Beijing University of Aeronautics and Astronautics 207 Teaching and Research Office (00083) Guo Zhiqiang CAI Zhiquan (Nanjing) Ministry of Information Industry, Ministry of Commerce and Economics, Ministry of Commerce, China (Nanjing) 20 (210016) Liu Jiang is a temperature compensated low-humidity dew point meter. One of the sensors is packaged in a dry gas, and the other sensor is in the environment to be measured. After the same C/F conversion circuit is used, the frequency is measured by a Philips P87LPC764 microcontroller, and the internal frequency difference, curve fitting and other means are performed by software. The temperature-compensated measurement data is processed to achieve the purpose of quickly measuring the low dew point using a simple device and a low-cost sensor. In this paper, the temperature is to be fitted to the interval table junctions in Table 3 and the temperature calibration point temperature in Table 4 is shown in Table 4.

When the actual test equipment design is calibrated according to this process, it is automatically completed by the program in conjunction with the calibration process. Node data, calibration data, and temperature compensation coefficients are stored in an external E2PROM, which also meets the requirements for regular calibration.

4 System Introduction The temperature section, display, and keyboard (the optional section is only used during calibration).

Among them, the CPU is a high-performance single chip which is compatible with the 8031 ​​series of command system, 4KOTP, 20-pin package (DIP or SO) and includes I2C interface, Watchdog, power supply monitoring, etc., and is especially suitable for use in small smart meters; the display uses I2C bus LCD driver The chip PCF8576; temperature measurement circuit uses Dallas integrated digital temperature measurement circuit DS1820; E2PROM also uses I2C bus 24CQ2. The above circuit can be related information, and will not be repeated here. The two outputs of the C/F circuit are connected to T0 and T1 respectively, and the spare 4 lines can be selected as the keyboard input interface.

The entire system circuit board is divided into three parts: LCD display board, keyboard board (standard time plug-in) and main board. It adopts SMT assembly, low power consumption, low voltage design, and is equipped with small rechargeable battery power supply, and the appearance is small and exquisite.

System software uses assembly and C51 mixed programming to optimize the design of the entire program, such as table data design to avoid floating-point operations try not to use repeated statements, and call the function and other measures, otherwise the internal 0TP space is insufficient.

The test instrument measures its accuracy within a measurement range of 45 to 90C. The dew point error learning electronic engineering department is studying graduate students.

Liu Jiang, male, an engineer, is currently engaged in the development and research of electronic products.

Cai Zhiquan, male, professor, is mainly engaged in the development and research of communications, measurement and control instruments and related products.

(:200001) Welcome to subscribe to the 2000 "Measurement and Control Technology Monthly subscription number: 82-533 Pricing: 6 (1) yuan / period monthly 18 monthly publication (continued from page 3) "high-tech industrialization" is a high-tech industrialization As one of the important components, the state will provide support for billions of dollars in funding.” The high-tech industrialization of process automation “includes five major blocks: software, hardware, and steel, refining, and light industry, and software is the first to bear. In this large block, the industrialization of advanced control and process optimization software is the main content.After the industrialization starts, in the next few years, the domestic advanced control field will catch up with the international advanced level.

The Institute of Advanced Control of Zhejiang University began advanced control in the late 1980s, in particular, conducted theoretical research and application development of multivariable predictive control, in FCCU, catalytic reforming, PTA (pure terephthalic acid), vinyl chloride Distillation, aromatic distillation and other devices have achieved great application results. At the same time, Zhejiang University is also aware of the importance of developing engineering and commercial software packages. In 1996, it collaborated with Adersa of France on the research and development work of the "Advanced Control and Optimization" engineering software package, fully absorbing international advanced technologies. The technology has successfully developed the APC-Hiecon multivariable predictive control software package and the APC-PFC predictive function control software package, forming an advanced control and optimization commercial software system APCSuite suitable for the domestic actual situation, and vigorously promoting advanced process control in China. Optimize the development of the software industry.