, the processing unit  222  determines the GPS location in response to detecting an event, while in alternative embodiments the processing unit  222  determines the GPS location of the truck  10  at periodic intervals, such as about every forty seconds. In further specific embodiments, the monitoring unit  202  may determine the GPS location of the truck  10  and/or tank each time a valve assembly sensor  56  indicates that an API valve is open. Throughout the embodiments, the processing unit  222  may store the GPS location as event information. 
     The monitoring unit  222  may additionally include a communication interface  234  that may further include a low power wireless interface  236  and a long range wireless interface  238 . The low power wireless interface  236  may communicate with other devices, such as the handheld data terminal  204  or the computer  206 , through a low-power wireless communication standard, such as BlueTooth, while the long range wireless interface  238  may communicate with other devices through a higher power wireless communication standard, such as Global System for Mobile communications (“GSM”) (including Enhanced Data rates for GSM Evolution, or “EDGE”), Universal Mobile Telecommunications System (“UMTS”), Code Division Multiplex Access “(CDMA”) (including CDMA2000), and/or another first generation, second generation, third generation, pre-fourth generation, radio, cellular and/or satellite wireless communication standard as is well known in the art. As such, the monitoring unit  202  may include at least one antenna  240  to connect to the communication interface  234 , low power wireless interface  236 , and/or long range wireless interface  238 . In specific embodiments, the at least one antenna  240  may include a first antenna to communicate through the low power wireless interface  236  and a second antenna to communicate through the long range wireless interface  238 . In further specific embodiments, the second antenna may be a satellite communications transceiver as is well known in the art. The communication interface  234  may further include a USB 2.0 transceiver as is well known in the art. As such, the monitoring unit  202  may further include a port  242 , such as a USB port, to communicate serially between the monitoring unit  202  and other devices. 
     In some embodiments, the monitoring unit  202  includes a display  244  to display truck  10  and/or tank  12  status, as well as event information, to an operator. In some embodiments, the display  244  includes LED drivers  86  and an LED array  88  similar to the monitoring unit  40  of  FIGS. 2-5 . Returning to  FIG. 8 , in alternative embodiments, the display  244  may be a video display that may display a diagrammatic representation of the truck  10 , including the status of each compartment  14   a,    14   b,    14   c,  or  14   d  of the tank  12 , and event information. In further alternative embodiments, the display  244  may be a touch-screen display operable to display video and receive operator input. In these further alternative embodiments, the monitoring unit  222  may not include the time reset module  230  and may receive data associated with the type and amount of fluid being loaded to and/or unloaded from the tank  12  through the display  244 . 
       FIG. 9  is a diagrammatic illustration  250  of an alternate embodiment of the terminal  204  for the system  200  of  FIG. 7  consistent with embodiments of the invention, The terminal  204  may include a terminal processing unit  252  coupled to a terminal memory  254 . The terminal  204  may be powered by an energy storage device  256 , such as a battery pack. The terminal processing unit  252 , in some embodiments, may be a processor, microprocessor, or microcontroller as is well known in the art, while the terminal memory  254  may be partially and/or fully comprised of EEPROM, RAM, DRAM, SRAM, flash memory, memristors, hard disk drive, and/or another digital storage medium. 
     The terminal  204  includes a display  258  to display truck  10  status and/or event information, to a user. In some embodiments, the display  258  is a touch-screen display that may receive operator input and display a diagrammatic representation of the truck  10 , including the status of each compartment  14   a,    14   b,    14   c,  or  14   d  of the tank  12 , and event information. After downloading the event information from the monitoring unit  202 , the user may interact with the display  258  to view and scroll through event information. The user may also interact with the display  258  to input data associated with the type and amount of fluid being loaded to and/or unloaded from the tank  12 , to the monitoring unit  202 . 
