Abstract:
A data acquisition apparatus that includes a recorder device of an event&#39;sime and date signified by the opening of an external trigger switching circuit in combination with a complimentary interrogator device for collecting data from the recorder device. The recorder device&#39;s components comprise a battery powered source with a power regulator, a processor, a dip-switch identifier, a programmable read only memory, a clock/ calender with random access memory, a timing/control subcircuit interface that connects to the external trigger switching circuit(s) and an output interface port for data transmissions with the interrogator device. The recorder&#39;s timing/control subcircuit interface extends battery life by sensing and transmitting electrical pulses through each external trigger switching circuit. The interrogator device is portable and has multiple functional capabilities. This interrogator comprise an regulated battery power source, a processor, a programmable ROM, an event storage RAM, a clock/calender subcircuit, an optional liquid crystal display display, and an input/output interface port to communicate with the recorder device.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without the payment of any royalties thereon. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to data acquisition apparatus and in particular, to portable battery powered recorder and interrogator devices for acquiring data of events denoted by switch openings. These recorder is intended for remote locations and includes a power management circuit for extended use. 
     BACKGROUND OF THE INVENTION 
     There are many instances when an event&#39;s time and date are desired observable data but are too difficult or costly to collect due to either environment, remote location or nature of a particular event. Existing methods of collecting such data use expensive data-loggers that monitor electrical circuits or devices. These data-loggers often require reliable AC power for their operation. When such data-loggers include a battery source, these battery sources are large and have limited operational life capabilities due to the data-logger&#39;s frequent scan rate. To attain uninterrupted monitoring for at least three months, such scan rates are set at large time cycles with periods at hour intervals making such data-loggers impractical to use. Moreover, typical data-loggers usually include superfluous hardware with complex data storage capabilities intended for elaborate transduced data measurements using voltages, resistances, or currents that are not needed for recording only an event&#39;s time and date of occurrence. Finally, these data-loggers usually must be adapted with weather-proof housings for outdoor use and may require irregular maintenance and monitoring. 
     Examples of such data-loggers include: i) U.S. Pat. 4,229,726 by Denton et al. entitled &#34;Portable Electronic Traffic Event Recorder&#34; which teaches of a battery powered processor based recorder device for traffic analysis use that can be interrogated by a central processor device. A limitation of this device includes limited use for extended time periods since there is no provision for an energy management scheme, thus requiring periodic checks for a low power condition. ii) U.S. Pat. 5,185,700 by Bezoes et al. entitled &#34;Solid State Event Recorder&#34; which teaches of a processor based data acquisition system for trains, planes or mobile units that monitors these platform operating conditions and use either telemetry transmitter units for transmitting data to wayside receivers, a laptop computer for downloading data from this data system or include a removable battery powered memory module in the system. Limitations of this system include either reliance on the mobile platform&#39;s main power source or continual monitoring of the memory module for a low power state. This teaching does not include a power management scheme for use in the battery operated memory module for extended use. iii) U.S. Pat. 5,311,449 by Adams entitled &#34;Sterilizable Hand-Held Programmer/Interrogator&#34; which teaches of a medical interrogation device for data communication for a patient&#39;s defibrillator device. This device is a processor based unit that can either receive or transmit data to a defibrillator device for analysis by a physician. This device has no power management scheme. iv) U.S. Pat. 5,317,914 by Franco Jr. entitled &#34;Hardened Data Acquisition System&#34; which teaches of a battery powered data recorder device for use in a moving projectile such as an artillery shell. This complex data recorder device includes a regulated power supply with a power shut down feature, but does not teach or suggest of a power management scheme for sensing an event caused by a switched triggering load as provided for by the instant invention. v) U.S. Pat. 5,502,656 by Fulcher et al. entitled &#34;Data Logger Having a RAM that Accepts Electro-Magnetically a Sensor Table and a Sample Table&#34; which teaches of a device for gathering data on fish behavior in open waters by attaching a data-logger to a fish. This device is battery powered and includes a standby battery for maintaining stored memory at low powered states, but does not include a means to shut power off and on to the processor unit. 
