Measuring instrument synchronization system and measuring instrument synchronization method

Abstract

To provide a measuring instrument synchronization system capable of simultaneously measuring the speed of the surface wave of the ground and minute acceleration such as the fine movement of a structure in a wide range.SOLUTION: This system is composed of plural measuring instruments 12, and each measuring instrument 12 is provided with an acceleration sensor 14, a RTC16, a GPS module 18, a WiFi20 and a MPU22, etc., and each equipment is connected to the MPU22. The GPS module outputs a GPS second clock, and the RTC transmits an RTC second clock. By adjusting the RTC second clock in consideration of the temporal operation deviation of the RTC16, the RTC second clock is corrected to an RTC second clock close to the GPS second clock, and the detection start timing of the acceleration in the plurality of measuring instruments 12 is controlled.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a measurement instrument synchronization system and a measurement instrument synchronization method that synchronize and measure multiple distant measurement instruments without connecting them with wires, and is suitable for measuring, for example, the velocity of surface waves in the ground or the microtremors of structures using an accelerometer. [Background technology]

[0002] Currently, the velocity of surface waves in the ground is tested to inspect the strength of the ground, and microtremor tests are conducted on structures to inspect the strength of buildings and other structures. Various methods have been used to measure the velocity of surface waves in the ground and the microtremors of structures. These methods generally use measuring devices called accelerometers or acceleration sensors, which detect and measure minute accelerations.

[0003] Furthermore, when measuring the velocity of ground surface waves or the microtremors of structures, it is necessary to measure the vibration transmission speed and vibration attenuation over a wide range, and for this reason, multiple accelerometers and other devices are sometimes installed and used to measure simultaneously. However, when measuring, it is not possible to accurately measure the vibration transmission speed and vibration attenuation unless the measurement start and end timings of the accelerometers and other devices are synchronized. For this reason, a measurement device synchronization system and method that can synchronize the measurement timing of multiple measurement devices is needed.

[0004] On the other hand, the following Patent Documents 1 to 4 are known as prior art methods for synchronizing measuring devices. The following Patent Document 1 indicates that matching the sampling timing and data acquisition time between devices is extremely important for relative evaluation of sensor signals at the same time. It also points out that the times in each device must be matched to an accuracy of less than half the sampling period, or even 5% of the sampling period or less.

[0005] On the other hand, a real-time clock (RTC) is also used. For example, a reference station device 10 having a timer 106 and an RTC 107 measures a reference count value and a reference RTC time value, and simultaneously transmits a trigger start command to multiple local station devices 20.

[0006] Furthermore, Patent Document 2 below describes that a GNSS receiver such as a GPS that receives time information measures displacement of the top floor of a building during an earthquake, and that a strong motion seismometer placed inside the building measures acceleration during an earthquake, and that the time of displacement measurement by the GNSS receiver and the time of acceleration measurement by the strong motion seismometer are synchronized with high precision.The invention also describes that it relates to a strong motion data observation system that measures displacement data of the top floor of a building during a strong earthquake and acceleration data of the bottom floor of the building in a time-synchronized manner.

[0007] Furthermore, Patent Document 3 below describes that the time axis of the time series data is corrected based on the difference between the current time included in the time series data and the accurate time information corresponding to the current time.

[0008] The following Patent Document 4 describes that multiple measurement units attached to a measurement target detect environmental state quantities and output the state quantities as analog measurement signals, which are analog voltage or current signals. It also describes that the measurement unit outputs analog measurement signals that measure acceleration. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2014-3573 A [Patent Document 2] Patent Publication No. 2021-21575 [Patent Document 3] Patent Publication No. 2021-81201 [Patent Document 4] Patent Publication No. 2021-113705 Summary of the Invention [Problem to be solved by the invention]

[0010] However, among the measuring instrument synchronization methods of Patent Documents 1 to 4 mentioned above, Patent Document 1 indicates the importance of matching the sampling timing and data acquisition time between each device in a multi-point measurement system, but only discloses sending a trigger start command from the reference station device 10 to all local station devices 20 simultaneously.

[0011] Furthermore, in Patent Document 2, the clock of the GNSS receiver, which can also be interpreted as an accelerometer, is used to synchronize measurements and transmit time information, and although there are multiple strong motion seismometers that are accelerometers, there is no mention of synchronization between the strong motion seismometers. On the other hand, Patent Document 3 uses only one ground motion sensor that measures acceleration, and Patent Document 4 describes suppressing the variation in relative measurement times, but does not mention "starting measurement when internal clocks cannot be synchronized."

