Patent ID: 8786220

Claim:
A device for taking a safety precaution in an electrical tool, said electrical tool comprising an electric motor with at least one field winding and an armature winding and said device comprising the following features: a sensor unit, which is designed to generate a first sensor signal in accordance with an armature voltage via the armature winding, a voltage via the field winding or a commutation frequency in the armature winding; the sensor unit being designed to generate a second sensor signal in accordance with an armature voltage via the armature winding, a voltage via the field winding or a commutation frequency in the armature winding, the second sensor signal being different from the first sensor signal; a unit detecting a change of the first sensor signal, which is designed to detect a temporal change of the first sensor signal and emit a corresponding first modification signal on the basis of the detected change; and a safety device, which is designed to take a safety precaution in the electrical tool dependent on a value of the first modification signal, particularly when the value of said first modification signal is exceeded or not met in relation to a threshold value.