Device, system and method for acquiring and monitoring of biometric electrical signals
There is provided a device for acquiring biometric electrical signals comprising at least two electrodes. The device also comprises a current supply comprising a direct current supply, an alternating current supply, and a switch actuatable to switch selectively between the direct current supply and the alternating current supply. The device further comprises a capacitive coupling to couple each electrode to the current supply, a direct coupling to couple each electrode to the current supply, and a switch actuatable to switch selectively between the direct coupling and the capacitive coupling. The device also comprises a data acquisition module.
1 . 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 dry 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 comprising a direct current (DC) supply, an alternating current (AC) supply, and
a switch mechanism actuatable to switch selectively between the direct current supply and the alternating current 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 dry electrodes and the data acquisition module,
wherein the second mode of operation allows AC coupled biometric data acquisition,
wherein in the first mode of operation, the voltage difference between the dry electrodes is an open circuit voltage corresponding to no connection between the dry electrodes and a skin of a subject; and
wherein the biasing switching component automatically switches to the second mode of operation via the switch when the voltage difference between the dry electrode meets a threshold which corresponds to a connection between the dry electrodes and the skin of the subject to begin detection of biometric electrical signals via the data acquisition module.
2 . The device according to claim 1 adapted to switch between the first and the second mode of operation, at an instigation of a user via a user actuatable mode switch.
3 . The device according to claim 1 further comprising a battery power source.
4 . The device according to claim 1 wherein the dry electrodes comprise or have surface coating comprising:
chromium-plated metal or plastic;
coloured or colourable nitrides;
stainless steels.
5 . The device according to claim 1 further comprising one or more of:
a data storage module to store acquired data and/or library data against which acquired data may be compared for identification of a subject;
a data comparator module to compare acquired data to stored library data.
6 . The device according to claim 1 further comprising a data transmission module to transmit data to a remote recipient, to enable further processing of the data.
7 . The device according to claim 1 wherein each dry electrode is provided with:
a capacitive coupling to couple the dry electrode to the current supply;
and a direct coupling in parallel to the capacitive coupling which is further provided with a selectively closable switch.
8 . The device according to claim 7 wherein the capacitive coupling of each dry electrode comprises an AC-coupling capacitor.
9 . The device according to claim 1 wherein the switch mechanism further comprises a mid-rail bias point, whereby the DC source and the AC source can be selectively switched in and out of the circuit via the mid-rail bias point.
10 . A system for acquiring biometric electrical signals, comprising:
a device according to claim 1 ,
an additional receiving device,
a wireless communication system operable to effect communication of data between the device and the additional receiving device,
a data storage module comprising a part of the device and/or the additional receiving device.
11 . The system according to claim 10 wherein the data storage module comprises stored library data.
12 . The system according to claim 10 further comprising a data comparator module to compare acquired data to stored library data, for identification identification/authentication purposes, or longer term biometric monitoring.
13 . A method for acquiring biometric electrical signals comprising:
providing a device having:
two dry electrodes;
two capacitors, each on one side connected to one of the dry 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 comprising a direct current (DC) supply, and an alternating current (AC) supply; and
a switch mechanism actuatable to switch selectively between the direct current supply and the alternating current 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,
whereby the device is selectively switchable between:
a first mode of operation, wherein the DC current supply and the DC connection are selected, and a direct current is supplied to each dry electrode; and
a second mode of operation, wherein the AC current supply and the capacitive coupling are selected and an alternating current is supplied to each dry electrode;
wherein, in the first mode of operation, the voltage difference between the dry electrodes is an open circuit voltage corresponding to no connection between the dry electrodes and a skin of a subject; and
wherein the biasing switching component automatically switches to the second mode of operation via the switch when the voltage difference between the dry electrode meets a threshold which corresponds to a connection between the dry electrodes and the skin of the subject to begin detection of biometric electrical signals via the data acquisition module;
operating the device in the first mode when the dry electrodes are not in contact with a subject;
operating the device in the second mode when the dry electrodes are in contact with the skin surface of the body of a subject; and
acquiring biometric electrical signals when the device is operating in the second mode.
14 . The method according to claim 13 wherein the device switches between the first mode of operation and the second mode of operation is via a mid-rail or ground.
15 . The method according to claim 13 wherein the acquired biometric electrical signal data is compared to older template signal traces.
16 . The method according to claim 13 , wherein the acquired biometric electrical signal data is transmitted to a remote recipient via wireless communication, following the acquisition of such data, allowing for further processing of the data.