Biopotential Sensors, Devices, and Processes

An apparatus operable to reconstruct a biopotential signal from a signal received at a surface of a body, the apparatus comprising:

• a sensor device which forms a first signal connection for the biopotential signal, the first signal connection having a first sensor impedance, and which forms a second signal connection for the biopotential signal, the second signal connection having a second sensor impedance, wherein the sensor device is arranged such that the second sensor impedance is linearly related to the first sensor impedance by an impedance relation;
• sensor circuitry which provides i) a first sensor signal related to the biopotential signal by a first channel expression which is dependent on parameter values for the sensor circuitry providing the first sensor signal, dependent on the first sensor impedance and dependent on the biopotential signal, and ii) a second sensor signal related to the biopotential signal by a second channel expression which is dependent on parameter values for the sensor circuitry, dependent on the second sensor impedance and dependent on the biopotential signal;
• and
• a processor operable to read data carrying information on parameter values of the sensor circuitry, operable to read data carrying information on the first sensor signal, operable to read data carrying information on the second sensor signal and operable to generate data carrying information on a reconstruction of the biopotential signal said reconstruction using a derived biopotential relation which is derived from a set of relations comprising the first channel expression, the second channel expression and the impedance relation, wherein the derived biopotential relation used to reconstruct the biopotential signal is independent of the first sensor impedance.

A process of capturing a biopotential signal at a surface of a body using a sensor receiver which forms a first signal connection with the body wherein one or more parameters of impedance of the first signal connection are unknown, the process comprising:

• receiving the biopotential signal at an output of a first signal channel having a first channel transfer function which is dependent on the one or more unknown first impedance parameters;
• receiving the biopotential signal at an output of one or more second signal channels each having a second channel transfer function dependent on the one or more unknown first impedance parameters;
• solving a set of relations to determine the captured biopotential signal wherein the set of relations is defined dependent on:
• i) the first channel transfer function,
• ii) the second channel transfer function, and
• iv) outputs of the first and second signal channels.

A sensing device for sensing biopotential signals in a sensing region at a surface of a body, the sensing device comprising:

• first and second input terminals for connection to first and second sensor receivers which each connect the biopotential received at the surface of the body to a respective receiver terminal, wherein a second sensor receiver has a second receiver impedance for the biopotential signal which has a defined relationship with a first receiver impedance of the first receiver;
• sensing circuitry operable to connect to first and second receivers to receive first and second receiver signals and to apply a defined transfer function to the first and second receiver signals to output first and second sensing signals;
• and
• a sensing processor operable to determine the biopotential signal dependent on the first and second sensing signals, dependent on parameters of the defined transfer function and dependent on the defined relationship of the first and second receiver impedances.