     Examples of devices for managing power of battery operated electronic devices for processor based devices include: i) U.S. Pat. 5,546,590 by Pierce entitled &#34;Powered Down State Machine For PCMCIA Card Applications&#34; which teaches of a PC card hardware based scheme. ii) U.S. Pat. 5,557,191 by Capurka entitled &#34;Apparatus for Minimizing Current Drain in a Battery Powered Data Collector&#34; which teaches of a power management scheme that uses a stimulus device for sensing a load state that is attached to the data collector device. 
     While the above devices do include power management schemes for longer battery life in a data-logger system, their designs and methods do not provide optimal power conservation as now provided by the instant invention. In particular, Capurka device uses a fixed pulse width with a duty factor determined by characteristics of the delayed one-shot component used therein. 
     In contrast, the instant invention automatically optimizes the duty factor whose pulse width is a function of the length of an external trigger circuit. When a short occurs across the invention&#39;s trigger circuit, the pulse width is at a minimum and is determined by a pulse travel time passing through a timing and control circuit of the timing and control interface which is about 100 nanoseconds. This pulse width increases as the trigger circuit&#39;s length increases at about 5 microseconds/ mile. For an ice motion detector acting as the external trigger circuit, the pulse width is about 300 nanoseconds which represents a large decrease in duty factor compared to a pulse generated by Capurka&#39;s fixed delayed one-shot component. Thus, the instant invention optimally conserves battery power for a given trigger circuit length yielding a many orders of decreased duty factor yielding improved prolonged battery life. In view of the above, there is a need for a portable, inexpensive and self-contained event/date based event data acquisition system that can operate in adverse conditions and be left unattended for months. 
     SUMMARY OF THE INVENTION 
     The invention is a data acquisition apparatus that includes a recorder device of an event&#39;s time and date signified by the opening of an external trigger switching circuit in combination with a complimentary interrogator device for collecting data from the recorder device. 
     The recorder device&#39;s components comprise a battery powered source with a power regulator, a processor, a dip-switch identifier, a programmable read only memory (ROM), a clock/ calender with random access memory (RAM), a timing/control subcircuit interface that connects to the external trigger switching circuit(s) and an output interface port for data transmissions with the interrogator device. The recorder can monitor long-term in extreme weather conditions at subfreezing temperatures. Each recorder device has a dip-switch that uniquely identifies a recorder device when multiple recorder devices are used for data collection. The recorder device is housed in a compact weather-proof housing that can operate for many months. The recorder monitors battery power. When the power is low, the recorder ceases sensing the state of each external trigger switching circuit. This low power condition is sufficient for maintaining events stored in memory. The recorder can use AA sized batteries. Operationally, the recorder stores the opening event&#39;s date and time of normally closed external trigger switching circuit(s) and can record multiple events, e.g. repeated opening of a door equipped with a magnetic switch. The identification (ID) number is enabled by a dip-switch setting in each recorder. This ID is stored with the time and date of each event, thus a series of synchronized recorders can be placed in the field to monitor the progression of unsteady events, e.g., the recorder can monitor an event&#39;s time and date of:i) a flood wave passage down a river, ii) a progression of a river ice breakup event, or iii) a door opening occurrence by a guard. 
     The interrogator device is portable and has multiple functional capabilities. This interrogator comprise an regulated battery power source, a processor, a programmable ROM, an event storage RAM, a clock/calender subcircuit, an optional liquid crystal display (LCD) display, and an input/output interface port to communicate with the recorder device. Operationally, the interrogator transmits time/calender data to each recorder device for synchronizing the time/date of each recorder, reads all or a specified number of events in stored memory of each recorder, clears the memory of each recorder, and performs diagnostic checks of a recorder for proper operation. When the interrogator reads data from a recorder, if the interrogator&#39;s voltage level is greater than a particular recorder, the interrogator provides power to the recorder to insure retrieval of recorded data. 
