Dual-Transducer Ultrasonic Fuel Level Sensor
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Solution Overview
Problem
Existing ultrasonic level measurement devices require knowledge of the speed of sound in the medium, which varies with temperature and medium type, making accurate fuel level determination challenging.
Innovation Solution
A dual-transducer system with a processor that switches between two modes to generate and receive signals, using a reference target to calculate distance independently of sound speed, allowing for accurate liquid level measurement without prior knowledge of sound speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transducer is used to measure liquid level by ultrasonic time of flight, then the device structure is simple, but measurement precision deteriorates because the speed of sound varies with temperature and medium type
Solution Approach 1:
The single transducer is divided into two separate transducers: a first transducer for transmitting ultrasonic signals and a second transducer for receiving reflected signals. This segmentation allows independent optimization of transmission and reception characteristics, improving measurement precision while maintaining relatively simple device structure
Solution Approach 2:
A reference target is introduced as an intermediary object at a known distance from the transducers. By measuring the time of flight to the reference target and comparing it with the time of flight to the liquid surface, the system can calculate the liquid level without needing to know the exact speed of sound in the medium, thereby resolving the precision problem caused by temperature and medium variations
2Device complexity
If the speed of sound is assumed to be constant for measurement, then the calculation is simple, but measurement precision deteriorates due to temperature and medium variations
Solution Approach 1:
The system uses the reference target to obtain feedback information about the actual ultrasonic propagation conditions in the medium. By continuously measuring the time of flight to the reference target and using this feedback to calculate the actual speed of sound, the system compensates for temperature and medium variations, maintaining high measurement precision without complex external sensors
Solution Approach 2:
The reference target is pre-positioned at a known distance from the transducers before actual liquid level measurements are taken. This preliminary setup allows the system to first determine the speed of sound in the current medium conditions, which is then used as a reference for subsequent liquid level measurements, eliminating the need for constant speed of sound assumptions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise liquid level determination in containers by calculating distance based on time of flight using both direct surface reflections and reference target reflections, mitigating the impact of varying sound speeds due to temperature and medium changes.
Implementation Method 1
An ultrasonic signal is generated by the transducer and the time it takes for the signal to travel from the top of the tank to the surface of the fuel, reflect off the surface of the fuel, and return to the transducer is measured
Implementation Method 2
A portion of the reflected sound energy returns towards the transducer in the form of an echo
Implementation Method 3
A relatively high-voltage electric signal is sent to a transducer (e.g. a piezo-electric transducer) causing the transducer to change shape and resonate at its natural mechanical frequency
Implementation Method 4
causing the transducer to change shape and resonate at its natural mechanical frequency (or at a multiple thereof). The mechanical resonance results in a short duration pulse of ultrasonic energy
Implementation Method 5
The ultrasonic sound wave travels through the liquid and reflects off a vapor/liquid interface due to differing speeds of sound between the vapor and the liquid. The time between the transmitted ultrasonic pulse and the received echo is directly proportional to the distance the sound wave traveled through the liquid as expressed in the equation below: Distance=Speed×(Time of Flight)/2 Where, Speed is the speed of sound within the fluid and is a function of the temperature and the density of the liquid
Data Source
AI summary
A level sensor includes a first transducer generating a first signal, a second transducer generating a second signal, and a processor configured to switch operation between a first mode and a second mode. In the first mode, the first transducer generates the first signal and the second transducer senses a reflection of the first signal from a surface. In the second mode, the second transducer generates the second signal and the first transducer senses a reflection of the second signal from a reference target. The processor determines a distance to the surface.