Data Acquisition Equipment

Abstract

To reduce a processing load of a control section by suppressing a reduction in a sampling frequency.SOLUTION: A data acquisition device 1 comprises a sensor 7 for detecting a physical quantity as analog data, an A / D converter 12 for converting the analog data into digital data, a storage circuit 14 for storing the physical quantity, a difference circuit 17 for calculating a difference (ΔV) between a previous value Vn-1 of the physical quantity stored in the storage circuit 14 and a present value Vn of the physical quantity detected as analog data, a comparison circuit 18 for comparing the difference with a predetermined threshold Vth, and a controller 13 for controlling execution of A / D conversion by the A / D converter. The controller 13, when the difference exceeds the threshold Vth, converters the present value Vn of the physical quantity detected as analog data into digital data by the A / D converter 12 to obtain as the present value Vn of the digital data, and when the difference is equal or less than the threshold Vth, keeps the previous value Vn-1 of the physical quantity stored in the storage circuit 14 as the present value Vn.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to data acquisition devices, and more particularly to data acquisition devices that acquire digital data from analog data. [Background technology]

[0002] An engine control circuit for controlling engine operation is known that includes an A / D converter that performs analog-to-digital conversion of a sensor's output voltage (see Patent Document 1). This engine control circuit reads a current A / D-converted value output from the A / D converter at predetermined time intervals and calculates the difference between the absolute value of the difference between the previous A / D-converted value and the current A / D-converted value and the absolute value of the difference between the A / D-converted value two years before last and the previous A / D-converted value. If this difference is equal to or less than a threshold, the engine control circuit determines that the current A / D-converted value is not noise and updates the input value with the current A / D-converted value. If this difference is greater than the threshold, the engine control circuit determines that the current A / D-converted value may be noise, does not update the input value, and maintains the previous input value as is. This engine control circuit also includes a multiplexer that selects sensor signals from multiple sensors and reads them via the A / D converter.

[0003] Furthermore, an A / D conversion circuit device capable of suppressing defects caused by sudden changes in analog signals is known that includes a comparison unit that compares a temperature detection signal (analog signal) from a temperature sensor with a D / A conversion voltage from a D / A converter, and a processing unit (control unit) that performs a judgment process based on the comparison result of the comparison unit and determines the A / D conversion result based on the judgment process so that the change in the current A / D conversion result relative to the previous A / D conversion result is equal to or less than a predetermined value (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 1999-62689 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-103660 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional A / D conversion circuit devices convert all analog signals into digital signals to obtain the A / D conversion results (i.e., digital data). Therefore, if the time required for A / D conversion is long, the sampling frequency decreases. As a result, when the digital data from the A / D conversion circuit device is used to control a robot, the robot's responsiveness deteriorates. Furthermore, if a judgment process or a process to determine the final result data is performed on all digital data to calculate the digital data, the processing load on the control unit increases. As a result, power consumption increases and the control unit becomes hot.

[0006] In particular, when analog data is input from a huge number of sensors, the time required for A / D conversion increases in proportion to the amount of data, and the sampling period of each sensor becomes longer. While the sampling period can be shortened by reducing the number of sensors, this results in a sparser distribution of sensors and a deterioration in spatial resolution. In other words, there is a trade-off between shortening the sampling period and improving spatial resolution, and it has been difficult to achieve both.

[0007] In view of this background, the present invention , regulation It is an object of the present invention to provide a data acquisition device that can reduce the processing load on the control unit. [Means for solving the problem]

[0008] In order to solve such a problem, one embodiment of the present invention is a data acquisition device (1) that acquires a predetermined physical quantity (e.g., pressure) A At least one sensor that detects analog data (voltage) (7) a sensor device (2) that outputs the physical quantity detected by the sensor at predetermined sampling intervals; and, The output from the sensor an A / D converter (12) for converting analog data into digital data; Digital dataa memory circuit (14) for storing the physical quantity; Digital data The previous value (Vn-1) of the physical quantity and the analog data detected Output from the sensor device The apparatus includes a difference circuit (17) that calculates a difference (ΔV) between the current value (Vn) of the physical quantity, a comparison circuit (18) that compares the difference with a predetermined threshold (Vth), and a control unit (13) that controls execution of A / D conversion by the A / D converter, wherein the control unit is configured to, when the difference exceeds the threshold, convert the current value of the physical quantity detected as analog data into digital data using the A / D converter, acquire it as a current value of digital data, and store it in the memory circuit, and, when the difference is equal to or less than the threshold, hold the previous value of the physical quantity stored in the memory circuit as the current value of digital data.

