JP5022343B2 - Physical quantity detection system - Google Patents

Description

  The present invention relates to a physical quantity detection system.

  Conventionally, physical quantity detection systems have been proposed. This includes a physical quantity sensor that detects various physical quantities and a management device (monitoring / controlling apparatus) that monitors and controls the physical quantity sensor.

  Here, examples of the physical quantity sensor include an acceleration sensor, an angular velocity sensor, a pressure sensor, a load sensor, and a magnetic sensor.

  For example, Patent Document 1 discloses a heating resistance type air flow rate measuring device as an example of a physical quantity sensor. The device disclosed in Patent Document 1 includes an adjustment terminal in addition to the three terminals of a power terminal (power terminal), an output terminal (output terminal), and a ground terminal (ground terminal). In this device, various adjustments such as output characteristics can be performed using the adjustment terminal. For this reason, it is possible to supply products with stable performance by eliminating variations such as output characteristics differing from product to product.

  However, providing the adjustment terminal causes an increase in the price of the physical quantity sensor and an increase in size. In addition, it is necessary to provide a special terminal for connecting the adjustment terminal even in the management device to which the physical quantity sensor is connected, which causes a problem that the configuration of the management device becomes complicated. Furthermore, there is a problem that current flows through the adjustment terminal during transportation or incorporation of the physical quantity sensor and the output characteristics are unexpectedly changed.

  Because of the disadvantages as described above, the customer's understanding is not always obtained for providing the adjustment terminal. Further, as a method for preventing an adverse effect caused by the adjustment terminal, it has been proposed that adjustment is performed during assembly so that the adjustment terminal is finally removed and cannot be used. However, in this case, there may be a problem that characteristics are different at the time of adjustment and at the time of completion of assembly due to the stress generated in the process after adjustment, the mold of the circuit, or the like.

  Thus, a physical quantity sensor has been proposed that allows adjustment of output characteristics and the like but eliminates an adjustment terminal (see, for example, Patent Document 2).

Patent Document 2 has a sensor circuit including a trimming circuit that performs electric trimming such as sensitivity adjustment, offset adjustment, and offset temperature characteristic adjustment in the sensor element. This sensor circuit has only a total of three terminals, two power supply terminals, one of which is used for grounding, and one output terminal. In such a device disclosed in Patent Document 2, the output terminal can be used as an input terminal for trimming data or the like, thereby eliminating the need for a dedicated terminal for trimming.
JP 2002-148077 A JP 2006-71336 A

  However, in the one disclosed in Patent Document 2, when adjustment is performed on a plurality of physical quantity sensors (for example, when adjustment is performed on a sensor module in which a plurality of physical quantity sensors are modularized), the following problem has occurred. . That is, in the one shown in Patent Document 2, since the output terminal is used as a communication terminal, it is necessary to provide the external device with a communication device in one-to-one correspondence with the physical quantity sensor. In addition, the number of communication lines for connecting the output terminal of the physical quantity sensor to the communication device of the management device increases. As described above, the conventional physical quantity detection system has a problem that it is difficult to simplify the configuration of the entire system.

  The present invention has been made in view of the above points, and an object thereof is to provide a physical quantity detection system capable of simplifying the configuration of the entire system and improving the communication accuracy of serial communication. It is in.

  In order to solve the above-described problem, the invention of claim 1 includes a physical quantity sensor and a management device that monitors and controls the physical quantity sensor, and the physical quantity sensor includes a first terminal unit, a detection unit, and a storage unit. Unit, an output unit, a first communication unit, a determination unit, and a first control unit, the first terminal unit has a power supply terminal, an output terminal, and a ground terminal, The detection unit is configured to detect a predetermined physical quantity, the storage unit is configured to store characteristic information, and the output unit outputs a detection output of the detection unit from the output terminal. And the determination unit is configured to determine an operation mode requested by the management device based on a potential of at least one of the power supply terminal and the output terminal, and the first control unit includes: It operates in the operation mode according to the discrimination result of the discrimination unit The management device includes a second terminal unit, a power supply unit, a second communication unit, and a second control unit, and the second terminal unit connects the power terminal. A power supply terminal and an input terminal connected to the output terminal, wherein the power supply unit is configured to supply power to the physical quantity sensor from the power supply terminal, and the second control unit includes the physical quantity sensor. Including a function for requesting switching of the operation mode and a function of causing the second communication unit to transmit characteristic information. The operation mode is a characteristic in which the first communication unit receives the characteristic information of the storage unit. A physical quantity detection system including an adjustment mode for rewriting information and a normal mode that does not permit rewriting of characteristic information of the storage unit, wherein the first communication unit uses the power supply terminal as an input / output terminal for a serial signal Configured as above The second communication unit is configured to use the power supply terminal as an input / output terminal for a serial signal, and one of the first communication unit and the second communication unit is the first communication unit. And the second communication unit are configured to transmit a synchronization signal before transmitting a serial signal to the other, and the other is a communication clock for serial communication based on the synchronization signal received from the one. Is configured to set.

  According to the present invention, since the operation mode requested by the management device is determined based on the potential of at least one of the power supply terminal and the output terminal, the shift to the adjustment mode can be performed without increasing the number of terminals. In the adjustment mode, the power supply line to the physical quantity sensor can also be used as a communication line. Therefore, it is not necessary to provide the management apparatus with a communication device in one-to-one correspondence with the physical quantity sensor, and it is possible to communicate with a large number of physical quantity sensors with one communication apparatus. Therefore, the configuration of the management device can be simplified and the wiring can be reduced, and the configuration of the entire system can be simplified. In addition, when performing serial communication, the physical quantity sensor and the management device are synchronized by the synchronization signal, so that the communication accuracy of serial communication can be improved.

  According to a second aspect of the present invention, in the first aspect of the invention, the determination unit requests an operation requested by the management device depending on whether or not the potentials of the power supply terminal and the output terminal satisfy a predetermined condition. The mode is distinguished.

  According to the present invention, it is possible to reduce the probability that an operation mode determination error occurs as compared with the case where the operation mode is determined using only one of the power supply terminal and the output terminal. Therefore, it is possible to prevent the operation mode from being changed unexpectedly. In addition, when a plurality of physical quantity sensors become communication partners of the management device, only the potential of the output terminal of the communication partner is changed to identify the communication target without adding an identification ID to the communication data. Is possible. The invention according to claim 3 is the invention according to claim 1 or 2, characterized in that the one is the first communication unit and the other is the second communication unit.

  According to the present invention, since the synchronization signal is transmitted from the physical quantity sensor to the management device, the clock circuit of the management device can be matched with the clock circuit of the physical quantity sensor. Therefore, it is possible to use a clock circuit provided in the physical quantity sensor with relatively low accuracy. As a result, the cost and size of the physical quantity sensor can be reduced.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, when the second communication unit receives the serial signal of the first communication unit, the phase of the communication clock is reset. It is characterized by doing.

  According to the present invention, it is possible to reduce the phase shift between the communication clock of the physical quantity sensor and the communication clock of the management device due to the measurement error of the synchronization signal.

  According to a fifth aspect of the present invention, a physical quantity sensor and a management device that monitors and controls the physical quantity sensor are provided. The physical quantity sensor includes a first terminal unit, a detection unit, a storage unit, an output unit, and a first unit. A communication unit, a determination unit, and a first control unit, wherein the first terminal unit has a power supply terminal, an output terminal, and a ground terminal, and the detection unit has a predetermined physical quantity. Configured to detect, the storage unit is configured to store characteristic information, the output unit is configured to output the detection output of the detection unit from the output terminal, the determination unit is Based on the potential of at least one of the power supply terminal and the output terminal, the operation mode requested by the management device is determined, and the first control unit responds to the determination result of the determination unit. The management device is configured to operate in an operation mode. A second terminal unit; a power supply unit; a second communication unit; and a second control unit, wherein the second terminal unit includes a power supply terminal that connects the power terminal and the output terminal. A power supply unit configured to supply power to the physical quantity sensor from the power supply terminal, and the second control unit requests the physical quantity sensor to switch an operation mode. And a function for causing the second communication unit to transmit characteristic information, and the operation mode includes an adjustment mode for rewriting the characteristic information in the storage unit with the characteristic information received by the first communication unit, and the storage A physical quantity detection system including a normal mode that does not permit rewriting of characteristic information of a part, wherein the physical quantity sensor includes a clock signal output unit, and the clock signal output unit is configured to perform the first mode in the adjustment mode. communication And the first communication unit synchronizes with the clock signal obtained from the clock signal output unit as a serial signal input / output terminal. The second communication unit is configured to perform serial communication in synchronization with a clock signal input to the input terminal, with the power supply terminal serving as an input / output terminal for a serial signal. It is characterized by.

