| Tobacco hazards to human health, but it have the more important status and role inthe economic life of many countries, so require appropriate controls rather thancomprehensive. In cigarette manufacture process, moisture indicators of control isimportant, it is one of the important parameters for measuring the quality of cigarette. Forthe shortcoming and high prices of infrared moisture meter, this article according to thespecific resistance and water relations, designed a four-electrode resistance-type tobaccomoisture meter. The instrument is moisture measuring systems based on single-chipmicrocomputer MSP430F149, mainly controlled by voltage transformation module,moisture measurement and control modules, measuring selection, resistancemeasurement, the probe device, liquid crystal display, data upload module such asseven-part. The instrument is free from material color, shape, size, and measuring theeffect of ambient light. It is not only fast and accurate, continuous measurement,measuring range large, also easy to carry, less cost. The application of moisture meterwill significantly reduce the investment in test equipment for tobacco factory,accordingly improve the production profits.This major includes three parts, which research and production of four-electroderesistance tobacco moisture meter, calibration of the instrument indication, test resultsand analysis of the instrument.1. Research and production of four-electrode resistance tobacco moisture meter. Bystudying on currently often used testing methods for moisture, introduction andperformance comparison for existing various types of infrared moisture meter, for theshortcoming and high prices of infrared moisture meter, put forward a overall designproposal about four-electrode resistance-type tobacco moisture meter. According to theoverall design of the instrument, the corresponding hardware circuits and software aremade. 2. Calibration of the instrument indication. This design used the principle of floatingcalibration to calibration the instrument. By constructed a mathematical model ofresistance and moisture, educed the relationship between two, then base upon therelational expression used moisture to denote the instrument indication.3. Instrument test and analysis of experimental results. Make the moisture datameasured by the Classic105℃constant-weight method as a standard, by comparing themeasurement results of this instrument and the standard moisture value, proved thefeasibility of this design. Then analyzed error for the measurement results, meanwhilecombined with the principle of the instrument itself, summarized the several influencefactors that maybe cause errors, and proposed appropriate solutions.According to the above work, we have known that make the specific function of therelationship between resistance and moisture as theoretical basis and use four electrodesto measure the resistance of material is one of the key technologies of this design. Thesecond key technology is the structure design of probe device. For the design of existingmoisture meter with only a pair of electrode, this article has improved and innovative,probe device is equipped with four electrodes, and square distribution, improve thecredibility of measurements. The accuracy of the resistance measurement and theinstrument calibration is the third key technology and the difficulty of this design. Thisquestion about the accuracy of the resistance measurement, we can solve by measuringthe resistance value many times, then processing data and removing abnormal values bytwo mathematical methods, eventually calculating the average of multiple sets of data.According to use the principle of floating calibration and combine with the fixed scalingmethod to implement this instrument’s calibration. This method of calibration, extendsthe application range of this moisture meter, it is not only applies to the tobacco industry,also suitable for the other areas, and reached the expected target of the design. |
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