Patent Publication Number: US-2021173016-A1

Title: Electrical test device and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 15/334,085, entitled “ELECTRICAL TEST DEVICE AND METHOD”, and filed on Oct. 25, 2016; which is related to U.S. Pat. No. 9,513,320 issued on Dec. 6, 2016 and U.S. Pat. No. 7,184,899, issued on Feb. 27, 2007 to Randy Cruz, and which is entitled ENERGIZABLE ELECTRICAL TEST DEVICE FOR MEASURING CURRENT AND RESISTANCE OF AN ELECTRICAL CIRCUIT, and to U.S. Pat. No. 5,367,250, issued on Nov. 22, 1994 to Jeff Whisenand, and which is entitled ELECTRICAL TESTER WITH ELECTRICAL ENERGIZABLE TEST PROBE, the entire contents of U.S. Ser. No. 15/334,085, U.S. Pat. Nos. 7,184,899, 5,367,250 and 9,513,320 being expressly incorporated by reference herein. 
     The present disclosure relates generally to electrical test equipment and, more particularly, to an electrical test device configured to diagnose one or more faults in an electrical system under test during the application of current to the electrical system. 
    
    
     BACKGROUND 
     Motor vehicles such as automobiles are increasingly dependent upon electronic circuitry for operation and require increasing levels of sophistication to efficiently diagnose and repair such motor vehicles, A wide variety of faults may occur in automotive electrical systems including short circuits, open circuits, and failed components such as failed connections, relays, switches, and computer modules, Another type of fault that may occur in electrical systems is arcing. Arcing may be defined as unwanted electric spark or arc jumping a gap between two isolated nodes or conductors and may occur on an intermittent or impulsive basis within an electrical system. 
     Arcing may be caused by the presence of solid or liquid contamination, by the presence of moisture in an electrical system, by carbon tracks from decaying plastics, and by other causes, all of which may lead to an increased probability of an electric spark jumping a gap between two isolated nodes, The occurrence of arcing may lead to improper operation and/or damage to the electrical system which may include pitting in a relay, surface damage to a conductor, premature electrical failure, or fire. 
     Known conventional multi-meters lack the capability to detect the occurrence of arcing. Because arcing can be the cause of an existing failure in an electrical system or a potential failure in an electrical system, the ability to identify and detect the occurrence of arcing is highly beneficial. For example, the ability to identify and detect the occurrence of arcing may allow a technician to diagnose and repair a malfunction in an electrical system before permanent damage occurs. In addition, the identification of arcing can itself be an indicator that permanent failure has occurred in an electrical system such that the technician may then repair or replace a damaged component or module. 
     Another type of fault that may be difficult to detect in an electrical system is a loss of integrity in low-resistance or low-impedance electrical paths that carry relatively high-amperage current to various locations within the electrical system. For example, such electrical paths may include a battery cable of a motor vehicle carrying current from the battery to the starter. The electrical resistance of such cables is relatively low due to the large diameter of such cables making measurement of the resistance difficult using conventional multi-meters. Specialized micro-ohm meters may be used to measure the resistance in such cables. Unfortunately, the testing of a low-resistance cable using a micro-ohm meter typically requires the disconnection or removal of the cable from the electrical system. Furthermore, such micro-ohm meters may apply a relatively high-amperage test current to the cable which could damage sensitive electrical components if the high-amperage test current were inadvertently applied for an extended period of time. 
     As can be seen, there exists a need in the art for a system and method for detecting the presence of arcing in an electrical system. In addition, there exists a need in the art for evaluating the integrity of relatively low-resistance electrical paths or cables of an electrical system. Furthermore, there exists a need in the art for evaluating the integrity of relatively low-resistance electrical paths or cables without requiring the disconnection or removal of such electrical paths or cables from the electrical system. 
     BRIEF SUMMARY 
     The above-noted needs associated with electrical test devices are specifically addressed and alleviated by the present disclosure which, in an embodiment, provides a test device comprising a power supply, a conductive probe element, and a spectral analyzer. The power supply may be connected to an external power source. The conductive probe element may be configured to be energized by the power supply and may be placed in contact with an electrical system for application of an input signal containing current for measuring at least one parameter of the electrical system. The spectral analyzer may be connected to the probe element and may be configured to receive an output signal from the electrical system in response to the application of the input signal. The spectral analyzer may analyze the frequency spectra of the output signal. The frequency spectra may have a low-frequency portion and a high-frequency portion and may contain energy contributed by periodic signals and non-periodic signals. The spectral analyzer may analyze the low-frequency portion and detect the potential occurrence of arcing when the energy contributed by the non-periodic signals exceeds a predetermined energy threshold in the low-frequency portion. The spectral analyzer may then analyze the high-frequency portion when the energy in the low-frequency portion exceeds the energy threshold. The spectral analyzer may detect the occurrence of arcing in the electrical system when the energy in the high-frequency portion exceeds the energy threshold. 
     Also disclosed is a method of detecting arcing in an electrical system. The method may comprise the step of placing a probe element in contact with an electrical system. The method may further include the step of providing power to the probe element from an external power source. An input signal containing current may be applied to the electrical system such as by using a probe element. The method may include the step of receiving an output signal from the electrical system in response to the application of the input signal. The method may further include analyzing the frequency spectra of the output signal wherein the frequency spectra has a low-frequency portion and a high-frequency portion and contains energy contributed by the periodic and non-periodic signals. The method may include analyzing the low-frequency portion and detecting the potential occurrence of arcing in the electrical system when the energy contributed by the non-periodic signals in the low-frequency portion exceeds a predetermined energy threshold. In addition, the method may include analyzing the high-frequency portion when the energy in the low-frequency portion exceeds the energy threshold. The occurrence of arcing in the electrical system may be determined when the energy in the high-frequency portion exceeds the energy threshold. 
     Also disclosed is a test device for assessing or testing the integrity of a relatively low-impedance electrical path such as a cable. The test device may include a power supply, a probe element, and a processor. The power supply may be connected to an external power source. The probe element may be placed in contact with the electrical path and may be energized by the power supply for applying an input signal of relatively low amperage to the electrical path. The processor may receive an output signal from the electrical path and determine a first voltage across the electrical path in response to application of the low-amperage input signal. The processor may further be configured to apply a relatively high-amperage current pulse to the electrical path and determine a second voltage across the electrical path in response to application of the high-amperage current pulse. In addition, the processor may determine a volt drop across the electrical path based upon the difference between the first voltage and the second voltage. The processor may calculate an electrical resistance of the electrical path based upon the voltage drop. 
     Also disclosed is a method of measuring a voltage drop in a relatively low-impedance electrical path. The method may comprise the steps of placing a probe element in contact with the electrical path. The probe element may be energized from a power supply. A relatively low-amperage input signal may be applied to the electrical path using the probe element. The method may include determining a first voltage across an electrical path in response to application of the low-amperage input signal. The method may further include applying a relatively high-amperage current pulse to the electrical path and determining a second voltage across the electrical path in response to the application of the high-amperage current pulse. The method may additionally include determining a voltage drop across the electrical path based upon the difference between the first voltage and the second voltage. The method may further include providing a pass/fail notification regarding whether the measured voltage drop exceeds a maximum specified voltage drop for the electrical path. Alternatively, the method may include providing a pass/fail indication of whether the calculated electrical resistance of the electrical path falls within a specified operating range. 
