Abstract:
In the disclosed method of measuring contact failure and contact failure measuring device, the magnitude of the excessive response fluctuation of the inductive magnetic field around a harness under measurement when an external force is applied to a terminal fitting part of the harness is detected by a magnetic sensor, and the result is displayed as an index of the quality of the contact state of the terminal fitting part.

Description:
TECHNICAL FIELD 
     The present invention relates to a contact fault measuring method (method of measuring contact failure) of and a contact fault measuring apparatus (contact failure measuring device) for measuring whether or not there is a contact fault in a terminal fitting portion of a harness in a wiring system. 
     BACKGROUND ART 
     There has heretofore been known a diagnosing apparatus for identifying the location of a fault in an electronic control system on a vehicle by reading a fault code that is recorded in an electronic control unit (ECU) incorporated in the vehicle. See, U.S. Pat. No. 5,491,631 (hereinafter referred to as “U.S. Pat. No. 5,491,631A”). According to U.S. Pat. No. 5,491,631A, in the event of a fault of a peripheral device connected to the ECU ( 1 ) of the vehicle, a self-diagnostic means ( 52 ) generates fault information and stores the generated fault information in a fault code storage means ( 53 ) (see, for example, column 13, lines 31-35). When the fault of a sensor ( 4 A) as the peripheral device is detected, the self-diagnostic means ( 52 ) identifies the location of the fault (systematic fault details, etc.) by displaying an inspection procedure on a fault diagnosing apparatus ( 2 ), based on the fault information and the fault code, which serves to identify the fault information (see, for example, column 18, line 32, through column 22, line 38, and  FIGS. 21 through 24 ). 
     SUMMARY OF INVENTION 
     A fault diagnosing method, which is carried out by the fault diagnosing apparatus disclosed in U.S. Pat. No. 5,491,631A, is useful as it can identify a system abnormality (i.e., an electric circuit suffering an abnormality) relatively easily. However, for actually repairing the system abnormality, it is necessary to identify not only the system abnormality, but also to identify a specific faulty component and a defective location, and to replace the component. It often is difficult or is highly tedious and time-consuming to identify the location to be repaired. 
     More specifically, locations to be repaired may include the ECU itself, sensors, an actuator, a wiring, couplers, etc. If a harness coupler (terminal fitting portion) suffers a contact failure thereby causing an electronic control system fault, then according to a simple component replacing process, the fault may be removed temporarily when the harness coupler is detached and attached again in the component replacing process. The operator may make a wrong diagnosis and replace the harness coupler with a new one, without realizing that the fault is due to a harness coupler contact failure, and the operator is unable to leave proof of the fault, which indicates the location of the failure. 
     When a wrong diagnosis is made or if the electronic control system is repaired as described above, even though the contact failure may be removed by detaching and attaching the harness coupler again, the same electronic control system fault tends to occur again, since the repair was not essential. If the electronic control system suffers the same fault again, then the customer is likely to lose confidence in the electronic control system. In addition, the normal harness coupler may possibly be unfairly treated as a defective component, and thus the manufacturer will be unable to carry out accurate quality analysis on the harness coupler. 
     It is highly difficult to diagnose contact failures that tend to take place temporarily due to vibrations caused while the vehicle is in motion. It is necessary to perform a fault diagnosis while the vehicle undergoes a test run until and the fault occurs again. 
     The present invention has been made in view of the above difficulties. It is an object of the present invention to provide a contact fault measuring method of and a contact fault measuring apparatus for measuring whether or not there is a contact fault in a terminal fitting portion of a harness while the harness remains connected in the same manner as when the abnormality occurred. 
     According to the present invention, there is provided a contact fault measuring method of measuring whether or not there is a contact fault in a terminal fitting portion of a harness in a wiring system, comprising placing a magnetic sensor in proximity to the harness to be measured, and applying external forces to the terminal fitting portion of the harness to be measured, detecting, with the magnetic sensor, a magnitude of a transient response variation in an induced magnetic field around the harness when the external forces are applied, and displaying the detected magnitude as an indicator of whether or not a contact state of the terminal fitting portion is acceptable. 
     According to the present invention, it is possible to determine whether or not there is a contact fault in the terminal fitting portion of the harness while the harness remains connected in the same manner as when an abnormality occurs. More specifically, while a contact fault is temporarily not occurring, even though the terminal fitting portion is connected unstably, current may continue to flow through the terminal fitting portion before external forces are applied thereto. However, when external forces are applied to the terminal fitting portion, a contact fault may be reproduced in the unstably connected region thereof, which instantaneously prevents current from flowing, and when the terminal fitting portion is connected again, a transient response variation in the induced magnetic field around the harness including the terminal fitting portion may increase temporarily. This also happens when the terminal fitting portion is electrically charged. According to the present invention, the magnitude of the transient response variation in the induced magnetic field around the harness when the external forces are applied is detected and displayed as an indicator of whether or not a contact state of the terminal fitting portion is acceptable. Consequently, it is possible to determine whether or not there is a contact fault in the terminal fitting portion based on the displayed indicator, without requiring the terminal fitting portion to be separated, i.e., while the harness remains connected in the same manner as when an abnormality occurs. 
     The phenomenon in which the transient response variation in the induced magnetic field becomes temporarily larger can be detected within a region around the harness, which is spaced slightly from the terminal fitting portion. Therefore, even in a space such as the engine compartment of a vehicle, for example, which is crammed full of wires and other components, the user can choose a measurement location where the magnetic sensor can be installed with ease. Consequently, the measuring process can be performed easily. 
     The method may further comprise judging whether or not the magnitude of the transient response variation in the induced magnetic field around the harness when the external forces are applied exceeds a threshold value for determining the occurrence of a contact fault, and displaying the judgment result as the indicator of whether or not the contact state is acceptable. 
     The threshold value for the magnitude of the transient response variation in the induced magnetic field, which is used to determine a contact fault, is represented by the value of a transient response variation in the induced magnetic field, which is too large to be generated by a range of noise produced if a current continues to flow in the terminal fitting portion. Therefore, even if there is something that generates a steady noise or magnetic field around the terminal fitting portion, it is possible to judge whether or not there is a contact fault essentially without being adversely affected by the steady noise or magnetic field. Therefore, the measurement process can be carried out even in a space such as the engine compartment of a vehicle, which is crammed full of wires and other components. 
     The magnetic sensor may continuously detect the magnitude of the transient response variation in the induced magnetic field around the harness, and judge whether or not the detected magnitude exceeds the threshold value, and when the detected magnitude exceeds the threshold value, the judgment result is displayed on a display unit as the indicator of whether or not the contact state is acceptable. If the magnitude of the transient response variation in the induced magnetic field around the harness when the external forces are applied exceeds the threshold value, the fact that the magnitude of the transient response variation exceeds the threshold value is displayed on the display unit. Thus, the user can easily confirm the occurrence of a contact fault based on the displayed data. 
     The method may further comprise storing the magnitude of the transient response variation in the induced magnetic field, which is continuously detected by the magnetic sensor, in a temporary storage unit, and when the magnitude of the transient response variation in the induced magnetic field is judged to exceed the threshold value, saving the magnitudes of transient response variations in the induced magnetic field, which are stored in the temporary storage unit before and after the magnitude of the transient response variation in the induced magnetic field is judged, in a saving unit. Accordingly, it is possible to effectively store the data of the transient response variations in the induced magnetic field before and after the contact fault occurs, without the need for the saving unit to have an excessively large storage capacity. 
     The magnetic sensor may secure the harness in a gripped state. Accordingly, it is possible to detect a transient response variation in the induced magnetic field while the detecting element of the magnetic sensor and the harness are secured in a relative positional relationship. Accordingly, the magnetic sensor can stably detect a transient response variation in the induced magnetic field even when external forces are applied to the terminal fitting portion. 
     The method may further comprise detecting the timing of the external forces applied to the terminal fitting portion of the harness to be measured, with an external force detecting sensor, and displaying the state of occurrence of a contact fault on a display unit, using the magnitude of the transient response variation in the induced magnetic field around the harness when the external forces are applied. The display unit displays the state of occurrence of the contact fault using the magnitude of the transient response variation in the induced magnetic field around the harness when the external forces are applied to the terminal fitting portion. It is thus possible to eliminate the effects of disturbance noise, magnetic field noise due to electromagnetic waves, etc. 
     The magnetic sensor may continuously detect the magnitude of the transient response variation in the induced magnetic field around the harness, and the method may further comprise judging, with a judgment section, whether or not the magnitude of the transient response variation when the external forces are applied to the terminal fitting portion exceeds a threshold value for determining the occurrence of a contact fault, and displaying on the display unit the judgment result as the indicator of whether or not the contact state is acceptable. Accordingly, it is possible to reliably detect the magnitude of the transient response variation in the induced magnetic field at the timing at which the external forces are applied to the terminal fitting portion. 
     A vibrating tool for applying the external forces to the terminal fitting portion of the harness may be provided, and the external force detecting sensor may be mounted on the vibrating tool. With the external force detecting sensor being mounted on the vibrating tool, it is possible to detect the timing of the external forces applied to the terminal fitting portion irrespective of the displacement of the harness. Accordingly, the measurement process is simplified. 
     The external force detecting sensor may comprise an acceleration sensor. The acceleration sensor, which is used as the external force detecting sensor, makes it easy to detect vibrations the instant that the external forces are applied. Therefore, whether or not external forces are applied can be detected effectively. 
     According to the present invention, there is also provided a contact fault measuring apparatus for measuring whether or not there is a contact fault in a terminal fitting portion of a harness in a wiring system, comprising a magnetic sensor detachably fixed in a position proximal to the harness to be measured, a display unit for displaying the magnitude of a transient response variation in an induced magnetic field around the harness, which is represented by an output signal from the magnetic sensor when external forces are applied to the terminal fitting portion of the harness to be measured, as an indicator of whether or not a contact state of the terminal fitting portion of the harness to be measured is acceptable. 