[0012] As described above, although Patent Documents 1 to 4 disclose technologies using GNSS receivers such as GPS and RTCs, they do not disclose a highly accurate synchronization method that takes into account the settable time interval and error of the RTC. As a result, with the conventional technologies, it was not possible to synchronize the RTC clock with the GPS clock on the order of microseconds, making it impossible to simultaneously measure minute accelerations such as the velocity of ground surface waves or micro-movements of structures over a wide area.

[0013] The present invention has been made in view of the above-mentioned background, and aims to provide a measuring instrument synchronization system and a measuring instrument synchronization method that can simultaneously measure minute accelerations such as the velocity of surface waves in the ground and micro-movements of structures over a wide range. [Means for solving the problem]

[0014] The invention described in claim 1 that solves the above problem comprises a GPS module that receives radio waves from GPS satellites and outputs a GPS second clock that is regarded as absolute time; RTC, which emits the RTC second clock, An accelerometer that detects acceleration at a timing synchronized with the time of the RTC second clock; an MPU that transmits a system clock and controls the operation of a GPS module, an RTC, and an accelerometer connected thereto; A measuring instrument synchronization system including a plurality of measuring instruments each having This is a measurement device synchronization system that adjusts the RTC second clock to take into account the time difference in the RTC's operation, correcting the RTC second clock to be closer to the GPS second clock, and controls the timing at which acceleration detection starts in multiple measurement devices.

[0015] According to the measuring device synchronization system of the invention of claim 1, the GPS module receives radio waves from GPS satellites and outputs the GPS second clock, which is regarded as absolute time, and the RTC transmits the RTC second clock. In accordance with this, the accelerometer detects acceleration at a timing that matches the time of the RTC second clock, and the MPU, which transmits the system clock, is connected to the GPS module, RTC, and accelerometer and controls their operations. Not only do the multiple measuring devices include each of these devices, but by adjusting the RTC second clock taking into account the time difference in the RTC's operation, the RTC second clock is corrected to be closer to the GPS second clock, and the acceleration detection start timing in the multiple measuring devices is controlled.

[0016] The velocity of ground surface waves and the microtremors of structures, which are the measurement targets of this invention, both require synchronized measurement of acceleration at multiple locations, and the phase difference of the waveforms is also an important measurement item. For this reason, multiple measuring instruments are required, but the RTC generates an RTC second clock that is close to the GPS second clock, which is considered the absolute time of the GPS module.

[0017] As a result, the RTC second clock is adjusted to take into account the delay in the RTC operation in each measuring device, and the acceleration measurement timing of each measuring device is synchronized. This makes it possible to simultaneously and widely measure minute accelerations such as the velocity of surface waves in the ground and micro-motions of structures with high precision and appropriate timing, and also enables accurate measurement of the speed at which vibrations are transmitted and the attenuation of vibrations.

[0018] According to a measuring device synchronization system such as the invention of claim 2, the time difference between the GPS second clock and the RTC second clock is calculated every minute so that it always falls within the range of 0 to 1 / 1024 seconds, and if it exceeds 0 to 1 / 1024 seconds, 1 / 1024 seconds is added or subtracted to adjust it so that it falls within the range of 0 to 1 / 1024 seconds. This makes it possible to adjust the RTC second clock taking into account the RTC's temporal operational discrepancy, correcting the RTC second clock to a time close to absolute time and enabling the acceleration detection start timing of multiple measuring devices to be synchronized.

[0019] According to the measuring device synchronization system of the invention of claim 3, a computer is provided, and multiple measuring devices are each connected to this computer. The computer aggregates the acceleration data of the synchronized acceleration measurements of each measuring device, making it possible to easily accumulate acceleration data detected in synchronization by multiple measuring devices.

[0020] According to the measuring instrument synchronization system of the invention of claim 4, the accelerometer of each measuring instrument detects acceleration at a maximum of every 1 / 1000 of a second, making it possible to detect acceleration with high accuracy even in the case of minute vibrations with a short period.

[0021] The invention described in claim 5, which solves the above problem, is a method for synchronizing a plurality of measuring instruments, in which a GPS module receives radio waves from a GPS satellite and outputs a GPS second pulse that is taken as absolute time, an RTC transmits an RTC second clock that is in accordance with this GPS second pulse, and an accelerometer sets the timing for detecting acceleration based on this RTC second clock, and the method comprises: After adjusting the RTC second clock to account for the RTC's time lag, This is a method for synchronizing measuring devices by generating an RTC second clock that is close to the GPS second pulse and controlling the acceleration detection start timing among multiple measuring devices.

