Speed detection for a tachograph system

A tachograph system for capturing registration-relevant vehicle data comprising:

• a plurality of sensors configured to detect a speed of the vehicle and output a signal representing the detected speed, wherein one of the sensors is a tachometer on an output side of a vehicle gearbox configured for speed detection;
• a computation unit coupled to the tachometer and the plural sensors configured to compare the signals output by the tachometer and the plural sensors and check the signal from the tachometer for plausibility using the plural sensors;
• a memory for storing at least the speed as a piece of registration-relevant information,
• wherein the computation unit is configured to:
• exclude erroneous signals and ascertain the speed using only those signals supplied by the sensors which are within particular limit values and
• the ascertained speed is determined using signals from a majority of the plural sensors.

A method of operating a tachograph system comprising:

• receiving a plurality of data from a first source;
• storing the received plural data with respective time stamps;
• storing sensor data from a plurality of sensors with respective time stamps;
• checking the stored received data for plausibility by comparing them to the stored data from the plural sensors;
• checking the first source that is a pilot sensor and has an associated pilot function for plausibility using the stored data from a majority of the plural sensors;
• calculating at least one of distance and speed based on the plausibility-checked signals for each of the sensor data and received data;
• comparing the at least one of the calculated distance and speed,
• wherein the steps of calculating and comparing are repeated when the compared calculated distance and speed are within prescribed limits and
• wherein an error message is generated and stored when the compared at least one of the calculated distance and speed are not within the prescribed limits.