     According to the present invention, it is possible to determine whether or not there is a contact fault in the terminal fitting portion of the harness while the harness remains connected, in the same manner as when an abnormality occurs. More specifically, while a contact fault temporarily does not occur even though the terminal fitting portion is connected unstably, current may continue to flow through the terminal fitting portion before external forces are applied thereto. However, when external forces are applied to the terminal fitting portion, the contact fault may be reproduced in an unstably connected region thereof, which instantaneously prevents current from flowing. Also, when the terminal fitting portion is connected again, a transient response variation in the induced magnetic field around the harness including the terminal fitting portion may increase temporarily. According to the present invention, the magnitude of the transient response variation in the induced magnetic field around the harness when external forces are applied is detected and displayed as an indicator of whether or not a contact state of the terminal fitting portion is acceptable. Consequently, it is possible to determine whether or not there is a contact fault in the terminal fitting portion based on the displayed indicator, without requiring the terminal fitting portion to be separated, i.e., while the harness remains connected in the same state as when an abnormality occurs. 
     The phenomenon in which the transient response variation in the induced magnetic field becomes temporarily larger can be detected in a region around the harness, which is spaced slightly from the terminal fitting portion. Therefore, even in a space such as the engine compartment of a vehicle, for example, which is crammed full of wires and components, the user can choose a measurement location where the magnetic sensor can be installed with ease. Consequently, the measuring process can be performed easily. 
     In addition, it is possible to detect a transient response variation in the induced magnetic field while the detecting element of the magnetic sensor and the harness are secured in a relative positional relationship. Accordingly, the magnetic sensor can stably detect a transient response variation in the induced magnetic field even when external forces are applied to the terminal fitting portion. 
     The apparatus may further comprise a judgment section for judging whether or not the magnitude of the transient response variation in the induced magnetic field around the harness, which is represented by an output signal from the magnetic sensor, exceeds a threshold value for determining the occurrence of a contact fault in the terminal fitting portion, wherein when the magnitude of the transient response variation in the induced magnetic field exceeds the threshold value, the display unit displays an indication that the magnitude of the transient response variation in the induced magnetic field has exceeded the threshold value. 
     The threshold value for the magnitude of the transient response variation in the induced magnetic field, which is used to judge a contact fault, is represented by the value of a transient response variation in the induced magnetic field, which is too large to be generated by a range of noise produced while current continues to flow in the terminal fitting portion. Therefore, even if something is performed for generating a steady noise or magnetic field around the terminal fitting portion, it is possible to judge whether or not there is a contact fault essentially without being adversely affected by noise or magnetic fields. Therefore, the measurement process can be carried out even in a space such as the engine compartment of a vehicle, which is crammed full of wires and other components. 
     When the magnitude of the transient response variation in the induced magnetic field exceeds the threshold value, the display unit displays an indication that the magnitude of the transient response variation in the induced magnetic field has exceeded the threshold value. Therefore, based on the displayed data, the user can easily confirm the occurrence of a contact fault. 
     The apparatus may further comprise a frequency filter for removing components of the output signal from the magnetic sensor, other than a component in a frequency band that can be generated upon the occurrence of the contact fault, and a peak hold circuit for holding a peak value of a value represented by an output signal from the frequency filter, wherein when the peak value exceeds the threshold value, the display unit displays an indication that the peak value has exceeded the threshold value. 
     With the above arrangement, the components of the output signal from the magnetic sensor, other than the component in the frequency band that can be generated upon the occurrence of the contact fault, are removed. Consequently, it is possible to avoid an erroneous decision due to causes other than a contact fault, and also to reliably display the occurrence of a contact fault in the terminal fitting portion and to store data concerning the contact fault, even in a location that is crammed full of wires or in an environment having a large amount of magnetic noise. 
     The apparatus may further comprise a temporary storage unit for continuously and temporarily storing the output signal from the magnetic sensor, and a saving unit for saving the output signal from the magnetic sensor, wherein the magnitude of the transient response variation in the induced magnetic field, which is continuously detected by the magnetic sensor, is stored in the temporary storage unit, and when the peak value exceeds the threshold value, the magnitudes of transient response variations in the induced magnetic field, which are stored in the temporary storage unit before and after the peak value exceeds the threshold value, are saved in the saving unit. 
     Thus, it is possible to effectively store the data of the transient response variations in the induced magnetic field before and after the contact fault occurs, without the need for the saving unit, such as a nonvolatile memory or the like, to have an excessively large storage capacity. 
     According to the present invention, there is also provided a contact fault measuring apparatus for measuring whether or not there is a contact fault in a terminal fitting portion of a harness in a wiring system, comprising a magnetic sensor for detecting the magnitude of a transient response variation in an induced magnetic field around the harness to be measured, an external force detecting sensor for detecting the timing of external forces applied to the terminal fitting portion of the harness to be measured, and a display unit for displaying the timing of the applied external forces, which is detected by the external force detecting sensor, and the magnitude, which is represented by an output signal from the magnetic sensor, of the transient response variation in the induced magnetic field around the harness. 
     According to the present invention, there is also provided a contact fault measuring apparatus for measuring whether or not there is a contact fault in a terminal fitting portion of a harness in a wiring system, comprising a magnetic sensor for detecting the magnitude of a transient response variation in an induced magnetic field around the harness to be measured, an external force detecting sensor for detecting the timing of external forces applied to the terminal fitting portion of the harness to be measured, a judgment section for judging whether or not the magnitude of the transient response variation in the induced magnetic field around the harness, which is represented by an output signal from the magnetic sensor, exceeds a threshold value for determining the occurrence of a contact fault in the terminal fitting portion, and a display unit for displaying a judgment result from the judgment section based on the timing of applied external forces detected by the external force detecting sensor. 
     According to the present invention, there is further provided a contact fault measuring method of measuring whether or not there is a contact fault in a terminal fitting portion of a harness in a wiring system, comprising detecting, with a magnetic sensor, the intensity of an induced magnetic field around the harness to be measured, detecting, with an external force detecting sensor, external forces applied to the terminal fitting portion of the harness to be measured, simultaneously displaying, on a display unit, an output waveform from the magnetic sensor and an output waveform from the external force detecting sensor, and measuring the state of occurrence of a contact fault based on the magnitude of a variation in the output waveform from the magnetic sensor immediately after the external forces are applied, with respect to the output waveform from the magnetic sensor before the external forces are applied, or based on a gradient of the output waveform from the magnetic sensor immediately after the external forces are applied. 
     According to the present invention, there is further provided a contact fault measuring method of measuring whether or not there is a contact fault in a terminal fitting portion of a harness in a wiring system, comprising detecting, with a magnetic sensor, the intensity of an induced magnetic field around the harness to be measured, and outputting the detected intensity of the induced magnetic field to a judgment section, detecting, with an external force detecting sensor, external forces applied to the terminal fitting portion of the harness to be measured, and outputting the detected external forces to the judgment section, and measuring, with the judgment section, the state of occurrence of a contact fault based on a change in the intensity of the induced magnetic field immediately after the external forces are applied, with respect to the intensity of the induced magnetic field before the external forces are applied, or based on a rate of change in the intensity of the induced magnetic field immediately after the external forces are applied. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram showing a general configuration of a contact fault measuring apparatus according to a first embodiment of the present invention; 
         FIG. 2  is a view showing the manner in which a contact fault is measured using the contact fault measuring apparatus; 
         FIG. 3  is a flowchart of an overall repair process according to the first embodiment; 
         FIG. 4  is a view showing by way of example a guidance image displayed by the contact fault measuring apparatus according to the first embodiment; 
         FIG. 5  is a flowchart of a user operation sequence and a processing sequence of the contact fault measuring apparatus, for confirming the occurrence of a temporary contact fault according to the first embodiment; 
         FIG. 6  is a view showing the contact fault measuring apparatus according to the first embodiment, which is installed in a vehicle for confirming the occurrence of a temporary contact fault; 
         FIG. 7  is a diagram showing by way of example output signals (representing waveforms displayed on the display screen of an oscilloscope) from a magnetic field detector and an external force detector prior to performing a wiggle test (i.e., when a temporary contact fault does not occur); 
         FIG. 8  is a view showing the manner in which the wiggle test is conducted; 
         FIG. 9  is a diagram showing by way of example output signals (representing waveforms displayed on the display screen of an oscilloscope) from the magnetic field detector and the external force detector when a contact fault does not occur (i.e., when a temporary contact fault does not occur) even if a coupler is vibrated in the wiggle test; 
         FIG. 10  is a diagram showing by way of example output signals (representing waveforms displayed on the display screen of an oscilloscope) from the magnetic field detector and the external force detector when a contact fault occurs (is reproduced) (i.e., when a temporary contact fault occurs) if the coupler is vibrated in the wiggle test; 
         FIG. 11  is a view showing the manner in which a contact fault is measured using a contact fault measuring apparatus according to a second embodiment of the present invention; 
         FIG. 12  is a view showing the manner in which a contact fault is measured using a contact fault measuring apparatus according to a third embodiment of the present invention; 
         FIG. 13  is a block diagram of a controller of the contact fault measuring apparatus according to the third embodiment; 
         FIG. 14  is a flowchart of a user operation sequence and a processing sequence of the contact fault measuring apparatus, for confirming the occurrence of a temporary contact fault according to the third embodiment; 
         FIG. 15  is a view showing the contact fault measuring apparatus according to the third embodiment, which is installed in a vehicle for confirming the occurrence of a temporary contact fault; 
         FIG. 16  is a diagram showing by way of example various signals generated in the third embodiment; 
         FIG. 17  is a perspective view of a contact fault diagnosing system including a diagnosing apparatus as a contact fault measuring apparatus according to a fourth embodiment of the present invention, and a harness to be measured by the contact fault diagnosing system; 
         FIG. 18  is a block diagram of the contact fault diagnosing system according to the fourth embodiment, with internal structural details of the harness being shown in cross section; 
         FIG. 19  is a view showing a pickup device with a closed clamp according to the fourth embodiment; 
         FIG. 20  is a perspective view of the harness and a portion to which the harness is connected according to the fourth embodiment; 
         FIG. 21  is a view showing the contact fault measuring apparatus according to the fourth embodiment, which is installed in a vehicle for confirming the occurrence of a temporary contact fault; 
         FIG. 22  is a flowchart of an operation sequence of the diagnosing apparatus according to the fourth embodiment, by which a user can judge whether or not a contact fault occurs in a terminal fitting portion using the diagnosing apparatus; 
         FIG. 23  is a diagram showing by way of example the waveform of a magnetic-field-rate-of-change signal generated when a contact fault does not occur according to the fourth embodiment; and 
         FIG. 24  is a diagram showing by way of example the waveform of a magnetic-field-rate-of-change signal generated when a contact fault occurs according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. First Embodiment 
     1. Configuration 
     (1) General Configuration of Contact Fault Measuring Apparatus  14  and Peripheral Regions Thereof 
       FIG. 1  is a block diagram showing a general configuration of a contact fault measuring apparatus  14  (hereinafter also referred to as a “measuring apparatus  14 ”) and peripheral regions thereof according to a first embodiment of the present invention.  FIG. 1  shows, in addition to the measuring apparatus  14 , a vehicle  10  to be measured together with a tester  12  for inspecting the vehicle  10 . Although only one vehicle  10 , one tester  12 , and one measuring apparatus  14  are illustrated in  FIG. 1 , plural vehicles  10 , plural testers  12 , and plural measuring apparatus  14  may be employed. 