     The features, functions and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features of the present disclosure will become more apparent upon reference to the drawings wherein like numerals refer to like parts throughout and wherein: 
         FIG. 1  is a block diagram of an embodiment of an electrical test device and which may include a power supply, a processor, a display device, a keypad, and an energizable probe element; 
         FIG. 2  is a perspective illustration of an embodiment of the electrical test device illustrating a pair of power leads and a ground lead that may be included with the electrical test device; 
         FIG. 3  is a partially exploded perspective illustration of the test device showing a circuit board assembly and having the power cable and the probe element extending out of the housing; 
         FIG. 4  is a top view illustration of the electrical test device showing an auxiliary cable that may be connectable to the electrical test device; 
         FIG. 5  is an end view of the electrical test device showing illuminating lamps and an auxiliary jack formed within the housing for receiving the auxiliary cable; 
         FIG. 6  is a flow diagram including one or more operations that may be included in a method for detecting the presence of arcing in an electrical system; and 
         FIG. 7  is a of plot of the frequency spectra of an output signal in response to the application of current to an electrical system under test and illustrating a low-frequency portion and a high-frequency portion of the frequency spectra; 
         FIG. 8  is a flow diagram having one or more operations that may be included in a method of detecting a voltage drop in an electrical path of an electrical system; 
         FIG. 9A  is an illustration of an electrical path configured as a power ground having a high-voltage side and a low-voltage side and illustrating the probe element placed in contact with the high-voltage side for testing of the voltage drop; 
         FIG. 9B  is an illustration of an electrical path configured as a power feed and illustrating the probe element placed in contact with the low-voltage side for testing of the voltage drop; and 
         FIG. 10  is a flow chart illustrating one or more operations that may be automatically performed during measurement one or more parameters of an electrical system under test. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings wherein the showings are for purposes of illustrating various aspects of the present disclosure, shown in  FIG. 1  is an electrical test device  10  that is configured for providing current sourcing or power to an electrical system  150  under test while simultaneously providing multi-meter functionality for measurement of one or more parameters of the electrical system  150 . In addition, the electrical test device  10  disclosed herein is configured to monitor the electrical system  150  under test for arcing behavior in the presence of non-arcing signals while simultaneously measuring one or more parameters of the electrical system  150 . 
     The electrical test device  10  disclosed herein is also configured to measure the integrity of low-impedance or low-resistance electrical paths  156  ( FIGS. 9A-9B ) such as a battery cable (not shown) extending between a battery (not shown) and a starter (not shown) of a motor vehicle (not shown). Advantageously, the test device  10  provides a means for measuring electrical resistance in low-impedance electrical paths  156  by providing a relatively high-amperage current pulse to generate a voltage drop that can be accurately measured. Once the voltage drop has been acquired, the test device  10  may calculate the electrical resistance and determine whether an electrical path  156  or cable is functioning properly. Advantageously, the determination of the electrical resistance of such electrical path  156  using the test device  10  disclosed herein may be performed without disconnecting or removing the suspect electrical path  156  or cable. 
     The test device  10 , advantageously, may also allow for automatically detecting and/or sequentially measuring several parameters of an electrical system  150  without user intervention. More particularly, the test device  10  is configured to allow for sequentially moving through the measurement of one or more parameters including, but not limited to, voltage, resistance, frequency, and other parameters. The test device  10  may measure and display one or more parameters for which a signal is available or for which testing conditions facilitate the measurement of such parameters. In this regard, the test device  10  is configured to allow the sequential measurement of several parameters without requiring manual manipulation or selection of the parameter to be measured. 
     In any one of the embodiments disclosed herein, the test device  10  may be configured to provide current flow through an electrical system  150  and may characterize or measure one or more parameters of the electrical system  150  including, but not limited to, impedance, wave form (e.g., fluctuation, frequency/speed), and current drain in addition to measurements performed by conventional multi-meters such as voltage, current, and electrical resistance. Advantageously, the unique configuration of the test device  10  disclosed herein eliminates the need for clip-on current sensors as may be required in conventional electrical test devices  10 . In addition, the unique configuration of the electrical test device  10  as disclosed herein may eliminate the need for a separate power cable and probe element  50  connection. 
     Referring to  FIG. 1 , shown is a block diagram of the electrical test device  10  which may comprise a conducive probe element  50 , a power supply  88 , a processor  92 , and a display device  54 . Importantly, the test device  10  may be configured to allow for selective powering of the electrical system  150  under test upon energization of the probe element  50  while parameters of the electrical system  150  are being measured. In the block diagram, shown are several functional blocks corresponding to the various measurement capabilities of the test device  10 . Each one of the functional blocks may be integrated with the processor  92  or may be under the control of the processor  92  which, as is shown in  FIG. 1 , may be configured as a microprocessor. The conductive probe element  50  may be coupled to the processor  92  and/or one or more of the functional blocks. The probe element  50  may be configured to be placed in contact with the electrical system  150  under test and provide an input signal to the electrical system  150 . The probe element  50  may be connected to a power supply  88  which may receive power from external power source  90 . The power source may be a battery such as a battery of a motor vehicle containing the electrical system  150  under test. However, the external power source  90  is not limited to a battery of a motor vehicle and may be provided in alternative configurations. 
     Referring still to  FIG. 1 , the power supply  88  may be connected to a reset control such as a microprocessor reset control  94 . The microprocessor reset control  94  may be comprised of circuitry that may provide a reset signal to the processor  92  or microprocessor under certain conditions such as when the operating voltage is out of tolerance. The power supply  88  is preferably configured to provide a voltage-regulated output for all circuitry contained within the electrical test device  10 . Preferably, the voltage-regulated output may be provided independent of any input signal to the electrical system  150 . 
     The microprocessor reset control  94  may be electrically connected to the processor  92  or microprocessor. The processor  92  or microprocessor may be electrically connected to the probe element  50  and may be configured to manipulate the input signal that is provided to the electrical system  150  and to receive the output signal in response to application of the input signal. The output signal may be representative of the measurement of at least one or more of the parameters of the electrical system  150  under test as indicated above. In manipulating and controlling the electrical test device  10  measurement functions, the processor  92  or microprocessor may be provided with an executable software program configured to provide control of the various measurement processes of the electrical test device  10 . In this manner, the processor  92  or microprocessor may regulate or control substantially all of the functions of the electrical test device  10 . 
     In  FIG. 1 , the electrical test device  10  may include a display device  54  which may be electrically connected to the processor  92  or microprocessor. The display device  54  may be configured to display a reading or indication of the output signal that may be extracted from the electrical system  150  during testing. The reading on the display device  54  may be representative of the parameter being measured. However, the test device  10  may also include an audible device for providing an audible indication of operating parameters being measured in the electrical system  150 . For example, the audible device may comprise a piezo element such as a piezo disk. The piezo disk may act as a speaker  66  for providing an indication regarding continuity measurements and/or voltage polarity of the electrical system  150  under test. 
     As was earlier indicated, the electrical test device  10  may be configured to allow for selective powering or current sourcing to the electrical system  150  upon energization of the probe element  50  during measurement of the parameters of the electrical system  150 . In this regard, the electrical test device  10  may be configured to automatically switch between an active mode and a passive mode. The active mode may be defined by measurement of one or more parameters of the electrical system  150  during the application of current or power to the electrical system  150 . As was previously indicated, such current or power may ultimately be supplied by an external power source  90  and which may be passed through the power supply  88  and into the probe element  50 . In this manner, the probe element  50  may apply current to the electrical system  150  under test. The passive mode of the electrical test device  10  may be defined by measurement of one or more parameters of the electrical system  150  without the application of power or current to the electrical system  150 . The application of power or current to the electrical system  150  may be controlled by a button or switch on the keypad or on the display device  54  and which may be connected to the processor  92  or microprocessor as illustrated in  FIG. 1 . The display device  54  may operative to indicate whether the test device  10  is in the passive mode or in the active mode. 
     In an embodiment, the display device  54  may be configured as a liquid crystal display or any other suitable configuration of the display device  54 . The test device  10  may also include a speaker driver that may be connected to the speaker  66  (e.g., the piezo element) and which may format and convert signals received from the processor  92  or microprocessor such that the speaker  66  may provide audible indications. In this same regard, the display driver illustrated in  FIG. 1  may be connected between the processor  92  or microprocessor and/or the display device  54  and may also format and convert signals from the processor  92  or microprocessor into a format required for display by the display device  54 . 
     Referring still to  FIG. 1 , shown are the functional blocks that may be representative of the measurement capabilities and features of the test device  10 . Included with the functional blocks are a dual continuity tester  118 , load impedance detector  120 , logic probe detector and generator  122 , frequency and totalizer measurement  124 , voltage measurement  126 , resistance measurement  132 , programmable reference voltage  133 , power output driver with over current protection  128 , current measurement with analog/digital (A/D) conversion  130 , and spectral analyzer  134 . Advantageously, due to the unique configuration of the test device  10  illustrated in the block diagram in the  FIG. 1 , the test device  10  may simultaneously measure current, voltage, and other parameters of the electrical system  150  during the application of current sourcing into the electrical system  150  under test. 
