Abstract: A system and method of measuring bioelectric signals generated by an individual, inclusive of humans or other living organisms, comprises a plurality of sensors, at least one of the plurality of sensors being constituted by a capacitive-type sensor. Sensor has an associated insulated layer of material preventing the conduction of direct current between an electrode and individual, wherein a bioelectric signal of individual can be measured underwater.

Abstract: A system and method for improving student learning includes learning material that is presented to a student and a device that is used to acquire physiological data from the student in real time during a learning session. A cognitive assessment algorithm determines a cognitive state of the student using the physiological data, and a learning action algorithm modifies the presentation of the learning material in response to the student's cognitive state. The learning material can include lectures, questions asked of the student or problems or activities being completed by the student. In one embodiment, the device directly measures the brain activity of the student to determine the student's cognitive state. The cognitive state of the student can include the student's cognitive load, engagement or fatigue.

Abstract: A system and method for improving student learning includes learning material that is presented to a student and a device that is used to acquire physiological data from the student in real time during a learning session. A cognitive assessment algorithm determines a cognitive state of the student using the physiological data, and a learning action algorithm modifies the presentation of the learning material in response to the student's cognitive state. The learning material can include lectures, questions asked of the student or problems or activities being completed by the student. In one embodiment, the device directly measures the brain activity of the student to determine the student's cognitive state. The cognitive state of the student can include the student's cognitive load, engagement or fatigue.

Abstract: A sensor mounting system includes a rigid main body portion defining a housing within which is mounted a compression element. In use, the compression element provides a predetermined biasing force to force a sensor against the skin of a subject. A secondary support structure provides an adjustable biasing force to retain the main body portion against the subject. Alternatively, the main body portion may be mounted to a rigid pod with one or more secondary compression elements, with the pod itself retained against the subject. An interface layer extending from the main body portion provides a cushion to improve the comfort of the subject. The interface layer and sensor interface elements may be in the form of fingers to increase contact of the sensor with a selected portion of the subject.

Abstract: A self-locating mounting apparatus for holding objects such as sensors at specific positions on a subject's head includes a central mount constituted by a plurality of inextensible elements adapted to fit over the top of a subject's head. In addition, the mounting apparatus includes an adjustable circumferential band adapted to circle the subject's head and connect the central mount to inextensible side elements via sliding joints. A plurality of biasing elements provide a force for biasing sensor mounting units on the mounting apparatus against a subject's head, allowing for long-term sensing while minimizing interference forces on the mounting units. Advantageously, the mounting apparatus holds sensors within approximately 5 mm of their desired measurement positions over a range of subject head sizes.

Abstract: A wearable ballistic impact protection system detects impacts to a body. The system includes multiple sensors for detecting vibration. The sensed vibrations are converted to electrical signals which are filtered. Electronic components are provided to determine whether the filtered signal have frequency and amplitude characteristics of impact that cause injury to a body. Preferably, the sensors are Piezo-electric film sensing elements. Information regarding the extent of the impact and injuries to the body may be transmitted to a remote location so that medics or other personnel may be informed to the extent of injuries to the body so that they may provide medical assistance.

Abstract: A system for determining if signals present at bioelectric sensors derive from an intended source or from different, localized sources or artifacts includes a first sensor placed to detect the electric potential of interest and generate a first electric signal possibly representative of the electric potential of interest and a second sensor placed near the first sensor and preferably a relatively large distance away from the source. The second sensor detects the electrical potential of interest and generates a second electrical signal which also possibly represents the electrical potential of interest. An electronic circuit determines whether a difference between the electrical signals exceeds a certain threshold, thus indicating that either one or both of the signals is a measure of an artifact and not the electric potential of interest.

Abstract: An amplifier circuit with current noise reduction employs first and second variable impedance devices between a signal source and an amplifier. A modulation frequency generator establishes a modulation frequency fmod to alter the first and second impedance values out of phase from one another at the modulation frequency so that the sum of the first and second impedance values at the input of the amplifier is relatively constant. The modulation at frequency fmod shifts the signal to side bands about the modulation frequency. The output from the amplifier is passed to a bandpass filter centered on the modulation frequency in order to remove all frequencies outside the bandwidth of interest. The signal itself is recovered by demodulating the output of the bandpass filter using a synchronization signal that is derived from the modulation signal.

Abstract: A self-locating mounting apparatus for holding objects such as sensors at specific positions on a subject's head includes a central mount constituted by a plurality of inextensible elements adapted to fit over the top of a subject's head. In addition, the mounting apparatus includes an adjustable circumferential band adapted to circle the subject's head and connect the central mount to inextensible side elements via sliding joints. A plurality of biasing elements provide a force for biasing sensor mounting units on the mounting apparatus against a subject's head, allowing for long-term sensing while minimizing interference forces on the mounting units. Advantageously, the mounting apparatus holds sensors within approximately 5 mm of their desired measurement positions over a range of subject head sizes.

