Abstract
The online measurement of moisture content for grains is an essential technology to realize real-time tracking and control, improve drying quality and reduce energy consumption of the drying process. To improve the measurement accuracy and reliability of the dynamic measurement process as well as expand the application scope of the device, the present work constructed an experimental equipment for determining dynamic resistance characteristics of a single grain. The relations between moisture content and real-time resistance waveform were revealed, and an analytical calculation method of peak value and peak area of waveform was proposed, which correctly revealed the electrical measurement properties of grain. The results demonstrated that the gap width between the electrodes had large influence on the sensor’s performance. Moreover, an online measuring device was developed based on the experimental analysis and calculation method, and the test results in both lab and field for different grains showed that online real-time absolute measurement error are within ±0.5% in the varied moisture content (10–35%w.b.) and the temperature (−20–50 °C). The main results and the developed device might provide technical support for developing intelligent grain drying equipment.
Highlights
Grain drying is a process of spontaneous dehydration under the environment of large inertia, nonlinear, humidity, heat, mixed dust and multiple uncertain disturbance factors [1,2]
The difference of grain moisture content is reflected in the change of electrical conductivity, which is generally characterized by the increase of resistance value with decreasing moisture content
We found that the grain with higher moisture content corresponded to a longer testing time in a single detection featuring a larger number of detecting resistance points compared with the grain with lower moisture content, and the peak area enclosed the resistance value decreases continuously
Summary
Grain drying is a process of spontaneous dehydration under the environment of large inertia, nonlinear, humidity, heat, mixed dust and multiple uncertain disturbance factors [1,2]. The moisture distribution of grain discharged from the dryer is often used to evaluate the uniformity of drying [3]. The overall uniformity of drying can be effectively inferred by analyzing the statistical moisture distribution law of dried grain samples. To reach the goal of real-time analysis of uniformity of drying and accurate feedback of moisture signals in the drying process, the moisture content of a single grain in the statistical analysis of samples should be measured accurately. It is difficult to measure the moisture content of a single grain by standard oven method [4] due to the light weight. It is of great significance to explore the online measurement technologies of single grain moisture content
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