Patent Publication Number: US-2006004545-A1

Title: Physical quantity sensor and apparatus for inspecting physical quantity sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is related to Japanese Patent Application No. 2004-195505 filed on Jul. 1, 2004, the contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a physical quantity sensor capable of detecting a physical quantity such as pressure, acceleration and a yaw rate, and connectable to a LAN. The present invention also relates to an apparatus for inspecting such a physical quantity sensor.  
      2. Description of Related Art  
      Some physical quantity sensors include, in addition to a physical quantity sensing part, a sensor data output part having a microcomputer for processing sensor data, and a communication processor. Generally, to inspect whether or not physical quantity sensors function normally and exhibit intended performance under certain temperature and humidity conditions, a constant temperature bath is used.  
      It takes time for the temperature of a physical quantity sensor put in a constant temperature bath becomes stable at a set temperature in its entire part. Furthermore, in some cases, the set temperature is changed during inspection. Accordingly, it is common that a plurality of physical quantity sensors (for example, 50 to 100 physical quantity sensors) are put in the same constant temperature bath to inspect them at a time.  
      Incidentally, most of the recent personal computers are provided with a LAN interface so that they can communicate with other computers or information units in accordance with a certain communication protocol such as the TCP/IP.  
      Such a networking trend is not limited to personal computers. For example, it is known, as disclosed in Japanese Patent Application Laid-open No. 2003-244779, to use the CAN (Controller Area Network) as an in-vehicle LAN for the communication system between ECUs (vehicle-mounted Electronic Control Units), or between the ECUs and physical quantity sensors. The CAN, which was standardized as ISO11898, is used also in the field of FA (Factory Automation) by the designation of “DeviceNet”.  
      For such reason, the physical quantity sensors including a LAN interface as standard equipment are increasing in number. Also, the physical quantity sensors not provided with any analog voltage signal output function but including a LAN interface as the only communication means are increasing in number.  
      Generally, to inspect physical quantity sensors through their LAN interfaces, a personal computer-based LAN analyzer is used. It is also known to use a CAN communication diagnostic unit to inspect physical quantity sensors connectable to an in-vehicle LAN, as disclosed in Japanese Patent Application Laid-open No. 2003-244779.  
      It is possible to inspect a plurality of physical quantity sensors connected to the same LAN by use of only a single LAN analyzer at a time if they have different IDs or addresses, because the single LAN analyzer can identify any intended physical quantity sensor from others based on their IDs or addresses by performing the handshake with each one of the physical quantity sensors. However, in a case where all the physical quantity sensors are set to the same ID or address before shipment, it is not possible to inspect them at a time by use of a single inspection unit such as the LAN analyzer.  
      In such a case, it becomes necessary to use a plurality of inspection units (LAN analyzers), so that the plurality of the physical quantity sensors are connected to the plurality of the inspection units in a one-to-one relationship, or alternatively to use a selector switch for selecting one of a plurality of the LAN interfaces of the physical quantity sensors to be connected to a single inspection unit (LAN analyzer). This increases the inspection costs.  
      Incidentally, data packets (data frames) flowing on a LAN have a predetermined format designated by a communication protocol used (the TCP/IP, or CAN protocol, for example). However, although the data packets flowing on the same LAN have the same packet type (frame type), and the same internal field structure (that is, the same sequence and the same lengths of the internal fields), they may have user-specified portions. For example, the bit configuration of the ID field (or address field) of the data packet (data frame) is a user definable portion. Accordingly, there has been a problem in that the setting of the LAN analyzer(s) must be changed to meet the user definable portions of the data packets (data frames).  
     SUMMARY OF THE INVENTION  
      The present invention provides a physical quantity sensor including:  
      a sensing part sensing a physical quantity and generating sensor data representing a sensed physical quantity;  
      a first communication part delivering the sensor data to a LAN in accordance with a predetermined communication protocol allowing a duplex communication;  
      a second communication part delivering the sensor data to the local area network a synchronously; and  
      a switching part selecting one of the first and second communication parts to be used for delivering the sensor data to the LAN.  
      The physical quantity sensor of the invention has both the capabilities of transmitting sensor data in accordance with a predetermined communication protocol allowing a duplex communication, and transmitting the sensor data a synchronously. Accordingly, the physical quantity sensor of the invention can send sensor data to any data processing unit, or ECU, or an inspection apparatus which supports a different communication protocol.  