     To interact with the monitoring unit  202 , as well as transfer the event information to the computer  206 , the terminal  204  may include a communication interface  260  that further includes a low power wireless interface  262  and a long range wireless interface  264 . The low power wireless interface  262  may communicate with other devices, such as the monitoring unit  202  or computer  204 , through a low-power wireless communication standard, such as BlueTooth, while the long range wireless interface  264  may communicate with other devices through a higher power wireless communication standard, such as GSM (including EDGE), UMTS, CDMA (including CDMA2000), and/or another first generation, second generation, third generation, pre-fourth generation, radio, cellular, and/or satellite wireless communication standard. As such, the terminal  204  may include at least one antenna  266  to receive and/or transmit signals to and/or from the communication interface  262 , In specific embodiments, the at least one antenna  266  may include a first antenna to communicate through the low power wireless interface  262  and a second antenna to communicate through the long range wireless interface  264 . The communication interface  260  may further include a USB transceiver as is well known in the art. As such, the terminal  204  may further include a port  268 , such as a USB port, to communicate serially between the terminal  204  and other devices. Moreover, the terminal  204  may include a time module  270  to maintain a relatively stable time and communicate that time to the terminal processing unit  252 , and in specific embodiments may be a part no. DS1307 real-time clock as distributed by Maxim. 
     Flowchart  300  in  FIG. 10  illustrates a method for a monitoring system consistent with embodiments of the invention to monitor a tanker truck. The monitoring system may include a monitoring unit coupled with a plurality of sensors to monitor the truck, tank, and/or connections to the monitoring unit for an event (block  302 ). When the monitoring unit detects an event (block  304 ) it also timestamps the event (block  306 ). The timestamp may include an indication of the time and date the event occurred. 
     After the event is timestamped, the monitoring unit may determine if a GPS receiver is connected (block  308 ). When a GPS receiver is connected, the monitoring unit may determine the GPS location of the truck (“Yes” branch of decision block  310 ). The monitoring unit may then store the event, the timestamp information, and/or the GPS location of the monitoring unit at the time of the event as event information (block  312 ). When it is determined that there is no GPS receiver connected to the monitoring unit (“No” branch of decision block  310 ) or after the determination of the location of the truck (block  310 ), the monitoring unit stores the event and timestamp information as event information (block  312 ). Alternatively, instead of determining the GPS location of the truck in response to an event, the monitoring unit may determine the GPS location of the truck at a set time interval, such as about every forty seconds. 
     The monitoring unit may then determine if a long range wireless interface is coupled to the monitoring unit (block  314 ). When a long range wireless interface is connected to the monitoring unit (“Yes” branch of decision block  314 ), the monitoring unit may communicate the event information across the network to a networked device, such as a handheld data terminal or computer (block  316 ). 
     After communication of the event to the networked device (block  316 ) or the determination that there is no long range wireless interface connected to the monitoring unit (“No” branch of decision block  314 ), the monitoring unit may determine whether the event should prohibit any fluid loading (block  318 ). When the event should prohibit fluid loading of some sort, for example, of a particular fluid or of a particular compartment (“Yes” branch of block  318 ) the monitoring unit determines whether to prohibit all fluid loading (block  320 ), When the event should not prohibit fluid loading of some sort (“No branch of block  318 ), the monitoring unit outputs a permissive signal with no restrictions that allows a gantry controller to load compartments of the tanker truck normally (block  322 ). 
