Please select the most similar patent number from A, B, C and D. Which number is?
A surface-mounted piezoelectric acceleration sensor, comprising a housing (20), a PCB board (10) fixed to the top of the housing (20), and a piezoelectric ceramic (30) sleeved in the housing (20). A conditioning circuit is provided on the inner side of the PCB board (10); attachment pads (14) are provided on the outer side of the PCB board (10); the piezoelectric ceramic (30) is sleeved in the housing (20); an electrode on one side of the piezoelectric ceramic (30) is connected to a signal pad (12) on the PCB board (10); an electrode on the other side of the piezoelectric ceramic (30) is connected to a ground pad (11) on the PCB board (10). The conditioning circuit is disposed in a shielding cover formed by the PCB board (10) and the housing (20) to ensure that a signal is not interfered, so that the test precision of the whole product is high. Moreover, a low-resistance circuit is disposed outside the sensor, the sensor itself forms a surface-mounted component, and the sensor is freely assembled by a user, thereby fully reducing the space occupied by the sensor itself, and lowering the production cost of the product. The application is more flexible, and the sensor is suitable for various test environments.
A: A charge output element (1), comprising: a support (10) comprising a connecting component (11); a piezoelectric element (20), which is an annular structural body and is sleeved on the connecting component (11), wherein the piezoelectric element (20) is provided with a first deformation groove (23), and the first deformation groove (23) passes through a side wall of the piezoelectric element (20) to disconnect the piezoelectric element (20) in a circumferential direction; and a mass block (30), which is an annular structural body and is sleeved on the piezoelectric element (20), wherein the piezoelectric element (20) is in interference fit with the connecting component (11) and the mass block (30), and the piezoelectric element (20), the mass block (30) and the support (10) of the charge output element (1) are in rigid contact with each other, so that the overall rigidity of the charge output element (1) can be effectively improved, thus improving the frequency response characteristics and resonance of the piezoelectric acceleration sensor. Moreover, the first deformation groove (23) provided on the piezoelectric element (20) causes the piezoelectric element (20) to deform to a greater extent so as to facilitate the assembly of the mass block (30), the piezoelectric element (20) and the support (10), thereby improving the assembly efficiency of the charge output element (1). Further disclosed are a method for assembling the charge output element (1) and a piezoelectric acceleration sensor.
B: A household flower planting monitoring instrument having a photographing function, comprising a housing (10) provided in a sealed manner. A PCB is provided in the housing (10); the PCB is provided with a temperature sensor (44), a photosensitive sensor (41), a soil nutrient measuring instrument (42) used for measuring soil nutrients, and a humidity sensor (43) used for measuring a soil humidity value; the PCB is further provided with a data processor (30) connected to the temperature sensor (44), the photosensitive sensor (41), the soil nutrient measuring instrument (42), and the humidity sensor (43), and a wireless transceiver module (50) connected to the data processor (30); the PCB is provided with measuring electrodes (20) which can be conveniently inserted into soil, the measuring electrodes (20) extend out of the housing (10), and positions where the measuring electrodes (20) and the housing (10) are connected are sealed; the PCB is further connected to a photographing module (60), and the photographing module (60) is connected onto the housing (10) by means of a scalable and flexible connecting rod (61). The monitoring instrument can achieve immediate and real-time monitoring to the flower growth condition by means of the photographing module (60), and can provide a user with optimal planting suggestions by means of a household host and a user terminal.
C: A double-board electric welding machine comprises a machine casing (10). A first PCB board (20) and a second PCB board (30) are provided in the machine casing (10), the first PCB board (20) and the second PCB board (30) are fixed together by using a threaded rod (10), and the first PCB board (20) and the second PCB board (30) are arranged in parallel and are parallel to the bottom of the machine casing (10). The second PCB board (30) is fixed to the machine casing (10) by using a mounting bracket (90), and electronic parts and components electrically connected to an interface and a control panel of the electric welding machine are mounted on the first PCB board (20) and the second PCB board (30). The internal circuit arrangement enables the structure of the electric welding machine to be more compact. In addition, when parts and components on one PCB board are damaged, only the PCB board is replaced, thereby reducing maintenance costs of the electric welding machine.
D: A fitness display apparatus and a fitness counterweight apparatus. The fitness display apparatus comprises an outer housing provided on guide rails (1) and capable of moving under the limit of the guide rails (1); a display screen (14) is provided on the outer housing, the outer housing is internally provided with a generator (11), a PCB (12), a tension sensor (9) and a rechargeable battery (10), the PCB (12) is provided with a charging circuit and a control chip; the generator (11) is connected to the rechargeable battery (10) by means of the charging circuit; a rotor of the generator (11) is in contact with the guide rails (1), and when the outer housing moves, the rotor of the generator (11) rotates; the rechargeable battery (10) is electrically connected to the PCB (12); the tension sensor (9) and the display screen (14) are respectively electrically connected to the PCB (12); and the tension sensor (9) is provided between an external device and a load bearing rod (3). By providing a display unit, exercise data can be intuitively displayed; obtained data can be sent to a mobile device or a cloud by means of a wireless module, and an exercise process is accurately described in combination with a suitable APP and other software, laying a foundation for datamation of training processes and training effects.
Answer: A