[0009] According to this configuration, when the change in the physical quantity is small and the difference is equal to or less than the threshold, the control unit does not convert the analog data into digital data using the A / D converter, thereby reducing the number of A / D conversions. .Ma Furthermore, the data difference calculation and data comparison that were previously performed by the control unit are now performed by a difference circuit and a comparison circuit, which are analog circuits, so these processes do not need to be performed by the control unit, thereby reducing the processing load on the control unit.

[0010] Preferably , this The data acquisition device further includes a first D / A converter (15) for converting the previous value of the physical quantity of the digital data stored in the memory circuit into analog data. Preferably, the memory circuit stores the threshold value of the digital data, and the data acquisition device further includes a second D / A converter (16) for converting the threshold value of the digital data stored in the memory circuit into analog data.

[0011] According to these configurations, the configuration of the storage circuit can be simplified.

[0012] Preferably, the memory circuit stores the threshold value, and the control unit supplies the threshold value stored in the memory circuit to the comparison circuit, and changes the threshold value to a smaller value when the difference exceeds the threshold value.

[0013] With this configuration, after the analog data of the physical quantity has changed by a difference larger than the threshold, the physical quantity can be accurately acquired with a smaller difference. Furthermore, since the memory circuit stores the threshold value of the digital data, the degree of freedom in setting the threshold value is high.

[0014] Preferably, at least one of the sensors constitutes a sensor unit (6) including a plurality of the sensors (7) connected to the A / D converter via a multiplexer (9), the memory circuit stores the physical quantity for each of the sensors, and the control unit via the first D / A converter The multiplexer is switched in synchronization with the switching of the physical quantity supplied to the difference circuit.

[0015] According to this configuration, the sensor unit including a plurality of sensors can realize high spatial resolution while reducing the processing load on the control unit. [Effects of the Invention]

[0016] Thus, according to the present invention , regulation It is possible to provide a data acquisition device that can reduce the processing load on the control unit. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a data acquisition device according to an embodiment. [Figure 2] A circuit diagram showing the detailed configuration of the differential circuit shown in FIG. [Figure 3] Flow diagram of data acquisition processing executed by the control unit [Figure 4] Flow diagram of threshold setting processing according to a modified example DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0019] 1 is a block diagram showing a schematic configuration of a data acquisition device 1 according to an embodiment. The data acquisition device 1 includes a sensor device 2 that detects a predetermined physical quantity as analog data at a predetermined sampling period, a controller 3 that acquires a physical quantity of digital data from the physical quantity of the analog data output from the sensor device 2, and a determination circuit 4.

[0020] The sensor device 2 includes a sensor unit 6 connected to a power source 5. The sensor unit 6 includes at least one sensor 7 (sensor portion). In this embodiment, the sensor unit 6 has a matrix structure with four channels in the Y direction and eight channels in the X direction, and includes a total of 32 sensors 7 arranged on a plane. Each sensor 7 detects a predetermined physical quantity as analog data. The predetermined physical quantity may be, for example, pressure, load, strain, temperature, etc., and outputs an analog electrical signal corresponding to these physical quantities. The sensor 7 of this embodiment is supplied with a predetermined applied voltage (e.g., 5 V) from the power source 5 and outputs a detection voltage corresponding to the pressure. The sensor unit 6 includes multiple sensors 7, thereby achieving high spatial resolution.

[0021] The sensor device 2 further includes a demultiplexer 8 provided on a signal line connecting the power supply 5 and the sensor unit 6, a multiplexer 9 provided on a signal line connecting the sensor unit 6 and the controller 3, a low-pass filter 10, and an amplifier 11. The demultiplexer 8 switches between the four channels in sequence as the channel to which the applied voltage is to be supplied from the power supply 5 in accordance with a command from the controller 3. The multiplexer 9 switches between the eight channels in sequence as the channel to which the detected voltage is to be output from the sensor unit 6 in accordance with a command from the controller 3. The demultiplexer 8 and the multiplexer 9 are switched by the controller 3, so that the sensor device 2 outputs the detected voltages of the 32 sensors 7 in sequence at predetermined sampling intervals.

