Sensor with a piezo-actuator

1. A method for operating a piezo-actuator in a piezo-operated injector for a fuel injection system, the method comprising:

producing a measuring pulse at a position at which the usable signal which is to be measured is expected;

then producing a reference pulse which corresponds to the measuring pulse, in the same cycle;

subtracting a first actuator voltage measured during the reference pulse from a second actuator voltage measured during the measuring pulse;

using a resulting voltage signal difference to calculate a force sensed by the piezo-actuator; and

using the force sensed to correct an injection amount for the injector.

2. The method as claimed in claim 1 , wherein the measuring pulse represents a force or a change in force acting on a servo valve in the fuel injector as a result of a pressure or a change in the pressure in a fuel chamber of the fuel injector.

3. The method as claimed in claim 1 , further comprising dynamically adapting a signal correction based on a respective operating point.

4. The method as claimed in claim 1 , wherein the measuring pulse is generated to detect closing of a nozzle needle during a main injection.

5. The method as claimed in claim 1 , further comprising carrying out digital signal processing after the measurement.

6. A motor vehicle comprising:

a fuel injection system; and

a control unit programmed to:

produce a measuring pulse at a position at which the usable signal which is to be measured is expected;

then produce a reference pulse which corresponds to the measuring pulse, in the same cycle;

subtract a first actuator voltage measured during the reference pulse from a second actuator voltage measured during the measuring pulse;

use a resulting voltage signal difference to calculate a force sensed by the piezo-actuator; and

use the force sensed to correct an injection amount for the injector.