     (2) Vehicle  10   
     The vehicle  10  has an electronic control unit  20  (hereinafter also referred to as an “ECU  20 ”), an ignition switch  22  (hereinafter also referred to as an “IGSW  22 ”) for turning on and off the ECU  20 , and various sensors  24 . The ECU  20  controls an engine, a transmission, a brake, etc., and includes an input/output unit  30 , a processor  32 , and a storage unit  34 . 
     (3) Tester  12   
     The tester  12  is used in the inspection of various parts of the vehicle  10  as a communication interface, which is connected to the ECU  20  of the vehicle  10  for reading data of the vehicle  10  in dealers, repair shops, etc. The tester  12  is connected to the ECU  20  by a cable  40 . The tester  12  is capable of reading fault codes required to diagnose faults from the ECU  20 . 
     (4) Contact Fault Measuring Apparatus  14   
     (1) Overall Configuration of Measuring Apparatus  14   
       FIG. 2  is a view showing the manner in which a contact fault is measured using the measuring apparatus  14 . The measuring apparatus  14  measures a temporary contact fault in a plurality of couplers (terminal fitting portions) on the vehicle  10 . As shown in  FIGS. 1 and 2 , the measuring apparatus  14  includes a magnetic field detector  60 , an external force detector  62 , and an oscilloscope  64 . 
     (b) Magnetic Field Detector  60   
     The magnetic field detector  60  has a detecting coil  70 , a signal amplifying circuit  72 , a ring-shaped ferrite core  74 , and a first cable  76 . The detecting coil  70  serves to detect a transient response variation in an induced magnetic field around a harness  80 . The detecting coil  70  comprises a coil wire wound in a single turn around the ferrite core  74 . The signal amplifying circuit  72  amplifies an output signal from the detecting coil  70  (magnetic-field-rate-of-change signal Sm) by a given amplification factor (e.g., 10) and sends the amplified signal to the oscilloscope  64  through the first cable  76 . The magnetic-field-rate-of-change signal Sm is directly indicative of a detected value D 1  (intensity of the induced magnetic field) from the detecting coil  70 , and also indicates a transient response variation (magnetic-field rate-of-change) based on a succession of detected values D 1 . The ferrite core  74  comprises two split cores, which are combined together with the harness  80  extending therethrough, for preventing noise disturbances from being introduced into the detecting coil  70 . 
     (c) External Force Detector  62   
     The external force detector  62  has an acceleration sensor  90 , a drive circuit  92  for the acceleration sensor  90 , a second cable  94  interconnecting the acceleration sensor  90  and the drive circuit  92 , and a third cable interconnecting the drive circuit  92  and the oscilloscope  64 . 
     The acceleration sensor  90 , which is mounted on a coupler  50  to be measured, detects vibrations of the coupler  50 . The acceleration sensor  90  is capable of detecting accelerations along a direction in which an external force is applied, and detects accelerations along a direction of at least one axis. If the acceleration sensor  90  detects accelerations along a plurality of axes, then the acceleration sensor  90  may add or multiply the detected acceleration values along the axes and output the result thereof. In  FIG. 2 , the acceleration sensor  90  is shown as being attached to the coupler  50 . However, the acceleration sensor  90  may be mounted in place on the coupler  50  by any of various known means, such as a clip that is integrally combined with the acceleration sensor  90  and which grips the side surfaces of the coupler  50 . 
     The drive circuit  92  supplies electric power to the acceleration sensor  90 . The drive circuit  92  amplifies an output signal (acceleration signal Sa) from the acceleration sensor  90 , and outputs the amplified signal to the oscilloscope  64 . 
     (d) Oscilloscope  64   
     The oscilloscope  64  is of a commercially available type, and has a plurality of input terminals  100 , a display unit  102 , and an operating section  104 . The oscilloscope  64  is capable of displaying input signals from the input terminals  100  as vertically spaced parallel data along the same time axis (see, for example,  FIG. 7 ). 
     2. Flow of Repair Process 
     
         
         (1) Overall Flow 
       
    
       FIG. 3  is a flowchart of an overall repair process according to the first embodiment. In the event of an abnormality in the vehicle  10 , in step S 1 , the ECU  20  energizes a warning lamp (not shown) on a meter, and saves a fault code (DTC: Diagnostic Trouble Code). The customer who has observed energization of the warning lamp recognizes the abnormality, and takes the vehicle  10  to the repair department of a dealer or the like. The fault code represents a fault event (e.g., the content of an abnormality occurring in the output value of a sensor). 
     In step S 2 , the repair worker (user) in the repair department connects the tester  12  to the ECU  20  with the cable  40 , and operates an operating section (not shown) to read the fault code. 
     In step S 3 , the user looks for a description of a diagnostic process and a repair process concerning the read fault code in a service manual, and identifies a region (faulty region) to be diagnosed. For example, if the fault code read in step S 2  is “P0102”, which represents a fault event indicative of a low air flow meter voltage, then the service manual contains a description  110  as shown in  FIG. 4 . In  FIG. 4 , the phrase “DTC P0102: Air flow meter voltage is low” represents the description of the fault code, the phrases “Note: Record . . . and confirm . . . prior to fault diagnosis” and “Reproduction test −1. Turn on . . . −2. Confirm . . . ” represent details of the diagnostic process and the faulty region, and the phrase “Whether roughly 0.1 V or lower . . . between ECU and air flow meter” represents a subsequent process depending on the diagnostic result. 
     In step S 4 , the user conducts a reproduction test based on the description  110 . In step S 5 , the user confirms whether or not the fault is reproduced (=whether roughly 0.1 V or lower is indicated). For example, according to the description  110  shown in  FIG. 4 , the user turns on the IGSW  22  and confirms an air flow sensor (included among the various sensors  24  shown in  FIG. 1 ) in a data list with the tester  12 . If the output signal from the tester  12  does not indicate roughly 0.1 V or lower, then since the fault is not reproduced, the user determines that the coupler  50  between the ECU  20  and the air flow meter (not shown) may possibly be suffering from a temporary contact fault. 
     If the fault is reproduced (=roughly 0.1 V or lower is indicated) in step S 5  (S 5 : YES), then in step S 6 , the user performs a normal diagnostic operation and a normal repair operation, which correspond to the reproduced fault, without using the measuring apparatus  14 . 
     If the fault is not reproduced in step S 5  (S 5 : NO), then in step S 7 , the user confirms whether or not a temporary contact fault has occurred using the measuring apparatus  14 . For example, if the coupler  50  between the ECU  20  and the air flow meter (not shown) is possibly suffering from a temporary contact fault (see  FIG. 4 ), then the user confirms whether or not a temporary contact fault has occurred with respect to each of the couplers  50  between the ECU  20  and the air flow meter. (A process of confirming whether or not a temporary contact fault has occurred will be described below.) 
     If the temporary contact fault in either one of the couplers  50  is reproduced as a result of the process of step S 7  (S 8 : YES), then in step S 9 , the user repairs or replaces the coupler  50  in which the temporary contact fault has been reproduced. In step S 10 , the user confirms normal operation of the coupler  50  (confirms that the temporary contact fault has been eliminated). If the fault has not been eliminated or another fault has occurred even though the coupler  50  has been repaired or replaced in step S 9 , then the sequence from step S 9  is carried out again. 
     If the temporary contact fault in either one of the couplers  50  is not reproduced (S 8 : NO), then the diagnostic process using the measuring apparatus  14  is completed, and control proceeds to step S 6 , in which the normal diagnostic operation and the normal repair operation are carried out.
     (2) Process of Confirming Whether or not a Temporary Contact Fault has Occurred   

       FIG. 5  is a flowchart of a user operation sequence and a processing sequence of the contact fault measuring apparatus  14  for confirming the occurrence of a temporary contact fault. Stated otherwise, the operational details and processing details shown in  FIG. 5  correspond to step S 7  shown in  FIG. 3 .  FIG. 6  is a view showing the measuring apparatus  14 , which is installed in the vehicle for confirming the occurrence of a temporary contact fault. 
     In step S 11 , the user installs the measuring apparatus  14  in preparation for confirming the occurrence of a temporary contact fault. More specifically, as shown in  FIGS. 2 and 6 , the user places the detecting coil  70  and the ferrite core  74  of the magnetic field detector  60  selectively in a position on the harness  80  in a wiring system to be measured. The position where the detecting coil  70  and the ferrite core  74  are placed may be any position on the harness  80 , insofar as the position is electrically connected to a wire to be measured. The user places the ferrite core  74  so as to encircle the harness  80 . The user then secures the acceleration sensor  90  to the coupler  50  to be measured. The user also connects the first cable  76  and the third cable  96  to desired ones of the input terminals  100  of the oscilloscope  64 . 
     In step S 12 , the user turns on the IGSW  22 , thereby energizing the circuits (including the ECU  20  and the harness  80 ) on the vehicle  10 . At this time, the user does not start the engine (not shown). The instant that a temporary disconnection occurs due to a contact fault, or when contact is reestablished, a magnetic field can be generated due to a transient response current in the harness  80  near the detecting coil  70 . 