     The recorder/interrogator devices are inexpensive to make and use. Both use off-the-shelf components and require AA dry cell batteries. The low cost of each recorder/interroqator device allows personnel to leave multiple recorder outdoors for months and incur minimal cost if loss occurs. Each devicer&#39;s housing is weatherproof with dimensions of 4×5×11/4 in. The connection interface of each recorder/interroqator device is an external CINCH connector. The event recorder is typically housed in an aluminum temperature and weatherproof housing. A weatherproof cap covers the interrogator interface port. Screw connectors are provided for the external trigger switching circuit(s) provided by a terminal strip. The interrogator housing is comparable to the recorder&#39;s that includes an RS-232 port for downloading stored data. User interaction is provided through the LCD display and the operator keyboard with enter and step keys. 
     The recorder&#39;s power management scheme extends battery life by sensing and transmitting electrical pulses through each external trigger switching circuit. The recorder&#39;s timing/control interface functionally: i) scans at second intervals each external trigger switching circuit and maintains a sleep mode to the recorder&#39;s processor when the trigger circuit is closed, and ii) maintains the processor in a sleep mode when there is a low voltage state for maintaining stored data. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1a and 1b show frontal views of the event recorder and interrogator devices respectively. 
     FIG. 2 shows a block diagram for the recorder&#39;s hardware design with heavy arrows indicating I 2  C data transmissions between the major subcomponents. 
     FIG. 3 shows a block diagram for the interroqator&#39;s hardware design with heavy arrows indicating I 2  C data transmissions between the major subcomponents. 
     FIG. 4 shows a detailed description of the timing control subcircuit interface for power management of the recorder. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The data acquisition system&#39;s event recorder and interrogator are shown in FIGS. 1a &amp; lb respectively. The event recorder 1 records and stores the time and date of multiple events. An event is defined as the opening of a normally closed electrical switch to a high impedance state. The switch is an electrical circuit component carrying negligible voltage with some form of switching sensory component acting as a switch in the circuit. The switch is normally in the closed position providing a complete circuit when connected to a source, e.g. a simple wire attached to a high impedence source. This switching element is the external trigger circuit 30 as discussed below. 
     The recorder is in a weatherproof housings made of cast aluminum with removable top sealed cover that is secured to the main housing by screws. The interrogator interface port 2 also has an integral weatherproof cap. The external trigger circuit connection 3 is provided by a terminal strip which is also weather isolated from the internal circuitry of the recorder 1. The circuit boards for the processor and other components is housed within the housing. The housing of the interrogator 4 need not be weatherproof but is recommended for field use where the housing is made of s aluminum and has similar weatherproof caps for the RS232 serial port 5 and the recorder interface port 6. The LCD display 7 and operator keyboard 8 are sealed to keep out water. 
     FIGS. 2 shows a block diagrams with I 2  C bus connections of the event recorder 1. Battery power source 10 is typically four AA size 1.5 VDC dry cell batteries for an unregulated power supply of 6 VDC. A power regulation component 20 takes the unregulated power from the battery source 10 that produces a constant 5 VDC for powering the recorder. A regulated 5 volt DC--DC converter IC such as a Maxim MAX777CPA can be used. The operation of the recorder is managed by a processor 40 such as Phillips Signet 87C751-2F24 8-bit CMOS controller which also stores the recorder&#39;s program in ROM. When battery power is present and an external dry switch circuit 30 is connected to the event recorder, the processor 40 directs the recorder to enter a sleep mode. In this state, a timing and control interface 100 samples the integrity of the external trigger circuit 30 every second by interface 100 transmitting a steep-fronted voltage step to external trigger circuit 30 from one end. The timing and control interface 100 continues transmission until the steep-fronted voltage step is detected at the other node of the external trigger circuit 30. Even for long electrical circuit leads, the time necessary between sending and receiving the steep-fronted voltage step is only a few hundred nanoseconds or less. If the timing and control interface 100 detects the steep-fronted voltage step on the return end of the external trigger circuit 30, the processor 40 remains in the idle state and the timing and control interface 100 resets itself to send another steep-fronted voltage step at the beginning of the next full second time interval. If the timing and control interface 100 does not detect