Abstract: The invention generally pertains to reducing artifact noise signals present when non-invasive capacitive-type signal measurements are taken of static electric fields produced by an object of interest. According to a first preferred embodiment of the invention, a given static artifact signal is reduced by minimizing the potential difference between a ground point of sensor circuitry and the potential of the object. According to a second preferred embodiment of the invention, the change in signal due to motion of the sensor in the field produced by the object is minimized by reducing the impact of changes in coupling to the signal source.

Abstract: An amplifier circuit with current noise reduction employs first and second variable impedance devices between a signal source and an amplifier. A modulation frequency generator establishes a modulation frequency fmod to alter the first and second impedance values out of phase from one another at the modulation frequency so that the sum of the first and second impedance values at the input of the amplifier is relatively constant. The modulation at frequency fmod shifts the signal to side bands about the modulation frequency. The output from the amplifier is passed to a bandpass filter centered on the modulation frequency in order to remove all frequencies outside the bandwidth of interest. The signal itself is recovered by demodulating the output of the bandpass filter using a synchronization signal that is derived from the modulation signal.

Abstract: A system for unobtrusively measuring bioelectric signals developed by an individual includes multiple sensors, one or more of which constitutes a capacitive sensor, embedded into or otherwise integrated into an object, such as a chair, bed or the like, used to support the individual. The object serves as mounting structure that holds the sensors in place. The sensors are preferably arranged in the form of an array, with particular ones of the sensors being selectable from the array for measuring the bioelectric signals which are transmitted, such as through a wireless link, for display and/or analysis purposes.

Abstract: The invention generally pertains to reducing artifact noise signals present when non-invasive capacitive-type signal measurements are taken of static electric fields produced by an object (10) of interest. According to a first preferred embodiment of the invention, a given static artifact signal is reduced by minimizing the potential difference between a ground point (G1) of sensor circuitry and the potential of the object (10). According to a second preferred embodiment of the invention, the change in signal due to motion of the sensor (30, 40; 30?, 40?; 230; 330; 430; 530; 630) in the field produced by the object (10) is minimized by reducing the impact of changes in coupling to the signal source.

Abstract: A system for unobtrusively measuring bioelectric signals developed by an individual includes multiple sensors, one or more of which constitutes a capacitive sensor attached to a holding device. The holding device serves as a mounting structure that holds sensors in place within a wearable garment. The holding device and sensors are horizontally and vertically adjustable relative to the garment, while the sensors are pressed against the individual and prevented from undesirable shifting upon movement of the individual.

Abstract: A sensor system accurately measures, with a high level of sensitivity, one or more vector components of a small electric field, through the use of multiple, relatively fixed sensors, at least one of which constitutes a weakly coupled capacitive sensor. The sensor system enables the electric field to be determined in a direction normal to a surface or along multiple orthogonal axes. Measurement of the electric field vector can provide improved resolution and characterization of electrical signals produced, for example, by organs within the human body.

Abstract: A system for measuring a free space electric field includes an ultrahigh impedance antenna positioned in the electric field to generate a signal from the electric field. An amplifier having an input port is provided to amplify the signal. The amplifier generates an input bias current which combines with the signal to create an input potential at the input port. An electrical circuit connects the input port to a ground connection and includes at least one circuit element for controlling the input potential to stabilize the signal at the input port.

Abstract: A system for measuring a biopotential signal produced by a body in free space at a location adjacent to the body, and if desired, through clothing, includes a probe that can be positioned adjacent to the body. The probe includes a conductive electrode to receive the biopotential signal and a conductor that is maintained at a fixed distance from the electrode. The potential of the conductor can be maintained substantially equal to the potential of the electrode to shield the electrode from stray electrical noise. The system further includes a high impedance first stage amplifier that is incorporated into the probe and electrically connected to the electrode using a relatively short connector to minimize connector noise. Functionally, the first stage amplifier compares the electrical potential of the electrode to a second potential (e.g. a local ground) and generates a signal that is indicative of the biopotential.

Abstract: An electronic circuit stabilizes an ultrahigh input impedance amplifier by altering the amplifier's input potential. This input potential includes both the desired input signal and the amplifier's input bias current. With an amplifier having an input port and a guard, both the input port and the guard will have the same input potential. Accordingly, the stabilizing circuit of the present invention provides the input potential at the guard to an electronic device which separates the input signal from the input bias current. This creates a corrective signal. The corrective signal is then used through a feedback path to alter the input potential so that the desired input signal can be fed into the amplifier without adverse consequences from the input bias current.