A method for diagnosing a bias power supply for an acquisition system including a matrix-array interface device having conductive rows and columns, each row being connected to an input port and to a bias power supply, each column being selectively connected to ground by controlling an output port, and at each intersection either a circuit or a shunt, connected between the intersected row and the intersected column, including the following steps: controlling an output port so as to ground a shunt, reading the input port corresponding to the shunt, a low state indicating a normal presence of the power supply, a high state indicating an abnormal absence.