To calculate fuel consumption, the system uses the data processed at the Data preparation and Filtration stages.

Fuel consumption by FLS (V_consumed) is calculated according to the formula:

V_consumed = V_initial − V_final + V_filled

where:

• V_initial  is the fuel volume at the beginning of the interval ;

• V_final  is the fuel volume at the end of the interval;
• V_filled  is the fuel volume filled within the interval.

Two options and a special case are closely connected with the consumption calculation:

• the Replace invalid values with those calculated mathematically option;
• the Exclude drains from fuel consumption option;
• a case where the interval beginning or end divides a filling or a drain into parts.

"Replace invalid values with those calculated mathematically" option

You can find this option in the General settings section of the sensor properties.

This option allows replacing invalid values calculated on the basis of FLS data by the values calculated mathematically. Mathematical calculation uses the data specified in the properties of the ignition sensors, relative and absolute engine hours (the Consumption, l/h option), as well as the value of the engine efficiency sensor.

Invalid values are detected in the following way:

• if the consumed fuel volume calculated for the interval according to the above formula is greater than 0 or equal to 0, the value is considered correct; 
• if the volume value is negative, it is considered invalid and mathematical calculation is used for the interval.

"Exclude drains from fuel consumption" option

You can find this option in the General section of the report template properties. It determines whether a fuel drain is considered as fuel consumption when calculating various indicators. This option allows excluding fuel consumption deviations related to the detected drains.

It may be necessary to disable the option in the cases where defuelling is authorized, for instance, when agriculture vehicles are filled by a refuelling tanker and the user wants to know the total turnover of the consumed fuel during the specified period of time.

How a filling and a drain are detected if they are split by an interval

Let's analyze this case on the example of a fuel filling. For instance, the beginning of the interval divides the filling into two parts. 

In this case, the second message in the interval is considered to be the starting message of the filling. This message shows that the fuel level has increased compared to the previous value. The first message serves as a reference and is used to determine the delta (d = V_current - V_previous) for the second. The delta for the first message can't be calculated because there is no previous message. The end message of the filling hasn't changed.

In this calculation, the filling volume is reduced compared to an undivided fillling, because the starting message of the filling is a later message.

The filling time may remain the same, as if the filling hadn't been split, or it may be shifted to a later time. This depends on whether the "undivided" filling time falls within the interval. If so, the filling time remains the same.