Design and implementation of an intrinsically safe liquid-level sensor using coaxial cable

Area of Science:

• Electrical Engineering
• Instrumentation and Measurement
• Safety Engineering

Background:

• Real-time liquid level detection in complex, hazardous environments presents significant challenges.
• Existing sensors may pose risks in flammable or explosive atmospheres due to energy limitations.
• The need for intrinsically safe systems is critical for operational safety.

Purpose of the Study:

• To design and implement an intrinsically safe liquid-level sensor system.
• To ensure safe and accurate real-time liquid level measurement in flammable and explosive environments.
• To analyze and optimize the sensing mechanism and associated circuitry.

Main Methods:

• Utilized a poly vinyl chloride (PVC) coaxial cable as the sensing element.
• Developed a capacitance-to-voltage conversion circuit with parameter optimization.
• Constructed an experimental platform encompassing measurement, conversion, filtering, processing, visualization, and communication.
• Incorporated intrinsic safety features by limiting circuit energy to prevent thermal effects and sparks.
• Applied piecewise linearization and software compensation algorithms for enhanced accuracy.

Main Results:

• The developed system demonstrated a maximum nonlinearity error of 0.8% full-scale span (FSS) over a 1.0 m measurement range.
• Maximum repeatability error was measured at 0.5% FSS.
• Hysteresis error was reduced from 0.7% FSS to 0.5% FSS through software compensation.
• The system successfully achieved intrinsic safety characteristics.

Conclusions:

• The designed intrinsically safe liquid-level sensor system effectively addresses the challenges of monitoring liquid levels in hazardous environments.
• The system provides accurate and reliable real-time measurements with improved error margins.
• The implementation of intrinsic safety features ensures operational safety, making it suitable for flammable and explosive applications.