Modular Capacitance Measurement System
Production-ready capacitance sensing with MODBUS RTU and RS-485 for harsh underwater environments
Image represents the actual instrumentation developed for this project. Technical details have been abstracted for confidentiality purposes.
Challenge
Research labs need reliable, portable capacitance measurement for field and deployment in harsh environments. Desktop LCR meters are accurate but bulky and delicate. Commercial boards are portable but they require integration. We developed a production-ready system combining lab precision with field robustness.
Solution
Custom-designed modular capacitance measurement system using oscillation-based sensing with embedded microcontroller processing and industrial communication protocols. The system was engineered from first principles using mathematical circuit modelling to achieve the required performance while maintaining low cost and ease of integration.
Key Technical Features
- • Oscillation-based measurement circuit for 1-3000pF range with 2pF resolution
- • 250Hz sampling rate with real-time processing
- • Single-IC integration: digitalisation, processing, control, and communication
- • MODBUS RTU protocol with CRC checksum for error detection
- • RS-485 differential signalling supporting 100m+ cable lengths
- • Standard USB cable (2 power + 2 signal + shield) for easy sourcing
- • Multi-drop network topology supporting up to 255 sensors on single bus
- • Runtime parameter adjustment (calibration, compensation, addressing)
- • Compact SMD PCB design for direct sensor integration
- • Underwater-rated with comprehensive EMC and high-voltage noise immunity
- • Low-cost components with reliable commercial sourcing
- • Complete technical documentation including schematics and firmware
Applications
Underwater Robotics
Distributed sensor networks for autonomous underwater vehicles with noise-resistant communication
Research Instrumentation
Portable capacitance measurement for field and laboratory applications
Industrial Sensing
Harsh environment monitoring with long cable runs and electrical noise
Multi-Sensor Arrays
Scalable networks with centralised control and minimal cabling complexity