On-body sensor system and method

A method of calibrating an on-body sensor system for determining position of a skin interface unit of the system,

• wherein the system comprises a plurality of skin interface units for coupling electrical signals into and/or out of the body of a subject, including two or more reference units, each for placement against a respective known region of the skin, and at least one positionable unit for placement at a further unknown position, each of the reference units comprising at least two pairs of skin coupling electrodes,
• the method comprising:
• positioning the two or more reference units against said respective known regions of the skin;
• sequentially controlling each of the reference units to transmit signals into the body toward the other reference units, and in each case deriving at one or more other reference units one or more signal characteristics associated with signals received at each electrode pair respectively of the other unit, and deriving based on this an indication of an angle of arrival of the signals at each of said reference units;
• generating and storing a dataset of information indicative of the derived angles of arrival of signals transmitted between the reference units, the dataset for use as a reference in subsequently deriving indications of position of the at least one positionable unit based on angles of arrival of signals transmitted between the positionable unit and the reference units.

A method of determining placement of skin interface units of an on-body sensing system, wherein the system comprises a plurality of skin interface units for coupling electrical signals into and/or out of the body of a subject, including two or more reference units, each for placement against a respective known region of the skin, and at least one positionable unit for placement at a further unknown position, each of the reference units comprising at least two pairs of skin coupling electrodes;

• and
• the method comprising:
• controlling transmission of signals through the body between the positionable unit and the reference units;
• deriving at each reference unit one or more signal characteristics associated with signals received at each pair of electrodes respectively of the unit, and, based on the one or more signal characteristics, deriving an indication of an angle of arrival of the signals at the reference unit;
• accessing a reference dataset comprising information indicative of known angles of arrival of signals at reference units if placed at said known regions of the skin, and if received from locations corresponding to one or more of said other known regions of the skin;
• and
• deriving an indication of position of the at least one positionable unit based on the derived angles of arrival of signals and on the information in the reference dataset, and generating output information based on the derived indication of position.