     Although each one of the functional blocks is indicated as a separate block, componentry may be shared between the functional blocks to facilitate one or more measurements of the electrical system  150 . Furthermore, as shown in  FIG. 1 , each one of the functional blocks may be connected to or integrated with the processor  92  or microprocessor which may control the overall operation of the electrical test device  10 . The dual continuity tester  118  functionality block shown in  FIG. 1  may be used in conjunction with the current source provided by the probe element  50  when energized by the power supply  88 . The electrical test device  10  disclosed herein is related to U.S. Pat. No. 5,367,250, issued to Jeff Whisenand on Nov. 22, 1994 and which is entitled “Electrical Tester with Electrical Energizable Test Probe”, herein incorporated by reference in its entirety. The test device  10  disclosed herein is also related to U.S. Pat. No. 7,184,899, issued on Feb. 27, 2007 to Randy Cruz, and which is entitled “Energizable Electrical Test device  10  for Measuring Current and Resistance of an Electrical Circuit”, herein incorporated by reference in its entirety. 
     Referring to  FIG. 1 , the test device  10  disclosed may include the dual continuity tester  118  which may operate in conjunction with one or more signal lamps  58  to provide a convenient means for testing the functionality of multi-pole relays (not shown). More specifically, the dual continuity tester  118  as incorporated into the test device  10  shown in  FIG. 1  may be configured to allow for testing of multiple contacts (not shown) with the pressing of a single button on the keyboard wherein the coil resistance of a relay may be easily measured. In addition, other test parameters may be obtained. The dual continuity tester  118 , when coupled with the measurement functionality of the test device  10 , enables the testing of contact switches (not shown) and relay devices. For example, in an electrical system  150  having two relays, the dual continuity tester  118  may provide for the capability of determining which one of two relays is activated and/or which one of the relays is deactivated. In this manner, the dual continuity tester  118  allows for checking of relays using a pair of signal lamps  58  or using other indicating means. When testing relays or switches, the speaker  66  may preferably be inoperative in order to avoid producing audible signals that may otherwise interfere with detection of noises in the relay switches and which may be indicative of a properly-functioning switch. However, the signal lamps  58  and/or the audible device may be used to provide an indication as to the activated or deactivated state of the relays. Furthermore, the dual continuity tester  118  may facilitate the checking of the status and operability of multiple contacts such as in a multi-pole/multi-contact relay or switch. 
     Referring still to  FIG. 1 , the load impedance detector  120  functional block allows for measurement of the magnitude of a voltage drop in an electrical system  150  such as when testing electrical junctions in an electrical circuit. The load impedance detector  120  functional block may facilitate testing a power feed  164  that may have loose or corroded connections. As will be described in greater detail below, when the probe element  50  is connected to the electrical system  150  under test, the impedance of the electrical system  150  may be tested and the electrical test device  10  may provide an indication, either audibly via the speaker  66  and/or visually via the display device  54  (i.e., the LCD  56 ), when a set point (i.e., a predetermined voltage level) is above a maximum specified voltage limit. The predetermined voltage level may be adjusted using the programmable reference voltage  133  block shown in  FIG. 1 . 
     The logic probe generator and detector  122  functional block may comprise a circuit that creates a sequence for outputting a signal into a device (not shown) of the electrical system  150  through the probe element  50 . For example, a digital pulse train may be inputted into a device of the electrical system  150  with the digital pulse train inserted into a terminal of a device under test in order to assess communication between components of the electrical system  150  (e.g., between an odometer of a motor vehicle in communication with a control unit of the motor vehicle). The logic probe generator and detector  122  functionality may also provide the electrical test device  10  with the capability to measure signal levels as well as frequency. High and low logic levels may be generated as well as pulse trains at various frequencies. 
     The frequency and totalizer measurement  124  functional block may allow the electrical test device  10  to assess the rate of voltage or current fluctuation in the electrical system  150  under test, and to accumulate occurrences of a particular state over time. Circuitry of the frequency and totalizer measurement  124  block may allow for processing of signal transition of a waveform in order to extract the frequency, revolutions per minute (RPM), duty cycle and number of pulses from a signal. The frequency aspect of the frequency and totalizer measurement  124  functional block may allow for determining the frequency or RPM or duty cycle component of the electrical system  150 . The totalizer aspect of the frequency and totalizer measurement  124  functional block may accumulate pulses or cycles and allows the electrical test device  10  to measure and check for intermittent output signals from the electrical system  150  under test. The frequency and totalizer measurement  124  functional block may also provide a means for checking switches in an electrical system  150  by providing a means for measuring the number of times that a contact within a switch bounces, for example, such as may occur in a relay switch. 
     The voltage measurement  126  block may allow for high speed voltage measurement  126  in the electrical system  150 . The voltage measurement  126  block may represent the ability of the electrical test device  10  to sample and detect positive and negative peaks of a signal as well as detecting and measuring an average of the signals and displaying results of the signal readout on the display device  54 . The voltage measurement  126  block may simplify voltage drop tests, voltage transient tests, and voltage fluctuation or ripple tests. The power output driver with over current protection  128  functional block may provide a buffer stage or a transistor for the electrical test device  10  such that the power output driver with over current protection  128  may regulate the amount of current that may be passed from the power supply  88  to the probe element  50  and ultimately into the electrical system  150  under test. In addition, the power output driver  128  may establish an appropriate drive impedance and protect the electrical test device  10  from damage due to automotive transients. The current measurement  130  functional block may allow for high speed current measurement  130  by the electrical test device  10  such as sampling and detection of current consumed in a load provided in the input signal which is inserted into the electrical system  150 . Such consumed current may be displayed on the display device  54 . 
     Referring now to  FIGS. 2-5 , shown is an embodiment of the electrical test device  10  schematically illustrated in  FIG. 1 . As best shown in  FIGS. 2-3 , the electrical test device  10  may include a housing  14  configured as a generally elongated, hollow, rectangular cross-sectional box. The housing  14  may have a top end  20  and a bottom end  22 . The top end  20  may be generally wider than a remaining portion of the housing  14  so that a display assembly  52  containing the display device  54  may be incorporated into the housing  14 . The display device  54  may be supported with display supports  44  which may orient the display device  54  at a convenient angle for observation by an operator of the test device  10 . The remaining portion of the housing  14  may have a narrower width to allow for single-hand operation of the test device  10 . 
     Contained within the housing  14  may be a circuit board assembly  36  comprising a circuit board  38  whereon the microprocessor  40  and the display device  54  along with the power supply  88 , the microprocessor  40  reset control  94 , the speaker driver  68 , and the display driver  96  may be enclosed and interconnected. The housing  14  may include an upper shell  18  and a lower shell  16  which may be fastened to one another such as by mechanical fasteners. As can be seen in  FIGS. 2 and 3 , the housing  14  may include an upper wall  24  disposed with the upper shell  18  and a lower wall  26  disposed with the lower shell  16 . In its assembled state, the housing  14  may include opposing side walls  28  and opposing end walls  30 . At the top end  20  of the housing  14  may be an aperture formed therein and into which a probe jack  98  may be fitted. The probe element  50  may be configured to be removably inserted into the probe jack  98 . A probe overmold  46  may be provided to encase a major portion of the probe element  50 . 
     At the bottom end  22  of the housing  14  nay be another aperture formed therein and through which a power cable  78  may protrude. The power cable  78  may be configured with a pair of power leads  80 , preferably one positive lead and one negative lead. In addition, a ground lead  82  may be also included in the power cable  78  extending out of the bottom end  22  of the housing  14 . Both power leads  80  may be configured as insulated conductors as may be the ground lead. The cable  50  may be encased in a cable sheathing  86  which passes through an annular shaped bushing  72  coaxially fitted within the aperture formed in the end wall  30  and which may prevent undue strain on the cable  50 . The cable  50  may include a proximal end  104  which may be disposed adjacent the housing  14  aperture and the strain relief bushing  72 . The cable  50  may also include a distal end  106  having a pair of high power alligator clips  76  disposed on extreme ends of each one of the power leads  80 . 
     As was earlier mentioned, the external power source  90  may be configured as a motor vehicle battery (not shown) with the alligator clips  76  being configured to facilitate connection thereto. The alligator clips  76  may be color-coded wherein a negative one of the power leads  80  may be provided in a black-colored alligator clip  76  and the positive one of the power leads  80  may be provided with a red-colored alligator clip  76 . Disposed at an end of the ground lead  82  may also be an alligator clip  76  to facilitate connection to a ground source. As can be seen in  FIG. 2 , the upper and lower shells  16 ,  18  of the housing  14  are configured to provide a hang loop  34  extending out of one of the side wall  28 . The hang loop  34  may provide a mechanism by which the electrical test device  10  may be attached to or hung from fixed objects such as a cable or a hook. 
