Calibrating Tank Sensors with Test Liquid for Accurate Level Monitoring
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Solution Overview
Problem
Current filling level sensors in tanks for liquid additives, such as urea-water solutions, face challenges due to varying chemical properties, potential freezing at low temperatures, and complex tank shapes, leading to inaccurate measurements and difficulties in precise calibration.
Innovation Solution
A method for manufacturing a tank with a calibrated sensor involves installing the sensor, partially filling the tank with a test liquid, determining the sensor signal, and calibrating it to ensure precise measurement, which can account for deformations and variations in liquid properties, using a feed module with components like a pump, temperature sensor, and evaluation electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filling level sensor is installed in a tank for liquid additive, then the filling level can be monitored, but the measurement accuracy deteriorates due to varying chemical properties of the liquid additive
Solution Approach 1:
The patent applies preliminary action by performing calibration of the filling level sensor before actual use. The calibration process involves filling the tank with a known quantity of liquid additive, measuring the sensor signal, and storing the relationship between signal and actual filling level in memory. This pre-calibration ensures accurate measurements even when chemical properties of the liquid vary, as the sensor is tailored to the specific tank geometry and liquid characteristics during calibration.
2Volume of moving object
If the tank is designed with a complex indented shape to adapt to installation space, then the space utilization is improved, but the filling level measurement becomes significantly more difficult
Solution Approach 1:
The calibration process performed during manufacturing serves as a preliminary action that captures the specific geometric characteristics of the complex tank shape. By filling the tank with a known volume of liquid and recording the sensor signal at various filling levels, the system creates a calibration curve that accounts for the indented geometry. This allows accurate filling level determination despite the complex shape, as the calibration data reflects the actual volume-signal relationship for that specific tank configuration.
3Reliability
If the liquid additive freezes at low temperatures, then the volume increases, but this leads to falsification of the filling level measurement
Solution Approach 1:
The patent incorporates temperature sensors that provide feedback about the liquid additive temperature to the control device. When freezing is detected or anticipated, the system can compensate for the volume expansion by referencing the temperature data against the calibration data. The control device uses this feedback to adjust or flag the filling level measurement, preventing falsification due to freezing conditions while maintaining operational reliability in cold environments.
4Manufacturing precision
If the sensor is calibrated during manufacturing, then the calibration can be performed under controlled conditions, but the tank deformation during installation may invalidate the calibration
Solution Approach 1:
The patent performs calibration as a preliminary action during manufacturing when the tank is still in its original, undeformed state. The calibration data captured at this stage reflects the precise geometric relationship between sensor position and filling level. While tank deformation during installation may occur, the preliminary calibration provides a baseline that can be used in conjunction with temperature and pressure compensation algorithms to maintain measurement accuracy under varying installation conditions.
Data Source
AI summary
A method for manufacturing a tank for a motor vehicle for storing a liquid additive with a calibrated sensor for determining at least one parameter of the liquid additive in the tank. In a step a) the sensor is installed in the tank. In a step b) the tank is at least partially filled with a predefined quantity of a test liquid. In a step c) a signal of the sensor is determined, and in a step d) the sensor is calibrated with the signal.