      The present invention also provides an apparatus for inspecting physical quantity sensors including:  
      a selector switch including an output port, and a plurality of input ports connectable to a plurality of physical quantity sensors in a one-to-one relationship, the selector switch being configured to connect the output port to one of the plurality of the input ports selected in accordance with a selection command signal; and  
      a data processing unit supplying the selection command signal to the selector switch, and processing sensor data received from the output port of the selector switch in order to determine whether or not one of the plurality of the physical quantity sensors outputting the sensor data functions normally.  
      With the inspection apparatus of the invention, it becomes possible to inspect a plurality of physical quantity sensors at a time even when they have the same ID or address. Furthermore, it becomes unnecessary to change the setting of the inspection apparatus to meet user definable portions of data packets (data frames) forming sensor data, if the physical quantity sensors have capability of performing asynchronous data transmission. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In the accompanying drawings:  
       FIG. 1  is a block diagram showing a structure of a sensor unit according to a first embodiment of the invention set in a CAN transmit mode;  
       FIG. 2  is a timing diagram for explaining electrical characteristics of the physical layer of the CAN protocol in accordance with ISO11898;  
       FIG. 3  is a block diagram showing the structure of the sensor unit according to the first embodiment of the invention set in a serial transmit mode;  
       FIG. 4  is a flowchart showing a mode switching process between the CAN transmit mode and the serial transmit mode performed by a CPU included in the sensor unit according to the first embodiment of the invention;  
       FIG. 5  is a block diagram showing a structure of a sensor unit according to a second embodiment of the invention set in the CAN transmit mode;  
       FIG. 6  is a block diagram showing the structure of the sensor unit according to the second embodiment of the invention set in the serial transmit mode; and  
       FIG. 7  is a block diagram showing a structure of an inspection apparatus for inspecting the sensor units of the invention. 
    
    
     PREFERRED EMBODIMENTS OF THE INVENTION  
      A sensor unit  20  according to a first embodiment of the invention is a physical quantity sensor mountable on a vehicle and capable of detecting a physical quantity such as acceleration, yaw rate, or impact acceleration of the vehicle. The sensor unit  20  is provided with a function of sending detected data to outer units such as ECUs through an in-vehicle LAN  100  which may be the CAN.  
      As shown in  FIG. 1 , the sensor unit  20  includes a sensor element  22 , a microcomputer  24 , and a CAN transceiver  26 .  
      The sensor element  22  includes a bridge circuit which may be constituted, for example, by four bridge-connected piezo resistors and an operational amplifier which produces an analog sensor signal based on the current flowing through the bridge circuit.  
      The microcomputer  24 , which is a one-chip microcomputer of the ASIC type, includes, other than a CPU  24   a  and a memory  24   b , peripheral devices including an A/D converter  24   c , a CAN controller  24   d  and a UART (Universal Asynchronous Receiver/Transmitter) unit  24   e . The CPU  24   a , which may be referred to as the MPU, includes a control unit, a program counter, an ALU, and a general-purpose register although they are not shown in  FIG. 1 . The memory  24   b  serving as a main memory of the CPU  24   a  includes a RAM which may be a DRAM or a SRAM, and a ROM which may be a PROM or an EEPROM. The memory  24   b  stores a control program and a communication mode switching program described later.  
      The A/D converter  24 c is for converting the analog sensor signal received from the sensor element  22  into digital data by sampling this analog sensor signal at a certain sampling rate, and quantizing each sample into 8-bit data. The digital data outputted from the A/D converter  24   c  is supplied to the CPU  24   a  as sensor data.  
      The CAN controller  24   d  lying between the CPU  24   a  and the CAN transceiver  26  serves as a communication control unit enabling the CPU  24   a  to send and receive data through the data link layer and the transport layer of the CAN protocol. In the data link layer, reconfiguration into CAN data frames together with arbitration and error detection of a message constituted by the sensor data are carried out. In the transport layer, retransmission control is carried out as required. The CAN controller  24   d  has a CAN transmit port  24  a connected to a transmit port TX of the CAN transceiver  26 , and a receive port  24  β connected to a receive port RX of the CAN transceiver  26 . The CAN data frames produced by the CAN controller  24   d  are supplied to the CAN transceiver  26  through the CAN transmit port  24  α. On the other hand, CAN data frames coming from the in-vehicle LAN  100  side and received by the CAN transceiver  26  are supplied to the CAN controller  24   d  through the CAN receive port  24  β.  