  According to the present invention, since the operation mode requested by the management device is determined based on the potential of at least one of the power supply terminal and the output terminal, the shift to the adjustment mode can be performed without increasing the number of terminals. In the adjustment mode, the power supply line to the physical quantity sensor can also be used as a communication line. Therefore, it is not necessary to provide the management apparatus with a communication device in one-to-one correspondence with the physical quantity sensor, and it is possible to communicate with a large number of physical quantity sensors with one communication apparatus. Therefore, the configuration of the management device can be simplified and the wiring can be reduced, and the configuration of the entire system can be simplified. In addition, the second communication unit transmits and receives a serial signal through the power supply terminal in synchronization with the clock signal input to the input terminal through the output terminal, and the first communication unit receives the clock obtained from the clock signal output unit. The serial signal can be transmitted and received through the power supply terminal in synchronization with the signal. Therefore, unlike using a synchronization bit, the influence of measurement errors and various disturbances can be reduced, and the communication accuracy of serial communication in the adjustment mode can be improved.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the determination unit performs an operation requested by the management device depending on whether the potentials of the power supply terminal and the output terminal satisfy a predetermined condition. The mode is distinguished.

  According to the present invention, it is possible to reduce the probability that an operation mode determination error occurs as compared with the case where the operation mode is determined using only one of the power supply terminal and the output terminal. Therefore, it is possible to prevent the operation mode from being changed unexpectedly. In addition, when a plurality of physical quantity sensors become communication partners of the management device, only the potential of the output terminal of the communication partner is changed to identify the communication target without adding an identification ID to the communication data. Is possible.

  According to a seventh aspect of the present invention, in the fifth or sixth aspect of the invention, the clock signal output from the clock signal output unit to the input terminal is a signal whose current magnitude changes over time. A potential holding unit is included, and the potential holding unit is configured to keep the potential of the input terminal constant during the adjustment mode.

  According to the present invention, it is possible to prevent the occurrence of problems due to fluctuations in the potential of the input terminal and the output terminal during the adjustment mode.

  The present invention can simplify the configuration of the entire system and can improve the communication accuracy of serial communication.

(Embodiment 1)
The physical quantity detection system according to the present embodiment is used, for example, for electrical control in driving an automobile engine by an electronic control unit (ECU). As shown in FIG. 1, this physical quantity detection system is composed of two physical quantity sensors (hereinafter abbreviated as “sensors”) 1 and a management device 2 comprising an ECU (however, in FIG. Only the sensor 1 is shown, and the other sensor 1 is not shown). In this device, the sensor 1 is used as a slave and the management device 2 is used as a master.

  As shown in FIG. 1, the sensor 1 includes a terminal unit (hereinafter referred to as a first terminal unit) 10, a detection unit 11, a storage unit 12, an output correction unit (output unit) 13, and a communication unit ( Hereinafter, it includes a determination unit 15, a control unit (hereinafter referred to as a first control unit) 16, and a power supply unit 17. Moreover, the sensor 1 is provided with the housing | casing (not shown) which accommodates the electric equipment etc. which comprise each part 10-17. In the physical quantity detection system of this embodiment, the two sensors 1 detect the same physical quantity and are housed in the same housing.

  The first terminal unit 10 is used for connection with the management device 2. The first terminal unit 10 includes a power supply terminal 10a, an output terminal 10b, and a ground terminal 10c. The power supply terminal 10 a is a terminal for supplying power to the sensor 1. The output terminal 10 b is a terminal for outputting the detection output of the sensor 1 to the management device 2. The ground terminal 10c is a terminal for giving a reference potential point. A bypass capacitor (abbreviated as bypass capacitor) C is inserted between the power supply terminal 10a and the ground terminal 10c. The bypass capacitor C is provided for measures against high frequency noise such as power supply noise and radiation noise.

  The detection unit 11 is a detection element for detecting a predetermined physical quantity. Specific examples include an acceleration sensor, an angular velocity sensor, a pressure sensor, a load sensor, and a magnetic sensor. For example, such a detection unit 11 outputs a signal (detection signal) having a potential corresponding to the detected value of the physical quantity as a detection output.

  The storage unit 12 includes, for example, a nonvolatile memory (for example, a flash memory, an EEPROM, a fuse, an OTPROM, or other electrically writable storage medium). The storage unit 12 stores characteristic information regarding the sensor 1. In the present embodiment, the characteristic information is a correction value used for correction of the detection output of the detection unit 11 (that is, correction of the detection value). The characteristic information may be information relating to the sensor 1 standard, product ID, clamp voltage, and other sensors 1.

  The output correction unit 13 is configured to correct and output the detection output of the detection unit 11. For example, when the output correction unit 13 obtains a detection output from the detection unit 11, the output correction unit 13 obtains a detection value from the detection output. Then, the output correction unit 13 corrects the acquired detection value using the correction value stored in the storage unit 12. After the correction, the output correction unit 13 outputs a signal having a potential corresponding to the corrected detection value to the output terminal 10b as a corrected detection output. In the present embodiment, the output correction unit 13 corrects the detection output by performing offset processing and gain processing. The offset process is a process of adding a predetermined addition value (offset value) to the detection value obtained from the detection output of the detection unit 11. The gain process is a process of multiplying the value after the offset process by a predetermined multiplication value (gain value). Therefore, in the present embodiment, the correction value stored in the storage unit 12 includes an offset value and a gain value. The offset value is a positive or negative value, and the gain value is a value excluding 0. Further, the output correction unit 13 is configured to operate only in a normal mode to be described later.

  By the way, the above-described offset processing and gain processing are performed for the purpose of setting the potential of the detection output output by the detection unit 11 to a value within a desired range, for example. For example, depending on the usage location and usage situation of the sensor 1, the magnitude of the potential of the detection output may be larger than the magnitude that can be detected by the management device 2, and a correct detection result may not be obtained. In such a case, the output correction unit 13 corrects the detection output so that the size is within a range that can be detected by the management apparatus 2. This makes it possible to obtain an appropriate detection result. By performing the offset processing and gain processing described above, it is possible to prevent the range of the detection output value from being different for each product due to variations in the characteristics of components and the like. Therefore, the detection output can be kept within a desired range in any product. Note that the output correction unit 13 performs not only the offset processing and gain processing described above, but also temperature correction processing (processing for correcting changes in detection output due to temperature) and other correction processing (for example, processing such as inversion of detection output). May be executed. Here, the output correction unit 13 may execute any of these various processes. In this case, what processing the output correction unit 13 executes can be included in the characteristic information. Further, the output correction unit 13 may have a function of outputting the intermediate result to the output terminal 10b instead of the final result obtained by correcting the detection output of the detection unit 11. Such switching of the function of the output correction unit 13 can be given by the characteristic information.

  The first communication unit 14 is for receiving characteristic information (correction value) to be stored in the storage unit 12 from the management device 2. The first communication unit 14 performs wired communication (serial communication) with the management apparatus 2 using the power supply terminal 10a as an input / output terminal for a serial signal. Such a first communication unit 14 includes a communication processing unit 14a, a clock circuit 14b, a determination circuit 14c, a switch Q10, and a resistor R10. The determination circuit 14c includes a comparator and the like, and determines whether the potential of the power supply terminal 10a is high or low by comparing the potential of the power supply terminal 10a with a threshold for signal reception. For example, in the present embodiment, the threshold for signal reception is 10V, and the determination circuit 14c determines that the level is high if the potential of the power supply terminal 10a exceeds 10V, and determines that the level is low if it is 10V or less.

  The switch Q10 is an n-channel MOSFET, and is inserted between the power supply terminal 10a and the ground (reference potential point). Note that the switch Q10 is not limited to a semiconductor switching element such as a MOSFET, and a switch capable of on / off control such as a relay can be used. The resistor R10 is for setting the potential of the power supply terminal 10a when the switch Q10 is on to a predetermined potential lower than when the switch Q10 is off.

  The communication processing unit 14a performs serial signal reception processing (that is, processing for identifying a bit string of a serial signal) using the determination result of the determination circuit 14c and the clock circuit 14b. In addition, the communication processing unit 14a performs serial signal transmission processing (processing for changing the potential of the power supply terminal 10 according to the bit string of the serial signal to be transmitted) using the switch Q10 and the clock circuit 14b. The communication processing unit 14a is configured by using, for example, a logic circuit or a microcomputer (microcontroller, abbreviated as a microcomputer, also referred to as a CPU in a broad sense).

  When performing serial communication with the management apparatus 2 (when transmitting a serial signal), the communication processing unit 14a in the present embodiment, as shown in FIG. 2, before transmitting the serial signal, the clock of the clock circuit 14b. The synchronization bit (synchronization signal) SYNC is transmitted in accordance with the timing.

  The first control unit 16 is a control device that performs overall control of the sensor 1. The first control unit 16 includes, for example, a microcomputer, and realizes various functions by executing a program stored in the memory by the CPU. The first control unit 16 may be configured integrally with the communication processing unit 14a of the first communication unit 14.

  The first control unit 16 in the present embodiment has two types of operation modes, that is, a normal mode and an adjustment mode (that is, the sensor 1 operates in one of the normal mode and the adjustment mode). ).

  In the adjustment mode, the first control unit 16 stops driving the detection unit 11 and the output correction unit 13 and drives the first communication unit 14. As a result, detection output is not output, and serial communication with the management apparatus 2 is enabled. When the correction value is acquired from the management device 2 by serial communication with the management device 2 in the adjustment mode, the first control unit 16 rewrites the correction value in the storage unit 12 with the correction value acquired from the management device 2. When the rewriting is completed, the first control unit 16 controls the first communication unit 14 to transmit the correction value of the storage unit 12 after the rewriting to the management device 2. As described above, the adjustment mode is a mode in which the detection output is not output, but the correction value in the storage unit 12 can be rewritten.

