FUEL MEASUREMENT
In design and development of subsequent versions of the fuel measurement system, Aksel has used microprocessor and computer technologies, improving the measurement accuracy by introducing calculation algorithms and appropriate corrections of characteristics (e.g. fuel density vs temperature, linearisation of measurement characteristics). Fuel level measurement is made by hydrostatic probes placed in the fuel tank. The probes measure the pressure of the fuel column, which is translated into fuel volume based on the calibration curve for the given tank. The probe includes a temperature sensor, which means that all non-linearities are mathematically compensated by the probe. Appropriate calibration is required – actual litres are translated into calculated litres based on temperature during calibration. The pressure measured by the probe is read out in digital form and filtered (several hundred samples per several seconds), and then recalculated based on calibration into instantaneous value of fuel volume. That value is then displayed.
Instantaneous values are additionally filtered, so fuel level fluctuations when starting and stopping the vehicle are eliminated. Only now this data is recorded as fuel level and used for refuelling detection and fuel consumption. The fuel level measurement system records the data in non-volatile memory. Each point in history has its distance and fuel consumption.
Such fuel consumption is the volume of fuel used from the beginning of recording history, determined based on fuel level analysis with refuelling taken into account. In order to determine the fuel consumption over the last 100 kms, the system searches the history for data 100 kms back. If that point is a stop, (i.e. there is more points with the same mileage), then the oldest entry from that stop is taken for calculations (the fuel burnt during the stop will also be included).
Fuel consumption per 100 kms is calculated as a difference between the historical and the current consumption.
The device has a built-in GSM modem, allowing for remote:
- firmware upgrade for the system cabinet, displays and device setup
- device diagnostics
- transmission of online data recorded from other devices (vehicle controller).