A device for acquiring biometric electrical signals, comprising: a data acquisition module; two dry electrodes; two capacitors, each on one side connected to one of the electrodes; and two bias resistors, each on one side connected to the other side of said capacitors and the same side of the resistors also being connected to a respective input of a differential amplifier and the other side of the bias resistors being connected to a bias switching component, the bias switching component comprising: a current supply, the current supply comprising a direct current, DC, supply (1001, 1002) and an alternating current, AC, supply (1201, 1202); and a switching mechanism actuatable to switch selectively between the DC supply and the AC supply so that: in a first mode of operation, the switching mechanism is configured to connect the DC supply to the bias resistors; and in a second mode of operation, the switching mechanism is configured to connect the AC supply to the bias resistors, wherein each of the capacitors is bridged by a switch, which is configured to be closed in the first mode and configured to be open in the second mode, wherein in the first mode of operation a direct electrical connection is made between the electrodes and the data acquisition module, wherein the second mode of operation allows AC coupled biometric data acquisition, and wherein the device is adapted to automatically switch from the first mode of operation to the second mode of operation when the device detects skin contact between the electrodes and the skin of a subject in use. a data acquisition module; two dry electrodes; two capacitors, each on one side connected to one of the electrodes; and two bias resistors, each on one side connected to the other side of said capacitors and the same side of the resistors also being connected to a respective input of a differential amplifier and the other side of the bias resistors being connected to a bias switching component, the bias switching component comprising: a current supply, the current supply comprising a direct current, DC, supply (1001, 1002) and an alternating current, AC, supply (1201, 1202); and a switching mechanism actuatable to switch selectively between the DC supply and the AC supply so that: in a first mode of operation, the switching mechanism is configured to connect the DC supply to the bias resistors; and in a second mode of operation, the switching mechanism is configured to connect the AC supply to the bias resistors, a current supply, the current supply comprising a direct current, DC, supply (1001, 1002) and an alternating current, AC, supply (1201, 1202); and a switching mechanism actuatable to switch selectively between the DC supply and the AC supply so that: in a first mode of operation, the switching mechanism is configured to connect the DC supply to the bias resistors; and in a second mode of operation, the switching mechanism is configured to connect the AC supply to the bias resistors, in a first mode of operation, the switching mechanism is configured to connect the DC supply to the bias resistors; and in a second mode of operation, the switching mechanism is configured to connect the AC supply to the bias resistors, wherein each of the capacitors is bridged by a switch, which is configured to be closed in the first mode and configured to be open in the second mode, wherein in the first mode of operation a direct electrical connection is made between the electrodes and the data acquisition module, wherein the second mode of operation allows AC coupled biometric data acquisition, and wherein the device is adapted to automatically switch from the first mode of operation to the second mode of operation when the device detects skin contact between the electrodes and the skin of a subject in use.