Design and Implementation of an Intrinsically Safe Liquid-Level Sensor Using Coaxial Cable

Sensors

Baoquan Jin¹  Xin Liu²  Qing Bai²  Dong Wang²  Yu Wang² 

[1] Key Laboratory of Advanced Transducers and Intelligent Control Systems, Ministry of Education, Taiyuan University of Technology, No.79 Yingzexi Street, Taiyuan 030024, China;

关键词: PVC coaxial cable;    capacitive liquid-level sensor;    intrinsically safe circuit;    piecewise linearization;   

DOI  :  10.3390/s150612613

来源: mdpi

【 摘 要 】

Real-time detection of liquid level in complex environments has always been a knotty issue. In this paper, an intrinsically safe liquid-level sensor system for flammable and explosive environments is designed and implemented. The poly vinyl chloride (PVC) coaxial cable is chosen as the sensing element and the measuring mechanism is analyzed. Then, the capacitance-to-voltage conversion circuit is designed and the expected output signal is achieved by adopting parameter optimization. Furthermore, the experimental platform of the liquid-level sensor system is constructed, which involves the entire process of measuring, converting, filtering, processing, visualizing and communicating. Additionally, the system is designed with characteristics of intrinsic safety by limiting the energy of the circuit to avoid or restrain the thermal effects and sparks. Finally, the approach of the piecewise linearization is adopted in order to improve the measuring accuracy by matching the appropriate calibration points. The test results demonstrate that over the measurement range of 1.0 m, the maximum nonlinearity error is 0.8% full-scale span (FSS), the maximum repeatability error is 0.5% FSS, and the maximum hysteresis error is reduced from 0.7% FSS to 0.5% FSS by applying software compensation algorithms.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.