only 120uV (ECG) amplitude in Cyton ?
@wjcroft and @retiutut
We used a single channel of the 8-channel Cyton board to record ECG. Our interest is to collect the raw data and perform some signal processing on the raw data. So far, the ECG we saw on the GUI looks fine (see the image) but the amplitude is less (90 - 120uV) when compared to the normal ECG (0.5mV - 1.5mV).
Please is there any method we could apply to boost the amplitude?
...NB: the gain was set to 24x.
Thanks for your time
Comments
Abummu, hi.
Where are you placing your electrodes, and what electrodes are you using? A typical placement is similar to the below diagram. With Green being the Ground / Bias lead:
William
@ wjcroft I really appreciate your reply. I spent the whole day reading previous post for possible clue, but I couldn't find much...
We placed the electrodes as described in the image above. Since we are using the N1P, the +ve electrode was connected to the top pin and -ve to the bottom plus a BIAS lead. Contrary to the setup above, our +ve electrode was placed on the left side. Please permit to ask the following:
1. In the image I posted, what is the difference between the amplitude on the left (+557uV and -557uV) and the 94.4uV shown on the right?
2. the Not railed displaced?
3. is the SRB1 and SRB 2 supposed to be off for the channel I am using?
thank you for your time
Generally you use the GUI settings panel to turn OFF SRB2 and SRB1 for ECG channels. If SRB2 is not turned off, then the SRB2 pin ('bottom' row, closest to board) acts as a common bus for all the positive pins (pin row on top). Thus the default state is intended for common reference EEG.
The 'N1P' labeling is somewhat of a misnomer. The bottom row of pins is actually labeled: IN1N, IN2N, ... IN8N. The top row of pins is labeled IN1P through IN8P.
https://docs.openbci.com/docs/01GettingStarted/02-Biosensing-Setups/ECGSetup
I should have mentioned it earlier, but there is nothing unusual with your screenshot. You have the GUI set on auto scale. Thus it adjusts max scale shown on axis, to correspond to your signal. Showing here plus and minus 577 uV. Thus your ECG peak to peak is about 1 mV. Totally normal.
The uV rms figure is just root mean square average of the signal amplitude. Since ECG is very narrow pulse, the RMS is low.
https://en.wikipedia.org/wiki/Root_mean_square