[0022] The controller 3 is an electronic processing device including a CPU, a ROM, a RAM, etc. The controller 3 includes an A / D converter 12 that converts an analog electrical signal into a digital electrical signal, a control unit 13 that controls the execution of A / D conversion by the A / D converter 12, and a memory circuit 14 that stores the physical quantity detected by the sensor device 2. The controller 3 may be configured as a single piece of hardware, or may be configured as a unit consisting of multiple pieces of hardware.

[0023] The memory circuit 14 may be configured with a ROM, a RAM, or the like and store the physical quantity of digital data, or may be configured with a capacitor and store the physical quantity of analog data. The memory circuit 14 of this embodiment is configured with a RAM and stores the physical quantity of digital data (in this embodiment, the detected voltage according to the pressure). The memory circuit 14 stores the physical quantity for each sensor 7. The memory circuit 14 resets the physical quantity when the data acquisition device 1 is stopped, and stores 0 as the initial value when the data acquisition device 1 is started.

[0024] Furthermore, the memory circuit 14 stores a threshold value Vth, which will be described later, in addition to the physical quantities. The memory circuit 14 may store the threshold value Vth for each sensor 7, or may store a common threshold value Vth for all sensors 7. In this embodiment, the threshold value Vth for each sensor 7 is set to a constant value. However, as in a modified example, which will be described later, the threshold value Vth may be set to a value that changes depending on conditions.

[0025] The A / D converter 12 performs comparison processing multiple times, for example, using a method similar to a successive approximation type, and converts the analog data into digital data represented by a multi-bit (e.g., 10-bit) A / D conversion result. The A / D converter 12 performs A / D conversion in accordance with a command from the control unit 13, and outputs the digital data to the controller 3. The A / D converter 12 of this embodiment performs A / D conversion at a timing corresponding to a sampling period only when it receives an execution command from the control unit 13, as will be described later, and does not perform A / D conversion at any other timing.

[0026] The control unit 13 is configured by a CPU, and executes various controls by reading programs stored in a ROM or the like and executing arithmetic processing in accordance with the programs. For example, the control unit 13 outputs a switching command to the demultiplexer 8 and the multiplexer 9 at a timing synchronized with the sampling period, thereby causing the physical quantities of analog data detected by the 32 sensors 7 to be output in sequence to the sensor device 2. The physical quantities of the analog data output from the sensor device 2 (current values ​​Vn of the detected voltages of the sensors 7) are supplied to the A / D converter 12 and the determination circuit 4 of the controller 3.

[0027] Furthermore, the control unit 13 supplies the physical quantity (the previous value Vn-1 of the detected voltage of each sensor 7 (initial value immediately after startup)) of digital data stored in the memory circuit 14 and a predetermined threshold value Vth of the digital data to the determination circuit 4. The control unit 13 supplies the previous value Vn-1 of the detected voltage and the threshold value Vth for each sensor 7 to the determination circuit 4 at a predetermined timing.

[0028] Furthermore, the control unit 13 determines the analog data that should be A / D converted by the A / D converter 12 from the current value Vn of the detected voltage of the analog data of each sensor 7 output in sequence from the sensor device 2, and controls the execution of A / D conversion by the A / D converter 12.

[0029] The decision circuit 4 has a first D / A converter 15 and a second D / A converter 16 that convert digital electrical signals into analog electrical signals, a difference circuit 17 that outputs the difference between two analog data, and a comparison circuit 18 that compares the two analog data. The difference circuit 17 and the comparison circuit 18 are analog circuits. The first D / A converter 15 converts the previous value Vn-1 of the detection voltage of the digital data into an analog voltage. The second D / A converter 16 converts the threshold Vth of the digital data into an analog voltage.

[0030] The difference circuit 17 outputs a difference voltage ΔV between the current value Vn of the detected voltage output from the sensor device 2 and the previous value Vn-1 of the detected voltage supplied from the first D / A converter 15. The comparison circuit 18 compares the difference voltage ΔV output from the difference circuit 17 with a threshold Vth supplied from the second D / A converter 16, and outputs the comparison result. The difference circuit 17 of this embodiment outputs 1 if the difference voltage ΔV exceeds the threshold Vth, and outputs 0 if the difference voltage ΔV does not exceed the threshold Vth. In other embodiments, the difference circuit 17 may output "1" and "0" interchangeably.

[0031] The determination circuit 4 executes these processes for each sensor 7 at timings corresponding to the switching of the demultiplexer 8 and the multiplexer 9.