  On the other hand, in the normal mode, the first control unit 16 drives the detection unit 11 and the output correction unit 13 and stops driving the first communication unit 14. Thus, the detection output (detection output corrected by the output correction unit 13) can be output to the output terminal 10b, and serial communication with the management apparatus 2 is not performed. Thus, the normal mode is a mode in which detection output is output, but rewriting of the correction value in the storage unit 12 is prohibited.

  Whether the first control unit 16 described above operates in the adjustment mode or the normal mode is determined according to a request from the management device 2.

  The determination unit 15 is configured to determine which operation mode the management device 2 is requesting, and to notify the first control unit 16 of the determination result. Therefore, the first control unit 16 controls each part of the sensor 1 in an operation mode according to the determination result of the determination unit 15.

  In the present embodiment, the determination unit 15 determines the operation mode requested by the management device 2 based on the potential of the power supply terminal 10a. For example, if the potential of the power supply terminal 10a exceeds 6V, the determination unit 15 determines that the management device 2 requests the adjustment mode. If the potential of the power supply terminal 10a is 6V or less, the management device 2 is normal. Determine that the mode is requested. The determination unit 15 can be obtained by using a comparison circuit that compares the potential of the power supply terminal 10a with the threshold value for determining the operation mode.

  The power supply unit 17 is configured to generate the operating voltage of the sensor 1 based on the power obtained from the power supply terminal 10a. For example, a three-terminal regulator that generates a predetermined voltage based on a potential difference (power supply voltage) between the power supply terminal 10a and the ground terminal 10c is used as the power supply unit 17 as necessary. When the potential of the power supply terminal 10a can be used as an operating voltage as it is, the power supply terminal 10a may be connected as it is to the electric circuit constituting each part without providing the power supply section 17.

  The management device 2 mainly includes a terminal unit (hereinafter referred to as a second terminal unit) 20, a power supply unit 21, a communication unit (hereinafter referred to as a second communication unit) 22, and a control unit (hereinafter referred to as a second communication unit). 23) (referred to as a second control unit). In addition, the management device 2 includes a housing (not shown) that houses electrical devices and the like that constitute the units 20 to 23.

  The second terminal unit 20 is used for connection of the sensor 1. The second terminal portion 20 is a three-terminal type including a power supply terminal 20a, an input terminal 20b, and a ground terminal 20c. The power supply terminal 20 a is a terminal for supplying power from the power supply unit 21 to the sensor 1. The input terminal 20 b is a terminal for obtaining a detection output from the sensor 1. The input terminals 20b are provided in a number corresponding to the number of sensors 1 to be connected. In the case of the present embodiment, two input terminals 20b are provided to connect two sensors 1, but they are not shown in FIG. The ground terminal 20c serves as a reference potential point for the sensor 1, and is connected to, for example, a car body. Therefore, in the sensor 1, the power supply terminal 10a is connected to the power supply terminal 20a with a wire (power supply line) L1, the output terminal 10b is connected to the input terminal 20b with a wire (output line) L2, and the ground terminal 10c is connected to the ground terminal 20c with a wire (ground wire). ) Connect to the management device 2 by connecting at L3. In the example shown in FIG. 1, the ground terminal 10 c of the sensor 1 is not necessarily connected to the ground terminal 20 c of the management device 2, and may be connected to a terminal that can supply a reference potential.

  The power supply unit 21 is a variable power source that can change the output voltage. The power supply unit 21 is connected to the power supply terminal 20a. The power supply unit 21 is configured using, for example, a battery mounted on an automobile or a circuit (such as a step-down chopper circuit or a band gap reference circuit) that can step down the DC voltage of the battery to a predetermined voltage. In the present embodiment, the power supply unit 21 can selectively select 5V and 12V as the output voltage. Since such a power supply unit 21 can be a conventionally known one, a detailed description thereof will be omitted. The power supply unit 21 includes a circuit for changing the output voltage, and is composed of two power supplies having different output voltages (in this embodiment, a 12 V power supply and a 5 V power supply). Also good.

  The second communication unit 22 is for performing wired communication (serial communication) with the sensor 1 (the first communication unit 14 of the sensor 1). The second communication unit 22 is configured to perform serial communication with the sensor 1 using the power supply terminal 20a as a serial signal input / output terminal. Here, the second communication unit 22 has the same configuration as the first communication unit 14, and includes a communication processing unit 22a, a clock circuit 22b, a determination circuit 22c, a switch Q20, and a resistor R20. It is configured. The determination circuit 22c is the same as the determination circuit 14c, and is determined to be at a high level if the potential of the power supply terminal 20a (equal to the potential of the power supply terminal 10a) exceeds a signal reception threshold (10 V in this embodiment). On the other hand, if it is less than or equal to the threshold for signal reception, it is determined as low level. The switch Q20 and the resistor R20 are the same as the switch Q10 and the resistor R10.

  The communication processing unit 22a is configured to perform reception processing and transmission processing similar to the communication processing unit 14a. The communication processing unit 22a is configured to acquire the clock information (phase and cycle) of the sensor 1 by measuring the synchronization bit SYNC and set the communication clock of the serial signal. For example, when the communication processing unit 22a obtains the synchronization bit SYNC, the communication processing unit 22a counts the time of the synchronization bit SYNC, and calculates the time per bit of the serial signal transmitted by the first communication unit 14 from the count result. . Then, the communication processing unit 22a performs on / off control of the switch Q20 based on the time per bit of the serial signal calculated in this way. The communication processing unit 22a is configured using a logic circuit, a microcomputer, and the like, similarly to the communication processing unit 14a.

  The second control unit 23 has a function (switching request function) for requesting the sensor 1 to switch the operation mode in response to an instruction from an input / output unit (not shown).

  Here, the input / output unit is a user interface including an input unit such as an operation button for a user to input information and an output unit such as an image display device for presenting information to the user. The input / output unit is provided integrally with the management device 2 or separately.

  When receiving an instruction from the input / output unit to set the operation mode to the normal mode, the second control unit 23 sets the output voltage of the power supply unit 21 to 5V. On the other hand, when receiving an instruction to set the operation mode to the adjustment mode, the second control unit 23 sets the output voltage of the power supply unit 21 to 12V.

  Here, in the management apparatus 2, a parallel circuit including a resistor R21 and a switch Q21 is inserted between the power supply unit 21 and the power supply terminal 20a. The switch Q21 is a switch capable of on / off control of a semiconductor switching element such as a MOSFET or a relay.

  The second control unit 23 turns on the switch Q21 when setting the output voltage of the power supply unit 21 to 5V, and turns off the switch Q21 when setting the output voltage of the supply power unit 21 to 12V. . Thereby, in the adjustment mode, the resistor R21 is inserted between the power supply unit 21 and the power supply terminal 20a. The resistor R21 is for lowering the potential of the power supply terminal 10a below the threshold for signal reception when the switches Q10 and Q20 are turned on. Therefore, when the voltage of the power supply unit 21 is 12 V, the voltage obtained by dividing the voltage of the power supply unit 21 by the resistors R10 and R21 and the voltage divided by the resistors R20 and R21 are the signals The resistance values of the resistors R10, R20, and R21 are set so as to be equal to or less than a reception threshold (10 V in this embodiment) (for example, 9 V).

  Further, the second control unit 23 functions to control the second communication unit 22 and transmit the characteristic information (correction value) input by the user using the input / output unit to the sensor 1 (characteristic information transmission function). )have. Here, the second control unit 23 transmits a correction value to the second communication unit 22 and then obtains a response from the sensor 1 (an updated correction value in the sensor 1) within a predetermined time. Then, it is determined that the correction value has been successfully updated, and the fact is notified to the user by the input / output unit. In addition, the second control unit 23 receives the response from the sensor 1 (the corrected value after the update in the sensor 1) within the predetermined time or when it is obtained or the corrected value is the sensor 1 When it does not match the correction value transmitted to, it is determined that the correction value update has failed. In this case, the second control unit 23 notifies the user that the correction value update has failed by the input / output unit.

  In addition, the second control unit 23 outputs the detection output input to the input terminal 20b to the input / output unit and causes the input / output unit to display the detection output of the sensor 1 (detection output display function). have. However, the operation by the detection output display function (the operation for displaying the detection output of the sensor 1 on the input / output unit) is performed only in the normal mode and not in the adjustment mode. In addition, the second control unit 23 has a function of executing various controls according to the detection output input to the input terminal 20b.

  Hereinafter, the operation of the physical quantity detection system of this embodiment will be described with reference to FIG. Note that FIG. 2 shows the time change of the potential of the power supply terminal 10a.

  First, it is assumed that the sensor 1 is in the normal mode in the initial state (before time T1 in FIG. 2). In this initial state, the second control unit 23 of the management device 2 sets the output voltage of the power supply unit 21 to 5 V and turns on the switch Q21. Since the operation mode of the sensor 1 is the normal mode, the sensor 1 uses the detection output (corrected detection output) obtained by correcting the detection output of the detection unit 11 with the correction value stored in the storage unit 12. Output to the output terminal 10b. The corrected detection output output to the output terminal 10b is input to the input terminal 20b, sent to the input / output unit by the second control unit 23, and presented to the user.

