System for sensing arterial pulse waveform

A method of offset calibration for a resistive bridge sensor of an arterial pulse waveform sensing system, the sensing system comprising a control system module and a sensing module coupled to the control system module and in which the sensing module is sized to be worn on the wrist or neck of a subject, wherein the control system module is configured to transmit control signals to the sensing module and the sensing module is configured to transmit arterial pulse waveform data from the sensing module to a processor of the control system module, the sensing module comprising the resistive bridge sensor and front end circuitry, the method comprising:

• coupling, by a first switch, a noninverting input of a comparator to an output of a first current digital to analog converter (IDAC) and a negative voltage port of the resistive bridge sensor, the first IDAC coupled to a first successive approximation register (SAR) within the sensing module;
• adjusting, by an SAR controller circuitry further disposed in the sensing module, each bit of the first SAR based, at least in part, on an output of the comparator, the comparator configured to compare a voltage on the negative voltage port to a common mode voltage;
• decoupling, by the first switch, the noninverting input to the comparator from the output of the first IDAC and from the negative voltage port;
• coupling, by a second switch, the noninverting input of the comparator to an output of a second IDAC and a positive voltage port of the resistive bridge sensor, the second IDAC coupled to a second SAR;
• adjusting, by the SAR controller circuitry, each bit of the second SAR based, at least in part, on an output of the comparator, the comparator configured to compare a voltage on the positive voltage port to the common mode voltage;
• decoupling, by the second switch, the noninverting input to the comparator from the output of the second IDAC and from the positive voltage port.

An arterial pulse waveform (APW) sensing system comprising:

• a control system module and a sensing module coupled to the control system module, the control system module providing control signals to the sensing module and the sensing module providing APW data from the sensing module to the control system module, wherein the sensing module is wearable on the neck or wrist of a subject and comprises a front end circuitry, the front end circuitry comprising an offset calibration circuitry comprising:
• a first current digital to analog converter (IDAC) coupled to a first successive approximation register (SAR) and configured to couple to a negative voltage port of a resistive bridge pressure sensor of the sensing module, the first SAR configured to store a first digital value, a second IDAC coupled to a second SAR and configured to couple to a positive voltage port of the resistive bridge sensor, the second SAR configured to store a second digital value, and an SAR controller circuitry configured to adjust each bit of the first SAR and each bit of the second SAR based, at least in part, on an output of a comparator, the comparator configured to compare a voltage on the negative voltage port or a voltage on the positive voltage port to a common mode voltage;
• an instrumentation amplifier configured to couple to the negative voltage port and the positive voltage port of the resistive bridge sensor;
• a low pass filter with a duty cycle controlled bandwidth;
• and
• an analog to digital converter.