[0032] The differential circuit 17 outputs the absolute value as the differential voltage ΔV between the current value Vn and the previous value Vn-1 of the detected voltage. FIG. 2 is a circuit diagram showing the detailed configuration of the differential circuit 17 shown in FIG. 1. As shown in FIG. 2, the differential circuit 17 includes a first subtractor 19, a second subtractor 20, and an adder 21. The current value Vn of the detected voltage is input to the first subtractor 19 as an added value, and the previous value Vn-1 of the detected voltage is input as a subtracted value. The previous value Vn-1 of the detected voltage is input to the second subtractor 20 as an added value, and the current value Vn of the detected voltage is input as a subtracted value. The output of the first subtractor 19 and the output of the second subtractor 20 are input to the adder 21. When the current value Vn of the detected voltage is greater than the previous value Vn-1 (Vn > V(n-1)), the first subtractor 19 outputs a value (Vn - V(n-1)) obtained by subtracting the previous value Vn-1 from the current value Vn. When the current value Vn of the detected voltage is less than the previous value Vn-1 (Vn < V(n-1)), the second subtractor 20 outputs a value (V(n-1) - Vn) obtained by subtracting the current value Vn from the previous value Vn-1. The adder 21 outputs the absolute value of the differential voltage ΔV by adding the output of the first subtractor 19 and the output of the second subtractor 20.

[0033] As shown in FIG. 1, when the comparison circuit 18 outputs 1 (when the differential voltage ΔV exceeds the threshold value Vth), the control unit 13 issues an execution command to the A / D converter 12. That is, the control unit 13 A / D-converts the current value Vn of the detected voltage of this sensor 7 output from the sensor device 2 by the A / D converter 12. Further, the control unit 13 records the digital data output from the A / D converter 12 in the storage circuit 14 as the current value Vn of the detected voltage of this sensor 7.

[0034] When the comparison circuit 18 outputs 0 (when the differential voltage ΔV does not exceed the threshold value Vth), the control unit 13 does not issue an execution command to the A / D converter 12. That is, the control unit 13 does not A / D-convert the current value Vn of the detected voltage of this sensor 7 output from the sensor device 2 by the A / D converter 12. Then, the control unit 13 holds the previous value Vn-1 of the detected voltage of this sensor 7 stored in the storage circuit 14 as the current value Vn. is maintained as is, that is, the detection voltage The previous value Vn-1 is held as the current value Vn.

[0035] In this way, the data acquisition device 1 acquires digital data by event-driven A / D conversion, which performs A / D conversion on analog data when the differential voltage ΔV exceeds the threshold value Vth.

[0036] The data acquisition device 1 can be used, for example, as a contact sensor in which the sensor unit 6 is attached to the skin of a robot's hand and detects contact with a substance. The data acquisition device 1 outputs the acquired digital data from each sensor 7 to a host computer. When each sensor 7 does not detect contact (when the differential voltage ΔV does not exceed the threshold Vth), the processing load on the control unit 13 is small even if there are a large number of sensors 7. Therefore, the responsiveness of the robot does not deteriorate due to a longer data acquisition time (sampling period). Furthermore, the amount of data processed by the control unit 13 does not become so large that it places a strain on communication.

[0037] Note that even if each sensor 7 detects contact (differential voltage ΔV exceeds threshold value Vth), if the contact pressure does not change, the differential voltage ΔV will not exceed threshold value Vth in the next sampling period. Therefore, the control unit 13 does not perform A / D conversion by the A / D converter 12, and holds the previous value Vn-1 as the current value Vn. This also reduces the processing load on the control unit 13.

[0038] Next, the data acquisition process executed by the control unit 13 will be described with reference to Fig. 3. Fig. 3 is a flow diagram of the data acquisition process executed by the control unit 13. As shown in Fig. 3, the control unit 13 executes the following routine at each predetermined sampling period.

[0039] First, the control unit 13 sets the channel of the demultiplexer 8 (step ST1). In this embodiment, the control unit 13 switches between the four channels of the demultiplexer 8 in sequence every eight routines. Next, the control unit 13 sets the channel of the multiplexer 9 (step ST2). In this embodiment, the control unit 13 switches between the eight channels of the multiplexer 9 in sequence every routine. In this way, the 32 sensors 7 are switched in sequence every routine. Either step ST1 or step ST2 may be performed first.

