Design And Application Of A New C~4D Sensor With Simulated Inductor Technique

Capacitively Coupled Contactless Conductivity Detection (C4D) is a new kind of conductivity detection technique, which has the advantages of non-contact, simple construction, etc.. C4D technique can avoid the electrochemical reaction and the polarization of the electrodes, which exists in the contact conductivity detection. However, the coupled capacitances limit the resolution and detection range of the C4D technique. Therefore, C4D technique is mainly applied in the research field of analytical chemistry in capillaries. Our research group has proposed a C4D method based on series resonance. The method can eliminate the influence of the coupling capacitances and be applied in the millimeter pipes successfully. But the practical inductor adopted in this C4D method has its drawbacks, such as the uneasily adjustable inductance, the high internal resistance and the large size, which limit the miniaturization and integration. Simulated inductor technique is implemented by using active elements together with resistors and capacitors, and can overcome the disadvantages of the practical inductor.Therefore, this work introduces the simulated inductor technique to the field of C4D, and develops a new C4D sensor with the new simulated inductor. The main works are summarized as follows:1. A new simulated inductor, which is on the basis of the Riordan circuit, is designed. The results of the inductor performance test experiments show that, compared with the practical inductor, the designed simulated inductor has advantages of low internal resistance and adjustable inductance. Moreover, it is easy to be miniaturized.2. A new C4D sensor is developed by introducing the new simulated inductor. The conductivity measurement experiments are carried out in five pipes with different inner diameters of 0.3mm,0.5mm,0.9mm,1.8mm, and 3.0mm, respectively. The conductivity measurement experimental results show that the maximum relative difference of the conductivity measurement is less than 5%. Compared with the C4D sensor with a practical inductor, the resonant frequency of the new C4D sensor with the simulated inductor can be adjusted conveniently. That makes the new C4D sensor easier to implement the conductivity measurement by series resonance principle and reduces the requirements for the AC source. Moreover, the new C4D sensor is easy to be miniaturized and integrated.3. The new C4D sensor with simulated inductor is applied in the parameters measurement of the gas-liquid two-phase flow. As a preliminary study, the parameters of the slug flow are measured including velocity, slug length and void fraction. The parameter measurement experiments are carried out in the pipes with inner diameters of 1.8mm and 3.0mm. The maximum relative difference of the velocity measurement is less than 5%, the maximum relative difference of the slug length measurement is less than 10% and the absolute difference of the void fraction measurement is less than 10%.This research work verifies the effectiveness of the application of the simulated inductor technique in the field of C4D sensor, and lays a good foundation for the miniaturization and integration of the C4D sensor in the future. Meanwhile, it expands the application field of simulated inductor technique, and provides a useful reference for others’research works.