Using attenuators to protect your scope

Using an attenuator will protect your scope from over-voltage which could zap the input stage of your scope.
A 10x attenuator devides the input voltage by 10,. The normal range of attenuators include 10x, 20, 100x and 1000x.
For car work 10x or 20x are used to protect the scope from input spikes from spikes inductive circuits such as coils and fuel injectors or piezo electric devices such as knock sensors or piezo injectors.

Most scopes have a setting on the probe menu to select the attenuation No-automotive scope generally don't have a 20x attenuation on the channel probe menu. Also be aware non-automotive scopes are not designed to handle the voltage spikes than can occur when measuring ignition primary voltages so using an attenuator is especially important.
*********An attenuator is not suitable for measuring ignition secondary (HT) voltage,*********

These are a selection of ty[ical attenuators that cn be bought from the internet.