      The UART unit  24   e  serving as a second communication control unit has a function of performing serial-to-parallel and parallel-to-serial conversions. The UART unit  24   e  delimits sensor data outputted from the CPU  24   a  into blocks having a certain number of bits (5 bits to 8 bits, for example), and adds a start bit, a stop bit and a parity bit to each block in order to form fixed-length transmit frames, thereby enabling a start-stop transmission (asynchronous serial transmission). That is, the UART unit  24   e  enables a serial transmission based on the simple bit synchronization, which does not require transmitting any synchronization signal separately.  
      The UART unit  24   e  has a transmit port  24  γ and a receive port  24  δ. The serial transmit port  24  γ is connected to the transmit port TX of the CAN transceiver  26  by a signal wire 28  so that the transmit frames produced by the UART unit  24   e  are supplied to the CAN transceiver  26 , and delivered to the in-vehicle LAN  100  through the physical layer of the CAN transceiver  26 .  
      Since the signal wire  28  also connects the CAN transmit port  24   a  of the CAN controller  24   d  to the serial transmit port  24  γ of the UART unit  24   e , there is a possibility of collision or wraparound between the transmit data produced by the CAN controller  24   d  and the transmit data produced by the UART unit  24   e . Accordingly, in this embodiment, the CPU  24   a  controls the settings of these transmit ports to avoid the collision or wraparound between these transmit data by executing the control program. In this embodiment, the receive port  24  δ of the UART unit  24   e  is unconnected.  
      The CAN transceiver  26 , which lies between the CAN controller  24   d  and the in-vehicle LAN  100  including a CAN bus constituted by CAN_H line and CAN_L line, is in conformity with ISO11898, and has the differential transmit capability to the in-vehicle LAN  100  and the differential receive capability to the CAN controller  24   d . The CAN transceiver  26  has CAN_H and CAN_L terminals. The CAN_H and CAN_L terminals are connected to the in-vehicle LAN  100  through communication ports  20   a ,  20   b  of the sensor unit  20 . The sensor unit  20  can communicate with CAN nodes (ECUs or other sensor units) connected to this in-vehicle LAN  100  through the communication ports  20   a ,  20   b.    
      Here, the electrical characteristics of the physical layer of the CAN protocol in accordance with ISO11898 are explained below with reference to  FIG. 2 . As shown in  FIG. 2 , the physical layer of the CAN protocol is defined to output a voltage of +2.5V to both the CAN_H line and the CAN_L line when it receives a logical “H” level, whereas to output a voltage of +3.5V to the CAN_H line and a voltage of +1.5V to the CAN_L line when it receives a logical “L” level.  
      Hence, the CAN transceiver  26  produces the voltage of 2.5V at the CAN_H and CAN_L terminals when the transmit data received at the transmit port thereof shows the logical “H” level, thereby setting the differential voltage between the CAN_H line and the CAN_L line at 0 volts, whereas produces the voltage of +3.5V at the CAN_H terminal and the voltage of +1.5V at the CAN_L terminal when the transmit data received at the transmit port thereof shows the logical “L” level, thereby setting the differential voltage between the CAN_H line and the CAN_L line at 2 volts. On the other hand, the CAN transceiver  26  outputs the logical “H” level to the CAN controller  24   d  when it receives the voltage of 2.5V at both the CAN_H and CAN_L terminals, whereas outputs the logical “L” level to the CAN controller  24   d  when it receives the voltage of 3.5V at the CAN_H terminal and the voltage of 1.5V at the CAN_L terminal. The data communication by the physical layer of the CAN protocol has high noise immunity, because bit data is transmitted in the form of the differential voltage between two lines constituting the CAN bus.  
      Although not shown in  FIG. 1 , the CAN_H and CAN_L lines are connected with each other through 120-ohm terminator resistors at both ends of the CAN bus.  
      Incidentally, when the CAN protocol used is in conformity with ISO11519 and not with ISO11898, the electrical characteristics of the physical layer are somewhat different from those shown in  FIG. 2 , however they are the same in the way of using the differential voltage.  
