JP2014153901A - Wireless tag with sensor and data collection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an accident that the processing of a data collection section is adversely affected by transmission of an A/D conversion result having a large error from a wireless tag with a sensor to the data collection section.SOLUTION: The wireless tag with a sensor receives electric power supply from a built-in battery 1, and repeats the A/D conversion of an analog signal acquired by a sensor 5 and the radio transmission of a digital value as an A/D conversion result to the data collection section. An MCU 10 of the wireless tag with the sensor performs invalidation processing so that, when the timing of the A/D conversion of the analog signal coincides with the timing of start or stop of an RF transmission IC 20, the digital value as the A/D conversion result is not used for processing of the data collection section.

Description

  The present invention relates to a wireless tag with a sensor, and more particularly to a wireless tag with a sensor that operates by receiving power from a battery without using a regulator, and a data collection method using the wireless tag with a sensor.

  A wireless tag with a sensor is used as a means for collecting measurement data such as vibration and distortion in an environment where it is difficult to supply power. The wireless tag with sensor includes various sensors such as a strain sensor and an acceleration sensor, an A / D converter that performs A / D conversion of an analog signal obtained by the sensor, and a digital value that is an A / D conversion result. A wireless communication device that performs wireless transmission to the data collection unit and a power supply device that supplies power to these units are modularized.

JP 2010-26838 A

  By the way, in a wireless tag with a sensor that requires high A / D conversion accuracy, it is necessary to reduce the power supply voltage fluctuation by reducing the internal impedance of the power supply device. Therefore, in such a wireless tag with a sensor, a power supply device is generally adopted that includes a battery and a regulator that stabilizes the output voltage and supplies the output voltage to each device in the tag (see, for example, Patent Document 1). ). However, the wireless tag with sensor provided with such a regulator has the following problems. First, if a sensor-equipped wireless tag is provided with a regulator, power loss and current consumption are caused by the regulator, and there is a problem that the battery life is shortened accordingly. Further, in order to operate the regulator, it is necessary to supply a voltage equal to or higher than the input voltage lower limit value from the battery to the regulator. For this reason, the sensor-equipped wireless tag provided with the regulator can be operated only during a period when the output voltage of the battery is equal to or higher than the lower limit value of the input voltage, and cannot be operated for a long time using all of the battery capacity. . In order to avoid such a problem, it is necessary to provide a configuration in which a battery is not directly provided with a sensor but a battery and a device in a module such as an A / D converter are directly connected. However, with this configuration, there is a problem that the power supply voltage fluctuation in the sensor-equipped wireless tag becomes large and the accuracy of the A / D conversion result deteriorates. Therefore, it is conceivable to provide a large-capacity capacitor between the power supply and ground of the wireless tag with sensor. However, since such a large-capacity capacitor is large, it is difficult to provide the sensor-equipped radio tag. However, on the other hand, if the wireless tag with sensor is not provided with a regulator and a large-capacity capacitor is not provided, the internal resistance of the battery is high. There is a problem that the error of the A / D conversion result transmitted from the sensor-equipped wireless tag to the data collection unit becomes large, and the data processing reliability of the A / D conversion result in the data collection unit is impaired.

  The present invention has been made in view of the circumstances as described above, and an A / D conversion result with a large error is transmitted from the wireless tag with sensor to the data collecting unit, and the processing of the data collecting unit is adversely affected. It aims to provide technical means to prevent.

  In the data collection method according to the present invention, a sensor-equipped wireless device that repeats wireless transmission to a data collection unit of an A / D conversion of an analog signal obtained by a sensor and a digital value, which is an A / D conversion result, is received from a battery Use tags. In the data collection method, in the wireless tag with sensor, when the timing of A / D conversion of the analog signal overlaps with the start or stop timing of a specific circuit in the wireless tag with sensor, the A The digital value that is the result of the / D conversion is not used in the data collection unit.

  According to this invention, when the A / D conversion timing overlaps with the start or stop timing of a specific circuit and a digital value which is an A / D conversion result having a large error is obtained, the digital value is converted into data. Removed from processing by the collection unit. Therefore, it is possible to prevent the data collection unit from being adversely affected.

