Refactoring - Breaking Dependencies

Currently I am working on the Racing-Car-Katas. The goal is to refactor a peach of code so that it follows the solid-principles.

I try to add the Dependency Inversion Principle. Where I can pass a dependency through the constructor.

Initial Situation

Insid the class Alarm is the dependency Sensor which generates a psiPressureValue.

public class Alarm {
    Sensor sensor = new Sensor();

    public void check()
    {
        double psiPressureValue = sensor.popNextPressurePsiValue();
        /* ... */
    }
}

Idea

public class Alarm {
    Sensor sensor;

    public Alarm() {
        this.sensor = new Sensor();
    }

    public Alarm(ISensor sensor) {
        this.sensor = sensor;
    }

    public void check()
    {
        double psiPressureValue = sensor.popNextPressurePsiValue();
        /* ... */
    }
}

If this would be a real application I don't want to break any dependency between Alarm and Sensor. There for I would created the following constructor

public Alarm() {
    this.sensor = new Sensor();
}

But my gut feeling says this is code small..

How to handle such dependencies in real world applications?