Resonance method for liquid level sensoring.

Principle of operation

Basis of the new, patented liquid level probe is the method of measuring according to the principle of resonance measurement.

The evaluating unit (ASIC) collects the various resonance frequencies at different liquid levels due to a physical amplitude increase of of the receiving signal.

An exact liquid level can thus be determined by evaluating the signal.

Features:

1. Design with a rigid measuring pipe or with a flexible measuring hose for complicated geometrical tank designs.

2. Wide range of applications such as the following media: Fues / Ethanol, Diesel / Biodiesel, Oil, AdBlue, Wiper washer

Left: Fuel tank
Right: Container for wiper washer, oil or urea solution (SCR-application)

Test results in the laboratory

Resolution of the sensor:

• Measured tank (Expansion tank) with 125 mm liquid level
• A change of +/-0,5 mm can be reproducibly recognized.
• This corresponds to a resolution accuracy of at least 250 measuring points.

Repetitive accuracy of the measuring system:

• Measured tank with a volume of 64 litres
• Accuracy between 0,15l liquid level reserve(5 l) and 0,23l of a full tank
• This corresponds to a relative deviation of 2,9 % liquid level reserve and 0,35 % of a full tank

3-D Drive at TÜV SÜD Automotives GmbH (Munich):

• Test of two probes regarding dynamic influences (=> Vibrations)
• Stationary vibration of the surface without influence (=> Evaluation of mean value)
• Dynamic, strong fluctuation (+/- 20°) hardly shows any effects due to internal liquid attenuation at the lower end of the measuring pipe
• Loud external noises without any influence (=> Noise dynamization)

Test results during the field test

Current attempts to optimize the design in the following vehicles:

• VW-Polo (Fuel tank simulation including ambient noises in the vehicle, e.g. radio)
• VW-Polo in the engine compartment (Wiper water container)
• Motorcycle (external container, attached to the tank)
• Unimog manufactured in 1980 (Exterior tank with extreme ambient noises 107dB C)

Further application advantages of Liquid level sensoring by means of the resonance method

• Reduced costs due to systematic installation by optionally separating the tip of the sensor from the measuring pipe or hose.
• A multiple hosing system attached to the tip of the sensor allows exact liquid leveling of an inclined construction vehicle

Application for complicated tank designs: Saddle tank of an automobile

Cost efficient determination of the liquid level in a complicated geometric tank design by a multiple hose system at the tip of the sensor

Summary

Touchless sensor

• in motionless operation
• with simple handling and mounting properties
• for complicated geometric tank designs