  In order to realize such a data collection method, the present invention includes an A / D conversion unit that converts an analog signal obtained by a sensor into a digital value, and a data collection unit that outputs the digital value output from the A / D conversion unit. A transmission unit that supplies power, a battery that supplies power to the A / D conversion unit and the transmission unit, and a timing of A / D conversion processing by the A / D conversion unit is a timing of starting or stopping a specific circuit There is provided a wireless tag with a sensor, comprising: a control unit that performs invalidation processing so that a digital value that is a result of the A / D conversion processing is not used by the data collection unit when they overlap.

  In a preferred aspect, the transmission unit includes a wireless communication circuit that wirelessly supplies the digital value to the data collection unit, and the specific circuit is the wireless communication circuit.

  In addition, the control unit executes the invalidation process by discarding a digital value that is a result of the A / D conversion, for example.

  In a preferred aspect, when discarding a digital value that is a result of the A / D conversion process, the control unit gives a dummy digital value to the data collection unit instead of the digital value to be discarded. The dummy digital value is, for example, a digital value obtained by A / D conversion before the time when the digital value discarded by the A / D conversion unit is A / D converted.

  Here, the digital value immediately before the digital value to be discarded is considered to be a value close to a digital value that would have been obtained if a large error did not occur in the A / D conversion. Therefore, adverse effects on the data processing of the data collection unit can be reduced.

  In a preferred aspect, the control unit invalidates all digital values obtained within a predetermined period from the start or stop of a specific circuit.

  Here, the predetermined time is, for example, the time required until the power supply noise converges and the error of A / D conversion becomes sufficiently small after starting or stopping a specific circuit. According to this aspect, the A / D conversion result having a large error can be made the object of invalidation processing without leaking.

It is a circuit diagram which shows the structure of the radio | wireless tag with a sensor which is 1st Embodiment of this invention. It is a time chart which shows operation | movement of the embodiment. It is a flowchart which shows the processing content of the main routine which MCU in the same embodiment performs. It is a flowchart which shows the processing content of the timer interruption routine which MCU performs in the same embodiment. It is a flowchart which shows the processing content of the A / D conversion completion interruption routine which MCU performs in the same embodiment. It is a flowchart which shows the processing content of the main routine which MCU10 of the wireless tag with a sensor which is 2nd Embodiment of this invention performs. It is a flowchart which shows the processing content of the timer A interruption routine which the MCU10 performs. It is a flowchart which shows the processing content of the timer B interruption routine which the MCU10 performs. It is a flowchart which shows the processing content of the A / D conversion completion interruption routine which the MCU10 performs.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
FIG. 1 is a circuit diagram showing a configuration of a sensor-equipped wireless tag according to the first embodiment of the present invention. In FIG. 1, a capacitor 2 is connected between positive and negative electrodes of a battery 1. The capacitor 2 has a necessary minimum capacity to absorb a sudden power supply noise, and is a small capacitor that can be accommodated in a wireless tag with a sensor. In the present embodiment, the output voltage of the battery 1 is directly supplied to each circuit in the tag.

  The reference voltage generation circuit 3 is a circuit that generates various reference voltages such as reference voltages Ref + and Ref− supplied to the A / D converter 9 based on the power supply voltage supplied from the battery 1. The voltage follower 4 constituted by an operational amplifier amplifies the reference voltage V1 = Ref + generated by the reference voltage generation circuit 3 with a gain of 1, and outputs it as a power supply voltage for the sensor 5. The sensor 5 is a strain gauge, for example.

  The amplifier 7 amplifies the analog signal V3 output from the sensor 5 and outputs it as a sensor value signal V4. The amplifier 7 includes an operational amplifier 70 and resistors 71 and 72. Here, the analog signal V3 output from the sensor 5 is given to the inverting input terminal of the operational amplifier 70. The resistor 71 is inserted between the non-inverting input terminal of the operational amplifier 70 and the ground, and the resistor 72 is inserted between the output terminal of the operational amplifier 70 and the non-inverting input terminal. When the resistance values of the resistors 71 and 72 are R71 and R72, the amplifier 7 amplifies the analog signal V3 output from the sensor 5 with a gain of (R71 + R72) / R71 and outputs it as a sensor value signal V4.

  The A / D converter 9 is a circuit that converts the sensor value signal V4 output from the amplifier 7 into a digital signal based on the reference voltages Ref + and Ref− supplied from the reference voltage generation circuit 3. In the present embodiment, as described above, the reference voltage V1 = Ref + output from the reference voltage generation circuit 3 is supplied to the sensor 5 via the voltage follower 4, so that the physical quantity measured by the sensor 5 is converted into a resistance value. In the case of such a sensor, the error of the A / D conversion result caused by the fluctuation of the reference voltage V1 = Ref + can be canceled.