     When the monitoring unit determines that all fluid loading should be prohibited (“Yes” branch of decision block  320 ), the monitoring unit prohibits a permissive signal to fill any of the compartments (block  324 ). In specific embodiments, the monitoring unit prohibits the loading of a first fluid in a first compartment and prohibits the loading of the first fluid in a second compartment, or the monitoring unit prohibits the loading of a first fluid in a first compartment and prohibits the loading of a second fluid in a second compartment. When the monitoring unit determines that all fluid loading should not be prohibited (“No” branch of decision block  320 ), the monitoring unit outputs a permissive signal for at least one fluid and for at least one compartment (block  326 ). In specific embodiments, the monitoring unit outputs a permissive signal that prohibits the loading of a first fluid in the first compartment while permitting the loading of the first fluid in a second compartment, or the permissive signal prohibits the loading of a first fluid in the first compartment while permitting the loading of a second fluid in a second compartment. After outputting the permissive signal with or without restrictions (blocks  326  and  322 , respectively, or prohibiting the permissive signal (block  324 ), the monitoring unit may return to monitor the truck, tank, sensors, or monitoring unit to detect an event (block  302 ). 
     Flowchart  340  in  FIG. 11  illustrates a method for connecting a handheld data terminal to the monitoring unit to retrieve event and monitoring unit information from, and/or input programming information to, the monitoring unit consistent with embodiments of the invention. The handheld data terminal may be connected to the monitoring unit through serial communications or through a wireless network (block  342 ). In some embodiments, the monitoring unit may declare the connection of the monitoring unit to the handheld data terminal as an event. In response to being connected to the monitoring unit, the handheld data terminal may automatically retrieve event and monitoring unit information from a memory of monitoring unit (block  344 ), store that event and monitoring unit information (block  346 ), and display at least a portion of the event and monitoring unit information (block  348 ). In alternative embodiments, the handheld data terminal may prompt a user to download event and monitoring unit information and, in response to the user requesting to download the event and monitoring unit information, retrieve the event and monitoring unit information from the monitoring unit (block  344 ). In alternative embodiments, the handheld data terminal may allow a user to scroll through event and monitoring unit information while displaying the event information (block  348 ). The event information may include an identification of the event, a timestamp of the event, and the GPS location of the tank at the time of the event. The monitoring unit information may include an indication of the number and type of sensors the monitoring unit is coupled with, a time for the monitoring unit to ignore particular events in response to activation of the timer reset module and/or user interaction, the firmware version of the monitoring unit, and/or a unique identification for the tanker truck and/or monitoring unit. 
     The handheld data terminal may be used to input data to the monitoring unit. This data may include the number of compartments monitored by the monitoring unit, the number and types of sensors connected to the monitoring unit, a unique identification of the monitoring unit and/or tanker truck, new firmware for the monitoring unit, a time to ignore at least one event after detecting a timer reset signal from a timer reset module and/or user interaction, and/or fuel information. As such, the handheld data terminal may prompt a user for data to input to the monitoring unit (block  350 ). The handheld data terminal may then determine whether there is data to upload to the monitoring unit (block  352 ). When the handheld data terminal determines that there is data to upload to the monitoring unit (“Yes” branch of decision block  352 ), the handheld data terminal uploads the data to the monitoring unit (block  354 ). When the handheld data terminal determines that there is not data to upload to the monitoring unit (“No” branch of decision block  352 ), or after uploading data to the monitoring unit (block  354 ), the handheld data terminal may disconnect from the monitoring unit (block  356 ). 
