The atomic force microscope (AFM) is a sensitive and gentle instrument to examine the topography of surfaces. The sensitivity of the AFM depends on the choice of the detector, which is used to measure the vertical motion of the cantilever tip. In this paper, a cantilever with an integrated Wheatstone bridge as a deflection sensor will be introduced. This detection system is based on the piezoresistive effect. We call this sensor the Wheatstone bridge Piezo Lever. The principle set-up of this cantilever is described and a theoretical study as well as experimental investigations of sensor sensitivity are made. Experimental results are in accordance with theoretical predictions. If one uses the ’lock-in’ technique, the resolution is limited mainly by the thermal vibration of the cantilever. However, this is no limitation to reach atomic resolution. The experimental study shows a voltage-dependable sensitivity resulting from heat generation of the voltage-supplied Wheatstone bridge. Measurements of various test structures are shown and special tip artefacts in the AFM are presented.