     In step S 13 , the user operates power supply switches (not shown) of the signal amplifying circuit  72  and the drive circuit  92  to turn on the detecting coil  70  and the acceleration sensor  90 . The user also operates a power supply switch (not shown) of the oscilloscope  64  to turn on the oscilloscope  64 . 
     In step S 14 , the magnetic field detector  60  starts to detect the magnitude of a transient response variation in an induced magnetic field (or more directly, the intensity of an induced magnetic field) around the harness  80 , and the external force detector  62  starts to detect an acceleration of the coupler  50  to be measured. As a result, the magnetic field detector  60  outputs a signal representative of the transient response variation in the induced magnetic field around the harness  80  (magnetic-field-rate-of-change signal Sm) to the oscilloscope  64 , and the external force detector  62  outputs a signal representative of the acceleration of the coupler  50  (acceleration signal Sa) to the oscilloscope  64 . The oscilloscope  64  then displays on the display unit  102  the respective waveforms of the magnetic-field-rate-of-change signal Sm and the acceleration signal Sa. 
     If the harness  80  has a normal signal transmitting capability or suffers from a complete disconnection, then the intensity of the induced magnetic field around the harness  80  remains substantially constant, causing essentially no transient response variation. Unless vibrations are applied to the coupler  50 , the acceleration sensor  90  remains still. At this time, therefore, the magnetic-field-rate-of-change signal Sm and the acceleration signal Sa produce respective waveforms, as shown in  FIG. 7 , for example. 
     In  FIG. 7 , the magnetic-field-rate-of-change signal Sm and the acceleration signal Sa undergo relatively small variations. The magnetic-field-rate-of-change signal Sm undergoes relatively small variations because the intensity of the induced magnetic field around the harness  80  is substantially constant, as described above. The acceleration signal Sa undergoes relatively small variations because the coupler  50  to be measured is currently in a still or non-moving state, as described above. 
     In step S 15 , the user conducts a wiggle test on the coupler  50  to be measured. If the wiring system to be measured includes a plurality of couplers  50 , which may possibly suffer from contact faults, then the user conducts a wiggle test successively on the couplers  50  to be measured. The wiggle test refers to a test for vibrating the coupler  50  or the harness  80  to reproduce a contact fault (see  FIG. 8 ). According to the first embodiment, the user taps his or her finger on the coupler  50  or the harness  80  to produce vibrations thereon. However, a manual tool such as a resin-made hammer or an automatic device including an actuator may be used to produce vibrations on the coupler  50  or the harness  80 . 
     If no contact fault occurs (a temporary failure does not occur) despite the vibrations imparted to the coupler  50  in the wiggle test, then the magnitude of the transient response variation in the induced magnetic field around the harness  80  essentially does not change, even though the coupler  50  is displaced. Therefore, when the vibrations are imparted to the coupler  50  in the wiggle test, the magnetic-field-rate-of-change signal Sm and the acceleration signal Sa produce respective waveforms, as shown in  FIG. 9 , for example. In  FIG. 9 , the transient response variation of the acceleration signal Sm becomes larger, however, the transient response variation of the magnetic-field-rate-of-change signal Sm remains small. 
     If a contact fault occurs (is reproduced) on account of vibrations imparted to the coupler  50  during the wiggle test, then the coupler  50  is displaced and the magnitude of the transient response variation in the induced magnetic field around the harness  80  changes significantly. Therefore, when vibrations are imparted to the coupler  50  in the wiggle test, the magnetic-field-rate-of-change signal Sm and the acceleration signal Sa produce respective waveforms, as shown in  FIG. 10 , for example. In  FIG. 10 , the transient response variation of the acceleration signal Sa and the transient response variation of the magnetic-field-rate-of-change signal Sm both become greater temporarily. 
     Consequently, the user can judge whether or not there is a temporary contact fault by observing the magnitude of the transient response variation of the magnetic-field-rate-of-change signal Sm (at least one of an amplitude, a peak value, a bottom value, a gradient of the waveform, e.g., an average value or envelope, and the shape of the waveform) at the time that the magnitude of the transient response variation of the acceleration signal Sa (at least one of the amplitude, the peak value, the bottom value, the gradient of the waveform, e.g., an average value or envelope, or the shape of the waveform) changes significantly in the wiggle test. 
     If a contact fault is reproduced during the wiggle test in an one of the couplers  50  in step S 15  shown in  FIG. 5  (S 16 : YES), then the user operation sequence and the processing sequence shown in  FIG. 5  are brought to an end, and control proceeds to step S 9  shown in  FIG. 3 . If no contact fault is reproduced during the wiggle test in any one of the couplers  50  in step S 15  (S 16 : NO), then in step S 17 , the user judges whether or not all the couplers  50  to be checked for the occurrence of a contact fault have been checked. If there is a coupler  50  remaining to be confirmed (S 17 : NO), then in step S 18 , the user switches to the coupler  50  to be confirmed. More specifically, the user installs the acceleration sensor  90  on the coupler  50  to be newly measured. Then, control returns to step S 15 . 
     When the user switches to another coupler  50  to be measured, the user needs to move the acceleration sensor  90 , but does not need to move the detecting coil  70 . This is because, insofar as the harness  80 , which is closely associated with the detecting coil  70 , is electrically connected to the coupler  50  to be measured, when a contact fault is reproduced in the coupler  50  to be measured, the intensity of the induced magnetic field around the harness  80  changes, thereby increasing the transient response variation. 
     If all the couplers  50  to be checked for the occurrence of a contact fault have been checked (S 17 : YES), then the user operation sequence and the processing sequence shown in  FIG. 5  are brought to an end, and control proceeds to step S 6  shown in  FIG. 3 . 
     3. Advantages of the First Embodiment 
     According to the first embodiment, as described above, upon the occurrence of an abnormality, it is possible to judge whether or not there is a contact fault in the coupler  50  (terminal fitting portion) while the coupler  50  remains connected. More specifically, if temporarily there is no contact fault even though the coupler  50  is unstably connected, then a current flows through the coupler  50  before external forces are applied to the coupler  50 . However, when external forces are applied to the coupler  50 , thereby causing a contact fault in the unstably connected region of the coupler  50 , which instantaneously stops current from flowing, the intensity of the induced magnetic field around the harness  80  including the coupler  50  is temporarily changed significantly (i.e., the transient response variation becomes greater). According to the first embodiment, the transient response variation in the induced magnetic field around the harness  80  at the time external forces are applied to the coupler  50  is detected, and the oscilloscope  64  displays the waveform of the magnetic-field-rate-of-change signal Sm on the display unit  102 . Accordingly, without any need for separating the coupler  50 , i.e., while the coupler  50  remains connected upon the occurrence of an abnormality, it is possible to judge whether or not there is a contact fault in the coupler  50  based on the displayed waveform of the magnetic-field-rate-of-change signal Sm. 
     The phenomenon in which the transient response variation in the induced magnetic field becomes temporarily larger can be detected in a region around the harness  80  that is slightly spaced from the coupler  50 . Therefore, even in a space such as the engine compartment of the vehicle  10 , for example, which is crammed full of wires and other components, the user can select a place for measurement where the detecting coil  70  and the ferrite core  74  of the magnetic field detector  60  can be installed with ease. Consequently, the measuring process can be performed easily. 
     According to the first embodiment, the display unit  102  displays the waveform of the acceleration signal Sa in addition to the waveform of the magnetic-field-rate-of-change signal Sm. Therefore, the user can identify without fail transient response variations in the induced magnetic field around the harness  80  at the time that external forces are applied to the coupler  50 . In addition, it is possible to eliminate the effects of noise disturbances, magnetic field noise due to light-flux noise signals, etc. 
     According to the first embodiment, the acceleration sensor  90  is used as a sensor for detecting external forces applied to the coupler  50 . Since the acceleration sensor  90  makes it easy to detect vibrations produced the instant that external forces are applied, it is possible to effectively detect whether or not external forces have been applied to the coupler  50 . 
     B. Second Embodiment 
     1. Configuration 
       FIG. 11  is a view showing the manner in which a contact fault is measured using a contact fault measuring apparatus  14 A (hereinafter also referred to as a “measuring apparatus  14 A”) according to a second embodiment of the present invention. Parts of the second embodiment, which are identical to those of the first embodiment, will be denoted by identical reference characters, and such features will not be described in detail below. 
     The second embodiment differs from the first embodiment in that, whereas the user&#39;s finger is used to apply external forces to the coupler  50  according to the first embodiment (see  FIG. 8 ), according to the second embodiment, a vibrating tool  120  is used to apply external forces to the coupler  50 . Furthermore, whereas the acceleration sensor  90  is fixed to the coupler  50  according to the first embodiment (see  FIG. 2 ), according to the second embodiment, the acceleration sensor  90  is fixed to the vibrating tool  120 . 
     The vibrating tool  120  is in the shape of a small-size version of a general hammer made of resin. The vibrating tool  120  has a grip  122 , which is gripped by the user, and a head  124  mounted on the tip end of the grip  122  for coming into contact with the coupler  50  by hitting the coupler  50 . As shown in  FIG. 11 , the acceleration sensor  90  is fixed to an end of the head  124  (or in any other position thereon). The vibrating tool  120  is made of light-weight plastic. When the head  124  of the vibrating tool  120  is brought into contact with the coupler  50  by hitting the same, the grip  122  of the vibrating tool  120  flexes, thereby causing the head  124  to vibrate relatively significantly. Thus, the acceleration sensor  90  is able to detect with high accuracy the application of external forces caused by the vibrating tool  120 . 
     2. Advantages of the Second Embodiment 
     The second embodiment offers the following advantages in addition to the advantages of the first embodiment. 
     According to the second embodiment, the vibrating tool  120  with the acceleration sensor  90  mounted thereon is used to apply external forces to the coupler  50 . Since the acceleration sensor  90  is mounted on the vibrating tool  120 , it is possible to detect the timing at which external forces are applied to the coupler  50 , irrespective of the displacement of the coupler  50  or the harness  80 . Therefore, the measuring process is easier to carry out. 