the return of the steep-fronted voltage step before the end of the full second time interval, it does not reset itself and the processor wakes up to an active mode. The processor then reads the device ID number from an ID dip-switch 70 in the recorder and the time and date from the clock/calendar device 50. The microcontroller 40 then stores the event information as device ID, month, day, year, hour, and minute in the RAM storage of the clock/calendar device 50, e.g. a Philips PCF8583P IC. The processor 40 then enters a sleep mode. The processor 40 will remain in the sleep mode with negligible power requirements until the external trigger circuit 30 is reclosed, e.g. reclosure of a switch causing the timing and control interface 100 to reset to send another steep-fronted voltage step at the next full second time interval and the processor 40 is put into the sleep mode. Multiple events are stored in serial order in the RAM storage of the clock/calendar device 50 until the RAM storage limit is reached. The storage of additional events results in the loss of the earliest events where only the most recent events are retained. Event data is retrieved by the interrogator 4 through an interrogator interface 60. If the unregulated battery power falls to 3 VDC or less, the timing and control interface 100 causes processor 40 go into a sleep mode. In this state, the stored data is safe so long as battery power is maintained. The recorder&#39;s stored data can be cleared by removing the batteries from the unit or pressing an internal reset button. Audible diagnostics can be incorporated with the recorder device to determine operational status and a speak emit beeps when either batteries are installed, the reset button is activated, or when an event is detected. These audible digonostics include a number of beeps to signify different conditions, e.g. one beep meaning the device is operational, two beeps meaning a low battery condition exist and three beeps meaning a bad communications bus. 
     FIG. 3 shows a block diagram of the interrogator 4. Similar to the recorder 1, power is supplied by four AA size 1.5 VDC dry cell batteries for an unregulated power source 81 of 6VDC. A power regulator 82 such as a Maxim MAX619CPA IC takes unregulated power and outputs a constant 5 VDC for the interrogator&#39;s power. The interrogator CPU operation is by an 8-bit processor 86 such as Phillips Signet 87C751 processor. The programing for the interrogator is stored in the program ROM 83 while the events retrieved from a recorder are stored in the event storage RAM 84. The interrogator allows storage of a predetermined number of events and if exceeded,any additional events are written over the earlier events. A clock/calendar component 91 such as Philips PCF8583 IC, is used for setting each recorder&#39;s time. A bus arbitration/device selection chip 87 directs the flow of information and commands along the I 2  C communications bus. An operator keypad 85 allows a user to control the interrogator operation with prompts, commands, and data visible on the LCD display 89. The interrogator can transmit data from RAM 84 to either a personal computer through an RS-232 serial port 88 or a recorder through an interface 90 as physically shown in FIG. 1b as 5 and 6 respectively. The interrogator programming as listed below with comments, can reset each recorder&#39;s clock 50, test a recorder&#39;s operation, read the recorder&#39;s stored events, and reset a recorder. The interrogator can be only two-buttons for a keyboard 85 as physically shown in FIG. 1b as keypad 8. The LCD display 89, as physically shown in FIG. 1b as displayed 7, shows prompts, commands or data in either the Interrogator or recorder and request input information from a user. The display 89 at turn-on shows the option of erasure of all the events in the event storage memory 84 with confirmation, the number of empty storage registers without stored events that can be stored without data loss, the interroqator&#39;s battery power level, and then the time and date with option to a user whether modification of the month, day, year, hour, or minute is required. When the time and date are accented, the interrogator performs a test of the I 2  C communications bus and also detects whether an event recorder is connected to the interrogator. If an event recorder is connected, the interrogator displays the recorder time and date and offers a user the option of reprogramming the recorder time and date to that of the interrogator. The interrogator then allows a user to retrieve all the events in the recorder or only the last 4 events. The display shows the total number of events held in the recorder. The interrogator then allows a user to step through all the events stored in its event storage memory. The display shows an event number i.e., #1 through #199, the recorder ID code number, the date, and the time of that event. After 30 seconds of inactivity by a user, the interrogator turns itself off to conserve power. When a recorder is connected to the interrogator, no additional events can be recorded. When the recorder&#39;s power is lower than the interrogator, the interrogator supplies Dower to the recorder. 
