Nondestructive Measurement oOf Fruits Quality by Electrical Impedance

本文的研究对象是果蔬内部质量的无损电气检测。研制了一种能够测量果蔬矢量阻抗并分析其介电特性的在线实时系统。在10Hz至13MHz范围内，新鲜水果和变质或受损水果的介电特性有明显差异。由于腐烂或损坏，果实的电阻、阻抗和电抗急剧下降，电容和介电损耗系数增大。在这些阻抗参数中，电阻r与新鲜度或成熟度的相关性在无损测量中最为明显。因此，可以采用电阻rs法对水果的新鲜度进行无损接触测量。接下来，我们尝试了采用电容连接法对水果的电阻进行非接触测量。很明显，如果水果是球形的，大小相同，新鲜度可以用无损和非接触的方式来测量。利用介电特性测量内部质量的最大难题是阻抗参数的测量值受果实形状和大小的影响。为了解决这一问题，我们尝试通过比较水果和水的介电性能来测量水果的介电性能。例如，当我们将水果放入一个两侧都有电极的容器中，如果水果的比电阻大于水的比电阻，则与下沉前的值相比，电极之间的电阻增加。如果水果的比电阻低于水的比电阻，则电极间的电阻减小。变化的幅度取决于水果的大小和形状，但变化的方向并不取决于水果或蔬菜的形状或大小。因此，我们可以用比阻法分离果实，制备具有比阻阈值的水。用该方法可以方便地对形状复杂的水果和蔬菜进行质量检测。少

The object of this study is nondestructive electrical inspection of internal quality of fruits and vegetables. On-line real time system which can measure vector impedance of fruits and vegetables and analyze the dielectric properties has been developed. Obvious differences in dielectric properties were distinguished between fresh and spoiled or damaged fruits in the range of 10Hz to 13MHz. According to rot or damage, resistance of fruits, impedance, and reactance decrease sharply, and capacitance and dielectric loss factor increase. Among these impedance parmeters, correlation between resistance Rs and freshness or maturity is the most obvious in nondestructive measurement. Thus, the freshness of fruits can be measured nondestructively and contactively by resistance Rs.Next, we tried noncontacting measurement of resistance of fruit by capacitive connection. It became clear that if the fruits are spherical and same size, the freshness can be measured nondestructively and noncontactively … More .The most difficult problem of inner quality measurement by dielectric property is that the measured values of impedance parameters are influenced by the shape and the size of fruits. To solve this problem, we tried to measure the dielectric properties of fruits by comparison with those of water. For example, when we sink fruit into water in a container which has electrodes on both sides , if the specific resistance of fruit is greater than that of water, the resistance between electrodes increases by comparison with the value before sinking. If the specific resistance of fruit is lower than that of water, the resistance between electrodes decreases. The magnitude of change depends on the size and shape of the fruit but the direction of change does not depend on the shape or size of the fruit or vegetable. Accordingly, we can separate fruits by specific resistance, preparing water which has a threshold value of specific resistance. By this metod, we can easily measure the quality of fruits and vegetables which have complex shapes. Less