     C. Third Embodiment 
     1. Configuration 
     (1) Differences from the First Embodiment and the Second Embodiment 
       FIG. 12  is a view showing the manner in which a contact fault is measured using a contact fault measuring apparatus  14 B (hereinafter also referred to as a “measuring apparatus  14 B”) according to a third embodiment of the present invention. Parts of the third embodiment, which are identical to those of the first embodiment and the second embodiment, will be denoted by identical reference characters, and such features will not be described in detail below. 
     The third embodiment differs from the first embodiment and the second embodiment in that, whereas the user judges whether or not there is a contact fault based on the waveforms displayed on the display unit  102  according to the first embodiment and the second embodiment, according to the third embodiment, the measuring apparatus  14 B itself determines whether or not a contact fault has occurred. 
     The measuring apparatus  14 B includes a controller  130  in addition to a magnetic field detector  60  and an external force detector  62 , which are identical to those according to the first embodiment. 
     (2) Controller  130   
       FIG. 13  is a block diagram of the controller  130  and related circuits. The controller  130  processes the magnetic-field-rate-of-change signal Sm from the magnetic field detector  60  (the detecting coil  70  and the signal amplifying circuit  72 ) and the acceleration signal Sa from the external force detector  62  (the acceleration sensor  90  and the drive circuit  92 ), produces specified output signals, and controls operation of the magnetic field detector  60  and the external force detector  62 . 
     As shown in  FIGS. 12 and 13 , the controller  130  includes a power supply  140 , a power supply switch  142 , a resetting switch  144 , a noise adjustment volume knob  146  (hereinafter also referred to as a “volume knob  146 ”), a power supply LED  148  (LED: Light-Emitting Diode), a judgment LED  150  (display unit), oscilloscope connection terminals  152   a ,  152   b , a judgment controller  154 , and a demagnetization controller  156 . 
     The power supply switch  142 , which comprises a seesaw switch, is used for selectively turning on and off the controller  130 . The resetting switch  144 , which comprises a pushbutton switch, outputs a resetting signal Sr to the judgment controller  154  and the demagnetization controller  156 . The noise adjustment volume knob  146 , which comprises a rotary volume knob, is used to manually adjust a threshold value TH_Sm, to be described later. The power supply LED  148  is energized when the measuring apparatus  14 B is turned on, and de-energized when the measuring apparatus  14 B is turned off. The judgment LED  150  is energized or de-energized depending on the detection performed by the magnetic field detector  60  (to be described in detail later). The oscilloscope connection terminals  152   a ,  152   b  are terminals for transmitting output signals from the controller  130 . 
     As shown in  FIG. 13 , the judgment controller  154  includes a filter  160  comprising a combination of a low-pass filter (LPF) and a high-pass filter (HPF) for passing only signals in a transient response frequency band, a signal amplifying circuit  162 , a threshold setting section  164 , a comparator  166 , a first one-shot circuit  168  (hereinafter also referred to as a “first OSC  168 ”), a second one-shot circuit  170  (hereinafter also referred to as a “second OSC  170 ”), an AND circuit  172 , a first prescribed value generating circuit  174 , and a first flip-flop circuit  176 . 
     The filter  160  cuts off frequencies other than frequencies residing within the frequency band (transient response frequency band) of the magnetic-field-rate-of-change signal Sm, which may be generated upon the occurrence of a temporary contact fault. The signal amplifying circuit  162  amplifies an output signal from the filter  160 . The threshold setting section  164  sets a threshold value TH_Sm depending on the angular displacement of the volume knob  146 , and outputs the threshold value TH_Sm to the comparator  166 . 
     As indicated by the broken-line arrows in  FIG. 13 , the threshold setting section  164  is supplied with the output signal from the filter  160  (or the signal amplifying circuit  162 ), and detects the noise level of the output signal from the filter  160  (or the signal amplifying circuit  162 ), whereby the threshold setting section  164  automatically sets the threshold value TH_Sm. 
     According to the above alternative, the threshold setting section  164  detects the noise level and automatically sets the threshold value TH_Sm. For example, the threshold setting section  164  monitors the amplitude of the output signal for a given period, and then sets a value representing the sum of the maximum level of the monitored amplitude and a prescribed value (a value that is exceeded only when a temporary contact fault occurs) as the threshold value TH_Sm. According to the above alternative, the judgment controller  154  also includes a second flip-flop circuit  180 , and a second prescribed value generating circuit  182 . 
     When the threshold setting section  164  has finished setting the threshold value TH_Sm, the threshold setting section  164  applies an ON signal Son, which is indicative of having finished setting the threshold value, to a trigger terminal T of the second flip-flop circuit  180 . Up to this point, the second prescribed value generating circuit  182  has been applying a prescribed value P 2  to a data terminal D of the second flip-flop circuit  180 . When the ON signal Son is applied to the trigger terminal T, the second flip-flop circuit  180  outputs an output signal Sff 2  (prescribed value P 2 ) from an output terminal Q thereof. The output signal Sff 2  is sent to the comparator  166  and to a preparation completion indicating LED  184 . 
     At the time that the comparator  166  receives the output signal Sff 2 , the comparator  166  sets the value received from the threshold setting section  164  as a new threshold value TH_Sm (when the comparator  166  does not receive the output signal Sff 2 , the threshold value TH_Sm is not updated). Upon receiving the output signal Sff 2 , the preparation completion indicating LED  184  is energized continuously. Therefore, the user is able to know that updating of the threshold value TH_Sm is finished. Thereafter, when the user presses the resetting switch  144 , a resetting signal Sr is applied to a resetting terminal RST of the second flip-flop circuit  180 , which ends transmission of the output signal Sff 2 , whereupon the preparation completion indicating LED  184  is de-energized. 
     The comparator  166  compares an output value from the signal amplifying circuit  162  (the magnetic-field-rate-of-change signal Sm processed by the filter  160  and the signal amplifying circuit  162 ) with the threshold value TH_Sm from the threshold setting section  164 . When the difference between the compared values is smaller than 0, the comparator  166  produces an output signal “L” (logic 0), and when the difference between the compared values is equal to or greater than 0, the comparator  166  produces an output signal “H” (logic 1). 
     The first OSC  168  and the second OSC  170  each comprise a one-shot pulse generator. More specifically, when the first OSC  168  is supplied with the output signal “L” from the comparator  166 , the first OSC  168  produces an output signal Sosc 1  “L”. When the first OSC  168  is supplied with the output signal “H” from the comparator  166 , the first OSC  168  produces an output signal Sosc 1  “H” for a given period tosc 1 . When the second OSC  170  is supplied with an output signal (the amplitude of the acceleration signal Sa) from the drive circuit  92  that is smaller than the threshold value TH_Sa, the second OSC  170  produces an output signal Sosc 2  “L” (logic 0). When the second OSC  170  is supplied with an output signal from the drive circuit  92  which is equal to or greater than the threshold value TH_Sa, the second OSC  170  produces an output signal Sosc 2  “H” for a given period tosc 2 . The given periods tosc 1 , tosc 2  are set to lengths that are large enough to sufficiently absorb the difference between the time for the magnetic field detector  60  to detect a magnetic field variation due to a temporary disconnection and the time for the external force detector  62  to detect vibrations. The given periods tosc 1 , tosc 2  may be set to the same length. 
     When the output signal Sosc 1  from the first OSC  168  and the output signal Sosc 1  from the second OSC  170  are both “H”, the AND circuit  172  produces an output signal Sand “H”. Otherwise, the AND circuit  172  produces an output Sand “L”. The first prescribed value generating circuit  174  outputs a value P 1  (fixed value), which is used to turn on the judgment LED  150 . 
     At the time that the first flip-flop circuit  176  is supplied with a voltage equal to or higher than a prescribed value at a trigger terminal T, the first flip-flop circuit  176  outputs the input value at the data terminal D from an output terminal Q thereof. When the AND circuit  172  applies the output Sand “H” to the trigger terminal T of the first flip-flop circuit  176 , the input value at the data terminal D (the value P 1  from the first prescribed value generating circuit  174 ) is output from the output terminal Q. Therefore, the first flip-flop circuit  176  outputs the value P 1  from the first prescribed value generating circuit  174  only when both the magnetic field detector  60  detects a magnetic field variation (transient response variation) due to a temporary disconnection and the acceleration sensor  90  detects variations in acceleration. When the value P 1  is output from the first flip-flop circuit  176 , the judgment LED  150  is energized. Consequently, when external forces are applied to the coupler  50 , the controller  130  automatically detects a magnetic field variation (transient response variation) due to a temporary disconnection, so that the user can determine the occurrence of the temporary disconnection based on energization of the judgment LED  150 . In addition, even if noise is produced in the first cable  76 , which interconnects the magnetic field detector  60  and the controller  130 , the controller  130  is prevented from detecting a magnetic field variation in error. 
     The demagnetization controller  156  demagnetizes the detecting coil  70  when undue magnetization of the detecting coil  70  could adversely affect the detection capability of the detecting coil  70 . 
     2. User Operation Sequence and Processing Sequence of Contact Fault Measuring Apparatus  14   b  for Confirming the Occurrence of a Temporary Contact Fault 
       FIG. 14  is a flowchart of a user operation sequence and a processing sequence of the contact fault measuring apparatus  14 B for confirming the occurrence of a temporary contact fault. Stated otherwise, the operational details and processing details shown in  FIG. 14  correspond to step S 7  shown in  FIG. 3  according to the first embodiment.  FIG. 15  is a view showing the contact fault measuring apparatus  14 B, which is installed in a vehicle  10 , for confirming the occurrence of a temporary contact fault. As shown in  FIG. 15 , if necessary, the controller  130  and the oscilloscope  64  may be connected to each other by a cable  190 , so that output waveforms (the magnetic-field-rate-of-change signal Sm and the acceleration signal Sa) from the controller  130  can be displayed on the display unit  102  of the oscilloscope  64 . 
     In step S 21 , the user installs the measuring apparatus  14 B in preparation for confirming the occurrence of a temporary contact fault. More specifically, as shown in  FIGS. 12 and 15 , the user places the detecting coil  70  and the ferrite core  74  of the magnetic field detector  60  selectively in a position on the harness  80  where the coupler to be measured is connected. If necessary, using the cable  190 , the user may connect the oscilloscope connection terminals  152   a ,  152   b  of the controller  130  to the input terminals  100  of the oscilloscope  64 . 