     As shown in  FIG. 3 , the power cable  78  may be electrically connected to the circuit board assembly  36 . As was previously mentioned in the description of  FIG. 1 , the external power source  90  may be connected via the power cable  78  to a power supply  88  which may be integrated with the circuit board assembly  36  and which is ultimately connected to the probe element  50  extending out of the top end  20  of the housing  14 . Included with the probe element  50  may be a probe tip  48  on an extreme end thereof. Advantageously, the probe element  50  may be configured to be removable from the electrical test device  10  via a probe jack  98  such that various electrical testing accessories may be plugged into the probe jack  98  for checking the electrical system  150  under test. 
     Referring now to  FIG. 5 , shown is a front view of the electrical test device  10  and illustrating openings or apertures formed within the housing  14  through which illumination lamps  60  may at least partially extend. The illumination lamps  60  may optionally be provided for illuminating an area adjacent to the test device  10 . Although four apertures and illumination lamps  60  are shown, any number may be provided. It is contemplated that the illumination lamp  60  or lamps may be configured as light emitting diodes  64  (LEDs). Activation and deactivation of the illumination lamps  60  may be provided by means of the keypad  84  which may be electrically connected to the processor  92  or microprocessor  40  located on the circuit board  38  and which may be disposed at a location adjacent to the display device  54 . 
     Also shown in  FIGS. 4-5  is an auxiliary jack  100  into which an auxiliary cable  102  may be inserted for facilitating continuity measurements as was described above with regard to the dual continuity tester  118  functionality block. The auxiliary cable  102  has a proximal end  104  and a distal end  106  and may comprise a pair of auxiliary test leads  108  and the auxiliary ground lead  110 . The auxiliary test leads  108  may comprise a first continuity test lead  112  and a second continuity test lead  114 . In addition, the auxiliary cable  102  may include an auxiliary ground lead  110  for use as a continuity test common ground  116 . The auxiliary jack  100  formed within the housing  14  may be electrically connected to the processor  92  or microprocessor  40 . As was previously mentioned, the auxiliary ground and test leads  110 ,  108  may be adapted to be selectively insertable into the auxiliary jack  100  at the proximal end  104 . 
     Referring to  FIG. 3 , mounted with the housing  14  may be the display device  54  which may be configured as a liquid crystal display  56  (LCD). In order to protect the display device  54  as well as the interior of the housing  14 , a display overlay  12  may be included and is preferably disposed generally flush or level with an upper wall  24  of the housing  14 . In addition, the display overlay  12  may extend along the upper shell  18  to form a protective barrier for the keypad  84  integrated into the electrical test device  10 . As was earlier mentioned, the keypad  84  may allow for manipulation of the processor  92  or microprocessor  40  for controlling the functionality of the electrical test device  10 . The keypad  84  may be comprised of any number of keys or buttons but preferably may include three (3) buttons for operation of the electrical test device  10 , The three (3) buttons of the keypad  84  may be preferably configured to allow for selective switching between different measurement modes of the electrical test device  10 . 
     In addition, the keypad  84  may allow for the measuring and displaying various parameters such as AC voltage and DC voltage measurements, resistance of an electrical circuit, current flowing within an electrical circuit, the frequency of signals, and any other parameter measured by any one of the test device  10  embodiments disclosed herein. In an embodiment, the electrical test device  10  may be manipulated such that parameters measurable by the electrical test device  10  include at least one of the following: circuit continuity, resistance, voltage, current, load impedance, and frequency, RPM, and pulse counting. In addition, further measurement modes may be facilitated through manipulation of the keypad  84 . For example, frequency, RPM, duty cycle, and totalizer measurements may be extracted from an electrical system  150  under test. In addition, signal level and frequency may be measured as well as testing of impedance. 
     Referring still to  FIG. 3 , shown included with the circuit board assembly  36  may be at least one fuse  42  and preferably a pair of fuses  42  which partially protrude through apertures formed in the housing  14  at the upper shell  18 . The fuses  42  may be incorporated into the electrical test device  10  as a safety precaution to prevent damage to the circuitry of the test device  10 . Also included with the electrical test device  10  may be a circuit breaker  62  such as an electronic circuit breaker  62  which may also have configurable trip levels and a manual circuit breaker reset. Also shown incorporated into the circuit board assembly  36  of the electrical test device  10  is a piezo element  70  which is shown configured as a piezo disk  74  and which is disposed adjacent the bottom end  22  of the housing  14 . 
     Speaker  66  holes  32  may be formed in the upper shell  18  of the housing  14  to allow for transmission of audible tones generated by the piezo disk  74  during operation of the electrical test device  10 . Also included with the circuit board assembly  36  may be an additional lamp configured as an LED  64  and which may protrude through an aperture formed in the upper shell  18  of the housing  14  as shown in  FIGS. 2 and 3 . Such LED  64  may be connected to the processor  92  or microprocessor  40  and may provide a means to indicate whether power is being applied to the electrical test device  10 . Alternatively, or in addition to, the LED  64  protruding through the upper shell  18  of the housing  14  may also be configured as a power-good indicator and may be de-activated to alert the user of a blown fuse  42 . 
     Regarding the operation of the electrical test device  10 , as was earlier discussed, the electrical test device  10  is operative in either one of a passive mode or an active mode. The passive mode is defined by measurements of parameters of an electrical system  150  with no power being supplied thereto by the probe element  50 . The active mode is defined by measurement of parameters of the electrical system  150  during application of power such as from an external power source  90  through the probe element  50  and into the electrical system  150 . 
     As was earlier discussed, the electrical test device  10  may be operated as a dual continuity tester  118  wherein the auxiliary cable  102  may be inserted into the auxiliary jack  100  at the top end  20  of the housing  14  as shown in  FIG. 4 . After insertion, the first continuity test lead  112  and second continuity test lead  114  as well as continuity test common ground  116  may be connected to the electrical system  150  under test. In the active mode, wherein power is supplied to the electrical system  150  under test, the continuity of a particular portion of the electrical system  150  may be verified by using the auxiliary cable  102  comprising the first continuity test lead  112  and/or the second continuity test lead  114  in combination with the continuity test common ground  116 . 
     As shown in  FIG. 3 , a pair of signal lamps  58  may be included with the test device  10  and may be positioned at the top end  20  of the housing  14  so as to protrude through apertures formed in the upper shell  18 . The signal lamps  58  may be configured as LEDs  64  and, more specifically, may be configured as a green LED and a red LED. In addition, as was previously mentioned, the piezo element  70  may be used in combination with or may be exclusively during continuity testing. Importantly, the dual continuity tester  118  may use the current source provided by the external power source  90  for inputting current into the electrical system  150  during continuity testing. 
     Load impedance detection  120  ( FIG. 1 ) functionality may be facilitated such that the magnitude of a voltage drop within an electrical system  150  ( FIG. 1 ) may be determined such as when testing electrical junctions in power feed circuits that may have loose or corroded connections. The electrical system  150  under test may be measured with differences therebetween being assessed and displayed on the display device  54  ( FIG. 1 ). The logic probe generator and detector  122  functional block, as was previously discussed, allows for testing of high logic, low logic, and pulsing logic signals. The electrical test device  10  is configured to allow forcing of the input signal into the electrical system  150  under test with manipulation of multiple functions of the logic detection functionality such that an appropriate input signal may be injected into the electrical system  150  under test. 
     The frequency and totalizer measurement  124  ( FIG. 1 ) functionality may allow for measuring signals from the electrical system  150  as well as providing the capability for entering a “divide ratio”, which may be equivalent to the number of cylinders of an engine of the motor vehicle being tested. In this manner, the electrical test device  10  may measure the revolutionary speed at which a motor vehicle engine is operating. In addition, as was previously discussed, rates of voltage or current fluctuation may be measured and signal transition components of a wave form may be analyzed to extract frequency, duty cycle, and number of pulses. Regarding the voltage measurement  126  functionality, the electrical test device  10  may measure and display average voltage as well as measure and display positive peak voltage and negative peak voltage. Importantly, the measurement of negative peak voltage enhances the ability to analyze and measure voltage of an alternator having a faulty diode. 
