EKG AFEs must meet a certain set of requirements to ensure the input ECG signal is appropriately handled, whilst preserving the integrity of the signal, and ensuring the data is fit for analysis. This requires well-defined input signal characteristics, dynamic range, and a data sample rate, all while maintaining a low power solution and minimising power dissipation.
EKGs are highly variable amongst the general population. The AFE choice is crucial to the device hardware design as an unsuitable AFE, external configuration, or register configuration will impact the end performance of the device. If set up incorrectly, the AFE may compromise the collected raw data and thus inhibit accurate and reliable algorithm performance.
Hardware schematic and layout design
Following AFE selection, there are additional hardware considerations which may be affected by your end application.
Good hardware layout design is crucial to a high performing EKG device as it will minimise the internal noise, which could interfere with the EKG signal.
A Lead I wrist wearable device will deal with different challenges than a chest-based device. It is vital that the use of the device is considered before designing the hardware. The overall goal of the hardware design of an EKG device is to minimise all forms of noise, both internal and external.
Despite its importance, the electrode design and performance will not matter if the internal hardware is poorly designed as this will infer significant noise e.g. mains noise, onto the raw signal. The performance of the EKG device will also be affected by PCB track routing, track length, mechanical constraints of the EKG device, and whether the device is wired or wireless.
Implementing health monitoring technology like EKG in wearable devices presents unique challenges. The AFE plays a vital role in overcoming these challenges and allowing acquisition of clinical-standard EKG signals on a personal device such as a smartwatch. This technology has immense potential to dramatically shift the healthcare system and change health monitoring forever.