     In step S 22 , the user turns on the IGSW  22 , thereby energizing circuits (including the ECU  20  and the harness  80 ) in the vehicle  10 . At this time, the user does not start the engine (not shown). Further, at this time, a magnetic field is generated around the harness  80  in proximity to the detecting coil  70 . 
     In step S 23 , the user operates the power supply switch  142  of the controller  130 , thereby turning on the measuring apparatus  14 B. As a result, the power supply  140  supplies electric power to the power supply LED  148 , which energizes the power supply LED  148 . The judgment controller  154  receives the magnetic-field-rate-of-change signal Sm from the magnetic field detector  60  as well as the acceleration signal Sa from the external force detector  62 , and outputs a judgment result to the judgment LED  150 . The threshold value TH_Sm used by the comparator  166  of the judgment controller  154  may be adjusted manually by the user using the noise adjustment volume knob  146 . The second flip-flop circuit  180 , the second prescribed value generating circuit  182 , and the preparation completion indicating LED  184  also allow the threshold value TH_Sm to be automatically adjusted. 
     If the measuring apparatus  14 B and the oscilloscope  64  are connected to each other, then the magnetic-field-rate-of-change signal Sm and the acceleration signal Sa are sent from the oscilloscope connection terminals  152   a ,  152   b  to the oscilloscope  64 . Waveforms of the magnetic-field-rate-of-change signal Sm and the acceleration signal Sa are displayed on the display unit  102  of the oscilloscope  64 . At this time, the user may operate the operating section  104  of the oscilloscope  64  in order to adjust the displayed data (time axis, amplitudes, etc.) that is output to the display unit  102 . 
     In step S 24 , the user conducts a wiggle test on each of the couplers  50 . According to the third embodiment, the user operates the vibrating tool  120  to vibrate the coupler  50  to be measured (i.e., to exert external forces thereto). As shown in  FIG. 16 , for example, the acceleration signal Sa from the external force detector  62  exceeds the threshold value TH_Sa (at time t 2 ). The second OSC  170  produces an output signal Sosc 2  “H” for a given period tosc 2  from the time that the acceleration signal Sa exceeds the threshold value TH_Sa (time t 2 ). 
     If no temporary contact fault (disconnection) is reproduced even when the user operates the vibrating tool  120  to vibrate the coupler  50  to be measured, then the amplitude of the magnetic-field-rate-of-change signal Sm from the magnetic field detector  60  does not change significantly and the amplitude of the magnetic-field-rate-of-change signal Sm (the magnetic-field-rate-of-change signal Sm processed by the filter  160  and the signal amplifying circuit  162 ) does not exceed the threshold value TH_Sm. Therefore, the output signal from the comparator  166  remains “H” and the output signal Sosc 1  from the first OSC  168  remains “L”. Therefore, the output signal Sand from the AND circuit  172  also remains “L”. Since the output signal Sff from the flip-flop circuit  176  is “L”, the judgment LED  150  remains de-energized in order to notify the user that no contact fault is reproduced. 
     If a temporary contact fault (disconnection) is reproduced when the user operates the vibrating tool  120  in order to vibrate (i.e., apply external forces to) the coupler  50  to be measured, then as shown in  FIG. 16 , for example, the magnetic-field-rate-of-change signal Sm from the magnetic field detector  60  exceeds the threshold value TH_Sm (at time t 1 ). Therefore, the first OSC  168  produces an output signal Sosc 1  “H” for a given period tosc 1  from the time that the magnetic-field-rate-of-change signal Sm exceeds the threshold value TH_Sm (time t 1 ). 
     The AND circuit  172  produces an output signal Sand “H” when both the output signal Sosc 1  from the first OSC  168  and the output signal Sosc 2  from the second OSC  170  are “H” (from time t 2  to time t 3  in  FIG. 16 ). When the output signal Sand from the AND circuit  172  is “H”, a voltage signal, which is equal to or higher than a prescribed value, is applied to the trigger terminal T of the flip-flop circuit  176 . As a result, the flip-flop circuit  176  produces an output signal Sff “H” (value P 1 ), thereby energizing the judgment LED  150  to notify the user that a contact fault is reproduced. 
     When the user presses the resetting switch  144  while the judgment LED  150  is energized, the flip-flop circuit  176  produces an output signal Sff “L”, thereby de-energizing the judgment LED  150  (time t 4 ). 
     As described above with respect to the first embodiment, the user conducts a wiggle test successively on the couplers  50  or the harness  80  for thereby confirming the occurrence of a contact fault with respect to the couplers  50 . 
     3. Advantages of the Third Embodiment 
     The third embodiment offers the following advantages in addition to the advantages of the first embodiment and the second embodiment. 
     According to the third embodiment, after the threshold value TH_Sm has been set based on the intensity of the induced magnetic field prior to the application of external forces to the coupler  50 , it is judged whether or not the intensity of the induced magnetic field at the time that external forces are applied to the coupler  50  is in excess of the threshold value TH_Sm, whereupon a judgment result is displayed by the judgment LED  150 . Consequently, the user can detect without fail transient response variations in the induced magnetic field at the time that external forces are applied to the coupler  50 . 
     According to the third embodiment, furthermore, the second flip-flop circuit  180 , the second prescribed value generating circuit  182 , and the preparation completion indicating LED  184  allow the threshold value TH_Sm to be adjusted automatically. 
     D. Fourth Embodiment 
     1. Configuration of Contact Fault Diagnosing System  210  and Harness  300   
     (1) Outline 
       FIG. 17  is a perspective view of a contact fault diagnosing system  210  (hereinafter also referred to as a “diagnosing system  210 ”) including a diagnosing apparatus  212 , which serves as a contact fault measuring apparatus according to a fourth embodiment of the present invention, and a harness  300  to be measured by the contact fault diagnosing system  210 .  FIG. 18  is a block diagram of the diagnosing system  210 , with the internal structural details of the harness  300  being shown in cross section. Parts of the fourth embodiment, which are identical to those of the first through third embodiments, are denoted by identical reference characters, and such features will not be described in detail below. 
     The diagnosing apparatus  212  according to the fourth embodiment, which is designed for use in vehicles, detects a transient response variation in the vicinity of a harness  300  to be measured while the harness  300  is energized, and judges whether or not a contact fault exists between terminals in a terminal fitting portion  302  of a coupler unit  301  of the harness  300  based on the magnitude of the detected transient response variation. In the present embodiment as well as in the other embodiments, a contact failure between terminals may be caused by the occurrence of an oxide film, breakage or removal of pins of the terminals, deposition of oil or dust, etc. 
     As shown in  FIG. 17 , the harness  300  includes, in addition to the coupler unit  301 , a wire bundle  305  and a sheath  307  that covers the wire bundle  305  (other components thereof will be described later with reference to  FIG. 20 ). 
     (2) Diagnosing System  210   
     The diagnosing system  210  basically includes the diagnosing apparatus  212  and a personal computer  214  (hereinafter also referred to as a “PC  214 ”) connected to the diagnosing apparatus  212  by a universal serial bus cable  216  (hereinafter also referred to as a “USB cable  216 ”). 
     The diagnosing apparatus  212  includes a pickup device  220  for detecting the magnitude of a transient response variation in an induced magnetic field (more directly, the intensity of an induced magnetic field) around the harness  300 , a main unit  222  for performing various control and calculating processes, and a cable  224  interconnecting the pickup device  220  and the main unit  222 . 
     The pickup device  220  includes a magnetic sensor  230  having a detecting element  232  and a signal processor  234 , and a clamp  236  that supports the magnetic sensor  230 . According to the fourth embodiment, the detecting element  232  comprises an amorphous magnetic element for detecting a transient response variation in an induced magnetic field around the harness  300 , and which generates a current depending on the magnitude of the detected transient response variation. The signal processor  234  processes, e.g., amplifies, an output signal from the detecting element  232 , and outputs a signal representative of the magnitude of the transient response variation (magnetic-field-rate-of-change signal Sm) to the main unit  222 . 
     The clamp  236  is shaped like a hair clip for bundling hairs. More specifically, the clamp  236  has two clamp members  240   a ,  240   b , which are hinged to each other by a pin  242 . The clamp  236  also includes a helical spring  244  disposed around the pin  242 . The helical spring  244  has one end that engages the clamp member  240   a  and another end that engages the clamp member  240   b . When the user grasps respective grips  246   a ,  246   b  (acting points) of the clamp members  240   a ,  240   b , respective fingers  248   a ,  248   b  of the clamp members  240   a ,  240   b  are spread apart from each other about the pin  242  (see  FIG. 17 ). When the user releases the grips  246   a ,  246   b , the fingers  248   a ,  248   b  are displaced toward each other. In the fourth embodiment, the magnetic sensor  230  is fixed to an inner surface of the finger  248   b  that confronts the finger  248   a.    
     As shown in  FIG. 19 , according to the fourth embodiment, for detecting the magnitude of a transient response variation in an induced magnetic field around the harness  300 , the harness  300  is gripped between the fingers  248   a ,  248   b . Therefore, the magnetic sensor  230  is secured with respect to the harness  300 . 
     As shown in  FIG. 17 , the detecting element  232  faces in a direction perpendicular to the axis of the harness  300 . Therefore, the detecting element  232  is arranged in alignment with or parallel to the direction of a magnetic field that is generated when the harness  300  is energized (the direction of a line tangential to a circle concentric to the harness  300 ). As a result, the detecting element  232  has a maximum detecting sensitivity. 
     The clamp  236  having the above structure is capable of handling the harness  300  even if the thickness of the harness  300  changes. 
     As shown in  FIG. 18 , the main unit  222  includes an input section  250 , a controller  252 , a storage unit  254 , a display unit  256 , and a USB port  258 . The input section  250  has a plurality of buttons  260 ,  262 ,  264  ( FIG. 17 ) for the user to enter commands to the controller  252  pertaining to the judgment of a contact fault. In response to commands entered through the input section  250 , the controller  252  controls the storage unit  254  and the display unit  256 . According to the fourth embodiment, the controller  252  includes a filtering function  270 , a peak hold function  272 , a display control function  274 , and an acceptance/rejection judging function  276 . Such functions will be described later. The storage unit  254  has both a volatile memory  278  and a nonvolatile memory  280 . 