     The electrical test device  10  may be operated as a digital volt meter for performing a voltage drop test and battery load test as well as transient voltage testing. In addition, the combination of the power output driver  128  with current measurement  130  ( FIG. 1 ) capability may allow the electrical test device  10  to measure current and voltage simultaneously. The electrical test device  10  may be placed in the active mode wherein a button of the keypad  84  may be placed in a “latched” mode or permanent operation mode wherein a constant supply of power is provided into the electrical system  150  under test through the probe element  50 . However, the electrical test device  10  can be placed in a “momentary” power mode wherein power may be supplied on an as-requested basis by to manual manipulation of one of the buttons of the keypad  84 . 
     The processor  92  or microprocessor  40  may be configured to cause periodic energization of the probe element  50  for powering the electrical system  150  under test at predetermined intervals for testing an electro-mechanical device that is part of an electrical system  150  under test. Examples of electro-mechanical devices that may be tested in this manner include, but are not limited to, relay switches, solenoids, motors, and various other devices. Power may be provided to the electrical system  150  under test on an automatic intermittent basis at predetermined intervals such as, for example, at one-second intervals or at other intervals. Advantageously, the ability to provide power in such varying modes allows for testing the proper operation of electro-mechanical devices such as relay switches as well as tracing the locations of such electro-mechanical devices. By connecting the electrical test device  10  to the external power source  90  and intermittently providing current into the electrical system  150  through the probe element  50 , a user may track the location of a faulty relay switch by listening for a clicking sound as power or current is intermittently applied to the electrical system  150  under test. Such method for checking for faulty relay switches may be especially valuable in detecting a relay switches that may be hidden underneath carpeting, seating, and/or plastic or metal molding commonly found in automotive interiors. 
     Referring still to  FIG. 1 , the electrical test device  10  disclosed herein is configured to monitor an electrical system  150  for arcing while simultaneously measuring one or more parameters of the electrical system  150  such as during the application of current to the electrical system  150 .  FIG. 1  graphically illustrates an arc  154  occurring between the electrical system  150  under test and a component  152  that is associated with the electrical system  150 . In the test device  10 , the spectral analyzer  134  block may cooperate with the power output driver with over current protection  128  block and the frequency and totalizer measurement  124  block to detect arcing in the electrical system  150 . Furthermore, the above-noted functional blocks may be operative to halt the application of current or power to the electrical system  150  in the event that arcing is detected. The above-noted functional blocks may cooperate to measure the time-varying nature (i.e., time domain) and the frequency spectrum (i.e., frequency domain) of the parameters being measured. In this regard, the test device  10  may analyze the frequency spectrum of an output signal to determine whether arcing is occurring by distinguishing non-periodic signals  144  (i.e., arcing signals) from periodic signals  142  such as AC voltage, DC voltage, logic/data waveforms, and other signals which may have spectral energy that may be more contained in a low-frequency portion of the frequency spectrum of an output signal. 
     As indicated earlier, an arc  154  ( FIG. 1 ) may be defined as an impulse of relatively short duration in the time domain and which may occur one or more times during the operation of an electrical system  150  depending upon operating conditions and other variables. In the frequency domain, arcing may be represented by an increase in energy in the broadband spectrum. The energy released during arcing may be detectable at relatively high frequencies within a frequency spectra ( FIG. 7 ) of the output signal. It should be noted that an increase in energy may occur in the low-frequency portion ( FIG. 7 ) of the frequency spectrum during application of current to the electrical system  150  which may be the result of arcing. However, the increase in energy in the low-frequency portion may also be the result of electrical noise within the electrical system  150 . Therefore, the test device  10  disclosed herein may be configured to perform separate evaluations of the low-frequency portion and the high-frequency portion ( FIG. 7 ) in order to reliably detect the occurrence of arcing within the electrical system  150 . 
     Referring to  FIG. 1 , for the embodiment of the test device  10  configured to detect arcing, the spectral analyzer  134  may be connected to the probe element  50 . The spectral analyzer  134  may also be connected to the processor  92  by one or more lines. The probe element  50  may also be connected to the power supply  88  which may be connected to an external power source  90  such as a battery of a motor vehicle. The probe element  50  may be placed in contact with the electrical system  150  and may be energized by the power supply  88  in order to apply to the electrical system  150  an input signal containing current for measuring at least one parameter of the electrical system  150  in a manner as described above. Upon application of current to the electrical system  150 , the spectral analyzer  134  may monitor the electrical system  150  for arcing behavior in the presence of non-arcing signals. Advantageously, the spectral analyzer  134  may monitor the electrical system  150  for arcing while simultaneously measuring the parameters of the electrical system  150 . 
     The test device  10  may include a suitable sensing element (not shown) which may be a passive or active device such as a resistor (not shown) or an inductor (not shown). The sensing element may sample or monitor output signals for possible arcing in response to the application of current to the electrical system  150  when the input signal is applied to the electrical system  150 . The test device  10  may also include one or more configurations of signal processing such as a digital signal processor  92  for examining the periodicity and/or spectrum of the monitored output signal in order to determine whether the output signal contains arcing. As was earlier indicated, the occurrence of arcing may generate an increase in the broadband spectrum of the output signal, both in a low-frequency portion ( FIG. 7 ) of the frequency spectra  140  and in a high-frequency portion ( FIG. 7 ) of the frequency spectra  140 . However, an increase in energy in a low-frequency portion of the frequency spectra  140  may be indicative of processes other than arcing such as electrical noise, and therefore may require an evaluation of the high-frequency portion of the spectrum in order to reliably determine the occurrence of arcing. In this regard, the spectral analyzer  134  may be configured to analyze a continuous spectra of low frequency and high frequency energy of the output signal. The spectral analyzer  134  may analyze the power spectra density of the output signal as may be measured in power (i.e., watts/Hz) ( FIG. 7 ) or in terms of voltage (i.e., volts/Hz) ( FIG. 7 ). 
     Referring briefly to  FIG. 7 , the frequency spectra  140  of the output signal may include the low-frequency portion and the high-frequency portion and may contain energy contributions from periodic signals  142  (e.g., discrete signals) and energy contributions from non-periodic signals  144 . The low-frequency portion of the frequency spectra  140  may contain a substantial majority of the periodic signals  142  in the frequency spectra  140  relative to the quantity of the periodic signals  142  that may be contained in the high-frequency portion. Conversely, the high-frequency portion of the frequency spectra  140  may contain a substantial majority of the non-periodic signals  144  relative to the quantity of non-periodic signals  144  contained in the low-frequency portion. In this regard, the low-frequency portion may be defined as the location where most of the known, periodic signals  142  reside and the location where the test device  10  is making measurements of voltage, current, and other parameters of the electrical system  150  under test. The high-frequency portion of the frequency spectra  140  may comprise the band of frequencies where a substantial portion of arcing power may be contained with relatively few periodic signals  142 . For example,  FIG. 9  illustrates two periodic signals  142  in the low-frequency portion of the frequency spectra  140  with no discernable periodic signals  142  occurring in the high-frequency portions. 
     The spectral analyzer  134  block of  FIG. 1  may be configured to analyze the spectral density of the low-frequency portion and detect, discern, or distinguish periodic signals  142  from non-periodic signals  144 . In this regard, the spectral analyzer  134  block may be configured to detect the potential occurrence of arcing in the electrical system  150  under test when the energy contributed by the non-periodic signals  144  in the low-frequency portion exceeds an energy threshold that may be predetermined and/or preprogrammed into the test device  10 . As indicated above, such periodic signals  142  may represent one or more of the parameters (i.e., voltage, current, etc.) being measured by the test device  10  during application of current to the electrical system  150 . If the energy in the low-frequency portion exceeds the predetermined energy threshold, the spectral analyzer  134  may then analyze the spectral density of the high-frequency portion. The spectral analyzer  134  may reliably detect the occurrence of arcing when the energy in the high-frequency portion exceeds the predetermined energy threshold. 
     In an embodiment, the predetermined energy threshold may be the same for the low-frequency portion and the high-frequency portion. However, the energy threshold for the low-frequency portion may be different than the energy threshold of the high-frequency portion. The spectral analyzer  134  may be configured to analyze the high-frequency portion for arcing using the high frequency energy threshold after the spectral analyzer  134  detects the potential occurrence of arcing during analysis of the low-frequency portion using the low frequency energy threshold. In this manner, the test device  10  may be operated with a reduced sensitivity during the initial analysis of the low-frequency portion of the frequency spectra  140 . Such reduced sensitivity of the test device  10  may reduce the occurrence of a false positive or false alarm in detecting the potential occurrence of arcing when analyzing the low-frequency portion. 