      The mode where the CAN controller  24   d  loads the CAN frames with the sensor data supplied from the CPU  24   a , and the CAN transceiver  26  delivers the CAN frames to the CAN bus is referred to as “CAN transmit mode” hereinafter. Likewise, the mode where the UART unit  24   e  converts the sensor data supplied from the CPU  24   a  into serial data blocks, and the CAN transceiver  26  delivers the serial data blocks to the CAN bus through the physical layer thereof is referred to as “serial transmit mode” hereinafter.  
      Below is an explanation about a switching control between the CAN transmit mode and the serial transmit mode.  
      As explained above, in the CAN transmit mode, the CAN controller  24   d  operates at the level of the data link layer of the CAN protocol to load the CAN frames with the sensor data supplied from the CPU  24   a , and the CAN transceiver  26  delivers the CAN frames to the in-vehicle LAN  100  (CAN bus). Also in the CAN transmit mode, the CAN transceiver  26  receives CAN frames from the CAN bus, and the CAN controller  24   d  analyzes the received CAN frames and supplies them to the CPU  24   a.    
      As understood from the above explanation, in the CAN transmit mode, the sensor unit  20  communicates with the ECUs or personal computers connected to the same in-vehicle LAN in accordance with the CAN protocol. The sensor unit  20  is in the CAN transmit mode when it is shipped from factory and mounted on a vehicle.  
      The UART unit  24   e  is not used in the CAN transmit mode. Accordingly, in the CAN transmit mode, the CPU  24   a  sets the serial transmit port  24  γ and the serial receive port  24  δ of the UART unit  24   e  at the disabled state as indicated by black circles in  FIG. 1 . On the other hand, in the CAN transmit mode, the CPU  24   a  sets the CAN transmit port  24  α and the CAN receive port  24  δ of the CAN controller  24   d  at the enabled state as indicated by white circles in  FIG. 1 .  
      With these settings, the UART unit  24   e  can be avoided from being affected by the CAN frames which go out of the CAN transmit port  24  α of the CAN controller  24   d  and reaches the serial transmit port of the UART unit  24   e  by way of the signal wire  28 , because the CAN frames reaching the serial transmit port of the UART unit  24   e  are prohibited from being used and are ignored by software processing (control program).  
      In the serial transmit mode, the UART unit  24   e  converts the sensor data supplied from the CPU  24   a  into serial data blocks, and the CAN transceiver  26  delivers the serial data blocks to the in-vehicle LAN  100  (CAN bus) through the physical layer thereof. Also in the serial transmit mode, the CAN transceiver  26  receives serial data blocks from the CAN bus, and the UART unit  24   e  analyzes the received serial data blocks, and supplies them to the CPU  24   a.    
      As understood from the above explanation, in the serial transmit mode, the sensor unit  20  communicates with the ECUs or personal computers connected to the same in-vehicle LAN in accordance with the star-stop (asynchronous) communication protocol. The sensor unit  20  is in the serial transmit mode when it undergoes factory inspection before shipment.  
      The CAN controller  24   d  is not used in the serial transmit mode. Accordingly, in the serial transmit mode, the CPU  24   a  sets the CAN transmit port  24   a  and the CAN receive port  24  β of the CAN controller  24   d  at the disabled state as indicated by black circles in  FIG. 3 . On the other hand, in the serial transmit mode, the CPU  24   a  sets the serial transmit port  24  γ of the UART unit  24   e  at the enabled state as indicated by a white circle in  FIG. 3 . The serial receive port  24  δ of the UART unit  24   e  is set at the disabled state even in the serial transmit mode, since the UART unit  24   e  is not used for receiving serial data in this embodiment.  
      With these settings, the CAN controller  24   d  unit  24   e  can be avoided from being affected by the serial data blocks which goes out of the serial transmit port  24  γ of the UART unit  24   e  and reaches the CAN transmit port  24  α of the CAN controller  24   d  by way of the signal wire  28 , because the serial data blocks reaching the CAN transmit port  24  α are prohibited from being used and are ignored by software processing (control program).  
      Likewise, the CAN controller  24   d  unit  24   e  can be avoided from being affected by serial data blocks coming from the in-vehicle LAN  100  and reaching the CAN receive port  24  β through the CAN transceiver  26 , because the serial data blocks reaching the CAN receive port  24  δ are prohibited from being used and are ignored by software processing (control program).  