     The PC  214 , which includes a controller  290 , a storage unit  292 , and a USB port  294 , can communicate with the main unit  222  through the USB cable  216 . After the main unit  222  has acquired data, the PC  214  can perform a detailed analysis of the data, generate a report, and create a database. 
     (3) Harness  300  and Periphery Thereof 
       FIG. 20  is a perspective view of the harness  300  and a portion to which the harness  300  is connected. 
     The harness  300  is disposed in an engine compartment and interconnects an electronic control unit  400  (hereinafter also referred to as an “ECU  400 ”) of a vehicle  218  ( FIG. 21 ) and a sensor (intake pressure sensor  500 ) of the vehicle  218 . The coupler unit  301  is connected to one end of the harness  300 , and another coupler unit  301   a  is connected to the other end of the harness  300 . The coupler units  301 ,  301   a  are connected to each other by wires  322  of the wire bundle  305 . 
     As shown in  FIG. 18 , each of the coupler units  301 ,  301   a  comprises a water-resistant coupler unit having a male-terminal coupler  304  and a female-terminal coupler  306 . 
     The male-terminal coupler  304  has a resin-made housing  310  accommodating a male terminal  308  therein, which is secured together with a water-resistant rubber spacer  312  interposed therebetween, and a wire  314  connecting the male terminal  308  to the ECU  400  or the intake pressure sensor  500 . Similarly, the female-terminal coupler  306  includes a female terminal  316 , a housing  318  accommodating the female terminal  316  therein, which is secured together with a water-resistant rubber spacer  320  interposed therebetween, and a wire  322  interconnecting the female terminal  316  of the coupler unit  301  and a female terminal  316  of the other coupler unit  301   a . In  FIG. 20 , the housings  310 ,  318  and the water-resistant rubber spacers  312 ,  320  are omitted from illustration. 
     The intake pressure sensor  500  measures the intake pressure Ps [kPa], which is indicative of the pressure of an intake air-fuel mixture in the intake manifold. The intake pressure sensor  500  includes a comparator  502  and a resistor  504 , which cooperates with a resistor  506  that is connected to a power supply voltage of +5 [V] in making up a voltage divider. The voltage divider generates a voltage Vps [V], which corresponds to the intake pressure Ps, and which is detected by the ECU  400 . 
     2. Measurement of Contact Fault 
     The user operation sequence for measuring a contact fault between terminals in the terminal fitting portion  302  according to the fourth embodiment is the same as with the first embodiment ( FIG. 3 ). In the fourth embodiment as well, it is judged whether the fault depending on the fault code is reproduced or not (S 5  in  FIG. 3 ), and if the fault is not reproduced (S 5 : NO), the user confirms whether or not a temporary contact fault has occurred. 
       FIG. 21  is a view showing the diagnosing apparatus  212 , which is installed in the vehicle  218  for confirming the occurrence of a temporary contact fault. According to the fourth embodiment, for confirming the occurrence of a temporary contact fault, the wire bundle  305  of the harness  300  to be measured is gripped by the clamp  236 , thereby securing the magnetic sensor  230  to the wire bundle  305  (see  FIG. 21 ). The clamp  236  may be attached to any portion of the harness  300  where the clamp  236  can easily be attached. The user then turns on the IGSW  22  in order to energize the harness  300  (target harness) to which the coupler unit  301  to be measured is connected. Then, the user operates the diagnosing apparatus  212  while oscillating or hitting the coupler unit  301  and the wire bundle  305  directly or indirectly by applying external forces to the terminal fitting portion  302 . For example, the user may perform a wiggle test successively on the coupler units  301  ( FIG. 21 ) (see, for example,  FIG. 8 ). 
     For example, while the user is conducting the wiggle test successively on the coupler units  301  in a wiring system identified as an abnormal system, the magnetic sensor  230  detects the magnitude of a transient response variation around the wire bundle  305 , thereby judging whether or not there is a contact fault in the terminal fitting portion  302  of each coupler unit  301 . 
       FIG. 22  is a flowchart of an operation sequence of the diagnosing apparatus  212  by which the user can judge whether or not a contact fault occurs in the terminal fitting portion  302  using the diagnosing apparatus  212 . 
     With a power supply (not shown) of the main unit  222  turned on, in step S 31 , the controller  252  of the diagnosing apparatus  212  asks the user to judge whether or not a measurement process should be started. More specifically, if preparations (including the positioning of the pickup device  220 ) for the measurement process have been completed, then the controller  252  displays a message on the display unit  256  requesting the user to press a certain one of the buttons of the input section  250 . 
     When the pickup device  220  is positioned, the detecting element  232  of the pickup device  220  is not necessarily required to be positioned in alignment with the terminal fitting portion  302 , but may be positioned in alignment with the wires  322  or the wire bundle  305 , which are identified as an abnormal system to be measured. 
     After the harness  300  has been identified, the user selects a position where the harness  300  can easily be gripped, and grips the selected position with the clamp  236 . The magnetic sensor  230  disposed inside the fingers  248   a ,  248   b  of the clamp  236  is thereby secured to the harness  300 . 
     In step S 32 , the controller  252  confirms whether or not the measurement process needs to be started (i.e., whether the certain button has been pressed). If the measurement process is not to be started (S 32 : NO), then control returns to step S 31 . If the measurement process is to be started (S 32 : YES), then control proceeds to step S 33 . In a subsequent sequence, the user applies external forces to the coupler unit  301 , the wire bundle  305 , and the clamp  236  at a desired timing, thereby applying external forces to the terminal fitting portion  302 . In this manner, a contact fault, which has occurred again due to the applied external forces, can be detected in a region where the terminal fitting portion  302  was originally in a normal contact state but is in an unstable contact state. 
     In step S 33 , the controller  252  supplies electric power to the magnetic sensor  230  from a power supply (not shown). The controller  252  then receives a magnetic-field-rate-of-change signal Sm, which is representative of the magnitude (detected value) of a transient response variation detected by the magnetic sensor  230 , and performs an analog-to-digital (A/D) conversion process on the data of the detected value from the magnetic sensor  230 . 
     In step S 34 , using the filtering function  270 , the controller  252  performs a filtering process on the A/D-converted magnetic-field-rate-of-change signal Sm. The filtering process is a bandpass process with a frequency pass band, which can be produced upon the occurrence of a contact fault in the terminal fitting portion  302 . Alternatively, the filtering process may be a high-pass process or a low-pass process. 
     In step S 35 , using the peak hold function  272 , the controller  252  performs a peak hold process on the filtered magnetic-field-rate-of-change signal Sm. The peak hold process is a process for holding the peak value of the amplitude of the magnetic-field-rate-of-change signal Sm. 
     In step S 36 , using the display control function  274 , the controller  252  performs a waveform displaying process for displaying the waveform of the amplitude of the magnetic-field-rate-of-change signal Sm on the display unit  256 . The waveform displaying process updates, as needed, the waveform of an amplitude in one control period (e.g., from several microseconds to several milliseconds). Therefore, by repeating step S 36 , the waveform displaying process displays a waveform of successive amplitudes. The displayed amplitude of the magnetic-field-rate-of-change signal Sm may be selected as one from among any of the amplitude after the magnetic-field-rate-of-change signal Sm is A/D-converted (S 33 ), the amplitude after the magnetic-field-rate-of-change signal Sm is filtered (S 34 ), and the amplitude after the peak of the magnetic-field-rate-of-change signal Sm is held (S 35 ). One of the above amplitudes is selected by the user using the input section  250 . 
     In step S 37 , the controller  252  judges whether or not a contact fault has occurred using the acceptance/rejection judging function  276 . If a contact fault has not occurred, the coupler unit to be measured is accepted. If a contact fault has occurred, the coupler unit to be measured is rejected. 
     More specifically, the controller  252  judges whether or not the peak value P 1  obtained by the peak hold process is equal to or greater than a threshold value TH_P 1 . The threshold value TH_P 1  is a threshold value that is used to judge the occurrence of a contact fault in the terminal fitting portion  302 . If a contact fault has not occurred (i.e., if the conductive state does not change to a non-conductive state), then since the intensity of the induced magnetic field around the harness  300  remains unchanged, the peak value P 1  does not exceed the threshold value TH_P 1 . On the other hand, if a contact fault has occurred (i.e., if the conductive state changes to an non-conductive state, or subsequently, the non-conductive state changes to a conductive state), then since the transient response variation in the induced magnetic field around the harness  300  becomes temporarily greater, the peak value P 1  exceeds the threshold value TH_P 1 . Accordingly, it is possible to determine whether or not a contact fault has occurred. 
     If a contact fault has not occurred (S 37 : NO), then in step S 38 , the controller  252  temporarily stores the data of the amplitude of the magnetic-field-rate-of-change signal Sm in the volatile memory  278  using the acceptance/rejection judging function  276 . The amplitude of the magnetic-field-rate-of-change signal Sm may be selected as one from among any of the amplitude after the magnetic-field-rate-of-change signal Sm is A/D-converted (S 33 ), the amplitude after the magnetic-field-rate-of-change signal Sm is filtered (S 34 ), and the amplitude after the peak value of the magnetic-field-rate-of-change signal Sm has been held (S 35 ). One of the above amplitudes is selected by the user using the input section  250 . The volatile memory  278  is a first-in first-out memory (serial-in serial-out memory) for storing the value of the amplitude for a certain period of time (e.g., from several seconds to several tens of minutes). 
     If a contact fault has not occurred continuously, then the magnetic-field-rate-of-change signal Sm is of the waveform shown in  FIG. 23 . The waveform of the magnetic-field-rate-of-change signal Sm shown in  FIG. 23  is produced after the magnetic-field-rate-of-change signal Sm is A/D-converted (S 33 ). 
     If a contact fault has occurred (S 37 : YES), then in step S 39 , the controller  252  indicates the occurrence of the contact fault on the display unit  256  using the acceptance/rejection judging function  276 . For example, the controller  252  may control the display unit  256  to display a message representing the occurrence of the contact fault, or may control the display unit  256  to output a warning sound or a voice output representing the occurrence of the contact fault. Alternatively, the display unit  256  may blink the image of the waveform of the amplitude of the magnetic-field-rate-of-change signal Sm, which is displayed by the waveform displaying process (S 36 ). 