  On the other hand, when the adjustment mode is selected by the input / output unit, the second control unit 23 sets the output voltage of the power supply unit 21 to 12 V and turns off the switch Q21 (time T1). In this case, a potential of 12 V is applied to the power supply terminal 10a of the sensor 1. More precisely, it is a potential obtained by subtracting the voltage drop of the resistor R21 due to the consumption current of the sensor 1 from the power supply terminal 10a. However, in the following description, the current consumption is ignored for the sake of simplicity.

  In this case, the determination unit 15 determines that the management device 2 requests the adjustment mode. As a result, the first control unit 16 sets the operation mode to the adjustment mode. Therefore, the first communication unit 14 is driven, and serial communication with the management apparatus 2 becomes possible. At this time, the first communication unit 14 transmits the synchronization bit SYNC by setting the potential of the power supply terminal 10a to 9 V for a predetermined time (time t10 to t11) according to the clock timing of the clock circuit 14b. . The second communication unit 22 of the management device 2 acquires the clock information (phase, cycle) of the sensor 1 by measuring the synchronization bit SYNC, and thereby sets the communication clock of the serial signal.

  When the user inputs a correction value using the input / output unit, the second control unit 23 controls the second communication unit 22 to transmit the input correction value to the sensor 1. . The second communication unit 22 sets the potential of the power supply terminal 10a to 12V or 9V by controlling the switch Q20 as described above, thereby transmitting a serial signal. For example, the correction value data transmitted by the serial signal is 3-byte data, of which 2 bytes indicate the correction value (each 1-byte offset value and gain value), and the remaining 1 byte indicates the product ID of the sensor 1. Yes. When transmitting the serial signal, the second communication unit 22 transmits the start bit STB1 by setting the potential of the power supply terminal 10a to 9 V for a predetermined time (time t12 to t13), and then the correction value. The bit string DB1 indicating data is transmitted. The second communication unit 22 transmits a stop bit (not shown) after the transmission of the bit string DB1 to notify the sensor 1 that the transmission has been completed.

  When the first control unit 16 receives the serial signal by the first communication unit 14, the first control unit 16 checks whether the product ID of the correction value data is the same as its own ID. If the IDs are the same, the first control unit 16 rewrites the correction value in the storage unit 12 to the correction value (offset value and gain value) indicated by the correction value data. If the IDs are not the same, the correction value data is discarded.

  When the rewriting is completed, the first control unit 16 controls the first communication unit 14 to cause the management device 2 to transmit response data indicating the correction value of the storage unit 12 after the rewriting. This response data is 3-byte data, similar to the correction value data, of which 2 bytes are the correction value (each 1-byte offset value and gain value), and the remaining 1 byte is the product ID of the sensor 1. When transmitting the serial signal, the first communication unit 14 transmits the start bit STB2 by setting the potential of the power supply terminal 10a to 9 V for a predetermined time (time t3 to t4), and thereafter the response data. The bit string DB2 indicating is transmitted. The first communication unit 14 transmits a stop bit (not shown) after transmitting the bit string DB2 to notify the sensor 1 that the transmission is finished.

  When the second control unit 23 receives the serial signal at the second communication unit 22, it determines whether the correction value and product ID included in the response data are equal to the correction value and product ID included in the correction value data. Check. As a result of the confirmation, the second control unit 23 determines that the update of the correction value has succeeded if they are equal, and determines that the update of the correction value has failed if they are not equal. The result of the confirmation is notified to the user by the input / output unit.

  Thereafter, when the normal mode is selected by the input / output unit, the second control unit 23 sets the output voltage of the power supply unit 21 to 5 V and turns on the switch Q21 (time T2). In this case, a potential of 5 V is applied to the power supply terminal 10a of the sensor 1. Therefore, the determination unit 15 determines that the management device 2 requests the normal mode. As a result, the first control unit 16 sets the operation mode to the normal mode.

  According to the physical quantity detection system of the present embodiment described above, since the operation mode requested by the management device 2 is determined based on the potential of the power supply terminal 10a, the shift to the adjustment mode can be performed without increasing the number of terminals. Yes. In the adjustment mode, the power supply line L1 to the sensor 1 can also be used as a communication line. Therefore, it is not necessary to provide the management device 2 with a communication device (second communication unit 22) in a one-to-one correspondence with the sensor 1, and it is possible to communicate with a plurality of sensors 1 with one communication device. Therefore, the configuration of the management device 2 can be simplified and the wiring can be reduced, and the configuration of the entire system can be simplified. Further, since the power supply terminal 10a is generally often grounded by the bypass capacitor C, the influence of high frequency noise can be reduced as compared with the case where communication is performed by the output terminal 10b.

  In the physical quantity detection system according to the present embodiment, the first communication unit 14 performs a process of synchronizing with the management apparatus 2 by transmitting a synchronization bit SYNC when starting serial communication with the management apparatus 2. To do. Therefore, the communication accuracy of serial communication can be improved.

  In particular, since the synchronization signal is transmitted from the sensor 1 to the management device 2, the clock circuit 22b of the management device 2 can be matched with the clock circuit 14b of the sensor 1. Therefore, it is possible to use a clock circuit 14b provided in the sensor 1 having a relatively low accuracy. As a result, the cost and size of the sensor 1 can be reduced. In the above example, the first communication unit 14 of the sensor 1 outputs the synchronization signal SYNC. However, the second communication unit 22 of the management device 2 may output the synchronization signal SYNC. That is, when starting serial communication, one of the first communication unit 14 and the second communication unit 22 is synchronized with the other of the first communication unit 14 and the second communication unit 22. The SYNC is output, and the communication clock may be set based on the length of the synchronization signal SYNC that the other receives from the one.

  By the way, the determination unit 15 in the above example requests the management device 2 depending on whether or not the potential of the power supply terminal 10a satisfies a predetermined condition, that is, whether or not the potential of the power supply terminal 10a is higher than 10V. The operation mode is determined. Not limited to this example, the determination unit 15 determines whether the potential of the power supply terminal 10a has changed in a predetermined pattern (for example, whether the potential has changed a predetermined number of times at a predetermined frequency), that is, the operation mode depending on the time change of the potential. It may be determined. As described above, the determination unit 15 may be any device that determines the operation mode based on the potential waveform of the power supply terminal 10a.

  In addition, the determination unit 15 does not determine the operation mode when the potential of the power supply terminal 10a satisfies a predetermined condition, but the period during which the potential of the power supply terminal 10a satisfies the predetermined condition continues for a predetermined time. It may be configured to confirm the determination of the operation mode when the operation is performed. In this way, it is possible to prevent the operation mode from being unexpectedly changed due to the influence of noise or the like, and it is possible to more accurately determine the operation mode.

  Further, in the above example, the determination unit 15 determines the operation mode requested by the management device 2 depending on whether or not the potential of the power supply terminal 10a is higher than the normal potential (5 V in this embodiment) by a predetermined value or more. Is determined. On the other hand, the determination unit 15 determines the operation mode requested by the management device 2 based on whether or not the potential of the power supply terminal 10a is lower than the normal potential (5V in this embodiment) by a predetermined value or more. It may be configured to. In this case, unlike the case where the potential of the power supply terminal 10a is increased (increased from 5V to 12V) in the adjustment mode, an electrical component that can withstand a potential (12V) higher than the normal potential (5V), that is, a high breakdown voltage. Therefore, it is not necessary to use an electrical component or the like having high performance, so that downsizing and cost reduction can be achieved.

  By the way, the determination unit 15 may be configured to determine the operation mode requested by the management device 2 based on the potential of the output terminal 10b instead of the power supply terminal 10a.

  Further, the determination unit 15 may be configured to determine the operation mode requested by the management device 2 depending on whether or not the potentials of the power supply terminal 10a and the output terminal 10b satisfy a predetermined condition. . In this way, the operation mode shifts from the normal mode to the adjustment mode only when the potential of the power supply terminal 10a is different from that in the normal mode and the potential of the output terminal 10b is different from that in the normal mode. . Therefore, the probability of occurrence of an operation mode determination error can be reduced as compared with the case where the operation mode is determined using only the power supply terminal 10a or the case where the operation mode is determined using only the output terminal 10b. Therefore, it is possible to prevent the operation mode from being changed unexpectedly.

  In the present embodiment, the communication destination sensor 1 is specified using the product ID. Here, as a method of selecting the sensor 1 that communicates with the management device 2, it is conceivable to use the output terminal 10 b of the sensor 1. That is, the sensor 1 is provided with means for detecting the potential of the output terminal 10b, and the management device 2 sets the potential of the output terminal 10b to a predetermined threshold (for example, short-circuits the output terminal 10b), thereby communicating with the sensor 1. You can be notified that you are selected as a partner.

(Embodiment 2)
In the physical quantity detection system of the present embodiment, the second communication unit 22 is different from that of the first embodiment. In addition, since the other structure in the physical quantity detection system of this embodiment is the same as that of Embodiment 1, the same code | symbol is attached | subjected about the same structure and illustration and description are abbreviate | omitted.