  The RF transmission IC 20 is a wireless communication circuit that modulates a carrier with a digital signal output from the A / D converter 9 and transmits the modulated signal to a data collection unit (not shown) as a wireless signal.

  The MCU (Micro Controller Unit) 10 is a control unit that controls each circuit in the wireless tag with sensor. The MCU 10 includes a ROM that stores various programs and a RAM as a work area. The MCU 10 repeats the control of causing the A / D converter 9 to execute A / D conversion and causing the RF transmission IC 20 to transmit a digital signal that is an A / D conversion result in accordance with a program in the ROM. The RF transmission IC 20 and the MCU 10 that causes the RF transmission IC 20 to transmit a digital signal that is an A / D conversion result function as a transmission unit that provides a digital value that is the A / D conversion result to the data collection unit.

  When a one-chip MCU is used as the MCU 10, it is preferable to provide the reference voltage generation circuit 3 and the A / D converter 9 in the same lip in order to cancel the error of the A / D conversion result described above.

  The feature of this embodiment is the control of the A / D converter 9 and the RF transmission IC 20 performed by the MCU 10. This control is summarized as follows. That is, the MCU 10 invalidates the digital value that is the result of the A / D conversion so that it is not used by the data collection unit when the timing of starting or stopping the RF transmission IC 20 overlaps with the timing of A / D conversion. To process. Specifically, the digital value that is the result of the A / D conversion is discarded, and the digital value that is the result of the previous A / D conversion is adopted as a dummy digital value instead of the digital value. When the timing of starting or stopping the RF transmission IC 20 and the timing of A / D conversion overlap, for example, the A / D conversion result within a period until a predetermined time elapses from the timing of starting or stopping the RF transmitting IC 20 Is obtained.

  FIG. 2 is a time chart illustrating a temporal change in the digital value DV4, which is the A / D conversion result of the sensor value signal V4, and the output voltage VB of the battery 1.

  In FIG. 2, IC_ON is a timing at which the power of the RF transmission IC 20 is turned on so that the MCU 10 can transmit a digital signal, and IC_OFF is a timing at which the MCU 10 finishes the transmission of the digital signal and turns off the power of the RF transmission IC 20. Show. In the present embodiment, the MCU 10 causes the A / D converter 9 to perform A / D conversion of the sensor value signal V4 by a timer interrupt repeated at a constant cycle. In addition, every time a predetermined number of A / D conversions are completed, the MCU 10 causes the RF transmission IC 20 to wirelessly transmit digital values that are the results of those A / D conversions. The largest current consumption occurs when the RF transmission IC 20 performs a transmission operation. For this reason, the output voltage VB of the battery 1 greatly decreases at the IC_ON timing and increases greatly at the IC_OFF timing.

  When the power supply voltage VB fluctuates in this way, a large error occurs in the digital value DV4 which is the A / D conversion result of the A / D converter 9 at the timing of fluctuation of the power supply voltage VB. Therefore, in this embodiment, the MCU 10 discards the digital value DV4 when the digital value DV4 is obtained within a period from the IC_ON timing or the IC_OFF timing until a predetermined time elapses, and serves as a dummy digital value instead. The digital value DV4 obtained by the previous A / D conversion is adopted as a transmission target to the data collection unit.

  According to the present embodiment, since such invalidation processing is performed, even in a configuration in which the battery 1 is directly connected to each circuit in the tag, an A / D conversion result with a large error is sent to the data collection unit. It is possible to prevent the data processing of the data collection unit from being adversely affected.

  Next, a specific program example for realizing such control will be described. 3 to 5 are flowcharts showing the processing contents of various routines executed by the MCU 10 in this embodiment. In the present embodiment, the MCU 10 starts executing the main routine shown in FIG. 3 when an initial setting command is given. Here, the initial setting command is, for example, when a power switch (not shown) provided in the wireless tag with sensor is turned on or when an activation command is given to the wireless tag with sensor from the outside. Is a command generated.

  When starting execution of the main routine, the MCU 10 first executes initial processing (SA1). In this initial process, initial setting of control flags, counters, and registers set in the built-in RAM is performed. Next, it is determined whether or not RF_TX_Flag for requesting transmission of a radio frame is “1” (SA2), and the same determination is repeated until the determination result is “YES”.

