This is an EKG/EMG shield which allows Arduino like boards to capture Electrocardiography Electromiography signals. The shield opens new possibilities to experiment with bio feedback. You can monitor your heartbeat and log your pulse, recognize gestures by monitoring and analize the muscule activity as it is done in this project.
SHIELD-EKG-EMG converts the analog differential signal (the ECG/EMG bio potentials generated by muscles), attached to its CH1_IN+/CH1_IN- inputs, into a single stream of data as output. The output signal is analog and have to be discretized further with aim to give the option of digital processing. Typically, this is done via dedicated ADC embedded in the MCU of the base board (like: OLIMEXINO-328, OLIMEXINO-32U4, OLIMEXINO-STM32, etc). In the demo example we have provided, "ShieldEkgEmgDemo.ino", we have used 10-bit ADC with 256Hz sampling rate.
SHIELD-EKG-EMG’s total gain is the product of the gains of each discretization stage: Instrumental Amplifier(G1=10), OAmp with regulated gain (G2=6..101) and 3rd order "Besselworth" filter (G3=3.56). Then, the Gtotal = G1*G2*G3 = 10*(6..101)*3.56. By default, we have set the G2 gain approximately ~80. Then, Gtotal = 10*(~80)*3.56 ~ 2848.
Vmaxanalog = 3.0V/2848 ~ 1mV
Note that the 3rd order "Besselworth" filter's cutoff frequency is set to fc = 40Hz.