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Innovative tank sensor with LED level display


Horstmar, September 2014 – Inadequate information about the fuel level in the temperature control unit's fuel tank on refrigerated semi-trailers is a day-to-day problem in refrigerated logistics – normally due to a lack of or imprecise measurement equipment. Schmitz Cargobull Telematics has addressed this issue by developing a new fuel level sensor with an LED level display which is mounted on the semi-trailer's bulkhead.


The electronic system has a capacitive sensor which enables a precise fuel level measurement to be displayed.  Previous, mechanical measurement systems utilised a less accurate floating arm to measure the fuel level.  This conventional technology delivered imprecise and thus unreliable measurements as a result of its design. As such, the new measurement system offers greater precision which, in turn, allows exact monitoring of the operating costs.

It is equipped with automatic calibration which is capable of compensating for impurities in the fuel or other liquids such as biodiesel or water.

Furthermore, the new sensor is also distinguished by the fact that it remains powered even when the refrigeration unit is switched off and continues to deliver measurements at the specified intervals.

The newly developed sensor system uses a standardised LIN bus interface. This makes it easy to connect the system to the existing telematics hardware.

It provides the following functions:

  • Indicates the tank level with the aid of an LED display (in litres) on the vehicle bulkhead. Nine green and three red LEDs are used to display the fuel level, with the red LEDs marking the reserve amount.
  • Improved accuracy through new measuring equipment (capacitive measurement procedure)
  • Transfer and presentation of the tank level in the telematics system portal (filling level in %)


The tank sensor is screwed into the upper maintenance opening of the Schmitz Cargobull refrigeration unit tank and connected to the LED level display. This is mounted on the trailer's bulkhead next to the light and brake bracket.

The LED level display is then connected to the refrigeration unit and optionally to the telematics system control unit. The power supply for the LED level display comes from the refrigeration unit battery.

The following customer benefits distinguish the new tank sensor and LED tank display:

  1. A quick and clear identification of the fuel level in the tank before the trailer sets off for a transport job
    • via an LED display directly on the trailer
    • via the telematics system in an online portal
  1. Identification of the refuelling and consumption patterns via the reporting function in the telematics portal
  2. The warning function (text message, e-mail) via the telematics system provides notification in the event of a critical tank level, preventing fuel-related breakdowns and possible load damage
  3. Reduces the frequency of workshop visits required to vent empty refrigeration unit tanks - as a warning is provided before this critical level is reached
  4. Constantly records the fuel remaining in the refrigeration unit tank Verifies orderly refuelling (comparison with fuel invoices)
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