      The settings of the CAN transmit port  24  α and CAN receive port  24  β of the CAN controller  24   d , and the serial transmit port  24  γ and serial receive port  24  δ of the UART unit  24   e  are carried out by the CPU  24   a  which executes the control program for an initialization process in accordance with hardware-setting data supplied to the CPU  24   a  through control lines (not shown), or hardware information supplied to the CPU  24   a  through a hardware switch such as DIP switch assembly or short pins (not shown) Below is an explanation about the switching process between the CAN transmit mode and the serial transmit mode performed by the CPU  24   a.    
      This mode switching process is carried out when the CPU  24   a  executes the communication mode switching program stored in the memory  24   b . Here, it is assumed that the CPU  24   a  sets the sensor unit  20  at the CAN transmit mode at power-on or at restart, and that the in-vehicle LAN  100  supports the CAN protocol.  
      As shown in  FIG. 4 , in the mode switching process, an initialization processing is executed in the first place at step S 101  where the capacity of a counter CNT (explained later) is set at an initial value (equivalent to a period of 30 seconds, for example).  
      Subsequently, a countdown processing where the count value of the counter CNT is decremented by one is executed at step S 102 .  
      Next, it is checked at step S 103  whether or not any response request signal originating from any of other nodes connected to the in-vehicle LAN has been received. If the check result at step S 103  is affirmative (“YES”), the CPU  24   a  recognizes that the sensor unit  20  is connected to any in-vehicle LAN supporting the CAN protocol, and terminates this mode switching process while keeping the sensor unit in the CAN transmit mode.  
      On the other hand, if the check result at step S 103  is negative (“NO”), the CPU  24   a  recognizes that the sensor unit  20  is not connected to any in-vehicle LAN supporting the CAN protocol, and the process moves to step S 104 . At step S 104 , it is checked whether or not the count value of the counter CNT has been decremented to zero, that is, whether or not the timeout period of 30 seconds has elapsed. If the check result at step S 104  is negative (“NO”), that is, if it is determined that the timeout period has not yet elapsed, then the process returns to step S 102  to decrement the count value of the counter CNT.  
      On the other hand, if the check result at step S 104  is affirmative (“YES”), then the process moves to step S 105  to switch the sensor unit  20  from the CAN transmit mode to the serial transmit mode, because the sensor unit  20  can be regarded as not being connected to any in-vehicle LAN supporting the CAN protocol in a case where the sensor unit  20  has not received any response request signal over the timeout period. As a result of this mode switch, it becomes possible for the sensor unit  20  to transmit sensor data (serial data blocks) through the physical layer of the CAN transceiver  26 .  
      As already described with reference to  FIG. 3 , to set the sensor unit  20  to the serial transmit mode, the CAN transmit port  24  α and the CAN receive port  24  β of the CAN controller  24   d  are disabled, and the serial transmit port  24  γ of the UART unit  24   e  is enabled.  
      As explained above, the sensor unit of this embodiment is configured to switch from the CAN transmit mode to the serial transmit mode if the sensor unit has received any response request signal from any of other nodes or ECUs within a predetermined timeout period. This configuration makes it possible to send sensor data through simplex serial data transmission to information processing units which do not support the CAN protocol.  
      Although the sensor unit  20  is described as including the microcomputer  24  provided with the CAN controller  24   d  having the CAN transmit port  24  α and CAN receive port  24  β and the UART unit  24   e  having the serial transmit port  24  γ and serial receive port  24  δ, the invention should not be construed as being limited thereto. For example, the present invention is applicable to a sensor unit  120  that has a structure shown in  FIG. 5 . As shown in this figure, the sensor unit  120  as a physical quantity sensor according to a second embodiment of the invention has, instead of the microcomputer  24 , a microcomputer  124  provided with a communication controller  124   d  which can function as the CAN controller and also the UART unit.  
      The communication controller  124   d  has a transmit port  124   a  serving as the CAN transmit port or the UART transmit port (serial transmit port), and a receive port  124  β serving as the CAN receive port or the UART receive port (serial receive port). The mode of the sensor unit  120  can be switched between the serial transmit mode and the CAN transmit mode by changing control programs to be executed by the CPU  24   a.    
