NTC Thermistor Sorter description

        NTC negative temperature coefficient of the English abbreviation, the so-called NTC thermistor Sorter is the negative temperature coefficient thermistor. It is based on manganese, cobalt, nickel and copper and other metal oxides as the main material, made of ceramic manufacturing process. These metal oxide materials have semiconductor properties, because the way completely similar to the conductive germanium, silicon and other semiconductor materials. Low temperature, these oxides materials, carriers (electrons and cavities) the number of small, so its resistance value is higher; as the temperature increases, the number of carriers increased, so resistance value decreased. Advantage of this feature, NTC thermistor can be measured by its resistance value to determine the appropriate temperature, so as to achieve the purpose of detection and control of temperature. A different method of production processes, structure, shape, access to a wide range of NTC thermistors, which are widely used in temperature measurement, temperature compensation and other fields. NTC came out in the production, each change in the characteristics of resistance with temperature is not uniform, which need to NTC resistance changes according to different scope of sorting. The system PIC16F877A chip as the next position control NTC separation process, using 8-bit high-speed MCU C8051F022 upper machine as the core data management, serial EEPROM chip to record the data; and use CH375 chip will record data security and accurate to dump to the U disk, it can be convenient for data storage and management, and coupled with liquid crystal display, human-computer interaction more friendly. The instrument has a sorting accuracy, stable operation, easy to operate man-machine interface is friendly, easy management advantages.

1. Resistor sorter under position control module
      PIC series of microcontrollers is introduced in the United States Microchip CMOS Microcontroller, the family reduced instruction set chip (RISC), Harvard bus architecture, 2-stage pipeline to take orders, with a practical, low-cost, instruction set is small, easy to learn, low-power, high speed, small size, functionality and other properties, reflect the development of a new trend microcontroller. PIC16F877A is the use of Microchips 14-bit RISC instruction set of the intermediate products. The chip includes A / D, the internal EEPROM memory, compare the output, capture input, PWM output, I2C and SPI interfaces, LCD driver, FLASH program memory read and write and other functions, is widely used. PIC16F877A first through the I2C bus from the A / D conversion part of the access to data. ADS1110 chip used here, A / D conversion. ADS1110 is a precision, continuously self-calibrating analog / digital (A / D) converter with differential inputs and up to 16 bits of resolution package for small SOT23 - 6. On-chip 2.048V reference voltage range of ± 2.048V to provide the input differential voltage. ADS1110 using the I2C-compatible serial interface at 2.7V to 5.5V single supply. ADS1110 can be 15,30,60 or 240 samples per second, times to be converted. On-chip programmable gain amplifier (PGA) gain of up to eight times, and allows high-resolution measurement of smaller signals. In the single-cycle conversion modes ADS1110 in a converted auto-power down during idle periods, after greatly reducing current consumption. ADS1110 connection circuit shown in Figure 2. RX diagram for the DUT resistance, R0 as a standard resistor, in order to ensure measurement accuracy, on which the increase of 2 volts from 10 volt precision voltage reference chip REF102 convert the input voltage of 24 V to 10 V voltage reference, after that, through the resistor divider and voltage follower arising after separation, the voltage is very stable. RX voltage across the resistor under test and then through a voltage follower isolation, as shown in Figure 3 on the OP07 circuit in order to prevent the right of the impedance of the circuit measuring the impact, and then filtered through a first-order transmitted to the ADS1110, so that exclude the interference of the outside world testing to ensure voltage stability across RX resistor under test, A / D conversion precision.
3 Resistance sorter system composition and working principle
      The resistor sorter system function consists of hardware and software, coordinating the completion of two parts, resistor sorter hardware, some of the major individual sensor signals the completion of the acquisition, conversion, electromagnetic valve movement, data storage and display all kinds of information; software key the completion of signal processing and control, data management and other functions. Software, first of all procedures are completed by the PIC chip signal conversion and control, while C8051F022 chip implanted into Small RTOS embedded operating system to run as fast, real-time and stability of higher and better data for management and storage. Resistance Sorter works by the entire system under test NTC first immersed in oil to maintain its temperature, and then both ends of voltage through a serial A / D converter ADS1110 devices convert the digital signal transmitted to the PIC16F877A microcontroller then PIC16F877A values obtained for the first measured with the standard resistance values compared with after the sub-file, and then through the 74LS595 shift register output control solenoid valve action, thus sorting out the correct NTC. At the same time the value of PIC16F877A file will be transmitted through the 485 communications to the C8051F022 chip. C8051F022 data in real time displayed on the LCD screen, and the data into the serial EEPROM chip, 24AA512, the operator can readily use U disk to copy the data stored away. C8051F022 can also enter a number of parameters, such as speed, sub-file value, etc., save and send to the PIC16F877, to control its operation.

 

 

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