     FIG. 4 shows a recorder&#39;s timing and control interface 100 in detail. The operation of this interface 100 includes a free running RC oscillator 101 operating at 1 hertz which initiates a steep fronted pulse of 5 VDC resetting a 14 bit binary ripple counter 102. These components are incorporated in a Motorola IC MC14060BP. The pulse passes through a current buffer 103 and then through the external trigger circuit 30. A low impedance termination 104 prevents false tripping caused by radio frequency noise. The pulse passes through a low pass RC network with a threshold voltage equal to one-half the pulse voltage before returning to reset counter 106. The trigger circuit lead length determines pulse width duration, i.e.the return travel time to the ripple counter 102 for optimal battery power conservation. If the external trigger circuit 30 is in a normally closed state, the binary ripple counter 102 resets itself, awaiting the next cycle of operation from the oscillator 101. A pulse 105 passes to the watchdog timer/power monitor 118, e.g. a Maxim IC MAX706CPA chip, and sets the output to a high state. Normally,, the status latch 119 is in a low state and the state change detector 108 detects no change. If the external trigger circuit 30 opens, a pulse is not sensed by the binary ripple counter 102 which in turn does not reset and the pulse 105 is not sensed by the watchdog timer/ power circuit 118. The watchdog timer 118 transmits a low power state output signal if another pulse is not sensed within 1.5 seconds. The NAND gate 107 switches this signal and the low state from the status latch 119 to a high state detected by the state change detector 108. The state change detector 108 provides an event and power wakeup pulse 110 to the processor 40. The Processor 40 can also becomes active when a manual reset switch 117 has been activated or when power goes below 3 VDC. Both of these events 116 set the status latch 119 and transmit a pulse signal to a NAND gate 109, which in turn transmits a wakeup pulse 110 to the processor 40. In the event of a low battery reset, the low battery threshold flag 113 is set to provide the processor 40 information on which diagnostic signal to display. If a power reset or event occurs, the status latch 119 sets and provides an event or Dower reset flag 111 to the processor 40 designating the proper diagnostic status. The processor 40 then reads the time and date and stores in the event RAM 84 and sends an interrupt clear 112 to reset the status latch 114. 
     In general, the recorder 1 can store in memory the times and dates of any event that can be triggered by interruption of the external trigger circuit 30, whether electrical, mechanical, or optical. In a preferred mode, many recorder units are Placed in a remote area along an ice-covered river with wires embedded in the ice acting as external trigger circuit 30 elements as taught in U.S. Pat. 5,446,448 by Zufelt et al. entitled &#34;River Ice Motion Detector,&#34; which is incorporated by reference. When an ice cover begins a breakup event, the external trigger circuit(s) 30 break causing an event whose time and date are recorded by the recorder (s). By analyzing these times and dates of river ice breakup, predictions of such future occurrences can be made to provide advanced warning systems for communities downstream. The invention can also be used for security purposes, e.g. monitoring the opening of a door equipped with a magnetic switch or infrared sensor that act as the can also be used circuit 30. The invention can also be used for general process monitoring. Temperature-sensitive switches can be used to monitor the times and dates when machinery reaches unsafe operating temperatures. A limit sensory external trigger circuit 30 can also be used to monitor the time and date when traveling machinery reaches the ends of its intended operating range. Relay type switches could also be used as the trigger switching circuit to monitor the time and date of power outages or reductions to electrical equipment. 
     While this invention has been described in terms of a specific preferred embodiment, it is understood that it is capable of further modification and adaptation of the invention following in general the principle of the invention and including such departures from the present disclosure as come within the known or customary practice in the arts to which the invention pertains and may be applied to the central features set forth, and fall within the scope of the invention and of the limits of the appended claims. The assembly language programming of the interrogator and event recorder devices are as follows: ##SPC1##