This is not correct. A distinction must be made between:[1]
a) Driving up to 15km/h too fast outside of a city/village for more than 5 minutes or in two cases after departure is fined with 140 EUR.
b) Exceeding the speed limit once for a short time by up to 10 km/h outside a town or village is finded with 30 EUR. (11-15km/h: 50 EUR; 16-20km/h: 140 EUR; ...)
There is a tolerance applied to the measurement of 3km/h for under 100km/h and 3% above 100km/h. That should take into account the inaccuracy of the measurement; however, it does not guarantee that you get away with driving 83km/h in the autobahn, because the measurement might be a little inaccurate to your disadvantage.