     Flowchart  360  in  FIG. 12  illustrates a method to allow loading and/or unloading of a compartment of a tanker truck by analyzing data received by the monitoring unit consistent with embodiments of the invention. In specific embodiments, the tanker truck is a fuel tanker truck, the fluid is a fuel, and the data includes fuel information. In some embodiments, fuel information may include data about the fuel type (i.e., unleaded gasoline with 87/88/89/90/91 octane, diesel fuel, kerosene, etc.), the fuel amount (i.e., up to about 9000 gallons), the compartment that each fuel type is to be loaded to when the tank is configured with more than one compartment, and the fuel type in a supply tank the compartment is to be unloaded into. Thus, by analyzing the fuel information, the monitoring unit may prevent erroneously mixing different types of fuel in a compartment into a “cocktail,” mixing different types of fuel in a supply tank into a cocktail, overfilling of a compartment, or loading of a compartment that should otherwise not be loaded. To determine whether to allow the loading and/or unloading of the compartment, the monitoring unit first receives fuel information (block  362 ). The fuel information may include the type of fuel, the amount of fuel, the compartment that is to be configured with that type and amount, and/or the type of fuel in a supply tank that compartment is to be unloaded to. Thus, the monitoring unit may determine whether the fuel amount to load or unload is acceptable (block  364 ). For example, the monitoring unit may determine how much fuel is in a compartment to be loaded, and whether that compartment contains room for the fuel to be loaded. Also for example, the monitoring unit may determine how much fuel is a supply tank to the fuel in a compartment into, and whether that supply tank contains room for the fuel to be unloaded Thus, the monitoring unit may determine that the fuel amount is unacceptable when there is not enough room to load or unload the desired amount of fuel (“No” branch of block  364 ), and determine that the fuel amount is acceptable when there is enough room to load or unload the desired amount of fuel (“Yes” branch of block  364 ). 
     When the compartment determines that the amount of fuel is acceptable (“Yes” branch of block  364 ), the monitoring unit may determine whether the type of fuel to load or unload is acceptable (block  366 ). For example, the monitoring unit may determine the type of fuel in the compartment, if any, and whether the type of fuel in the compartment matches the type of fuel to be loaded to the compartment. Also for example, the monitoring unit may determine the type of fuel in the compartment, and whether that type of fuel is the same as the type of fuel in a supply tank in which to unload that compartment. When the fuel amount to load or unload is acceptable (“Yes” branch of decision block  364 ) and the fuel type to load or unload is acceptable (“Yes” branch of decision block  366 ), the monitoring unit may permit loading or unloading (block  368 ). In some embodiments, the monitoring unit may output a permissive signal to load the compartment. 
     When the fuel amount to load or unload is unacceptable (“No” branch of decision block  364 ), or the fuel type to load or unload is unacceptable (“No” branch of decision block  366 ), the monitoring unit may prohibit loading or unloading (block  370 ). In some embodiments, the monitoring unit may prohibit a permissive signal to load the compartment, or declare an event that the compartment should not be unloaded. After permitting loading or unloading of the compartment (block  368 ), or prohibiting loading or unloading of the compartment (block  370 ) the monitoring unit may continue to monitor the tanker truck for an event (block  372 ). One having ordinary skill in the art will appreciate that although flowchart  360  illustrates a method for determining whether to allow loading or unloading of a compartment of the tank of the tanker truck, the method illustrated in flowchart  360  is applicable to a tank having a single compartment, or the method may be iterated for a tank having a plurality of compartments. 
     The handheld data terminal may display event and monitoring unit information, as well as transfer the event information to a computer through serial communications or a wireless network. In turn, the computer may be configured with an event display application to display the event and monitoring unit information.  FIG. 13  is a block diagram of one embodiment of an event screen  380  displayed by the computer to allow a user to view event and monitoring unit information. Additionally, and/or alternatively, in some embodiments the handheld data terminal may be configured to display the event screen  380 . The event screen  380  allows the user to view events and monitoring unit information, including events and their timestamps, information about the sensors connected to the monitoring unit, a unique identification of the tanker truck and/or monitoring unit, firmware versions of the monitoring unit, and/or the timer to ignore particular events. 
     While the present invention has been illustrated by a description of the various embodiments and the examples, and while these embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the invention in its broader aspects is therefore not limited to the specific details, representative apparatus, and method. In particular, although some aspects of some embodiments of the invention have been described in connection with fuel tanker trucks, one having ordinary skill in the art will appreciate that some embodiments of the invention are applicable to any tanker truck configured to transport a fluid. Moreover, one having ordinary skill in the art will appreciate that the handheld data terminal and computer may be incorporated together, and in some embodiments may be a tablet computer as is well known in the art. Accordingly, departures may be made from such details without departing from the scope of applicants&#39; general inventive concept.