  In this embodiment, a timer (not shown) generates a timer interrupt signal at a constant cycle. The MCU 10 executes the timer interrupt routine shown in FIG. 4 each time this timer interrupt signal is generated. First, the MCU 10 increments A / D_Counter indicating the number of times of execution of the timer interrupt routine by 1 (SA16).

  Next, the MCU 10 determines whether or not TX_ON_OFF_Flag is greater than 0 (SA17). This TX_ON_OFF_Flag is a flag indicating the remaining time from the ON timing or OFF timing of the RF transmission IC 20 to the timing at which a predetermined time elapses. If the determination result in SA17 is “YES”, TX_ON_OFF_Flag is decremented by 1 (SA18), and the process proceeds to SA19. On the other hand, when the determination result of SA17 is “NO”, the process proceeds to SA19 without executing SA18. Accordingly, when a predetermined time elapses from the ON timing or OFF timing of the RF transmission IC 20 and TX_ON_OFF_Flag = 0, TX_ON_OFF_Flag will remain at 0 thereafter.

  Next, when proceeding to SA19, it is determined whether or not the content of the A / D_Counter has reached the A / D conversion cycle (more precisely, a numerical value obtained by converting the A / D conversion cycle into the number of executions of the timer interrupt routine). (SA19) If the determination result is “NO”, the timer interrupt routine is terminated. On the other hand, if the determination result in SA19 is “YES”, the MCU 10 causes the A / D converter 9 to start A / D conversion of the sensor value signal V4 output from the amplifier 70 (SA20). Next, A / D_Counter is set to 0 (SA21), A / D_Flag is set to "1" (SA22), and the timer interrupt routine is terminated. Therefore, whenever the number of executions of the timer interrupt routine indicated by the A / D_Counter reaches the number of executions corresponding to the A / D conversion cycle, A / D conversion of the sensor value signal V4 is started.

  When the timer interrupt routine ends, the processing of the MCU 10 returns to the main routine. Here, when the return destination is, for example, SA2 of the main routine, it is determined whether or not RF_TX_Flag is “1”. When the determination result is “NO”, the same determination is repeated.

  When completing the A / D conversion instructed by the MCU 10, the A / D converter 9 supplies an A / D conversion completion interrupt signal to the MCU 10. Thereby, the MCU 10 executes the A / D conversion completion interrupt routine shown in FIG.

  First, the MCU 10 acquires a digital value DV4 that is an A / D conversion result of the sensor value signal V4 from the A / D converter 9 (SA23). Next, the MCU 10 determines whether or not TX_ON_OFF_Flag is 0 (SA24). When a predetermined time or more has elapsed from the ON timing or OFF timing of the RF transmission IC 20 and TX_ON_OFF_Flag is 0, the MCU 10 performs A / D of the sensor value signal V4 acquired from the A / D converter 9 in SA23. The digital value DV4 as the conversion result is stored in the built-in RAM as a transmission target (SA25), and the process proceeds to SA26. On the other hand, when the predetermined time has not elapsed from the ON timing or OFF timing of the RF transmission IC 20 and TX_ON_OFF_Flag is 1 or more, the MCU 10 detects the sensor value signal acquired from the A / D converter 9 in SA23. The digital value DV4 which is the A / D conversion result of V4 is discarded (SA31). Then, the previously acquired A / D conversion value, that is, the digital value DV4 stored in the RAM as the transmission target immediately before is read, stored in the RAM as a dummy digital value instead of the discarded digital value DV4 (SA25), and the process goes to SA26. Proceed with

  Next, in SA26, A / D_Count indicating the number of A / D conversions is incremented by one. Next, since A / D conversion is completed, A / D_Flag indicating that A / D conversion instructed to start is not completed is set to “0” (SA27).

  Next, it is determined whether A / D_Count has reached a predetermined number of A / D conversions. If the determination result is “NO”, the A / D conversion completion interrupt routine is terminated. On the other hand, when A / D_Count has reached the predetermined number of A / D conversions (SA28; YES), RF_TX_Flag for requesting transmission of a radio frame is set to “1” (SA29), and A / D_Count is initialized to 0. (SA30), and the A / D conversion completion interrupt routine is terminated.

