The fuel level in the tank fluctuates due to engine operation, acceleration, braking, turning, road bumps, vehicle tilt, and so on.

The higher the filtration level, the stronger is the smoothing used to compensate for FLS readings fluctuations. The stronger the smoothing, the easier it is to analyze the processed data, but the more distorted is the input information. Thus, to obtain the needed accuracy, you should set the filtration level to the minimum required. If the filtration level is too high, the processed data may no longer contain the fuel level difference corresponding to the drain. In most cases, it’s not recommended to use a filtration level higher than 10.

Often, test fuel drains are not displayed for this very reason: they are performed immediately after or before the filling, that’s why a short-term fuel level change is ignored due to smoothing. Actual drains don’t assume the return of the fuel level to the previous state, so they will not be missed for the indicated reason.

The 1% FLS accuracy declared by some manufacturers often doesn’t allow detecting small drains in real conditions due to the fuel fluctuations in the tank mentioned above. That’s why it would be quite optimistic to set, for example, a 1-liter Minimum fuel drain volume right away. This option acts as a kind of coarse filter separating drain and normal fuel level fluctuations, which will remain even despite the use of filtration. Consequently, you should choose the Minimum fuel drain volume in proportion to the value of these fluctuations that in some cases can even reach 20 liters or more.

If you set a too high Minimum fuel drain volume, the actual drain may disappear from the report results.

During a short stop, the fuel level can change significantly, therefore the analysis of short stops will result in detecting wrong drains. Using the Minimum stop duration to detect a fuel drain option, you can configure the system to monitor drains only during long stops and idle time.

If you set a too long Minimum stop duration to detect a fuel drain, then a long stop or idle time can be excluded from the analysis, and drain will not be registered.

Speed determined by the tracker and displayed in the monitoring system doesn’t always clearly indicate that the unit is moving. This happens due to the inaccuracy of satellite navigation systems (GPS, GLONASS, and so on). To determine the fact of driving, the Min moving speed is used, which defines the minimum threshold of the speed value recognized by the system as a movement.

In rare cases, speed value inaccuracy reaches large values, which can be associated with both the tracker quality and the environment (terrain, being in a building, the presence of large metal structures nearby, and so on). Some trackers can independently mark messages with inaccurate speed as invalid. However, using Messages validity filtration, you can find and filter out such invalid messages already in Wialon. This filtration applies only to messages that arrive on the server after enabling the appropriate settings, that’s why you’ll have to delete previous invalid messages manually.

There is a possibility to mark drains as false in the reports. It is done when current settings of the fuel level sensor are regarded as optimal for the unit, but the system still display incorrect drains according to the incoming messages.

Drains marked as false are shown in the report only when the corresponding option is enabled.