Nondestructive Measurement oOf Fruits Quality by Electrical Impedance

本研究以果蔬内在品质的无损检测为研究对象。研制了一种可在线实时测量果蔬介电特性的矢量阻抗测量系统。在10~13 MHz频率范围内，新鲜水果和变质或受损水果的介电特性有明显的差异。随着果实腐烂程度的加重，果实的电阻、阻抗和电抗急剧下降，电容和介电损耗因数增大。在这些阻抗参数中，电阻Rs与新鲜度或成熟度之间的相关性在无损检测中最为明显。因此，水果的新鲜度可以用电阻R值进行非破坏性和接触式测量。其次，我们尝试了电容连接非接触式测量水果的电阻。很明显，如果水果是球形的且大小相同，则可以非破坏性和非接触式地测量新鲜度…介电特性测量内部品质最困难的问题是阻抗参数的测量值受水果形状和大小的影响。为了解决这个问题，我们尝试通过比较水果和水的介电特性来测量水果的介电特性。例如，当我们把水果放在两边都有电极的容器里放入水中时，如果水果的比阻大于水的比阻，那么电极之间的电阻就会比沉入之前的值增加。如果水果的比阻低于水的比阻，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，但变化的方向不取决于水果或蔬菜的形状或大小。因此，我们可以通过比阻分离水果，制备具有比阻阈值的水。通过这种方法，我们可以很容易地检测形状复杂的水果和蔬菜的质量。较少

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