  Accordingly, the A / D conversion completion interrupt routine is started a number of times corresponding to a predetermined number of A / D conversions, and digital values corresponding to the number of A / D conversions are stored in the built-in RAM (SA25 or SA32). Each time D_Count becomes the same A / D conversion count, RF_TX_Flag is set to “1”. When the A / D conversion completion interrupt routine ends, the processing of the MCU 10 returns to the main routine.

  Here, when the return destination is, for example, SA2 of the main routine, it is determined whether or not RF_TX_Flag is “1”. When the determination result is “NO”, the same determination is repeated. When RF_TX_Flag becomes “1” and the determination result of SA2 becomes “YES”, the process proceeds to SA3.

  Next, when proceeding to SA3, RF_TX_Flag is set to “0”. Next, a radio transmission frame including digital values DV4 corresponding to the predetermined number of times of A / D conversion stored in the RAM is created (SA4).

  Next, it is determined whether A / D_Flag is “0” (SA5). If the determination result is “YES”, the process proceeds to SA6. On the other hand, if the determination result of SA5 is “NO”, the determination of SA5 is repeated.

  As a case where the determination result of SA5 is “NO”, the following cases are conceivable. That is, after RF_TX_Flag = “1” and A / D_Count = 0 in the A / D conversion completion interrupt routine, the routine returns to the main routine and the determination result of SA2 becomes “YES”, and then the timer interrupt routine starts. In this case, A / D_Flag is set to “1” (SA22), and then the process proceeds to SA5 before the A / D conversion completion interrupt signal is generated.

  As described above, in this embodiment, a predetermined number of digital values DV4 to be transmitted are prepared in the RAM, and even if RF_TX_Flag becomes “1”, the A / D converter 9 performs A / D conversion at that time. When A / D_Flag is “1”, the start of processing after SA6 is waited until A / D conversion is completed and A / D_Flag = “0”. It is. In this embodiment, since the time required for A / D conversion is several μS, the waiting time until the processing after S6 is started after proceeding to S5 is several μS at the maximum.

  Next, when proceeding to SA6, TX_ON_OFF_Flag is set to a predetermined time (more precisely, a numerical value obtained by dividing the predetermined time by the timer interrupt cycle). The predetermined time set in SA6 is a time required until the power supply voltage in the tag is stabilized and the error of the A / D conversion result is within an allowable range after the RF transmission IC 20 is turned on or off. is there. When SA6 ends, the MCU 10 turns on the RF transmission IC 20 (SA7).

  When the power of the RF transmission IC 20 is turned on (SA7), the MCU 10 performs control to divide the contents of the wireless transmission frame into several times and write it to the transmission register of the RF transmission IC 20. Specifically, first, it is determined whether or not the number of writes to the transmission register has reached a specified value (SA8). When the determination result is “NO”, it is determined whether or not the transmission register of the RF transmission IC 20 is in a writable state (SA13), and the same determination is repeated while the determination result is “NO”. When the determination result in SA13 is “YES”, the content of the wireless transmission frame is written to the transmission register by a certain amount (SA14). Next, the write count to the transmission register is incremented by 1 (SA15), and the process returns to SA8. Thereafter, SA8, SA13, SA14, and SA15 are similarly repeated. When the write count to the transmission register becomes the specified value and the determination result of SA8 is “YES”, the write count to the transmission register is initialized to 0 (SA9). At this time, the RF transmission IC 20 has finished transmitting the wireless transmission frame.

  Next, it is determined whether A / D_Flag is “0” (SA10). If the determination result is “YES”, the process proceeds to SA11. On the other hand, while the determination result of SA10 is “NO”, the SA10 determination is repeated.

  As a case where the determination result of SA10 is “NO”, the following cases are conceivable. That is, after RF_TX_Flag = “1” and A / D_Count = 0 in the A / D conversion completion interrupt routine, the routine returns to the main routine, and after the determination result of SA5 becomes “YES”, the timer interrupt routine starts. In this case, A / D_Flag is set to “1” (SA22), and then the process proceeds to SA10 before the A / D conversion completion interrupt signal is generated.

  As described above, in this embodiment, even when the number of times of writing to the transmission register reaches the specified value and the timing at which the power of the RF transmission IC 20 can be turned off (SA8; YES), the A / D converter at that time 9 is executing A / D conversion, and when A / D_Flag is “1”, SA11 or later until A / D_Flag = “0” after A / D conversion is completed. The start of the process is awaited.

