Abstract: In order to explore the dielectric properties of pellet feed and achieve the rapid detection of moisture content in pellet feeds, livestock and poultry and aquatic pellet feed is taken as the research object. This paper studied the effects of frequency (1～200 kHz), temperature (10～30℃) and moisture content (8.8%～19.1%) on the relative dielectric constant and established the corresponding prediction model of moisture content using coaxial-line cylinder capacitor. The results showed that the dielectric constant of pellet feed increased with the increase of moisture content and temperature, decreased with the increase of the frequency. With the coefficient of determination and the standard deviation as evaluation index, the moisture content of pig and poultry pellet was the best at 10 kHz. And the coefficient of determination was 0.996 6 and 0.998 4, respectively. At 200 kHz, the moisture content model of the aquatic product feed was the best, the determination coefficient was 0.999 2. It was verified by experiment that the absolute error range of moisture content of pellet feed was predicted to be ±1.1%, indicating that it was feasible to predict the moisture content of pellet feed based on the dielectric properties, which was instructive to develop moisture dector for pellet feed.

Key words: pellet feed, dielectric properties, moisture content, temperature, nondestructive testing

摘要： 为了探究颗粒饲料的介电特性，实现颗粒饲料含水率快速检测，以畜禽、水产颗粒饲料为研究对象，采用同心轴圆筒式电容器，研究了信号频率（1～200 kHz）、温度（10～30 ℃）和含水率（8.8%～19.1%）对颗粒饲料相对介电常数的影响，建立了相应的含水率预测模型。结果表明，颗粒饲料的相对介电常数随着含水率和温度的增加而增加，随着测量信号频率的增加而减小；以决定系数R2和标准差SE为评价指标，通过比较，在10 kHz下猪、禽颗粒饲料含水率模型最佳，其决定系数R2分别为0.996 6、0.998 4；在200 kHz下，水产颗粒饲料含水率模型最佳，其决定系数R2为0.999 2。经过实验验证，预测颗粒饲料含水率的绝对误差范围在±1.1%，说明基于介电特性预测颗粒饲料含水率是可行的，为基于介电特性颗粒饲料水分检测仪的开发提供了指导意义。

关键词: 颗粒饲料, 介电特性, 含水率, 温度, 无损检测