[0022] According to the measuring device synchronization method of the invention of claim 5, in multiple measuring devices, the GPS module receives radio waves from GPS satellites and outputs a GPS second pulse that is used as absolute time, and the RTC each transmits an RTC second clock that is synchronized with the GPS second pulse of the GPS module. Furthermore, the accelerometer sets the acceleration detection timing based on this RTC second clock. Then, in each measuring device, the RTC second clock is adjusted to take into account the time difference in the RTC's operation, and an RTC second clock that is close to the GPS second pulse is generated, controlling the acceleration detection start timing between multiple measuring devices.

[0023] As with the invention of claim 1, the velocity of ground surface waves and the microtremors of structures, which are the measurement targets of this invention, both require synchronized measurement of acceleration at multiple locations, and the phase difference of the waveforms is also an important measurement item. For this reason, multiple measuring instruments are required, but the RTC generates an RTC second clock that is close to the GPS second clock, which is considered the absolute time of the GPS module.

[0024] As a result, similar to the invention of claim 1, the RTC second clock is adjusted in each measuring device taking into account the delay in the RTC operation, and the acceleration measurement timing of each measuring device is synchronized. This makes it possible to simultaneously and widely measure minute accelerations such as the velocity of surface waves in the ground and micro-movements of structures with high precision and appropriate timing, and also makes it possible to accurately measure the speed at which vibrations are transmitted and the attenuation of vibrations.

[0025] According to the measuring device synchronization method of the invention of claim 6, the time difference between the GPS second pulse and the RTC second pulse is calculated as D RTC year, The RTC time is set to a timing range of 0 to 1 / 1024 seconds relative to the GPS absolute time, and the value at that time is set to D RTC By substituting into, it is substituted and DRTC As the value of is increased, the RTC can be synchronized for a longer period of time.

[0026] According to the measuring device synchronization method of the invention of claim 7, the number of counts per second of the RTC second clock is C RTC The number of counts per second of the MPU system clock is C SYS year, C between the first RTC second clock and the second RTC second clock SYS The difference between RTC By substituting into, the assigned C RTC As the value of becomes new, the time for which the RTC is synchronized can be increased in the same way as above.

[0027] According to the measuring instrument synchronization method of the invention of claim 8, the number of counts per second of the MPU system clock is C SYS year, C between the first GPS second clock and the second GPS second clock by the GPS second pulse SYS The difference between the new C SYS By doing so, it is substituted and C SYS As the value of is updated, the MPU system clock can be adjusted accordingly. [Effects of the Invention]

[0028] As described above, the present invention has the excellent effect of providing a measuring instrument synchronization system and a measuring instrument synchronization method that can simultaneously measure minute accelerations such as the velocity of surface waves in the ground and micro-tremors of structures over a wide range. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a block diagram showing an outline of a measuring device applied to a measuring device synchronization system according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram showing an overall measurement device synchronization system according to an embodiment of the present invention; [Figure 3]FIG. 2 is a diagram showing a time chart of RTC synchronization parameters in a measurement device synchronization system according to an embodiment of the present invention. [Figure 4] FIG. 10 is a timing chart illustrating the time difference and correction of the RTC second clock relative to the GPS second clock. [Figure 5] This is a flow diagram of the procedure for setting the RTC in seconds and obtaining the delay time DRTC. [Figure 6] This is a flow diagram of the procedure for obtaining the second clock value CRTC of the RTC clock. [Figure 7] FIG. 10 is a flow diagram of a procedure for obtaining a clock value CSYS per second in the system clock of the MPU. DETAILED DESCRIPTION OF THE INVENTION

[0030] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a measuring device synchronization system and a measuring device synchronization method according to the present invention will be described in detail below with reference to the accompanying drawings. 1 and 2, the main part of a measuring device synchronization system 10 according to this embodiment is composed of multiple measuring devices 12, each of which includes a high-precision acceleration sensor 14, a real-time clock (hereinafter referred to as "RTC") 16, a GPS module 18, WiFi 20 which is a wireless LAN, and an MPU 22 which is a microprocessor, and each device is connected to the MPU 22. The MPU 22 is also connected to an SD card 24 and a USB interface 26. The measurement targets of the measuring device synchronization system 10 according to this embodiment are the velocity of surface waves in the ground and microtremors of structures.

