The EKG-EMG shield when combined with a duino device can provide a low cost ekg signal of the hearts actions
The shield attempts to reduce or remove 50 or 60hz interference from the measured signal. Interference from the electrical systems around the person under measurement is a well known challenge for EKG devices.
The human body acts as an antenna, the EKG shield amplifies signals by 205 times. The voltage levels picked up at the skin due to heart action is around 1mV. Noise pick up from an electrical cable close to the user can easily approach 1mV. When both the heart influenced voltage and the electrical noise voltage feeds into the system both are amplified.
A butterworth filter is present on the output of the shield with the aim of reducing this noise. A challenge exists when filtering the noise. The QRS peak in the wave form (fast spike up due to heart action) is often affected by filtering at 50 / 60hz. No filters are prefect therefore attempts to filter the output of an EKG often affects the QRS peak which is a signal of interest when analizing heart action
Several reports have identified significant noise being measured when using the EKG and a duino device. A common method to address this is software filtering. A project has addressed this.
youtube video on project
Link to software code for project