  In the second communication unit 22 in the present embodiment, the operation of the communication processing unit 22a is different from that in the first embodiment. The communication processing unit 22a in the present embodiment sets a communication clock based on the synchronization bit SYNC obtained from the sensor 1 as in the first embodiment. Here, in the first embodiment, the communication clock once set is used as it is, but the communication processing unit 22a in the present embodiment receives the serial signal of the first communication unit 14 at the start of the reception of the serial signal. Then, the phase of the communication clock is reset (that is, the phase is equal to the initial phase of the communication clock of the sensor 1).

  Hereinafter, the operation of the second communication unit 22 in the present embodiment will be described with reference to FIG.

  Here, FIG. 3A shows a communication clock of the first communication unit 14. FIG. 3B shows a serial signal transmitted by the first communication unit 14. In this example, the communication processing unit 14a of the first communication unit 14 changes t20, t21, t22, t23, t24, t25... At the rising edge of the communication clock (when changing from low level to high level). The level / low level switching timing is set, and a serial signal of a bit string “010010...” Is transmitted from time t20. Here, the first “0” bit of the serial signal is a start bit. FIG. 3C shows the potential of the power supply terminal 10a. In FIG. 3C, the potential of the power supply terminal 10a is dull because the rise and fall are delayed because the bypass capacitor C is connected as described above.

  FIG. 3D shows the waveform of the communication clock of the second communication unit 22. The communication processing unit 22a determines the high level / low level of the serial signal when the communication clock is at the low level. In the communication processing unit 22a according to the present embodiment, the potential of the power supply terminal 10a (that is, the potential of the power supply terminal 20a) is equal to or lower than the threshold for signal reception (Vth in FIG. 3C) and is determined to be low level by the determination circuit 22c. At this time, the phase of the communication clock is reset (time t30). Note that, once the communication processing unit 22a resets the phase of the communication clock, the communication processing unit 22a does not reset until the serial communication is completed (stop bit is received).

  As described above, the communication processing unit 22a in the present embodiment detects the falling edge of the start bit and resets the phase of the communication clock. In FIG. 3D, the broken line indicates the waveform of the communication clock whose phase is not reset, and the solid line indicates the waveform of the communication clock whose phase is reset.

  Here, the phase of the communication clock of the management device 2 (the communication clock of the management device 2 before time t30) before the phase is reset is significantly different from the phase of the communication clock of the sensor 1 (in the illustrated example, a half cycle). It ’s out of place.) This is due to the measurement error of the synchronization bit SYNC time by the management device 2. That is, the period of the communication clock differs slightly between the sensor 1 and the management device 2 due to the measurement error, and as a result, the phase shift increases or decreases with time. For this reason, when the phase shift is large, as shown in FIG. 3D, the phase may be shifted by nearly a half cycle. In such a case, the serial signal cannot be correctly received.

  Here, when receiving the serial signal (start bit) of the first communication unit 14, the communication processing unit 22 a in this embodiment resets the phase of the communication clock. Therefore, as shown by a broken line in FIG. 3D, even if the phase of the communication clock of the management device 2 is greatly deviated from the phase of the communication clock of the sensor 1, the phase difference can be made sufficiently small. Become.

  As described above, according to the physical quantity detection system of this embodiment, the phase shift between the communication clock of the sensor 1 and the communication clock of the management device 2 due to the measurement error of the length of the synchronization signal (synchronization bit SYNC) is reduced. can do. Therefore, the phase difference between the communication clock of the sensor 1 and the communication clock of the management device 2, that is, the time t20, t21, t22, t23, t24, t25. It is possible to suppress the time difference from time t30, t31, t32, t33, t34, t35. Therefore, highly accurate serial communication can be performed in the adjustment mode.

  By the way, as shown in FIG. 3C, the potential waveform of the power supply terminal 10a often becomes dull. In such a case, for example, the period during which the potential of the power supply terminal 10 is lower than the signal reception threshold Vth is shorter than one cycle of the communication clock of the management apparatus 2 and the start bit may not be recognized. In consideration of this point, the communication processing unit 22a detects the falling edge of the start bit and resets the communication clock, so that the reception of the serial signal can be reliably detected.

  In addition, once the synchronization bit SYNC is received from the sensor 1, communication clocks are not generated, and thereafter the communication clock phase is reset every time serial reception is performed, thereby enabling highly accurate communication. Therefore, it is not necessary to perform synchronization processing with the sensor 1 every time serial communication with the sensor 1 is started, and the efficiency of communication processing can be improved.

  Note that it is preferable to use a clock circuit 22b in the present embodiment having a frequency sufficiently higher than the frequency of the communication clock of the sensor 1. For example, when the communication clock is generated by the management device 2, the necessary number of clock pulses of the high-frequency clock circuit 22b may be integrated to generate a communication clock closest to the measured communication clock of the sensor 1.

(Embodiment 3)
The physical quantity detection system according to the present embodiment includes the sensor 1 and the management device 2 as in the first embodiment. However, as illustrated in FIG. 4, the clock signal output unit 18 that outputs a clock signal includes the sensor 1. The point provided for is greatly different from the first embodiment. Note that the physical quantity detection system of the present embodiment is also used for electrical control in the engine operation of an automobile by the ECU, for example, as in the first embodiment.

  The management device 2 in this embodiment includes a power supply unit 21, a second communication unit 22, and a second control unit 23.

  The power supply unit 21 in the present embodiment includes a first power supply unit 21a and a second power supply unit 21b. The first power supply unit 21a and the second power supply unit 21b are DC power supplies having different output voltages. The first power supply unit 21a is a power supply for a normal mode, and the second power supply unit 21b is a power supply for an adjustment mode. In the present embodiment, the output voltage of the first power supply unit 21a is set to 5V, and the output voltage of the second power supply unit 21b is set to 12V.

  In the present embodiment, the second control unit 23 has a function as the communication processing unit 22 a of the second communication unit 22. For this reason, the second communication unit 22 in the present embodiment includes a second control unit 23, a determination circuit 22c, two switches Q22 and Q23, and a resistor R22. The switch Q22 is an n-channel MOSFET, and is inserted between the power supply terminal 20a and the ground, and the resistor R22 is inserted between the switch Q22 and the power supply terminal 20a. The switch Q23 is a p-channel MOSFET, and is inserted between the power supply terminal 20a and the second power supply unit 21b.

  The second control unit 23 in the present embodiment performs reception processing and transmission processing similar to the communication processing unit 22a. However, in the transmission process, the second control unit 23 in the present embodiment sets the serial signal to a high level by turning off the switch Q22 and turning on the switch Q23. In this case, since the second power supply unit 21b is connected to the power feeding terminal 20a by the switch Q23, the high-level potential of the serial signal is 12V. The second control unit 23 turns on the switch Q22 and turns off the switch Q23, thereby setting the serial signal to a low level. In this case, the low-level potential of the serial signal is a value obtained by lowering the potential of the output terminal 10b by a voltage drop circuit 14d described later (9.9 V in this embodiment). Note that the second control unit 23 sets both the switches Q22 and Q23 to OFF in the idle state (waiting to receive a serial signal from the sensor 1).

  Further, the second control unit 23 in the present embodiment has a function of requesting the sensor 1 to switch the operation mode, as in the first embodiment.

  Here, the first power supply unit 21a is connected to the power supply terminal 20a via the switch Q24. The second power supply unit 21b is connected to the input terminal 20b via the switch Q25. Further, the second power supply unit 21b is connected to the power supply terminal 20a via the switch Q26 and the resistor R26, and to the input terminal 20a via the switch Q27 and the resistor R27. All the switches Q24 to Q27 are p-channel MOSFETs.

  When the second control unit 23 in this embodiment receives an instruction from the input / output unit to set the operation mode to the normal mode, the second control unit 23 sets the switch Q24 on and the switches Q25 to Q27 off. In this case, the potential of the power supply terminal 20a is 5V. Further, when receiving an instruction to set the operation mode to the adjustment mode, the second control unit 23 sets the switches Q25 to Q27 to be on and the switch Q24 to be off. In this case, the potential of the power supply terminal 20a is 12V (more precisely, a potential obtained by subtracting the voltage drop of the resistor R26 due to the consumption current of the sensor 1 from 12V. However, in the following description, for the sake of simplicity, the consumption current is And the potential of the input terminal 20b is 12V.

  As described above, when the management device 2 in this embodiment requests the sensor 1 to shift to the adjustment mode, the potentials of both the power supply terminal 10a and the output terminal 10b are set higher than those in the normal mode (in this embodiment). Set to 12V).

  In addition, after requesting switching to the adjustment mode, the second control unit 23 in the present embodiment sets the switch Q25 to OFF and waits for a clock signal from the clock signal output unit 18. When the second control unit 23 obtains the clock signal from the clock signal output unit 18, the second control unit 23 sets a communication clock based on the cycle and phase of the clock signal. Then, the second control unit 23 performs serial communication based on the communication clock using the power supply terminal 20a as an input / output terminal for a serial signal.

  The sensor 1 in this embodiment includes the clock signal output unit 18 as described above. Moreover, in the sensor 1 in this embodiment, the 1st communication part 14 and the discrimination | determination part 15 differ from Embodiment 1. FIG. In addition, since the other structure of the sensor 1 in this embodiment is the same as that of Embodiment 1, detailed description is abbreviate | omitted.