[0031] Since each measuring device 12 is also equipped with WiFi 20, in this embodiment, it is possible to transmit acceleration data measured synchronously in each measuring device 12 to another computer, a tablet PC 30, via WiFi 20, without connecting multiple measuring devices 12 that are far from each other. Furthermore, the operation of each measuring device 12 is controlled by its own MPU 22, which has a system clock that is a base clock of 12 MHz, and measurement and time management are performed by this MPU 22.

[0032] The acceleration sensor 14, which is an accelerometer, is an inertial sensor that measures the change in the velocity of an object over time (i.e., acceleration), and the one adopted in this embodiment is a sensor capable of measuring minute acceleration. Furthermore, the GPS module 18, which also functions as a GPS receiver, receives radio waves from four or more GPS satellites (not shown), each of which contains time data from an onboard atomic clock, enabling it to obtain not only location information but also time information. Accordingly, the GPS second pulse output from the GPS module 18 can be used as an accurate reference clock (absolute time) for each measuring device 12.

[0033] The RTC 16 is a device that uses a quartz oscillator as its clock source and is capable of generating digital data such as time, date, etc., and outputting clocks such as an RTC second pulse. The GPS module 18 and the RTC 16 are capable of transmitting a GPS second pulse and an RTC second pulse of 1 pps clock (pps = Pulse per second) shown in Figure 1 to the MPU 22, respectively.

[0034] On the other hand, the MPU22 system clock and the RTC16 clock are considered to be ahead or behind this reference clock. There is an error between the MPU22 system clock and the RTC16 clock, but this error is thought to depend mainly on temperature and electrical and magnetic conditions, and is particularly heavily dependent on temperature.

[0035] However, the temperature change from the time the MPU 22 system clock and the RTC 16 clock are synchronized with reception by the GPS module 18 until measurement is small, and it can be assumed that the temperature remains constant from the time of synchronization by the GPS module 18 until measurement. Although no statistical evaluation was performed, even after turning the power on and off and leaving it for about a day, the change in the one-second delay between the MPU 22 system clock and the RTC 16 clock (deviation from one second of the reference clock) was less than 1 μsecond, although it was not the absolute value of the delay.

[0036] Specifically, the MPU22's system clock, or operating clock, is sufficiently fast. As mentioned above, the base clock is 12 MHz, and the code execution speed is 133 MHz. The count value can be read from a counter register with an accuracy of 50 ppm (approximately 2 minutes per month) at 12 MHz. Accordingly, the MPU22 is responsible for measurement and time management. The minimum time unit is 1 / 12 μs, but the time is managed in 1 μs increments (floating point). Meanwhile, the RTC16's operating clock is slower than the MPU22's. Its base clock is 32.768 kHz, with an accuracy of 2 ppm, and the second can be set in 1 / 1024th of a second increments.

[0037] Each measuring device 12 has its own RTC 16, but the RTCs 16 are not synchronized between the measuring devices 12. Therefore, even if a GPS module 18 or a time server with an accurate reference clock is used, the RTCs 16 between the measuring devices 12 can deviate from synchronization by up to 1 / 1024 of a second when receiving radio waves from a GPS satellite, as mentioned above. An even bigger problem is the accuracy of the RTC 16 itself. Even a highly accurate RTC 16 can have an error of about 2 ppm (±2 μs per second = 5 seconds per month). In other words, the RTC 16 can experience a time difference of up to 7.2 / 1000 of a second (7.2 ms) over one hour.

[0038] In contrast to the above, the measurement targets of this embodiment are the velocity of surface waves in the ground and the microtremors of structures, as mentioned above, but in order to accurately measure the vibration transmission speed, vibration attenuation, etc., it is necessary to measure both of them synchronously at multiple locations. Furthermore, since the phase difference of the waveform is also an important measurement item, a synchronization accuracy of about 1 / 5 to 1 / 10 of the sampling speed is required between multiple locations.

[0039] Here, since the maximum sampling rate is 1 kHz (1000 samples / sec), the required synchronization accuracy between the RTCs 16 of each measuring device 12 is 1 / 10000 seconds (100 μsec). In contrast, an RTC 16 with an accuracy of 2 ppm exceeds this condition in just 50 seconds.

[0040] For example, consider the case where the GPS modules 18 in each measuring device 12 receive radio waves from GPS satellites outdoors to synchronize the RTCs 16 between the measuring devices 12, and then these measuring devices 12 are brought underground or into a building and measurements are started with the RTCs 16 synchronized. Because the RTC 16 synchronization error reaches 1 / 10,000 of a second (100 μs) 50 seconds after receiving a signal from a GPS satellite, causing synchronization to be lost, the measuring devices 12 must be transported, installed, and measured within 50 seconds. However, the measurement time normally requires 5 to 10 minutes, and at least 30 minutes are required to transport, install, and measure the measuring devices 12, making it clear that synchronized measurements using multiple measuring devices 12 are currently impossible.

