Development of a Battery-Powered Ultrasonic Fluid Level Measurement Device
Client Challenge
Our long-term client approached us with a request to develop an autonomous battery-powered device for measuring fluid levels in tanks. The key requirements included:
- Long battery life: Minimum 1 year, ideally 2 years.
- Outdoor operation: Designed to withstand harsh environmental conditions.
- Connectivity: Reliable communication with the client’s server.
- Integrated locator: GNSS functionality for mobile tank monitoring.
This project presented several challenges:
- Selecting the appropriate measurement method.
- Developing an ultra-low-power solution for extended battery life.
- Designing an energy-efficient wireless communication system.
- Ensuring reliable performance across a wide range of temperatures and humidity levels.
Solution Development
1. Measurement Method Selection
We began by evaluating various measurement technologies:
ToF (Time of Flight) sensors: Popular and cost-effective, these infrared-based sensors measure distance by timing the travel of light pulses. However, our tests revealed that in high ambient light conditions (70,000 lux) typical of outdoor environments, the sensors were highly susceptible to interference. This was particularly problematic for tanks made of translucent materials that allowed infrared light to pass through. The accuracy and range of ToF sensors degraded significantly, making them unsuitable for this application.
Microwave FMCW radars: These proved to be robust against temperature changes and light interference, but the affordable options lacked the precision required for our client’s needs.
Ultrasonic radar: Ultimately, we chose ultrasonic technology due to its excellent accuracy, cost-effectiveness, and reliability in outdoor environments. While it required calibration during production and thermal compensation (as the speed of sound varies with temperature), these minor trade-offs were outweighed by its advantages.
2. Power Management
To meet the client’s requirement for extended battery life, we selected a proven ultra-low-power microcontroller. Its multiple energy management modes allowed us to optimize power consumption, achieving the target battery life of up to two years.
3. Communication and Localization
For connectivity, we integrated the COMBO module, which combines a GNSS receiver for location tracking and a GPRS/GSM communication module for reliable data transmission. The custom-developed firmware enabled precise measurements, event detection, and periodic bidirectional communication with the client’s server.
4. Production Readiness
To support mass production, we designed a dedicated assembly station and a specialized calibration and testing system. The testing system ensured accurate calibration of the ultrasonic measurement path, incorporating thermal compensation parameters for reliable operation in varying environmental conditions.
Results
- Precise measurement with a resolution of 1 mm.
- Up to 2 years of battery life, verified under real-world conditions.
- Robust performance in outdoor environments, unaffected by temperature or light variations.
- Seamless connectivity with the client’s backend server for real-time monitoring.
- Reliable GNSS tracking for mobile tank management.
The device is now in mass production, with INVENTRONICS providing regular deliveries to the client. The project underscores our ability to tackle complex engineering challenges and deliver innovative, tailored solutions that meet and exceed client needs.