     The selection of the energy threshold may be based on historical data regarding the magnitudes of arcing energy emitted by one or more electrical circuit systems such as automotive circuits tested under one or more operating or testing conditions. Furthermore, the energy threshold may be based upon the minimum sensitivity of the test device  10 . As indicated above, if the energy threshold is set too low, very weak levels of arcing may be detected which may create a large number of false positives which may interrupt the overall test sequence that the technician is performing when testing multiple locations of an electrical system  150  or when testing multiple electrical systems  150 . Ideally, the predetermined energy threshold is selected to provide a substantially reliable indication of arcing in a substantial majority of electrical circuits that may be tested using the test device  10 . For example, the energy threshold, which may be different for the low-frequency portion relative to the energy threshold of the high-frequency portion, may be selected to provide a probability of greater than approximately 80 percent that arcing is present in when the increase in broadband energy of the frequency spectra  140  exceeds the energy threshold. In this regard, the test device  10  may provide the ability to adjust the energy threshold for different electrical system  150  such that the energy threshold is compatible with the electrical systems  150  to be tested. 
     In an embodiment, the spectral analyzer  134  ( FIG. 1 ) may detect the presence of arcing by first determining the total spectral power or the sum of arcing and non-arcing signals (i.e., respectably, non-periodic and periodic signals  142 ) contained within the frequency spectra  140  of the output signal. The output signal may be in the form of a voltage signal, a power signal, or other suitable signal for analysis by the spectral analyzer  134 . In this regard, the total spectral power may be measured in terms of power (e.g., watts/Hz) or in terms of voltage (e.g., volts/Hz) or in other terms. The spectral analyzer  134  may then determine the contribution of the periodic signals  142  to the total spectral power. The periodic signals  142  may be identified and measured by the existing functional blocks of the test device  10  as described above. For example, periodic signal  142  power may be a measured parameter (i.e., voltage, frequency) of the electrical system  150  in response to application of the current to the electrical system  150 . The spectral analyzer  134  may then determine the contribution of the non-periodic signals  144  as the difference between the total spectral power and the contribution of the periodic signals  142 . 
     The spectral analyzer  134  may determine the increase in the broadband energy of the frequency spectra  140  by comparing the contribution of the non-periodic signals  144  to the total spectral power. The spectral analyzer  134  may then determine whether the increase in the broadband energy exceeds a detection sensitivity of the test device  10 . If the sensitivity of the test device  10  is not exceeded, the spectral analyzer  134  may compare the increase in the broadband energy to the predetermined energy threshold and may transmit a signal to an indicating device such as to the display device  54  or to the speakers  66  to indicate when the increase in broadband energy exceeds the energy threshold. The processor  92  may be coupled to the spectral analyzer  134  and may be configured to halt the application of current to the electrical system  150  when the energy of a high-frequency portion exceeds the predetermined energy threshold as a means to avoid damage to the electrical system  150  or to other components that may be arcing with the electrical system  150 . 
     As indicated earlier, the spectral analyzer  134  block ( FIG. 1 ) may be equipped with spectral analysis circuitry such as digital signal processing software that can analyze the output signal in the frequency domain and/or the time domain and measure the broadband low frequency and high-frequency portions of energy present within the output signal and which may indicate the presence of arcing. The spectral analyzer  134  block may employ a Fourier Transform or other suitable technique to obtain a spectral portrait of the output signal and facilitate discernment of the contents of the low-frequency portion and the high-frequency portion of the frequency spectra  140  as shown in  FIG. 7 . The results of the arcing test may be displayed on the display device  54  and/or may be indicated by the speaker  66  to alert the technician of the occurrence of arcing. In this regard, the spectral analyzer  134  block may be configured to digitally process the output signal and analyze in the frequency domain and/or the time domain the output signal for detection of arcing during application of current to the electrical system  150 . The testing of an electrical system  150  for arcing may occur continuously during measurement of the various parameters as current is applied to the electrical system  150 . Alternatively, the electrical system  150  may also be tested for arcing on an intermittent basis or on a preprogrammed basis. 
     Referring to  FIG. 6 , shown is a flow chart including one or more operations that may be performed during a method of detecting arcing in an electrical system  150 . In step  602 , the conductive probe element  50  ( FIG. 1 ) may be placed in contact with the electrical system  150  under test as shown in  FIG. 1 . Power may be provided to the probe element  50  from a power source such as an external power source  90  such as the battery of a motor vehicle. 
     Step  606  of the method of  FIG. 6  may comprise applying an input signal to the electrical system  150  ( FIG. 1 ) using the conductive probe element  50  ( FIG. 1 ). The input signal may contain current to facilitate the measurement of one or more parameters of the electrical system  150  as was discussed above. The parameters may include circuit continuity, resistance, voltage, current, impedance, and other parameters. 
     Step  608  may comprise receiving an output signal from the electrical system  150  ( FIG. 1 ) at the spectral analyzer  134  ( FIG. 1 ). The output signal may be received in response to application of the input signal to the electrical system  150 . The output signal may be in the form of a voltage signal, a power signal, or other signal form. Step  608  may further comprise analyzing, using the spectral analyzer  134 , the frequency spectra  140  ( FIG. 7 ) of the output signal which may include a low-frequency portion ( FIG. 7 ) and a high-frequency portion ( FIG. 7 ). As illustrated in  FIG. 7 , the frequency spectra  140  may contain energy contributed by periodic signals  142  and non-periodic signals  144  as discussed above. 
     Step  610  may comprise analyzing, using the spectral analyzer  134  ( FIG. 1 ), the low-frequency portion ( FIG. 7 ), and detecting one or more periodic signals  142  ( FIG. 7 ) among the non-periodic signals  144  ( FIG. 7 ) in the frequency spectra  140  ( FIG. 7 ). The spectral analyzer  134  may be configured to detect the potential occurrence of arcing in the electrical system  150  when the energy contributed by the non-periodic signals  144  in the low-frequency portion exceeds a predetermined energy threshold as illustrated in  FIG. 7 . The predetermined energy threshold may be programmed into the test device  10  as was indicated above to account for the sensitivity of the test device  10  and prevent false positives or false alarms during the sequential testing of a number or parameters of the electrical system  150  under test. In this regard, if the energy in the low-frequency portion exceeds the energy threshold in step  610 , then the spectral analyzer  134  block analyzes the high-frequency portion. 
     In step  612 , the spectral analyzer  134  ( FIG. 1 ) may compare the energy in the high-frequency portion ( FIG. 7 ) to a predetermined energy threshold which may be different than the energy threshold of the low-frequency portion ( FIG. 7 ). In step  614 , the energy threshold in the high-frequency portion may be set or programmed into the test device  10  in a manner to provide reliable detection of arcing as discussed above. 
     In step  616 , the application of current to the electrical system  150  may be halted when the energy of the high-frequency portion exceeds the predetermined energy threshold which may be indicative of arcing in the electrical system  150  under test. In this manner, the test device  10  prevents damage that may otherwise occur to the electrical system  150  if current were continuously applied to the electrical system  150  under test. 
     In step  618 , if the energy in the high-frequency portion is less than the predetermined energy threshold, application of current to the electrical system  150  may allow for continuing measurement of one or more parameters of the electrical system  150 . Such parameters that may be measured by the test device  10  may include, but are not limited to, circuit continuity, resistance, voltage, current, impedance, and frequency. In addition, the test device  10  may be configured to provide a signal to an indicating device such as a display device  54  or a speaker  66  to indicate to a user the occurrence of arcing in the electrical system  150 . As discussed above, the test device  10  may be configured such that the magnitude of the energy threshold may be set to prevent false alarms of the detection of arcing. 
     Referring to  FIGS. 1 and 8 , in a further embodiment, the test device  10  may be configured to measure the health or integrity of relatively low-impedance cables or electrical paths  156  ( FIGS. 9A-9B ). The measurement of low-impedance electrical paths  156  such as power feeds  164  or power grounds  162  may be performed with the cooperation of the voltage measurement A/D converter  126 , the current measurement A/D converter  130 , and optionally, the auxiliary ground lead  110 . The voltage measurement A/D converter  126  and the current measurement A/D converter  130  may be operated in cooperation with the processor  92 . The measurement of low-impedance electrical paths  156  may be facilitated by first applying a relatively low-amperage input signal to the electrical path  156  and determining a first voltage. A relatively high-amperage current pulse may then be applied to the electrical path  156  to determine a second voltage. A voltage drop may be determined based on the difference between the first voltage and the second voltage. The test device  10  may then calculate the electrical resistance of the electrical path  156  based on the voltage drop and display the value of the voltage drop and/or provide a pass/fail indication regarding the health of the electrical path. 