[0041] The purpose of this embodiment is to extend the time (period) that the RTC 16 remains synchronized within an allowable range after it has been synchronized with the reference clock (absolute time) of the GPS module 18. Specifically, the purpose is to extend the time that the RTC 16 remains synchronized from 50 seconds to 30 minutes, approximately 40 times longer.

[0042] Next, we will explain how to synchronize with the reference clock using GPS and how to obtain parameters. As mentioned above, when the GPS module 18 receives radio waves from four or more GPS satellites, it outputs position information and at the same time outputs a GPS second pulse, which is time information and has a width of 100 ms and rises every second, as shown in Figure 3. This GPS second pulse is synchronized between the GPS modules 18 of each measuring instrument 12 with an accuracy of better than a microsecond.

[0043] This GPS second pulse must be measured to synchronize the RTC 16 clock, and at the same time, information must be acquired to achieve the desired high-precision synchronization. The information to be acquired consists of the following five parameters. In Figure 3, the GPS second pulse is represented by the GPS second clock, the RTC second pulse is represented by the RTC second clock, and the system clock of the MPU 22 is represented by the MPU clock. D RTC :Time difference between GPS second pulse and RTC second pulse C SYS : Number of counts per second of the MPU system clock (GPS second clock count) C RTC : RTC second clock count per second t CAL : The time when the GPS and synchronization parameters were acquired Δt RTC :RTC clock delay (C RTC - C SYS )

[0044] Although the temperatures of the acceleration sensor 14 and the MPU 22 are also measured, these temperatures are not used as parameters here. RTC The contents excluding " are shown in Figure 3. Here, [count] is the count number of the RTC second clock and the MPU clock in microseconds (μ seconds).

[0045] The values ​​in Figure 3 are examples, but in this example, Δt RTC = C RTC - C SYSThe value of is 0.7 counts. This means that the RTC 16 lags behind the MPU 22 by 0.7 μsec per second. If this state continues, after about 150 seconds the RTC second clock will lag behind the absolute time by about 1 / 10000 seconds (100 μsec). The essential feature of this embodiment is to generate an RTC second clock that is close to absolute time by adjusting the RTC second clock taking into account this RTC 16 lag.

[0046] D RTC is time t CAL The RTC second clock can only be set in 1 / 1024 second increments, so if you try to set the RTC second clock to be ahead of the GPS second clock as shown in Figure 3, RTC The value ranges from 0.0 to 976.6 counts. In the example in Figure 3, it is set to 322.0 counts.

[0047] Next, a method for synchronizing with the RTC 16 when the signal from the GPS satellite is blocked will be described. First, as shown in Figure 2, n measuring devices 12 (1st to nth) are placed outdoors where they can receive signals from GPS satellites, and the synchronization parameters of the RTC 16 are acquired. The parameters acquired by the ith measuring device 12 are respectively calculated as t CAL (i),D RTC (I C RTC (I C SYS (i),Δt RTC (i) Thereafter, each measuring device 12 is moved to a measurement location where signals from GPS satellites cannot be received, for example, to measure microtremors of a structure.

[0048] From this point on, each measuring device 12 operates independently according to commands sent from the tablet PC 30 via WiFi 20. Each measuring device 12 samples acceleration data in sync with its built-in RTC second clock and temporarily stores the acceleration data on the SD card 24.

[0049] The RTC second clock shown in Figure 3 has a delay of Δt RTC Assuming (i) is constant, it flows in one direction relative to the GPS second clock. Δt RTC When (i) is positive, the RTC second clock in Figure 3 flows to the right, and Δt RTC If (i) is negative, it flows to the left. Therefore, D RTC (i) changes depending on time t. D RTC (i)(t) = D RTC (i) + Δt RTC (i) × (t - t CAL (i)) Equation (1)

[0050] Δt RTC (i) is a function of temperature, but the MPU 22 of each measuring device 12 is RTC If (i) is assumed to be a constant value, then equation (1) gives the delay of the RTC second clock from the absolute time at the sampling time t, D RTC Therefore, the MPU 22 of each measuring device 12 can know the absolute time of the RTC second clock, and can sample acceleration data in accordance with the absolute time.

