User guide

Ultrasonic Fuel Sensor User Guide
ACCEUF100UG001 - 11 -
3. Principle Analysis
This chapter mainly illustrates the principle of the ultrasonic fuel sensor and the common fuel
sending units and partitions.
Figure 2. Principle Diagram
3.1. Principle
Liquid level in a container is measured by coupling the transducer to the bottom of the container
using couplant. The transducer generates a short ultrasonic sound pulse which is transmitted
through the container wall and into the liquid. The pulse travels up through the liquid until it reaches
the surface where it is reflected and returns back through the liquid to be received by the transducer.
The liquid level then could be calculated by the round-trip transit time and the sound velocity in the
liquid.
According to the principle, the depth of the liquid calculated in this method could be wrong if the
ultrasonic wave is reflected before the due time when there are obstacles
in the transmission path.
Therefore, users should avoid obstacles that could hinder the transmission of ultrasonic wave such
as common fuel sending units, supply tubes, return tubes and partitions inside the fuel tank.
3.2. Obstacles in Fuel Tank
Figure 3. Obstacles in Fuel Tank
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