  The first communication unit 14 in this embodiment includes a communication processing unit 14a, a determination circuit 14c, switches Q11 and Q12, a resistor R11, and a voltage drop circuit 14d. Note that the determination circuit 14c is the same as that of the first embodiment, and thus the description thereof is omitted.

  The switch Q11 is an n-channel MOSFET, and is inserted between the power supply terminal 10a and the ground. The resistor R11 is inserted between the switch Q11 and the power supply terminal 10a. The switch Q12 is a p-channel MOSFET, and is inserted between the power supply terminal 10a and the output terminal 10b.

  The voltage drop circuit 14 d is for defining a low-level potential of the serial signal transmitted to the management device 2. This voltage drop circuit 14d has a series of a plurality of diodes D inserted between the output terminal 10b and the power supply terminal 10a, with the anode connected to the output terminal 10b and the cathode connected to the power supply terminal 10a. Circuit. In the present embodiment, the number of diodes D is three, and the diode D having a voltage drop of 0.7 V is used. Therefore, the voltage drop circuit 14d lowers the cathode side potential by 2.1V with respect to the anode side. The voltage drop circuit 14d may be composed of a single diode D, but the use of a plurality of diodes D makes it easier to set the low-level potential of the serial signal. The diode D also serves to protect the output terminal 10b from static electricity and surge in the normal mode.

  The communication processing unit 14a in the present embodiment performs reception processing and transmission processing in the same manner as described in the first embodiment. However, in the transmission processing, the communication processing unit 14a in the present embodiment sets the serial signal to a high level by turning off the switch Q11 and turning on the switch Q12. In this case, since the output terminal 10b and the power supply terminal 10a are short-circuited by the switch Q12, the high-level potential of the serial signal is 12V. Further, the communication processing unit 14a turns on the switch Q11 and turns off the switch Q12, thereby setting the serial signal to a low level. In this case, since the power supply terminal 10a is grounded via the resistor R11 and the switch Q11, the low-level potential of the serial signal is a value obtained by reducing the potential of the output terminal 10b by the voltage drop circuit 14d (in this embodiment). 9.9V). Note that the communication processing unit 14a sets both the switches Q11 and Q12 to OFF in the idle state (waiting to receive a serial signal from the management device 2).

  Thus, in the first communication unit 14 in the present embodiment, the communication processing unit 14a and the determination circuit 14c constitute a reception unit that receives a serial signal input to the power supply terminal 10a. The communication processing unit 14a, the switches Q11 and Q12, and the voltage drop circuit 14d constitute a transmission unit that outputs a serial signal to the power supply terminal 10a.

  The determination unit 15 in the present embodiment includes a first voltage detection unit (not shown), a second voltage detection unit (not shown), and an AND circuit (not shown).

  The first voltage detection unit is an overvoltage detection circuit that detects whether or not the potential of the power supply terminal 10a exceeds a predetermined voltage. The first voltage detector outputs a high level signal to the AND circuit if the detected potential of the power supply terminal 10a exceeds 6V, and a low level signal if it is 6V or less. On the other hand, the second voltage detection unit is an overvoltage detection circuit that detects whether or not the potential of the output terminal 10b exceeds a predetermined voltage. The second voltage detector outputs a high level signal to the AND circuit if the detected potential of the output terminal 10b exceeds 6V, and a low level signal if it is 6V or less. Since the first voltage detection unit and the second voltage detection unit can be realized using a comparator or the like, detailed description thereof will be omitted.

  The AND circuit is an AND circuit. Therefore, the AND circuit outputs a high-level signal to the first control unit 16 when both the signals output from the first voltage detection unit and the second voltage detection unit are both at a high level. If one of them is low level, a low level signal is output to the first controller 16.

  That is, the determination unit 15 according to the present embodiment determines the operation mode requested by the management device 2 based on whether or not the potentials of the power supply terminal 10a and the output terminal 10b satisfy a predetermined condition. Therefore, the probability of occurrence of an operation mode determination error can be reduced as compared with the case where the operation mode is determined using only one of the power supply terminal 10a and the output terminal 10b. Therefore, it is possible to prevent the operation mode from being changed unexpectedly.

  The first control unit 16 in this embodiment sets the operation mode to the adjustment mode when receiving a high level signal from the AND circuit of the determination unit 15 and sets the operation mode to the normal mode when receiving a low level signal. To do.

  The clock signal output unit 18 includes a clock control unit 18a, a switch Q13, and a resistor R13. The switch Q13 is an n-channel MOSFET, and is inserted between the output terminal 10b and the ground, and the resistor R13 is inserted between the switch Q13 and the output terminal 10b.

  When the operation mode of the sensor 1 is the adjustment mode, the clock control unit 18a outputs a clock signal (first clock signal) to the output terminal 10b. The first clock signal is generated when the clock controller 18a alternately switches on / off the switch Q13 at a predetermined cycle based on a clock of a built-in clock circuit (not shown). In the adjustment mode, the clock control unit 18a outputs a clock signal (second clock signal) having the same period and phase as the first clock signal to the communication processing unit 14a.

  Note that the clock control unit 18a does not output a clock signal when the operation mode of the sensor 1 is the normal mode. At this time, the switch Q13 is set to OFF, whereby the detection output of the sensor 1 is output from the output terminal 10b.

  When transmitting the serial signal, the communication processing unit 14a according to the present embodiment serially transmits a period from when the second clock signal falls (when switching from the high level to the low level) until the next falling time. A 1-bit period of the signal is used. Then, the communication processing unit 14a controls the switches Q11 and Q12 so that the serial signal is at the high level or the low level during the period in which the second clock signal is at the high level. Also, when receiving the serial signal, the communication processing unit 14a determines the period from the falling edge of the second clock signal (when switching from the high level to the low level) to the next falling edge of the serial signal. The period is 1 bit. Then, the communication processing unit 14a obtains the bit value of the serial signal based on the determination result of the determination circuit 14c when the second clock signal rises during the period.

  In this way, the first communication unit 14 receives the serial signal input to the power supply terminal 10a in synchronization with the clock signal (second clock signal) obtained from the clock signal output unit 18, and supplies the signal to the power supply terminal 10a. (Serial communication is performed using the power supply terminal 10a as an input / output terminal for a serial signal).

  Hereinafter, the operation of the physical quantity detection system of the present embodiment will be described. First, it is assumed that the sensor 1 is in the normal mode in the initial state. In this initial state, the second control unit 23 of the management device 2 sets the switch Q24 on and the switches Q22, Q23, Q25, Q26, Q27 off. In this case, a potential of 5 V is applied to the power supply terminal 10a of the sensor 1. Since the operation mode of the sensor 1 is the normal mode, the sensor 1 uses the detection output (corrected detection output) obtained by correcting the detection output of the detection unit 11 with the correction value stored in the storage unit 12. Output to the output terminal 10b. The corrected detection output output to the output terminal 10b is input to the input terminal 20b, sent to the input / output unit by the second control unit 23, and presented to the user.

  On the other hand, when the adjustment mode is selected by the input / output unit, the second control unit 23 turns on the switches Q25 to Q27 and turns off the switches Q22, Q23, and Q27. In this case, a potential of 12 V is applied to each of the power supply terminal 10a and the output terminal 10b of the sensor 1. More precisely, the power supply terminal 10a has a potential obtained by subtracting the voltage drop of the resistor R26 due to the consumption current of the sensor 1 from 12V. However, in the following description, the current consumption is ignored for the sake of simplicity.

  For this reason, both the first voltage detection unit and the second voltage detection unit of the determination unit 15 output a high level signal, whereby a high level signal is output from the determination unit 15. As a result, the first control unit 16 sets the operation mode to the adjustment mode. Therefore, the first communication unit 14 is driven, and serial communication with the management apparatus 2 becomes possible. When the operation mode is set to the adjustment mode, the clock control unit 18a of the clock signal output unit 18 starts operation, and the second clock signal is input to the communication processing unit 14a.

  The second control unit 23 sets the switch Q25 to OFF at a predetermined timing after requesting the adjustment mode. When the switch Q25 is off, the resistor R27 is inserted between the second power supply unit 21b and the input terminal 20b. Therefore, the potential of the input terminal 20b is changed by turning on / off the switch Q13 of the clock signal output unit 18. That is, the second control unit 23 obtains the first clock signal from the clock signal output unit 18 of the sensor 1 by setting the switch Q25 to OFF. Note that the timing at which the second control unit 23 sets the switch Q25 to be off (that is, the timing at which the first clock signal is received) is a predetermined number of times (for example, five times) for serial signal transmission / reception. A suitable timing can be set every time.

  When the user inputs a correction value using the input / output unit, the second control unit 23 transmits the input correction value. At this time, the second control unit 23 sets a communication clock based on the first clock signal and transmits / receives a serial signal.

  When the first communication unit 14 receives the serial signal, the first control unit 16 rewrites the correction value in the storage unit 12 with the correction value received from the management device 2. When the rewriting is completed, the first control unit 16 controls the first communication unit 14 to transmit the correction value of the storage unit 12 after the rewriting to the management device 2.

  The second control unit 23 checks whether or not the correction value received from the sensor 1 is equal to the correction value transmitted to the sensor 1, and if equal, determines that the correction value has been successfully updated. It is determined that the correction value update has failed. The determination result is notified to the user by the input / output unit.