[0051] Next, a method of synchronization during measurement will be specifically described. In the example in Figure 3, Δt RTC is 0.7 count. For example, at t = 11:00:00, one hour after the start of synchronization at t = 10:00:00, D RTC = 322.0 - 0.7 × 3600 = -2198. 1000 Hz sampling (1000 samples / sec) results in a synchronization error of two or more samples from the absolute time. With such a large synchronization error, it is difficult for each measuring device 12 to sample acceleration data in accordance with the absolute time.

[0052] For the above reasons, the MPU 22 must execute the following process to prevent significant synchronization loss among the measuring devices 12. First, the MPU 22 observes the rising edge of the RTC second clock, and then starts sampling the acceleration data for that second. RTC Therefore, in the actual MPU22 process, for example, D RTC Adjust the value so that it is between 0 and 976.6 counts. For example, D RTC is updated by the following formula, and D RTC If it becomes negative, advance the RTC second clock by 1 / 1024 seconds. RTC Add 976.6 count to the above.

[0053] On the other hand, D RTC If the count exceeds 976.6, the RTC second clock is delayed by 1 / 1024 seconds. RTC The following formula (2) is the delay D per minute. RTC This is the renewal procedure. D RTC = D RTC + Δt RTC × 60 formula (2)

[0054] Next, a specific example will be described below in which the RTC second clock is adjusted to take into account the delay of the RTC 16 and generate an RTC second clock that is close to the GPS second clock, which is regarded as absolute time. First, an example of the measurement results is shown in FIG. 4, where each value is, for example, as shown in FIG. 3 and is as follows: t CAL :10:00:00 D RTC :322.0 count(μ seconds) C RTC :999,993.5 count C SYS :999,992.8 count Δt RTC :0.7μsec

[0055] The time t when the GPS and synchronization parameters were acquired CAL At the time of 10:00:00, the RTC second clock is ahead of the GPS clock by D.RTC is 322.0 μsec. And the RTC clock delay time Δt RTC is 0.7μs per second. RTC As the value of becomes negative, the parameter D RTC shall be adjusted.

[0056] As mentioned above, it can be adjusted every minute, but specifically, at 10:08:00, 8 minutes later (480 seconds later), the RTC second clock will be 322.0 -0.7 × 480 = -14.0 μsec, which is a negative value. At this point, the RTC clock delay time Δt RTC The adjustment can be done in 1 / 1024 second increments, so the adjusted time of 10:08:01 is RTC is -14.0-0.7+(1,000,000 / 1024)=961.9μsec.

[0057] Further time passes, and although not shown, for example, 23 minutes later at 10:31:00, D RTC becomes negative again -3.4μs, so D RTC can be set to 972.5 μsec. By adjusting this RTC clock, the GPS second clock, which is absolute time, can be reproduced. Here, the GPS second pulse shown in Figure 4 is considered to be a virtual clock pulse, and the D after the RTC second pulse corrected by the above-mentioned RTC clock adjustment is RTC By assuming that an absolute time GPS second pulse comes afterwards, absolute time can be determined.

[0058] D every minute RTC The reason for checking and adjusting the value is that sampling data is saved every minute, and the RTC16's one-minute delay (or advance) is expected to be smaller than the target synchronization deviation of 1 / 10,000 seconds (100 μsec). Also, since adjusting the 1 / 1024 second RTC second clock requires timing and sending a command to the RTC16, it is easier to incorporate this as a periodic process.

[0059] Next, based on the explanation so far, the sampling process of each measuring device 12 at each measurement point and the synchronization process of the RTC second clock will be described. Since the sampling process and the RTC second clock synchronization process are performed as separate processes, the sampling process will be described first. The sampling of acceleration data in the sampling process is performed every second from 0 to 59 seconds of each minute, and is continuously saved to the SD card 24. The sampling of acceleration data for each second is performed by the MPU 22 reading the change in the RTC second clock via the I / O port. If the MPU 22 observes the rising edge of the RTC 16 clock, after this rising edge, the D RTC Then, the measurement data for that second is acquired at a predetermined sampling interval. RTC If is negative, sampling begins immediately after the rising edge of the RTC clock, and this is repeated every second.

[0060] On the other hand, the RTC second clock synchronization process is CAL (i),D RTC (I C RTC (I C SYS (i),Δt RTC The process is divided into two parts: a calibration process to find the five synchronization parameters (i) and an update process of the RTC second clock. However, since there are n measuring devices 12, these processes are performed in each of the n measuring devices 12.

