Calibrate 10x prober

What I must calibrate on probe 10x ? (2.81).

On wiki is only - select suitable range and adjust A3. But what calibrate ? Level ? Rectangulars ?

nobody from support on this forum ?

There is dc calibration and frequency response adjustment. They are independent of each other.

The dc calibration takes place through a software procedure and supplying appropriate test voltages.

For frequency compensation there are three trim capacitors per channel. The idea here is to get a square signal from a test signal of a 1Khz square wave with no overshoot and as little rounding as possible. In this state the scope will have a flat frequency response.

Two of the capacitors are used to achieve this for the basic scope input using a X1 probe. You do that first. Then the 3rd one is specifically an extra adjustment for the frequency response of the probe itself when in X10 mode.

But 3rd trimmer has o effect to rectangle, only max. value is changed.

The trimmer for the x10 mode is effectively adjusting the parallel input capacitance across the 1M input resistance. The idea is to adjust it give the same time constant as the 9M probe resistor plus stray capacitance around that.

To adjust, the probe must be in the x10 mode and you should use a 1KHz square wave as the test signal.