Tachograph calibration

Tachograph calibration is important for ensuring tachographs are functioning correctly. Calibration verifies the accuracy of the vehicle’s technical measurements. During preventive maintenance inspection, the mechanic should calibrate the analogue or digital tachograph to ensure compliance with the relevant regulations. A tachograph is a precision measuring instrument with an algorithm for calculating distance and other relevant information. The algorithm is also based on the technical condition. Therefore, it should be correctly calibrated to ensure the information recorded is accurate.

What is tachograph calibration?

Tachographs, whether digital or analogue, record data on commercial vehicles and trucks. They provide accurate information on the speed, acceleration and distance covered for route tracing purposes. A tachograph must be calibrated to record accurate information. Calibration involves configuring the measuring device for higher accuracy. The parameter for calibrating tachographs is called variable or coefficient (K). The parameter (coefficient) expresses the number of electrical impulses the tachograph should receive when a driver drives the truck for one mile. Another coefficient measures the speed sensor’s number of pulses in a gearbox at a one-kilometre distance.

Tachograph Calibration

During the calibration process, the coefficients are matched to ensure the electrical impulses and the pulses from the sensor are in line. The calibration process relies on the tachograph programmer to check and ensure the tachograph works properly and correctly. It programmes all variables, from mileage and time to sensor type and dates.

In tachograph calibration, technical indicators of the vehicle are checked before measuring the state of the tachograph and adjusting it. The entire process consists of the following:

  • Checking the measuring device for serviceability.
  • Measuring the technical parameters like speed as the driver drives on the test strip or special stand.
  • Based on the information from the measurement of technical parameters, the mechanic can configure and programme the tachograph operating mode.
  • After the entire process, the gearbox sensor and the tachograph are sealed to prevent further interference.

When the calibration process is complete and the tachograph is sealed, the service provider attaches a special label indicating the parameters and date of calibration. The mechanic also writes a protocol showing the results of the tachograph checks. All calibrated tachographs must have the necessary seals to avoid fines within the territory of the EU.

Fleet companies should calibrate precision measuring instruments due to the algorithms they use to measure speed and distance. Unlike navigation devices, a tracker system relies on its algorithm to measure various parameters. Hence, any changes in the vehicle’s technical condition affect the tachograph’s accuracy. After manipulations to the technical units, like replacing tyres or repairing the transmission, the driver should ensure the tachograph is calibrated for accuracy.

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What are the tachograph calibration rules?

Digital tachograph calibration rules state that calibration should be performed every two years. The same applied to analogue tachographs. However, the calibration can be done before the two years lapse if the vehicle registration changes or there is an alteration on the vehicle. Other circumstances for tachograph calibration include:

  • When the tachograph is installed, repaired or replaced, the fleet company should ensure it is calibrated for accurate data records. Repairs on the tachograph may alter its functionality, and calibration ensures the precision equipment functions as expected.
  • If there is an alteration to the tyres’ circumference, the tachograph should be recalibrated. Any vehicle elements responsible for movement require calibration due to the changing technical conditions.
  • If the tachograph plate is damaged during repairs, it may affect its functioning. Hence, the tachograph must be recalibrated.
  • If the tachograph sensor is damaged or the seal on the gearbox is removed, the driver should take the vehicle for recalibration and seal the gearbox to avoid penalties and fines.
  • Changes made to the vehicle that could impact the accuracy of the tachograph should be followed by calibration.
  • When the owner changes or the licence plates are replaced, calibration is necessary to match the registration protocol with the company car.

A tachograph can only be calibrated if it is working. Repairs must be completed before calibration if the device is out of order. Vehicles that use autonomous batteries with a digital tachograph require replacement during calibration. Otherwise, the tachograph could stop working when the battery is disconnected.

Tachograph calibration centres attach a sticker to the vehicle following calibration. The sticker is put on the B pillar of the driver’s door on the seat base. Before driving a commercial vehicle, drivers should ensure the calibration is within the date shown on the tachograph calibration sticker. Both the employer and driver commit an offence if the calibration period has lapsed.

In the UK, tachograph workshop card is used for digital tachograph calibration. Technicians with the workshop card are usually nominated technicians working in an approved tachograph centre and with a digital training certificate. Tachograph calibration costs can vary since the fees were deregulated by the UK government in 2012.


Tachographs are useful in recording drivers’ hours and crucial information for commercial vehicles. The tachographs should be calibrated regularly for accurate vehicle and fleet tracking. It is a legal requirement to calibrate the measuring devices since the information from the tachographs can be used for legal proceedings. Failure to comply with the calibration laws attracts penalties and fines.


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