A device detects electric potentials with measuring inputs (7) for connection to measuring electrodes (9), which can be placed on the body of a patient (3). Measuring amplifiers (Op1, . . . , OpN) have a first and a second input as well as an output (11). A summing unit (13, 23) is connected to the outputs of the measuring amplifiers and sends a signal proportional to a mean value of the signals of the outputs of the measuring amplifiers to an output (15, 17) of the summing unit. Each of the measuring inputs is connected to a first input of a measuring amplifier. The second input of each measuring amplifier is connected to the output (17) of the summing unit. A potential output (19) connects to an electrode and to an output of a further amplifier Opc), with an input connected to the output (15) of the summing unit.