[0040] Next, the control unit 13 sets the previous value Vn-1 of the detected voltage of the sensor 7 to be determined selected in steps ST1 and ST2 (step ST3). Specifically, the control unit 13 acquires the previous value Vn-1 of the detected voltage of the sensor 7 to be determined from the memory circuit 14, and supplies this value to the difference circuit 17 via the first D / A converter 15. The control unit 13 also sets a threshold value Vth set for the sensor 7 to be determined (step ST4). Specifically, the control unit 13 acquires the threshold value Vth set for the sensor 7 to be determined from the memory circuit 14, and supplies this value to the comparison circuit 18 via the second D / A converter 16. Either step ST3 or step ST4 may be performed first.

[0041] Thereafter, the control unit 13 checks the output (comparison result) from the comparison circuit 18 of the determination circuit 4 to determine whether the differential voltage ΔV of the sensor 7 being determined exceeds the threshold value Vth (step ST5). If the output from the comparison circuit 18 is 1 and the differential voltage ΔV exceeds the threshold value Vth (step ST5: Yes), the control unit 13 A / D converts the current value Vn of the detected voltage of the sensor 7 being determined using the A / D converter 12 and acquires the current value Vn of the detected voltage of the digital data (step ST6). Next, the control unit 13 records the current value Vn of the detected voltage of the digital data in the memory circuit 14 as the current value Vn of the detected voltage of the sensor 7 being determined (step ST7), and repeats the above procedure.

[0042] In step ST5, if the output from the comparison circuit 18 is 0 and the differential voltage ΔV does not exceed the threshold value Vth (step ST5: Yes), the control unit 13 repeats the above procedure without performing the processes of steps ST6 and ST7. Because the process of step ST7 is not performed, the previous value Vn-1 of the detected voltage of the sensor 7 to be determined stored in the memory circuit 14 is held as the current value Vn. Furthermore, because the process of step ST6 is not performed, the number of A / D conversions is reduced.

[0043] In this way, when the differential voltage ΔV exceeds the threshold value Vth, the control unit 13 converts the current value Vn of the physical quantity detected as analog data into digital data using the A / D converter 12, and acquires it as the current value Vn of the digital data. Also, when the differential voltage ΔV is equal to or less than the threshold value Vth, the control unit 13 converts the previous value Vn-1 of the physical quantity stored in the memory circuit 14 into the current value Vn of the digital data. As it is It is configured to hold.

[0044] Therefore, when the change in the physical quantity is small and the differential voltage ΔV is equal to or less than the threshold value Vth, the control unit 13 does not convert the analog data into digital data using the A / D converter 12, thereby reducing the number of A / D conversions. This makes it possible to suppress a decrease in the sampling frequency. Furthermore, the data difference calculation and data comparison that were previously performed by the control unit 13 are now performed by the differential circuit 17 and the comparison circuit 18, which are analog circuits, respectively, and it is not necessary for the control unit 13 to perform these processes. This reduces the processing load on the control unit 13.

[0045] The data acquisition device 1 also includes a first D / A converter 15 and a second D / A converter 16 that convert the previous value Vn-1 of the physical quantity and the threshold value Vth, which are stored as digital data in the memory circuit 14, into analog data. Therefore, the memory circuit 14 can be configured using a ROM, RAM, or the like that stores the physical quantity and threshold value Vth as digital data, and the configuration of the memory circuit 14 is simple.

[0046] In this embodiment, the data acquisition device 1 includes a sensor unit 6 having a plurality of sensors 7 connected to an A / D converter 12 via a multiplexer 9, thereby achieving high spatial resolution. The memory circuit 14 stores the physical quantity for each sensor 7, and the control unit 13 switches the multiplexer 9 in synchronization with the switching of the physical quantity supplied to the difference circuit 17, thereby achieving both high spatial resolution and a reduced processing load on the control unit 13.

[0047] Next, a modified example of the data acquisition device 1 will be described. In the above embodiment, the threshold Vth for the sensor 7 was stored as a constant value in the memory circuit 14. Therefore, in step ST4 of FIG. 3, the control unit 13 set the same value as the threshold Vth for the sensor 7 to be determined in all routines. In contrast, in this modified example, the memory circuit 14 stores, as the threshold Vth for each sensor 7, a first value to be set immediately after startup and a second value smaller than the first value. The control unit 13 sets the threshold Vth to the first value immediately after startup, and changes the threshold Vth to a value smaller than the initial value when the differential voltage ΔV of the sensor 7 to be determined exceeds the initial value of the threshold Vth and the determination result in step ST5 becomes Yes.