  Thereafter, when the normal mode is selected by the input / output unit, the second control unit 23 turns on the switch Q24 and turns off the switches Q22, Q23, Q25, Q26, and Q27. In this case, a potential of 5V is applied to the power supply terminal 10a of the sensor 1, and as a result, the operation mode of the first control unit 16 of the sensor 1 is set to the normal mode.

  In the sensor 1 of the present embodiment described above, the sensor 1 transmits the first clock signal to the management device 2 in the adjustment mode. The management device 2 can synchronize with the sensor 1 by receiving the first clock signal from the sensor 1. Therefore, the communication accuracy of serial communication can be improved. Further, according to the physical quantity detection system of the present embodiment, as in the first embodiment, the shift to the adjustment mode can be performed without increasing the number of terminals. Furthermore, in the adjustment mode, since the power supply line L1 to the sensor 1 can be used as a communication line, it is possible to communicate with a plurality of sensors 1 with one communication device. Therefore, the configuration of the management device 2 can be simplified and the wiring can be reduced, and the configuration of the entire system can be simplified.

  The switches Q11 to Q13 and Q22 to Q27 described above are not limited to semiconductor switching elements such as MOSFETs, but may be switches that can be turned on / off, such as relays.

(Embodiment 4)
In the physical quantity detection system of the present embodiment, the management device 2 is mainly different from the third embodiment.

  As shown in FIG. 5, the management device 2 in the present embodiment includes a power supply unit 21, a second communication unit 22, a second control unit 23, and a potential holding unit 24.

  The power supply unit 21 in the present embodiment includes a first power supply unit 21a and a second power supply unit 21b, as in the third embodiment. Here, as in the third embodiment, the first power supply unit 21a is connected to the power supply terminal 20a through the switch Q24, and the second power supply unit 21b is connected to the power supply terminal 20a through the switch Q26 and the resistor R26. Has been.

  The potential holding unit 24 includes an operational amplifier OP, a switch Q28 made of an n-channel MOSFET, a resistor R28, and a power supply unit 24a. The non-inverting input terminal of the operational amplifier OP is connected to the second power supply unit 21b, the inverting input terminal is connected to the source of the switch Q28, and the output terminal is connected to the gate of the switch Q28. The source of the switch Q28 is connected to the input terminal 20b via the switch Q25. On the other hand, the drain of the switch Q28 is connected to the power supply unit 24a via the resistor R28. The output voltage of the power supply unit 24a is set higher than the output voltage of the second power supply unit 21b (15 V in this embodiment). According to the potential holding unit 24, the potential of the switch Q28, that is, the potential of the input terminal 20b is maintained at a constant value, that is, a value equal to the output voltage of the second power supply unit 21b by the negative feedback of the operational amplifier OP.

  Therefore, in the present embodiment, the potential of the input terminal 20b is maintained at 12V without depending on on / off of the switch Q13 of the clock signal output unit 18. Instead, the magnitude of the current flowing through the switch Q28 changes according to whether the switch Q13 is on or off. Therefore, in the present embodiment, the first clock signal output from the clock signal output unit 18 to the input terminal 20b is not a signal whose potential changes with time, but a signal whose current size changes (current clock). Signal).

  As in the third embodiment, the second control unit 23 in the present embodiment has a function of requesting the sensor 1 to switch the operation mode. When receiving an instruction from the input / output unit to set the operation mode to the normal mode, the second control unit 23 sets the switch Q24 on and the switches Q25 and Q26 off. In this case, the potential of the power supply terminal 20a is 5V. In addition, when receiving an instruction to set the operation mode to the adjustment mode, the second control unit 23 sets the switches Q25 and Q26 on and the switch Q24 off. In this case, the potential of the power supply terminal 20a is 12V (more precisely, a potential obtained by subtracting the voltage drop of the resistor R26 due to the consumption current of the sensor 1 from 12V. However, in the following description, for the sake of simplicity, the consumption current Will be explained). Further, since the input terminal 20b is connected to the source of the switch Q28 via the switch Q25, its potential is 12V. In FIG. 5, connection lines (connection lines for detection output) between the input terminal 20b and the second control unit 23 are not shown.

  Also in this embodiment, the second control unit 23 has a function as the communication processing unit 22 a of the second communication unit 22. Therefore, the second communication unit 22 in the present embodiment is also configured with a second control unit 23, a determination circuit 22c, two switches Q22 and Q23, and a resistor R22, as in the third embodiment. .

  As in the third embodiment, the second control unit 23 in the present embodiment performs serial signal transmission by performing on / off control of the switches Q22 and Q23. The second control unit 23 in the present embodiment detects the magnitude of the current (drain-source current) flowing through the switch Q28, and thereby obtains the first clock signal. The second control unit 23 transmits / receives a serial signal in synchronization with the first clock signal.

  For example, when the second control unit 23 transmits a serial signal, the second control unit 23 determines a period from when the first clock signal falls (when switching from the high level to the low level) to the next falling time. A 1-bit period of the signal is used. Then, the second control unit 23 controls the switches Q22 and Q23 so that the serial signal is at the high level or the low level during the period in which the first clock signal is at the high level. Also, when receiving the serial signal, the second control unit 23 determines the period from when the first clock signal falls (when switching from the high level to the low level) to the next falling time. A 1-bit period of the signal is used. Then, the second control unit 23 obtains the bit value of the serial signal based on the determination result of the determination circuit 22c at the rising edge of the first clock signal in the period.

  As described above, the second control unit 23 receives the serial signal input to the power supply terminal 20a in synchronization with the clock signal (first clock signal) obtained from the clock signal output unit 18, and supplies the serial signal to the power supply terminal 20a. The serial signal is output (serial communication is performed using the power supply terminal 20a as the serial signal input / output terminal).

  Hereinafter, the operation of the physical quantity detection system of the present embodiment will be described. First, it is assumed that the sensor 1 is in the normal mode in the initial state. In this initial state, the second control unit 23 of the management device 2 sets the switch Q24 to ON, switches Q22, Q23, Q25, and Q26 to OFF, and a potential of 5 V is applied to the power supply terminal 10a. Further, since the sensor 1 is in the normal mode, the detection output (corrected detection output) obtained by correcting the detection output of the detection unit 11 with the correction value stored in the storage unit 12 is output to the output terminal 10b. Output. The corrected detection output output to the output terminal 10b is input to the input terminal 20b, sent to the input / output unit by the second control unit 23, and presented to the user.

  On the other hand, when the adjustment mode is selected by the input / output unit, the second control unit 23 sets the switches Q25 and Q26 on and the switch Q24 off. In this case, the electric potentials of the power supply terminal 20a and the input terminal 20b are each 12V.

  In this case, the determination unit 15 outputs a high level signal from both the first voltage detection unit and the second voltage detection unit. Therefore, the signal output from the determination unit 15 is also at a high level. As a result, the first control unit 16 sets the operation mode to the adjustment mode. Therefore, the first communication unit 14 is driven, and serial communication with the management apparatus 2 becomes possible.

  Further, when the operation mode is set to the adjustment mode, the clock signal output unit 18 starts operation. As a result, the second clock signal is output to the communication processing unit 14a of the first communication unit 14. A first clock signal is output to the input terminal 20b.

  When the user inputs a correction value using the input / output unit, the second control unit 23 transmits the input correction value to the sensor 1. As described above, the second control unit 23 performs serial signal transmission by performing on / off control of the switches Q22 and Q23 in synchronization with the first clock signal.

  As described above, the first communication unit 14 receives the serial signal in synchronization with the second clock signal. When the first communication unit 14 receives the serial signal, the first control unit 16 rewrites the correction value in the storage unit 12 with the correction value received from the management device 2. When the rewriting is completed, the first control unit 16 controls the first communication unit 14 and transmits the corrected value after the rewriting to the management device 2. As described above, the first communication unit 14 performs serial signal transmission by performing on / off control of the switches Q11 and Q12 in synchronization with the second clock signal.

  As described above, the second control unit 23 receives the serial signal in synchronization with the first clock signal. When the second control unit 23 receives the serial signal, the second control unit 23 checks whether the correction value received from the sensor 1 is equal to the correction value transmitted to the sensor 1, and if equal, determines that the correction value has been successfully updated. If they are not equal, it is determined that the update of the correction value has failed. The determination result is notified to the user by the input / output unit.

  Thereafter, when the normal mode is selected by the input / output unit, the second control unit 23 sets the switch Q24 on and the switches Q22, Q23, Q25, Q26 off. In this case, a potential of 5 V is applied to the power supply terminal 10a of the sensor 1. Therefore, the signal of the first voltage detection unit of the determination unit 15 becomes a low level, and a low level signal is output from the determination unit 15. As a result, the first control unit 16 sets the operation mode to the normal mode. As a result, the clock signal output unit 18 stops operating (the switch Q13 is set to OFF).

  As described above, according to the physical quantity detection system of this embodiment, the second communication unit 22 receives the clock signal (first clock signal) of the clock signal output unit 18 that is input to the input terminal 20b through the output terminal 10b. The serial signal is transmitted / received through the power supply terminal 20a in synchronization with (). The first communication unit 14 transmits / receives a serial signal through the power supply terminal 10 a in synchronization with the clock signal (second clock signal) obtained from the clock signal output unit 18. Therefore, unlike the case of using a synchronization bit, the influence of measurement errors and various disturbances can be eliminated, and the communication accuracy of serial communication in the adjustment mode can be improved.