  Next, when proceeding to SA11, the predetermined time is set to TX_ON_OFF_Flag as in SA6 described above. Next, the power of the RF transmission IC 20 is turned off (SA12).

  When the power of the RF transmission IC 20 is turned off (SA12), the processing of the MCU 10 returns to SA2, and a predetermined number of digital values DV4 to be transmitted are stored in the RAM again, and waits until RF_TX_Flag becomes “1”. Then, when RF_TX_Flag becomes “1”, the processes after SA3 described above are repeated.

  As described above, according to the present embodiment, the A / D conversion result obtained before the predetermined time elapses from the timing of power-on or power-off of the RF transmission IC 20 is discarded (SA31), instead. The previous A / D conversion result is adopted. Therefore, the A / D conversion result that is highly influenced by the power supply noise caused by the power ON / OFF of the RF transmission IC 20 is removed, and only the A / D conversion result that is less affected by the power supply noise is wirelessly transmitted. Therefore, the reliability of the A / D conversion result transmitted wirelessly can be improved.

  Further, according to the present embodiment, even when a predetermined number of A / D conversion results are obtained and transmission of a radio frame becomes possible, the A / D converter 9 is currently executing A / D conversion at that time. In some cases, power-on of the RF transmission IC 20 is awaited until the A / D conversion is completed. Further, according to the present embodiment, even if transmission of a radio frame is completed, if the A / D converter 9 is executing A / D conversion at that time, the A / D conversion is completed. In the meantime, the power-off of the RF transmission IC 20 is awaited. Therefore, according to the present embodiment, it is possible to reduce the number of times that the power ON / OFF of the RF transmission IC 20 adversely affects A / D conversion.

Second Embodiment
Next, a sensor-equipped wireless tag according to a second embodiment of the present invention will be described. The wireless tag with sensor according to the present embodiment is a modification of each routine executed by the MCU 10 of the wireless tag with sensor according to the first embodiment. 6 to 9 are flowcharts showing processing contents of various routines executed by the MCU 10 in the present embodiment. The main routine shown in FIG. 6 is the main routine (FIG. 3) of the first embodiment, the timer A interrupt routine shown in FIG. 7 is the timer interrupt routine (FIG. 4) of the first embodiment, and the A routine shown in FIG. The / D conversion completion interrupt routine corresponds to the A / D conversion completion interrupt routine (FIG. 5) of the first embodiment. In this embodiment, a timer B interrupt routine shown in FIG. 8 is added.

  In the first embodiment, the determination of TX_ON_OFF_Flag and the decrement (SA17, SA18) are performed in the timer interrupt routine (FIG. 4), thereby measuring the predetermined time from the power ON timing and the power OFF timing of the RF transmission IC 20. It was. In the present embodiment, the timer A interrupt routine (FIG. 7) does not include SA17 and SA18 of the first embodiment. In the present embodiment, the TX_ON_OFF_Flag is not used, and a predetermined time from the power ON timing and the power OFF timing of the RF transmission IC 20 is measured by the timer B interrupt routine (FIG. 8).

  In the main routine shown in FIG. 6, SA6 executed before the power of the RF transmission IC 20 is turned on (SA7) in the first embodiment is replaced with SB6a and SB6b. In the main routine, SA11 executed before the power of the RF transmission IC 20 is turned off (SA12) in the first embodiment is replaced with SB11a and SB11b.

  Here, in SB6a and SB11a, RF_ON_OFF_Flag indicating that a predetermined time has not elapsed since the power ON or power OFF timing of the RF transmission IC 20 is set to “1”. In SB6b and SB11b, the timer B compare value (time value) is set and the timer B interrupt is permitted. As a result, the timer B starts measuring the compare value. When the timer B finishes timing, a timer B interrupt signal is generated, and the MCU 10 executes a timer B interrupt routine shown in FIG. Then, the MCU 10 sets RF_ON_OFF_Flag to “0” (SB33), and prohibits the timer B interrupt (SB34).

  Therefore, in this embodiment, RF_ON_OFF_Flag maintains “1” until the timer B interrupt routine is started after the time corresponding to the compare value has elapsed from the timing of power ON or power OFF of the RF transmission IC 20. “0” is maintained during other periods.