     In step S 40 , the controller  252  acquires the data of the amplitude of the magnetic-field-rate-of-change signal Sm over a given period (e.g., several seconds) using the acceptance/rejection judging function  276 , continues to store the acquired data in the volatile memory  278 , and saves the data from the volatile memory  278  in the nonvolatile memory  280  (automatic trigger function). As a result, the waveform shown in  FIG. 24  is acquired. In  FIG. 24 , since the contact fault occurs again at time t 11  in the terminal fitting portion  302 , the intensity of the induced magnetic field temporarily varies significantly, followed subsequently for a given period by a large transient response variation. Instead of performing the automatic trigger function, the user may perform an operation to save the data without deleting the data (manual trigger function). 
     If the main unit  222  includes a clock function, then time information may also be saved. The stored data may be transferred to the PC  214  over the USB cable  216 , whereupon the PC  214  processes the transferred data. 
     After step S 38  or step S 40 , the controller  252  judges whether or not the measurement process should be brought to an end, by determining whether or not a certain button in the input section  250  has been pressed. If the measurement process is to be completed (S 41 : YES), then the controller  252  saves all of the data collected so far in the nonvolatile memory  280  of the storage unit  254 , after which the measurement process is brought to an end. If the measurement process is not to be ended (S 41 : NO), then control returns to step S 33 , whereupon the operation sequence is started again for a subsequent control cycle. The process according to steps S 33  through S 38  and S 41  is performed during a period ranging from several microseconds to several milliseconds. 
     3. Advantages of the Fourth Embodiment 
     The fourth embodiment offers the following advantages, in addition to the advantages of the first through third embodiments. 
     According to the fourth embodiment, the result of a judgment is indicated as to whether or not the peak value P 1  exceeds the threshold value TH_P 1  at the time that external forces are applied. More specifically, if the peak value P 1  does not exceed the threshold value TH_P 1 , the display unit  256  continues to update the waveform of the magnetic-field-rate-of-change signal Sm, thereby indicating to the user that the peak value P 1  does not exceed the threshold value TH_P 1 . If the peak value P 1  exceeds the threshold value TH_P 1 , then the display unit  256  displays a message, indicating to the user that the peak value P 1  has exceeded the threshold value TH_P 1 . Accordingly, without the need for separating the terminal fitting portion  302  (i.e., while the terminal fitting portion  302  remains connected), upon the occurrence of an abnormality, it is possible to judge whether or not there is a contact fault in the terminal fitting portion  302  based on the judgment result. 
     The threshold value TH_P 1  for the intensity of the induced magnetic field, which is used to judge a contact fault, is represented by the value of a variation in the induced magnetic field, which is too large to be generated if current continues to flow in the terminal fitting portion  302  before and after external forces are applied thereto. Therefore, even if there is something that generates a steady noise or a magnetic field around the terminal fitting portion  302 , it is possible to judge whether or not there is a contact fault essentially without being adversely affected by the noise or the magnetic field. Therefore, the measurement process can be carried out even in a space such as the engine compartment of the vehicle  10 , which is crammed full of wires and other components. 
     Since the coupler unit  301  is water-resistant, the coupler unit  301  does not need to be disassembled, and the water resistance of the coupler unit  301  is not impaired in hermetically sealed applications. 
     According to the fourth embodiment, the magnetic sensor  230  continuously detects a transient response variation in the induced magnetic field around the harness  300 , which is being energized, during which time the diagnosing apparatus  212  continuously judges whether or not the peak value P 1  exceeds the threshold value TH_P 1  at the time that external forces are applied. If the peak value P 1  exceeds the threshold value TH_P 1 , the diagnosing apparatus  212  controls the display unit  256  to display an indication that the peak value P 1  has exceeded the threshold value TH_P 1 , thereby allowing the user to easily confirm the occurrence of a contact fault. 
     According to the fourth embodiment, the transient response variation in the induced magnetic field, which is continuously detected by the magnetic sensor  230 , is temporarily stored in the volatile memory  278 . When the controller  252  determines that the peak value P 1  at the time external forces are applied exceeds the threshold value TH_P 1 , the controller  252  stores the data, which are indicative of the transient response variations in the induced magnetic field before and after the peak value P 1  exceeds the threshold value TH_P 1 , in the nonvolatile memory  280 . Therefore, it is possible to effectively store the data of the transient response variations in the induced magnetic field before and after the contact fault occurs, without requiring the nonvolatile memory  280  to have an excessively large storage capacity. 
     The magnetic sensor  230  is of a magnetic impedance effect type having an amorphous magnetic element as the detecting element  232 . Also, the magnetic sensor  230  is fixed to the clamp  236  that grips the harness  300 . The pickup device  220  detects a transient response variation in the induced magnetic field while the clamp  236  grips the harness  300 , and with the detecting element  232  being arranged perpendicularly to the harness  300  to be measured. It is thus possible for the pickup device  220  to detect a transient response variation in the induced magnetic field while the detecting element  232  and the harness  300  are secured in a relative positional relationship by the clamp  236  and with the detecting element  232  being of maximum sensitivity. Accordingly, the pickup device  220  can stably detect a transient response variation in the induced magnetic field, even when external forces are applied to the terminal fitting portion  302 . 
     The controller  252  of the diagnosing apparatus  212  includes the filtering function  270  for passing only a component in a frequency band of the magnetic-field-rate-of-change signal Sm that can be generated upon the occurrence of a contact fault. Therefore, only a component in a frequency band of the magnetic-field-rate-of-change signal Sm, which can be generated by the occurrence of a contact fault in the terminal fitting portion  302 , is extracted, and data are stored in the storage unit  254  and displayed on the display unit  256  based on the peak value P 1  of the component. Consequently, it is possible to avoid an erroneous decision due to causes other than a contact fault, and also to reliably display the occurrence of a contact fault in the terminal fitting portion  302 , and to store data concerning the contact fault. 
     E. Modifications 
     The present invention is not limited to the above-described embodiments, but may adopt various arrangements based on the disclosure of the present description. For example, the following alternative arrangements may be adopted. 
     In the first through third embodiments, the contact fault measuring apparatus  14 ,  14 A,  14 B are constructed and intended for use in vehicles. However, the contact fault measuring apparatus  14 ,  14 A,  14 B are not limited to such an application, but may be used in other applications as well. Similarly, although the diagnosing apparatus  212  according to the fourth embodiment is constructed for use in vehicles, the diagnosing apparatus  212  may be used in other applications that employ the coupler units  301 ,  301   a.    
     In the first through third embodiments, the magnetic field detector  60  includes the single-turn detecting coil  70 , and in the fourth embodiment, the pickup device  220  includes the magnetic sensor  230 . However, the detecting element for detecting a transient response variation is not limited to such devices. The single-turn detecting coil  70  may be replaced with a detecting coil having more wire turns therein. In the first through third embodiments, the magnetic field detector  60  includes the ring-shaped ferrite core  74 . However, the magnetic field detector  60  may include a ferrite bar. According to such a modification, the detecting coil is wound on the ferrite bar, and the ferrite bar is placed such that the axis thereof lies perpendicularly to the harness  80 . Alternatively, the ferrite core  74  may be dispensed with, and a detecting coil made up of a plurality of wire turns may be disposed as an air core coil adjacent to the harness  80 . The size of the ferrite core  74  may be adjusted to increase the detecting sensitivity of the detecting coil  70 . 
     In the first through third embodiments, the IGSW  22  is turned on to energize the harness  80  (target harness) to which the coupler  50  to be measured is connected. However, it is possible to detect a contact fault in the coupler  50  to be measured without energizing the target harness, but by energizing an adjacent harness  80  in order to keep the target harness electrically charged. Similarly, a contact fault in the coupler  50  to be measured may be detected while the target harness is electrically charged by means of a dark current (a certain constant level of noise) or while the target harness is electrically charged by a device disposed outside of the target harness to electrically charge the target harness, or while the target harness is electrically charged naturally by ions in the air. Such a situation also applies to the fourth embodiment. 
     External forces are applied to the coupler  50  by the user&#39;s finger in the first embodiment and by the vibrating tool  120  in the second and third embodiments. External forces are applied to the coupler units  301 ,  301   a  by the user&#39;s finger in the fourth embodiment. However, a vibration applying mechanism for automatically vibrating the harness  80  may also be employed. The occurrence of a contact fault may be confirmed by continuously monitoring the timing at which the external forces are applied and the detected value D 1  from the magnetic field detector  60 , while the coupler  50  is directly or indirectly vibrated by means of the vibration applying mechanism. Such a modification is particularly useful in an application for inspecting finished products on a production line for automobiles or the like. 
     In the first through third embodiments, the application of external forces to the coupler  50  is detected by the acceleration sensor  90 . However, the application of external forces to the coupler  50  may be detected by another device. For example, instead of the acceleration sensor  90 , the application of external forces to the coupler  50  may be detected by a pressure sensor. 
     In the third embodiment, the threshold value TH_Sm concerning the intensity (peak value) of the induced magnetic field is used to judge a contact fault. However, a threshold value concerning amplitude, a bottom value, an average value, or an envelope of the magnetic-field-rate-of-change signal Sm may be used. In the third embodiment, the detected value is compared with the threshold value TH_Sm in order to judge whether or not a contact fault has occurred. However, it is possible to determine that a contact fault has occurred if a moving average of the detected value D 1  has changed at a certain rate per unit time (i.e., if the rate of change or gradient of the magnetic-field-rate-of-change signal S exceeds a certain value). Such a situation also applies to the fourth embodiment. 
     In the third embodiment, an output from the judgment LED  150  takes place in the event of a temporary contact fault. In the fourth embodiment, an output on the display unit  256  takes place in the event of a temporary contact fault. However, the occurrence of a contact fault may be indicated by other processes. For example, if the measuring apparatus  14 B or the diagnosing apparatus  212  is incorporated in an automated system, an electric signal representative of the occurrence of a contact fault may be output to a controller of the automated system, whereby the controller shuts down the automated system in response to the electric signal. 
     In addition to the above modifications, the configurations or processes according to the first through fourth embodiments may be applied to each other.