     In the embodiment of the test device  10  ( FIG. 1 ) for measuring the health of low-impedance electrical paths  156  ( FIGS. 9A-9B ), the test device  10  may include the power supply  88  ( FIG. 1 ) and the probe element  50  ( FIG. 1 ). The power supply  88  may be connected to the external power source  90  ( FIG. 1 ). The probe element  50  may be placed in contact with the electrical path  156  and energized by power from the power supply  88  such that a relatively low-amperage input signal is applied to the electrical path  156 . The processor  92  ( FIG. 1 ) or other functional blocks discussed above may be connected to the probe element  50  and may be configured to receive an output signal from the electrical path  156  in order to determine the first voltage measurement across the electrical path  156  in response to application of the low-amperage input signal. 
     The processor  92  may then be configured to apply the relatively high-amperage current pulse to the electrical path  156  for a relatively short time period in order to determine a second voltage measurement across electrical path  156  in response to application of the high-amperage current pulse. The processor  92  may then determine the difference between the first voltage and the second voltage in order to determine a voltage drop across the electrical path  156 . The test device  10  may include an indicating device such as a display device  54  or speaker  66  that may be coupled to the processor  92  to provide an indication of the voltage drop and the electrical resistance of the electrical path  156 . As indicated above, the test device  10  may also be configured to provide a pass/fail indication of whether the voltage drop exceeds a maximum specified voltage drop for the electrical path  156 . In addition, the test device  10  may provide an indication regarding whether the measurement of the current in the electrical path  156  is less than magnitude of the high-amperage current pulse applied to the electrical path  156 . The indication may in the form of an audible indication, a visual indication, or a tactile (i.e., vibration) indication, or any combination thereof. During measurement of the second voltage, if the measured current in the electrical path  156  is less than the high-amperage current pulse, the auxiliary ground lead  110  may be connected from the test device  10  to the electrical path  156  to provide additional current to the electrical path  156 . 
     The processor  92  ( FIG. 1 ) and the test device  10  ( FIG. 1 ) may be configured to halt or prevent the application of the high-amperage current pulse to the electrical path  156  when the first voltage falls outside of a predetermined or preset (e.g., normal) operating range of the electrical path  156 . In this regard, during application of the low-amperage input signal, the test device  10  may be configured to monitor the electrical path  156  to determine whether the electrical path  156  has any obvious faults and is durable enough to receive the high-amperage current pulse. For example, the electrical path  156  may comprise a cable such as the power cable extending from a battery (not shown) of a motor vehicle (not shown) to a starter (not shown) of an engine (not shown) of the motor vehicle. If the application of the relatively low-amperage input signal to the electrical path  156  results in the first voltage being outside of the normal operating range for the power cable, then the cable may have an obvious fault and may not be durable enough to receive the high-amperage current pulse. In this example, the test of the electrical path  156  may be aborted in order to safeguard the electrical system  150  from damage and avoid the risk of damage to any electrical circuits that may be connected to the electrical path  156 . 
     The magnitude of the high-amperage current pulse applied to the electrical path  156  may be preprogrammed into the test device  10  and/or may be manually adjustable. The magnitude of the high-amperage current pulse may be dependent upon the capacity of the electrical path  156 . In an embodiment, the high-amperage current pulse may have an amperage of at least approximately 10 amps, However, depending upon the operation and construction of the electrical path  156  or cable, the high-amperage current pulse may have an amperage of up to 100 amps or more. The duration or length of time during which the high-amperage current pulse is applied to the electrical path  156  may be relatively short to avoid damage to the electrical path  156  or to components that may be connected to the electrical path  156 . In a non-limiting example, the high-amperage current pulse may be applied to the electrical path  156  for a duration of less than approximately 5 milliseconds. However, longer or shorter durations for application of the high-amperage current pulse are possible. Advantageously, the test device  10  allows for testing the health and integrity of relatively low-impedance electrical paths or cables by contacting the probe element  50  to a single location on the electrical path  156  instead of applying test devices  10  on opposite ends of the electrical path  156 . 
     Referring to  FIGS. 9A-9B , the test device  10  may be configured to test an electrical path  156  functioning as a power ground  162  ( FIG. 9A ) or as a power feed ( FIG. 9B ). In testing the integrity of a power ground  162  ( FIG. 9B ), the probe element  50  may be placed in contact with a high-voltage side  158  of the power ground  162  and may source current into the power ground  162  in response to application of the relatively high-amperage current pulse. The test device  10  ( FIG. 1 ) may also be adapted to test an electrical path  156  functioning as a power feed  164  ( FIG. 9B ) wherein the probe element  50  may be placed in contact with a low-voltage side  160  of the power feed  164 . The probe element  50  may be configured to sink current from the power feed  164  into the test device  10  using a load resistance (not shown) that may be integrated into the test device  10 . The probe element  50  may sink current from the power feed  164  into the test device  10  during application of the relatively high-amperage current pulse. In each case of  FIGS. 9A and 9B , the processor  92  may determine a second voltage across the electrical path  156  in response to application of the relatively high-amperage current pulse. 
     In the case of the power ground  162  ( FIG. 9B ) or power feed  164  ( FIG. 9B ), the processor  92  may determine a voltage drop across the electrical path  156  based on the difference between the first voltage (i.e., measured during application of the low-amperage input signal) and the second voltage (i.e., measured during application of the high-amperage current pulse). The test device  10  may be configured to determine an electrical resistance of the electrical path  156  proportional to the voltage drop across the power feed  164  or power ground  162 . The test device  10  may be configured to provide an indication of whether the electrical resistance of the power feed  164  or power ground  162  falls within the normal operating range. If a failure is detected in the power feed  164  or power ground  162  electrical paths  156  (i.e., electric resistances are below the normal operating range), the test device  10  may be configured to display or otherwise indicate such failure. In this regard, the voltage measurement A/D converter  126  and the current measurement A/D converter  130  may respectively collect voltage and current readings from the electrical path  156  and send such readings to the processor  92 . The processor  92  may take such readings or data and compute the electrical resistance for the electrical path  156  under test and send a pass/fail result to the display device  54 . As indicated above, a failure may be detected and displayed if a voltage drop exceeds a maximum voltage drop expected for the electrical path  156 . A failure may also be detected and displayed if the current flow within the electrical path  156  is below the level that the test device  10  may apply to the electrical path  156  with the relatively high-amperage current pulse. 
     Referring to  FIG. 8 , shown is a method for measuring a voltage drop and/or electrical resistance in a relatively low-impedance electrical path  156  ( FIG. 9A-9B ). Step  802  of the method of  FIG. 8  may include placing the conductive probe element  50  in contact with the electrical path  156 . Step  804  may comprise energizing the probe element  50  such as by using power from a power supply  88 . Step  806  of the method of  FIG. 8  may include applying, using the probe element  50 , a relatively low-amperage input signal to the electrical path  156 . Step  808  of the method of  FIG. 8  may comprise determining, using the processor  92 , a first voltage across the electrical path  156  in response to the application of a low-amperage input signal. Step  808  may include determining whether the first voltage within the electrical path  156  resulting from application of the low-amperage input signal is within a normal operating range of the electrical path  156 . Once the first voltage has been determined to be within the normal operating range of the electrical path  156 , step  810  may comprise, using the probe element  50 , a relatively high-amperage current pulse to the electrical path  156 . In this regard, a technician may depress a button on the keypad which may then display a ready indication on the display device  54 . The technician may then push the appropriate button on the keypad to initiate application of the momentary high-amperage current pulse to the probe element  50  and into the electrical path  156  under test, The current in the high-amperage current pulse may be supplied by the power output driver with over current protection  128 . 
     Step  812  may comprise determining, using the processor  92  and one or more of the functioning blocks illustrated in  FIG. 1 , the second voltage across the electrical path  156  in response to application of the high-amperage current pulse. Voltage and current readings may be collected by respective ones of the voltage measurement A/D converter  126  and current measurement A/D converter  130  and sent to the processor  92 . 