[0061] First, the calibration process will be described. This calibration process is performed while the GPS second clock is continuously generated. RTC (I C RTC (I C SYS (i) is D RTC ,C RTC ,C SYS is calculated as follows. In addition, the actual D RTC ,C RTC ,C SYS The procedure takes place over several seconds, RTC (I C RTC (I CSYS The average value of (i) is calculated. The central time of the multiple seconds is registered as tCAL(i). Also, Δt RTC (i) = C RTC (I C SYS (i) Calculate the RTC second clock delay per second.

[0062] Each step of the calibration process will now be described in detail. First, set the RTC16 seconds and delay time D RTC The procedure for obtaining this will be explained with reference to FIG. This procedure begins with "START," but from "START" onward, a determination is made in step S11 as to whether the GPS second clock has started. If the determination is "NO," the procedure returns to step S11, and the same determination is repeated until the GPS second clock starts. If the GPS second clock has started and the determination is "YES," the procedure moves to step S12, where the process "sets the RTC time so that the RTC time is 0 to 1 / 1024 seconds earlier than the GPS time" is performed, and the procedure moves to step S13.

[0063] In step S13, the process waits 0.99 seconds until the next second pulse arrives. Here, "GPS time" means the time based on the GPS second pulse obtained from the GPS satellites, and "RTC time" means the time based on the RTC second pulse stored inside the RTC 16. Next, in step S14, a determination is made as to whether the RTC second clock has risen. If the determination is "NO," the process returns to step S14, and the same determination is repeated until the RTC second clock rises. If the RTC second clock has risen and the determination is "YES," the process moves to step S15, where the MPU clock counter value is assigned to Start, and the process moves to step S16.

[0064] In step S16, a determination is made as to whether the GPS second clock has risen. If the determination is "NO," the process returns to step S16, and the same determination is repeated until the GPS second clock rises. If the GPS second clock has risen and the determination is "YES," the process moves to step S17, where the MPU clock counter value is assigned to End, and the process moves to step S18.

[0065] In step S18, "End-Start" is RTC and the time at that time is t CAL In other words, the difference between "End" and "Start" is detected, and if it is within a predetermined range, this value is assigned to D RTC Then it is "finished" and the RTC16 seconds setting and delay time D RTC The processing procedure for obtaining the value is completed.

[0066] Next, the second clock value C of the RTC16 clock RTC The procedure for obtaining this will be explained with reference to FIG. This procedure starts with "Start," but from "Start," a determination is made in step S21 as to whether the RTC second clock is rising. If the determination is "NO," the process returns to step S21 and the same determination is made repeatedly until the RTC second clock rises. If the RTC second clock rises and the determination is "YES," the process moves to step S22, where the "MPU clock counter value is assigned to Start" is performed, and the process moves to step S23.

[0067] In step S23, a determination is made as to whether the RTC second clock has risen after m seconds. If the determination is "NO," the process returns to step S23 and the same determination is repeated until the RTC second clock rises for the second time. If the RTC second clock rises and the determination is "YES," the process moves to step S24, where the MPU clock counter value is assigned to End, and the process moves to step S25.

[0068] In step S25, "(End-Start) / m is C RTCIn other words, the average value of the difference between "End" and "Start" is assigned to C RTC Then it is "ended" and the RTC16 clock value C RTC The processing procedure for obtaining the value is completed.

[0069] Next, the second clock value C of the system clock of the MPU 22 SYS The procedure for obtaining this will be explained with reference to FIG. This procedure begins with "START," but from "START" onwards, a determination is made in step S31 as to whether the GPS second clock has started. If the determination is "NO," the process returns to step S31 and the same determination is made repeatedly until the GPS second clock starts. If the GPS second clock has started and the determination is "YES," the process moves to step S32, where the "MPU clock counter value is assigned to Start" is performed, and the process moves to step S33.

[0070] In step S33, a determination is made as to whether the GPS second clock has risen m seconds later. If the determination is "NO," the process returns to step S33, and the same determination is repeated until the second rise of the GPS second clock. If the GPS second clock has risen and the determination is "YES," the process proceeds to step S34, where the MPU clock counter value is assigned to End, and the process proceeds to step S35.

[0071] In step S35, "(End-Start) / m is C SYS In other words, the average value of the difference between "End" and "Start" is assigned to C SYS Then, the "end" is reached and the second clock value C SYS The processing procedure for obtaining the value is completed.

[0072] Next, the RTC second clock update process will be described. This update process is performed periodically every minute after the calibration process. Using equation (2), D RTCIf this value is negative, the RTC second clock is advanced by 1 / 1024 seconds. RTC Add 976.6 count to D RTC If the count exceeds 976.6, the RTC second clock is delayed by 1 / 1024 seconds. RTC Subtract 976.6 count from the time. This process is performed at the last second (59 seconds) of each minute.

