电激励信号的频率和电压对果品电特性的影响

Influence of frequency and voltage of electric excitation signal on electric property of fruits

采用无损接触检测及交叉试验法研究了电激励信号的频率和电压对果品电特性的影响。研究结果表明:在0.2～2.5V的电压范围内,苹果电参数存在一电压临界值。若信号电压小于临界值,苹果的电容、电阻以及损耗角正切值保持不变,若电压大于该值,随着电压的增大,电容和电阻值迅速下降,损耗角正切值急剧增大;电压临界值与频率有关,在5～100kHz的频段内,30kHz下的电压临界值最大;猕猴桃、梨同苹果电参数的频率特性相同,而且也存在电压临界值;10kHz下,苹果、猕猴桃和梨的电压临界值分别为0.8、1.8和1.4V。文中提出了基于电压临界值的果品种类识别方法,验证结果表明,该方法对苹果、猕猴桃和梨的识别率分别为100%,93%和90%。

The influences of frequency and voltage of electric excitation signal on electric property of fruits with non-destructive and orthogonal experiment method were studied. The results show that when the voltage is in (0.2)~2.5 V, the electric parameters of apple have critical voltage value. If the voltage is less than the critical value, the capacitance, resistance and loss angle tangent keep constant; if it is bigger than the values, with the increase of voltage, the values of capacitance and resistance decrease rapidly and loss angle tangent increases sharply. The critical voltage value is correlated with frequency. During the frequency band of 5~100 kHz, the biggest critical value is at 30 kHz. The electric parameters of kiwifruit and pear also have the same frequency characteristic as apple and different critical voltage values, which are 1 V, 1.8 V and 1.4 V, respectively for apple, kiwifruit and pear under 10 kHz. Based on the differences of critical voltage value, the identification method on species of fruits is proposed. The test result shows that the identification rates for apple, kiwifruit and pear are 100%, 93% and 90%, respectively.