     Step  814  may comprise determining, using the processor  92 , a voltage drop across the electrical path  156  based upon the difference between the first voltage and the second voltage. The method of  FIG. 8  may include, indicating using an indicating device, the voltage drop, and/or electrical resistance across the electrical path  156  based upon (i.e., proportional to) the voltage drop. Step  816  of  FIG. 8  may comprise providing a pass/fail indication of whether the voltage drop exceeds the maximum specified voltage drop for the electrical path  156 . A pass/fail indication may also be provided if the measurement of current in the electrical path  156  is less than the magnitude of the high-amperage current pulse. 
     Step  818  of the method of  FIG. 8  may include preventing the application of high-amperage current pulse to the electrical path  156  when the first voltage is outside of the normal operating range for the electrical path  156 . In this regard, step  818  may comprise aborting the test for the integrity of low-impedance electrical path  156  in order to avoid the risk of damage to the electrical path  156  or any circuits that may be connected to the electrical path  156  that may otherwise be caused by application of the high-amperage current pulse. 
     Referring again briefly to  FIGS. 9A and 9B , the method of testing the integrity or health of an electrical path  156  may also comprise testing a power feed  164  or a power ground  162 . As shown in  FIGS. 9A and 9B , the electrical path  156  may have a high-voltage side  158  and a low-voltage side  160 . For testing a power ground  162 , the probe element  50  may be placed in contact with the high-voltage side  158 . In  FIG. 9A , the method may include applying the relatively low-amperage input signal to the electrical path  156  at the high-voltage side  158  of the power ground  162 . If the first voltage measured by the test device  10  falls within the normal operating range for the electrical path  156 , then the relatively high-amperage current pulse may be sunk into the test device  10  by means of a load resistance that may be incorporated into the test device  10 . The processor  92  may determine a second voltage of the electrical path  156  in response to application of the high-amperage current pulse and may calculate the voltage drop and/or the electrical resistance of the power ground  162  electrical path  156  based upon the difference between the first voltage and the second voltage. 
     In  FIG. 9B , for electrical paths  156  functioning as power feeds  164 , the probe element  50  may be placed into contact with the low-voltage side  160  of the electrical path  156 . The relatively low-amperage input signal may be applied to the electrical path  156  at the low-voltage side  160  of the power feed  164  and a first voltage may be determined. If the first voltage measured by the test device  10  falls within the normal operating range for the electrical path  156 , then the high-amperage current pulse may be sourced into the electrical path  156  from the test device  10 . The second voltage may be then determined and compared to the first voltage to arrive at the voltage drop across the power ground  162  electrical path  156 . Electrical resistance may also be determined and compared to the specified resistance for the electrical path  156  to determine the integrity of the electrical path  156 . 
     Advantageously, in testing relatively low-impedance electrical paths  156  of cables using the test device  10  and method described above in the examples shown in  FIGS. 9A and 9B , a user may safely evaluate the integrity of the electrical path  156  or cable without disconnecting or removing the electrical path  156  from the electrical system  150 . The high-amperage current pulse is advantageously applied over a relatively short time period to avoid damage to the electrical path  156 . However, the high-amperage current pulse is applied for a long enough duration to acquire the second voltage measurement that may be used to determine the voltage drop across the electrical path  156  and provide an accurate assessment of the electrical resistance of the electrical path  156 . 
     In any one of the above-described embodiments of this device, measurement of any one of the parameters such as voltage, resistance, frequency, DC voltage, DC current, and AC voltage, may be performed in a sequential manner without user intervention and without manual selection of the parameter to be measured. In this manner, sequential measurement of one or more parameters may free up one or both hand of a user to allow the efficient testing of various portions of a diagnostic sequence. In this regard, the test device  10  as disclosed here may facilitate automatic scanning of a multiplicity of parameters of an electrical system  150  under test and automatically select the parameter to be tested and displayed. In an embodiment, the test device  10  may be configured such that more than one parameter may be displayed in a sequence after measuring a plurality of parameters. 
     Referring now to  FIGS. 1 and 10 , any of the embodiments of the test device  10  disclosed herein may include the capability to sequentially measure a variety of parameters of an electrical system  150  under test without user invention. The test device  10  may facilitate automatic sequential measurement of the parameters with the cooperation of the load impedance detector  120  block, the frequency and totalizer measurement  124  block, the voltage measurement A/D converter  126  block, the resistance measurement  132  block, and the processor  92 . The keypad of the test device  10  may include one or more buttons or switches which may be activated to initiate the automatic sequencing of the measuring of various parameters. 
     The flow chart in  FIG. 10  illustrates one or more operations that may be performed during sequential measurement of one or more parameters of an electrical system  150  under test. In step  1002 , the probe element  50  may be placed in contact with the electrical system  150  under test. After placing the probe element  50  in contact with the electrical system  150 , in step  1004 , current may be applied to the electrical system  150  by activating a switch or button on the keypad. In step  1006 , the test device  10  may measure the current (e.g., in terms of amperage) and/or resistance (e.g., in terms of ohms) in the electrical system  150  in response to application of the input signal. The display device  54  may display a reading of the amperage and/or a reading of the ohms measured during application of the input signal to the electrical system  150 . 
     In step  1008 , the test device  10  may initiate automatic measurement of one or more parameters of the electrical system  150  without accessing the keypad to select a parameter to be measured. During such automatic sequential measurement, the functional blocks for low-impedance detection  120 , frequency measurement  124 , voltage measurement  126 , and resistance measurement  132  ( FIG. 1 ) may be coordinated by the processor  92  to sequence the test device  10  in a logical manner to prevent damage to the electrical system  150  and to the test device  10 . The display device  54  and/or the speaker  66  may be used to provide an indication of the measurement of such parameters such as an audible signal or a visual indication of measured parameters. 
     The test device  10  may be configured to begin measurement of the most dominating parameter or the parameter which prevents other parameters from being measured. For example, voltage of the electrical system  150  may be the initial parameter measured. If a voltage reading is detected and measured, the voltage measurement may be displayed and/or stored in the test device  10  in step  1010 . The next most sensitive measurement may then be measured such as, for example, a measurement of resistance in step  1012  ( FIG. 10 ) using the resistance measurement  132  block illustrated in  FIG. 1 . The resistance measurement may be displayed by a display device  54  in step  1014 . The test device  10  may be configured to insert or apply an input signal of current to the electrical system  150  via the probe element  50  to provide the capability for measuring the electrical resistance, 
     Step  1016  may comprise measuring a frequency of the electrical system  150  in response to application of the input signal containing current. Upon measurement of the frequency, step  1018  may comprise displaying the frequency on the display device  54  or providing an audible indication of the measurement of the frequency such as through the speakers  66 . Step  1020  may comprise detecting the presence of an AC voltage in an electrical system  150 . Detection and measurement of the AC voltage in an electrical system  150 , step  1022  may comprise displaying the measurement of the AC voltage such as on the display device  54 . As may be appreciated, the sequential measurement of the parameters may include a variety of other parameters not described above and/or not illustrated in  FIG. 10 . 
     By proceeding in a manner described above and illustrated in  FIG. 10 , the processor  92  and/or test device  10  may coordinate the measurement of one or more parameters of the electrical system  150  in an automatic and/or pre-defined sequence. The display device  54  and/or speaker  66  may be used to notify the user of stored data. An alert may be sounded by the speaker  66  when all parameters have been measured and to notify the user of the conclusion of all possible measurements at the particular node in the electrical system  150 . In this manner, the technician may efficiently move the probe element  50  to a different position on the electrical system  150  or to another electrical system  150  for initiating another sequence of automatic measurements. In an embodiment, the speaker  66  may be configured to provide audible feedback to the user regarding which parameter is being measured and avoiding the need for the user to constantly view the display to determine which parameter is being measured. Optionally, at any point during the testing sequence, the test device  10  may be moved into a manual mode wherein the user may manually select which parameters are to be measured. For example, a user may halt the automatic sequencing of the measurement of parameters by manipulating the keypad and entering a manually controlled and more focused sequence for measuring one or more particular parameters of interest. 
     Additional modifications and improvements of the present disclosure may be apparent to those of ordinary skill in the art. Thus, the particular combination of parts described and illustrated herein is intended to represent only certain embodiments of the present disclosure and is not intended to serve as limitations of alternative embodiments or devices within the spirit and scope of the disclosure.