DSP tension, depth and speed measurement system

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DSP tension, depth and speed measurement system [Copy link]

During the oilfield logging process, ground operators need to know the depth of the oil well, the cable downhole speed and the load carried by the cable. Only by mastering these data in a timely and accurate manner can the logging work proceed smoothly to ensure the safety and reliability of the logging process. Therefore, we have developed a tension, depth and speed measurement system based on DSP. The system has high accuracy, strong reliability and fast processing speed, and is an ideal monitoring tool for ground operators. 2 Strain sensor and photoelectric encoder The tension on the strain sensor cable causes the strain sensor to produce mechanical deformation, and the sensor converts the mechanical deformation into an electrical signal output, thereby measuring the tension. . Working voltage: DC 12V . Output range: 0~12mV . Output sensitivity: 1mv/v Photoelectric encoder The rotating shaft of the photoelectric encoder is coaxially fixed on the center of a measuring wheel with a known circumference. When the measuring wheel rotates, the encoder rotates synchronously and outputs a pulse signal. In this way, a certain length corresponds to a certain number of pulse signals, and the depth value can be converted by calculating the pulse signal. The speed value is obtained by sampling the depth value per unit time. Working voltage: DC 5V Working current: 40mA Pulse type: Two orthogonal pulse signals, through the logic circuit, the identification of the rotation direction of the photoelectric encoder and the output of the depth pulse can be completed. 3 System structure and working principle The millivolt signal generated by the strain sensor is input into the amplifier for amplification, and then sent to the A/D converter for analog-to-digital conversion, converted into a binary sequence and sent to the DSP for processing. In order to ensure the reliability of the A/D conversion, the V/F device LM331 is used to realize the analog-to-digital conversion and convert the voltage signal into a frequency signal. This device has high reliability and occupies less resources. The two orthogonal signals generated by the photoelectric encoder are input into the CPLD, and after processing, two signals are generated. One is a direction identification pulse, which is used to identify the rotation direction of the photoelectric encoder. The other is a counting pulse, which is used to complete the conversion of the depth parameter. Both pulses are input to the DSP. See Figure 1. 4 Core Hardware Circuit Design TMS320VC33 processor This chip is a 32-bit floating-point high-performance digital signal processor launched by TI. The instruction cycle is divided into 13ns and 17ns, and 32-bit integer and 40-bit floating-point multiplication operations are completed in a single cycle. The on-chip 34K 32-bit SRAM is divided into 2 16K and 2 2K blocks, and the blocks integrate a DMA channel, a synchronous serial port, and two 32-bit timers; the total storage space is 16M 32bits, and the program, data and I/O space are all included in it. The address space can be divided according to different requirements; it has a program boot function. After the system is reset, the program can be loaded from the slow external memory to the fast on-chip RAM for operation; it supports IEEE Std 1149.1 (JTAG) standard; 0.18-m process, 1.8V core voltage, 3.2VI/O voltage; low power consumption (<200mW@150MFLOPS). The chip combines the advantages of floating-point and fixed-point operations, has high calculation accuracy and fast calculation speed, and is suitable for fast processing occasions. High-precision real-time clock/calendar SD2001E records the test data in real time within 24 hours (i.e. "black box" function), so the real-time clock device SD2001E with I2C bus interface is selected to record the measurement parameters, the operator's name and the specific operation time (year, month, day, hour) as the data for problem analysis. The device can provide 32k bits and 10 billion times of non-volatile SRAM; the crystal oscillator, battery and power management circuit are integrated inside, which can ensure the normal operation of the chip when the system loses power, and the clock running time is more than 10 years; I2C bus interface (including real-time clock part and SRAM part); built-in high-precision crystal oscillator, accuracy < 5ppm, that is, within a month, the running error does not exceed 13 seconds (25C); BCD code input/output for year, month, day, week, hour, minute and second; automatic calendar to 2099 (including leap year automatic conversion function). SST39VF320 memory chip is a CMOS multi-purpose FLASH device with a capacity of 2M 16, which is an ideal large-capacity memory. It can meet the requirements of data recording within 24 hours in this measurement system, and the recorded content is the measured values of tension, depth and speed. The device provides 2.7-3.6V operating voltage; ultra-reliability, 100,000 erase and write cycles, permanent data storage; low power consumption, active current 9mA, standby current 3A, automatic low power mode 3A; fast read time of 70ns and 90ns; address and data latch function; 2KWord sector erase and write capability and 32KWord block erase and write capability; fast erase and word programming capability; compatible with CMOS I/O port. Serial E2PROM AT24C512 chip is a 64k byte serial E2PROM with I2C bus interface. The measurement data is stored in it, and the data will not be lost when the system loses power, which brings great convenience to the operator. The device has a limited number of erase and write cycles. During operation, the data can be written into the NVRAM in the SD2001E chip first, and then the data can be transferred to the AT24C512 when the NVRAM is full. This can greatly reduce its refresh times, thereby extending its service life. 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