[0073] As described above, according to this embodiment, it is possible to measure not only the velocity of surface waves in the ground and minute accelerations such as micro-movements of structures simultaneously and over a wide range with high precision and appropriate timing, but also to accurately measure the speed at which vibrations are transmitted and the attenuation of vibrations.

[0074] In the above embodiment, the sampling rate is set to 1 / 1000 of a second, but it may be set to, for example, 1 / 100, 1 / 200, or 1 / 500 of a second depending on the type of measurement target. Furthermore, in the above embodiment, the GPS module 18 is a GPS receiver that receives signals from GPS satellites, but it may also be a GNSS receiver that can receive signals from satellites other than GPS satellites.

[0075] Meanwhile, in the above embodiment, commands are sent from tablet PC 30 to each measuring device via WiFi 20 to control and operate each measuring device, but each measuring device can also be operated manually (by button operation) or by application software on tablet PC 30 connected to USB interface 26. Note that operation here refers to synchronization with the GPS module clock before measurement, acquisition of synchronization data, starting and stopping measurement, etc.

[0076] In addition, in the above embodiment, the data measured by the accelerometer of each measuring device is temporarily stored on the SD card 24 and then collected by the tablet PC 30 via WiFi 20 after the measurement is completed, but the tablet PC 30 may also collect the data via the USB interface 26.

[0077] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. [Industrial Applicability]

[0078] The measuring instrument synchronization system and measuring instrument synchronization method of the present invention can simultaneously measure minute accelerations such as the velocity of surface waves in the ground and micro-tremors of structures over a wide range, and can also be applied to disasters such as earthquakes and vibration measurements on various devices. [Explanation of symbols]

[0079] 10. Instrument synchronization system 12 Measuring instruments 14 Acceleration sensor (accelerometer) 16 RTC 18 GPS module 20 WiFi 22 MPU 24 SD cards 26 USB interface 30 Tablet PC (computer)

Claims

1. a GPS module that receives radio waves from GPS satellites and outputs a GPS second clock that is regarded as absolute time; an RTC that emits an RTC second clock; an accelerometer that detects acceleration at a timing synchronized with the time of the RTC second clock; an MPU that transmits a system clock and is connected to a GPS module, an RTC, and an accelerometer to control their operations; A measuring instrument synchronization system including a plurality of measuring instruments each having A measuring device synchronization system that controls the acceleration detection start timing of multiple measuring devices by adjusting the RTC second clock to be closer to the GPS second clock by taking into account the temporal operation deviation of the RTC.

2. 2. The measuring device synchronization system according to claim 1, wherein the time difference between the GPS second clock and the RTC second clock is calculated every minute so that the time difference is always within the range of 0 to 1 / 1024 seconds, and if the time difference exceeds 0 to 1 / 1024 seconds, 1 / 1024 seconds is added or subtracted to adjust the time difference so that the time difference is within the range of 0 to 1 / 1024 seconds.

3. 2. The measuring device synchronization system according to claim 1, further comprising a computer, wherein the plurality of measuring devices are connected to the computer, and the acceleration data measured by each measuring device is compiled by the computer.

4. 2. The measurement device synchronization system according to claim 1, wherein the accelerometer of each measurement device detects acceleration at a maximum interval of 1 / 1000 of a second.

5. A method for synchronizing a plurality of measuring devices, in which a GPS module receives radio waves from a GPS satellite and outputs a GPS second pulse that is taken as absolute time, an RTC transmits an RTC second clock that is in line with the GPS second pulse, and an accelerometer sets the timing for detecting acceleration based on the RTC second clock, comprises: After adjusting the RTC second clock to account for the time lag of the RTC, A measurement device synchronization method that generates an RTC second clock that is close to the GPS second pulse and controls the acceleration detection start timing among multiple measurement devices.

6. The time difference between the GPS second pulse and the RTC second pulse is D RTC year, Set the RTC time in the range of 0 to 1 / 1024 seconds relative to the GPS absolute time, and set the value at that time to D RTC 6. The measuring device synchronization method according to claim 5, wherein:

7. The number of counts per second of the RTC second clock is C RTC Let the number of counts per second of the MPU clock be C SYS year, C between the first RTC second clock and the second RTC second clock SYS The difference between RTC 6. The measuring device synchronization method according to claim 5, wherein:

8. The number of counts per second of the MPU system clock is C SYS year, C between the first and second GPS second clocks using the GPS second pulse SYS The difference between the new C SYS 6. The measuring device synchronization method according to claim 5, wherein:

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