      When the sensor unit  120  is in the CAN transmit mode, the CAN controller function of communication controller  124   d  is enabled, and the UART function of the communication controller  124   d  is disabled as indicated in  FIG. 5 . As a result, the transmit data (CAN frames) outputted from the transmit port  124  α of the communication controller  124   d  operating as the CAN controller are delivered to the in-vehicle LAN  100  through the CAN transceiver  26 . On the other hand, receive data (CAN frames) coming from the in-vehicle LAN  100  and received by the CAN transceiver  26  are inputted to the receive port  124  β of the communication controller  124   d  serving as the CAN controller.  
      When the sensor unit  120  is in the serial transmit mode, the CAN controller function of communication controller  124   d  is disabled, and the UART function of the communication controller  124   d  is enabled as indicated in  FIG. 6 . As a result, the serial transmit data (serial data blocks) outputted from the transmit port  124  α of the communication controller  124   d  operating as the UART unit are supplied to the CAN transceiver  26  and delivered to the in-vehicle LAN  100  through the physical layer of the CAN receiver  26 . Although serial receive data (serial data blocks) coming through the in-vehicle LAN  100  and received by the CAN transceiver  26  are outputted to the receive port  124  β of the communication controller  124   d  operating as the UART unit, the sensor unit  124  is not affected by the serial receive data, because it is ignored by software processing (control program).  
      As explained above, the sensor units according to the first and second embodiments of the invention can transmit sensor data in accordance with a predetermined communication protocol allowing a duplex communication, or transmit sensor data a synchronously through a physical layer of the transceiver thereof allowing at least a simplex communication. Accordingly, the sensor units according to the first and second embodiments of the invention can send sensor data to any data processing unit, or ECU, or an inspection apparatus which supports a different communication protocol.  
      Although the sensor units and the in-vehicle LAN are described as supporting the ISO11898 or ISO11519 in the above described embodiments, the present invention should not be construed as being limited thereto. For example, the invention is applicable to sensor units supporting any wired LAN protocol such as the TCP/IP, IEEE802.1, LIN (Local Interconnect Network), FlexRay, TTP, MOST, IEEE1394, and USB.  
      Next, an inspection apparatus  10  for inspecting the sensor unit  20  or  120  is explained below.  
       FIG. 7  is a block diagram showing a schematic structure of the inspection apparatus  10  capable of inspecting n (100, for example) sensor units  20  ( 120 ) put in a constant temperature bath 200 at a time.  
      As shown in  FIG. 7 , the inspection apparatus  10  includes a selector switch  30  and a personal computer  50 . The selector switch  30  has an output port  30   b , and a plurality of input ports  30   a   1  to  30   an . The n input ports  30   a   1  to  30   an  are for receiving serial transmit data from the n sensor units  20  ( 120 ) as sensor data through the in-vehicle LAN  100  in a one-to-one relationship. The selector switch  30  is configured to select one of the input ports  30   a   1  to  30   an  in accordance with a selection command received from the personal computer  50 , and forwards the sensor data being received by the selected one of the input ports  30   a   1  to  30   an  to the output port  30   b . As a means for selecting one of the input ports  30   a   1  to  30   an , a relay circuit of the electromagnetic type or semiconductor type may be used.  
      The personal computer  50  includes a CPU  50   a  having an input port P 1  for receiving the sensor data from the selector switch  30 , a memory  50   b  as a main memory thereof and a driver circuit  50   c  for generating the selection command. The personal computer  50  is configured to supply the selection command to the selector switch  30  and determine whether or not the sensor units  20  ( 120 ) are functioning normally on the basis of the sensor data received from the output port  30   b  of the selector switch  30 . The memory  50   b  stores a control program, and an inspection program for inspecting the functions and performances of the sensor units  20  ( 120 ).  
      With this inspection apparatus having the above described structure, it becomes unnecessary to provide the personal computers  50  as many as the number of the sensor units  20  ( 120 ) to be inspected at a time even when all the sensor units  20  ( 120 ) have the same ID or address, because this inspection apparatus has capability of selecting any one of the plurality of the sensor units  20  ( 120 ).  
      The inspection apparatus  10  described above also can address the case where the sensor units  20  ( 120 ) have different IDs or addresses specific to their different destinations by changing setting of the personal computer  50 .  
      The above explained preferred embodiments are exemplary of the invention of the present application which is described solely by the claims appended below. It should be understood that modifications of the preferred embodiments may be made as would occur to one of skill in the art.