[0048] Specifically, the control unit 13 performs the process of setting the threshold value Vth executed in step ST4 of FIG. 3 as follows. FIG. 4 is a flowchart of the threshold value setting process according to the modified example. The control unit 13 determines whether the previous value Vn-1 of the detected voltage of the sensor 7 to be determined, which is stored in the memory circuit 14, is 0 (step ST11). This determination is made to confirm whether the previous value Vn-1 of the detected voltage has been changed from its initial value due to the fact that, in a previous routine, the differential voltage ΔV of the sensor 7 to be determined exceeded the initial value of the threshold value Vth, resulting in a Yes determination result in step ST5. If the previous value Vn-1 is 0 (ST11: Yes), the control unit 13 sets a first value as the threshold value Vth for the sensor 7 to be determined (step ST12). On the other hand, if the previous value Vn-1 is not 0 (ST11: No), the control unit 13 sets a second differential value for the sensor 7 to be determined (step ST12). Thereafter, the control unit 13 proceeds to step ST5 of FIG. 3.

[0049] By setting the threshold value Vth in this manner by the control unit 13, after the analog data of the physical quantity has changed with a differential voltage ΔV larger than the threshold value Vth, the physical quantity can be accurately acquired with a smaller differential voltage ΔV. Furthermore, since the memory circuit 14 is configured with a ROM, RAM, or the like and stores the threshold value Vth of the digital data, there is a high degree of freedom in setting the threshold value Vth.

[0050] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and can be widely modified and implemented. For example, in the above embodiment, the data acquisition device 1 has been described as being used as a contact sensor for a robot, but the data acquisition device 1 can be widely applied to devices other than robots. Furthermore, the specific configuration, arrangement, quantity, and predetermined procedure of each component and part can be changed as appropriate within the scope of the present invention. Meanwhile, not all of the components shown in the above embodiment are necessarily required and can be selected as appropriate. [Explanation of symbols]

[0051] 1. Data acquisition device 2. Sensor device 3 Controller 4 Judgment circuit 6 Sensor Unit 7 Sensors 8 Demultiplexer 9 Multiplexer 12 A / D converter 13 Control Unit 14 Memory circuit 15 1st D / A converter 16 Second D / A converter 17 Differential circuit 18 Comparison circuit Vn Current value of detected voltage Vn-1 Previous value of detected voltage Vth threshold ΔV differential voltage

Claims

1. A data acquisition device, a sensor device including at least one sensor that detects a predetermined physical quantity as analog data, and that outputs the physical quantity detected by the sensor at every predetermined sampling period; an A / D converter that converts analog data output from the sensor device into digital data; a storage circuit that stores the physical quantity of digital data and a predetermined threshold value of the digital data; a first D / A converter that converts the physical quantity of the digital data stored in the memory circuit into analog data; a differential circuit that calculates, as analog data, an absolute value of a difference between the physical quantity converted into analog data by the first D / A converter and the physical quantity output from the sensor device; a second D / A converter that converts the threshold value of the digital data stored in the memory circuit into analog data; a comparison circuit that compares the absolute value of the difference between the analog data and the threshold value of the analog data converted by the second D / A converter; a control unit that controls execution of A / D conversion by the A / D converter, supply of the physical quantity as digital data to the first D / A converter, and supply of the threshold value as digital data to the second D / A converter, the control unit is configured to, for each sampling period, convert the physical quantity of analog data output from the sensor device into digital data by the A / D converter when the comparison result of the comparison circuit indicates that the absolute value of the difference exceeds the threshold value, and store the physical quantity of the converted digital data in the storage circuit, and to hold the physical quantity stored in the storage circuit as is when the comparison result of the comparison circuit indicates that the absolute value of the difference is equal to or less than the threshold value, the storage circuit stores a first value and a second value smaller than the first value as the threshold value of the digital data; The control unit, immediately after startup, supplies the first value stored in the memory circuit to the second D / A converter as the threshold value of the digital data, and when the absolute value of the difference exceeds the threshold value, changes the threshold value of the digital data supplied from the memory circuit to the second D / A converter to the second value.

2. The sensor device further includes a multiplexer and a plurality of the sensors, the plurality of sensors constituting a sensor unit connected to the A / D converter via the multiplexer; The data acquisition device according to claim 1 , wherein the control unit switches the multiplexer in synchronization with switching of the physical quantity supplied to the difference circuit via the first D / A converter.

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