  In the A / D conversion completion interrupt routine (FIG. 9), SA24 in the first embodiment (FIG. 5) is replaced with SB24. In the A / D conversion completion interrupt routine in the present embodiment, when RF_ON_OFF_Flag is “0” (SB24; YES), the A / D conversion result acquired in SA23 is stored in the RAM (SA25), and “0”. If not (SB24; NO)), the acquired A / D conversion result is discarded (SA31), and the previous A / D conversion result is stored in the RAM.

  As described above, also in this embodiment, the same operation as in the first embodiment is performed. Therefore, according to the present embodiment, the same effect as the first embodiment can be obtained.

<Other embodiments>
Although the first and second embodiments of the present invention have been described above, other embodiments are conceivable for the present invention. For example:

(1) In each of the above embodiments, when the digital value DV4 which is the A / D conversion result is obtained within a predetermined time from the timing of starting or stopping the RF transmission IC 20, the invalidation process for discarding the digital value DV4 is performed. This prevents the digital value DV4 from being used for data processing of the data collection unit. However, the mode of invalidation processing is not limited to this. For example, when the digital value DV4 as the A / D conversion result is obtained within a predetermined time from the start or stop timing of the RF transmission IC 20, information indicating that the digital value DV4 is invalid is added to the digital value DV4. The data collection unit may discard the invalid digital value DV4 or substitute the immediately preceding digital value DV4. A serial number may be generated each time A / D conversion is performed, and the serial number may be added to the digital value DV4 that is not discarded and transmitted to the data collection unit. In this case, the data collection unit side can detect the location where the digital value is discarded based on the discontinuity in the serial number added to the digital value DV4.

(2) In each of the above embodiments, the immediately preceding digital value is adopted as the digital value instead of the discarded digital value, but the method of generating the alternative digital value is not limited to this. For example, when a moving average of digital values that are not discarded is always calculated and the digital values are to be discarded, the moving average at that time may be sent instead of the digital value that is discarded. Alternatively, an interpolation operation using a predetermined number of digital values before and after the digital value to be discarded may be executed to calculate a digital value instead of the digital value to be discarded. Note that arithmetic processing for generating a digital value instead of a digital value to be discarded may be executed by the MCU 10 or may be executed by a data collection unit.

(3) In the above embodiments, the present invention is applied to a wireless tag with a sensor having no regulator. However, the present invention can of course be applied to a wireless tag with a sensor having a regulator.

DESCRIPTION OF SYMBOLS 1 ... Battery, 2 ... Capacitor, 3 ... Reference voltage generation circuit, 4 ... Voltage follower, 5 ... Sensor, 7 ... Amplifier, 9 ... A / D converter, 10 ... MCU, 20 ... RF transmission IC.

Claims (7)

An A / D converter that converts an analog signal obtained by the sensor into a digital value;
A transmission unit that gives the digital value output by the A / D conversion unit to a data collection unit;
A battery for supplying power to the A / D converter and the transmitter;
When the timing of A / D conversion processing by the A / D conversion unit overlaps with the timing of starting or stopping a specific circuit, a digital value as a result of the A / D conversion processing is used for the data collection unit A wireless tag with a sensor, comprising: a control unit that performs invalidation processing so as not to be performed. The transmission unit includes a wireless communication circuit that wirelessly provides the digital value to the data collection unit,
The wireless tag with sensor according to claim 1, wherein the specific circuit is the wireless communication circuit.   The wireless tag with a sensor according to claim 1, wherein the control unit executes the invalidation process by discarding a digital value that is a result of the A / D conversion process.   The said control part gives a dummy digital value to the said data collection part instead of the digital value to discard, when canceling the digital value which is the result of the said A / D conversion process, The said collection part is characterized by the above-mentioned. The described wireless tag with sensor.   5. The dummy digital value according to claim 4, wherein the dummy digital value is a digital value obtained by performing A / D conversion before the time when the digital value to be discarded is A / D converted by the A / D conversion unit. Wireless tag with sensor.   The said control part performs the invalidation process of all the digital values obtained within the predetermined period from the time of starting or stopping of the said specific circuit, The claim of any one of Claims 1-5 characterized by the above-mentioned. Wireless tag with sensor. In a data collection method using a sensor-equipped radio tag that receives power supplied from a battery and repeats A / D conversion of an analog signal obtained by a sensor and wireless transmission of a digital value that is an A / D conversion result to a data collection unit ,
When the timing of A / D conversion of the analog signal overlaps with the timing of starting or stopping a specific circuit, the digital value resulting from the A / D conversion is not used in the data collection unit. Characteristic data collection method.

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