  In addition, since it is not necessary to perform a synchronization process using a synchronization bit, the time required for such a process can be saved. Therefore, the efficiency of serial communication can be improved (the amount of data that can be transmitted per unit time can be increased). In addition, a clock signal is transmitted from the management device 2 to the sensor 1 to be communicated. For this reason, it is not necessary to identify the sensor 1 to be communicated by adding an ID or the like to the serial signal, and a bit string for the ID or the like becomes unnecessary. Therefore, the efficiency of serial communication can be improved.

  By the way, in the sensor 1 in the present embodiment, when the potential of the output terminal 10b changes during the adjustment mode, the potential of the power supply terminal 10a also changes. Therefore, when the potential of the output terminal 10b changes due to the on / off of the switch Q13, the potential of the power supply terminal 10a also changes. Furthermore, since the bypass capacitor C is connected to the power supply terminal 10a, the potential waveform of the power supply terminal 10a becomes dull. Therefore, the serial signal cannot be received accurately unless a configuration for preventing these effects is added to the determination circuit 14c.

  However, the management device 2 in this embodiment includes a potential holding unit 28 that keeps the potential of the input terminal 20b constant when a current clock signal is input. Therefore, it is possible to prevent the occurrence of the above-described problem due to the fluctuation of the potential of the input terminal 20b during the adjustment mode.

  Moreover, according to the physical quantity detection system of the present embodiment, the following effects can be obtained. That is, according to the physical quantity detection system of the present embodiment, since the operation mode requested by the management device 2 is determined based on the potentials of the power supply terminal 10a and the output terminal 10b, the number of terminals of the terminal unit 10 is increased. It is possible to switch to the adjustment mode without any changes. Furthermore, in the adjustment mode, since the power supply terminal 10a is used for communication with the management device 2, the power supply line L1 to the sensor 1 can also be used as a communication line. Therefore, the management device 2 does not need to be provided with the second communication unit (communication device) 22 in a one-to-one correspondence with the sensor 1, and can communicate with a large number of sensors 1 with one second communication unit 22. become. Therefore, the configuration of the management device 2 can be simplified. In addition, since the power supply terminal 10a is generally grounded by the bypass capacitor C, the influence of high frequency noise can be reduced as compared with the case of communication by the output terminal 10b.

  In the present embodiment, the determination unit 15 determines the operation mode requested by the management device 2 based on whether or not the potentials of the power supply terminal 10a and the output terminal 10b satisfy a predetermined condition. In this regard, the determination unit 15 may determine the operation mode requested by the management device 2 depending on whether one potential of the power supply terminal 10a and the output terminal 10b satisfies a predetermined condition. However, depending on whether or not the potentials of the power supply terminal 10a and the output terminal 10b satisfy a predetermined condition, the operation mode determined by the management device 2 is determined by only one of them. Compared to the case, it is possible to reduce the probability that an operation mode determination error occurs, and to prevent the operation mode from being changed unexpectedly.

  As mentioned above, although the embodiment of the physical quantity detection system of the present invention has been described, the above is only one embodiment. Therefore, the technical scope of the present invention is not limited to the above example, and the above-described embodiment can be changed without departing from the spirit of the present invention.

  For example, in the sensor 1, at least the part excluding the detection unit 11 may be configured by a monolithic IC. In this way, the sensor 1 can be downsized. In addition, if the detection part 11 is an acceleration sensor using MEMS technology, the detection part 11 can also be integrated as a monolithic IC. When the detection unit 11 is a magnetic sensor including a Hall element and its detection circuit, the detection circuit of the detection unit 11 may be integrated as a monolithic IC.

  In each of the above embodiments, the first communication unit 14 of the sensor 1 has a function of receiving a serial signal input to the power supply terminal 10a and a function of outputting the serial signal to the power supply terminal 10b. However, the first communication unit 14 may have only a function of receiving a serial signal.

It is a block diagram of the physical quantity detection system of Embodiment 1. It is explanatory drawing of the serial communication in the same as the above. It is explanatory drawing of the other examples of the serial communication in the physical quantity detection system of Embodiment 2. It is a block diagram of the physical quantity detection system of Embodiment 3. It is a block diagram of the physical quantity detection system of Embodiment 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Physical quantity sensor 2 Management apparatus 10 Terminal part (1st terminal part)
10a power supply terminal 10b output terminal 10c ground terminal 11 detection unit 12 storage unit 13 output correction unit (output unit)
14 Communication unit (first communication unit)
15 discriminating unit 16 control unit (second control unit)
18 Clock signal output section 20 Terminal section (second terminal section)
20a Power supply terminal 20b Input terminal 21 Power supply unit 22 Communication unit (second communication unit)
23 Control unit (second control unit)
24 Potential holding part

Claims (7)

A physical quantity sensor and a management device for monitoring and controlling the physical quantity sensor,
The physical quantity sensor includes a first terminal unit, a detection unit, a storage unit, an output unit, a first communication unit, a determination unit, and a first control unit, and the first terminal unit. Has a power supply terminal, an output terminal, and a ground terminal, the detection unit is configured to detect a predetermined physical quantity, the storage unit is configured to store characteristic information, and the output The unit is configured to output the detection output of the detection unit from the output terminal, and the determination unit performs an operation requested by the management device based on the potential of at least one of the power supply terminal and the output terminal. The first control unit is configured to operate in an operation mode according to a determination result of the determination unit;
The management device includes a second terminal unit, a power supply unit, a second communication unit, and a second control unit, and the second terminal unit includes a power supply terminal that connects the power terminal. The power supply unit is configured to supply power to the physical quantity sensor from the power supply terminal, and the second control unit is configured to operate the physical quantity sensor in an operation mode. A function of requesting switching, and a function of causing the second communication unit to transmit characteristic information,
The operation mode is a physical quantity detection system including an adjustment mode in which the characteristic information of the storage unit is rewritten to the characteristic information received by the first communication unit, and a normal mode in which rewriting of the characteristic information of the storage unit is not permitted. And
The first communication unit is configured to use the power supply terminal as an input / output terminal for a serial signal,
The second communication unit is configured to use the power supply terminal as an input / output terminal for a serial signal,
One of the first communication unit and the second communication unit transmits a synchronization signal before transmitting a serial signal to the other of the first communication unit and the second communication unit. Configured to
The physical quantity detection system, wherein the other is configured to set a communication clock for serial communication based on the synchronization signal received from the one.   The said discrimination | determination part discriminate | determines the operation mode which the said management apparatus has requested | required according to whether each electric potential of the said power supply terminal and the said output terminal satisfy | fills predetermined conditions. Physical quantity detection system.   The physical quantity detection system according to claim 1, wherein the one is the first communication unit, and the other is the second communication unit.   The physical quantity detection system according to claim 1, wherein the second communication unit resets the phase of the communication clock when receiving the serial signal of the first communication unit. . A physical quantity sensor and a management device for monitoring and controlling the physical quantity sensor,
The physical quantity sensor includes a first terminal unit, a detection unit, a storage unit, an output unit, a first communication unit, a determination unit, and a first control unit, and the first terminal unit. Has a power supply terminal, an output terminal, and a ground terminal, the detection unit is configured to detect a predetermined physical quantity, the storage unit is configured to store characteristic information, and the output The unit is configured to output the detection output of the detection unit from the output terminal, and the determination unit performs an operation requested by the management device based on the potential of at least one of the power supply terminal and the output terminal. The first control unit is configured to operate in an operation mode according to a determination result of the determination unit;
The management device includes a second terminal unit, a power supply unit, a second communication unit, and a second control unit, and the second terminal unit includes a power supply terminal that connects the power terminal. The power supply unit is configured to supply power to the physical quantity sensor from the power supply terminal, and the second control unit is configured to operate the physical quantity sensor in an operation mode. A function of requesting switching, and a function of causing the second communication unit to transmit characteristic information,
The operation mode is a physical quantity detection system including an adjustment mode in which the characteristic information of the storage unit is rewritten to the characteristic information received by the first communication unit, and a normal mode in which rewriting of the characteristic information of the storage unit is not permitted. And
The physical quantity sensor is provided with a clock signal output unit,
The clock signal output unit is configured to output a clock signal to the first communication unit and the input terminal during the adjustment mode,
The first communication unit is configured to perform serial communication using the power supply terminal as an input / output terminal of a serial signal in synchronization with the clock signal obtained from the clock signal output unit,
The second communication unit is configured to perform serial communication using the power supply terminal as an input / output terminal of a serial signal in synchronization with a clock signal input to the input terminal. system.   The said discrimination | determination part discriminate | determines the operation mode which the said management apparatus has requested | required according to whether each electric potential of the said power supply terminal and the said output terminal satisfy | fills predetermined conditions. Physical quantity detection system. The clock signal output from the clock signal output unit to the input terminal is a signal whose current magnitude changes over time,
The management device includes a potential holding unit,
The physical quantity detection system according to claim 5, wherein the potential holding unit is configured to keep the potential of the input terminal constant during the adjustment mode.

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