Digital Tachograph Calibration Intervals and the SA Legal Context

How often must a digital tachograph be calibrated?

A digital tachograph must be recalibrated at least every two years, and again whenever the vehicle changes in a way that affects the recorded speed or distance. The two-year interval is the baseline for operators running the AETR-style digital tachograph on cross-border routes into neighbouring countries. For purely domestic South African fleets the device is not yet a national legal requirement on every vehicle, so the calibration discipline follows the route and the contract rather than a single act of Parliament.

The practical rule for a fleet manager is simpler than the legal patchwork. If a truck or bus carries a digital tachograph and crosses a border where the AETR rules are enforced, treat two years as the hard ceiling and book the recalibration before the seal date expires, not after.

What triggers an early recalibration?

Several changes invalidate the existing calibration before the two-year clock runs out. Book a workshop slot when any of these happen:

• A tyre change to a different rolling circumference, or a switch in tyre size on the driven axle.
• A final-drive or differential ratio change.
• Replacement of the KITAS speed sender or the gearbox sender drive.
• A repair that breaks the calibration seal between the sender and the tachograph head.
• A correction of the vehicle registration or VIN held in the device.
• Any sign that the recorded distance has drifted against a measured kilometre.

The sender side matters most here. The KITAS II+ pulse generator (for example a 19.8 mm probe, 4-pin round terminal unit with encrypted output) is a sealed, paired part. Once it is swapped, the cryptographic pairing with the tachograph head is broken and the whole chain has to be recalibrated by an approved workshop. You cannot fit a new sender and drive away certified.

What is the certified chain, and why does it matter?

The certified chain runs from the gearbox drive, through the speed sender, to the tachograph head, and into the printout and download file. Calibration ties the sender pulses to a real distance over a measured track, sets the characteristic coefficient (w), and writes the vehicle parameters into the head. The seal proves the chain has not been tampered with since.

For an operator this means three things. Keep the calibration certificate and the workshop card record with the vehicle file. Do not let a roadside repair break a seal without a follow-up recalibration. And source the sender as a genuine, correctly specified part so the pairing and the encrypted output behave as the head expects.

How does the KITAS sender choice affect compliance?

The sender has to match the head generation and the gearbox drive. A KITAS II+ unit pairs with the matching head and outputs an encrypted signal that the head authenticates. Fit the wrong probe length or the wrong connector and the drive will not seat, or the head will flag a sensor fault and refuse to certify. Confirm the probe length (for instance 19.8 mm), the connector (4-pin round terminal), and the generation before ordering, then have the approved workshop pair and seal it.

We supply genuine KITAS II+ senders and the fleet speed pulse generators that feed older analogue and electronic heads, so the certified part is the one that goes in.

How to order or request a quote

Send us the vehicle make, the tachograph head generation and the current sender part number, and we will confirm the correct genuine KITAS sender and lead time before you book the calibration slot. Order by part number on Omnipart, for example the VDO KITAS II+ sender with a 19.8 mm probe (2171-20002115).