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Elemyo | 14 February 2020

Sensor MH-BPS101.
Examples of signals.

In this article, we showed various forms of EMG and ECG signals obtained when working with the MH-BPS101 sensor, as well as variants of interference arising under various conditions.

Before working with the MH-BPS101 sensor, we strongly recommend you to read detailed instructions.
An example of an EMG signal from MH-BPS101
An example of interference with the MH-BPS101
I. An example of an EMG signal from MH-BPS101.
1. An example of an EMG signal.
The sensor is located along the flexor muscle of the ring finger. The signal was recorded using an AKIP-4107 oscilloscope. When recording a signal, the computer was disconnected from the power supply network and located at a distance at least 0.5 m from household power sources.
EMG signal from the sensor. Electromyography (EMG) signal recorded during forearm muscle activity. EMG waveform during a single muscle contraction.
Fig. 1: Single, continuous muscle contraction.
EMG signal recorded during muscle activity. Electromyography (EMG) waveform during forearm muscle contraction..
Fig. 2: Three consecutive muscle contractions.
2. An example of an ECG signal.
The sensor is located on the left side of the chest along the longitudinal axis of the heart. The signal was recorded using an AKIP-4107 oscilloscope. When recording a signal, the computer is disconnected from the power supply network and is located at a distance of at least 0.5 m from household power sources.
Heart activity biosignal captured by the MH‑BPS101 biomedical sensor.
Fig. 3: An example of an ECG signal.
An example of an ECG signal with one muscle contraction.
Fig. 4: An example of an ECG signal with one muscle contraction.
3. EMG signal with poor skin contact.
The sensor is located on the calf muscle. Sensor contact with the skin occurs through a thick hairline. The signal was recorded using an AKIP-4107 oscilloscope. When recording a signal, the computer is disconnected from the power supply network and is located at a distance of at least 0.5 m from household power sources.
Fig. 5: Example of an EMG signal obtained under poor sensor‑to‑skin contact (calf muscle). The EMG signal shows increased 50 Hz interference, which becomes minimal once the electrode–skin contact is stable and secure.
Fig. 5: Example of an EMG signal obtained under poor sensor‑to‑skin contact (calf muscle).
The EMG signal shows increased 50 Hz interference, which becomes minimal once the electrode–skin contact is stable and secure.
Fig. 6: EMG signal with a single muscle contraction, showing increased 50 Hz interference.
Due to the poor contact of the electrodes with the skin, the electric potentials of the skin and the sensor do not "have time" to equalize, as a result of which there is a strong interference from the household power supply network.
II. An example of interference with the MH-BPS101.
1. The signal when the sensor is connected to a PC disconnected from the power supply.
EMG signal from the sensor without 50 Hz interference, showing the clean waveform of a single muscle contraction.
Fig. 7: EMG signal from the sensor without 50 Hz interference, showing the clean waveform of a single muscle contraction.
2. The signal when connecting the sensor to a PC connected to the power supply.
EMG signal heavily contaminated by 50 Hz mains interference.
Fig. 8: EMG signal heavily contaminated by 50 Hz mains interference.
The interference occurs due to a direct connection to a PC that is grounded through the household electrical network.
3. The signal when connecting the sensor to a PC through galvanic isolation. The PC is connected to the power supply.
Fig. 9: EMG signal is partially noisy with 50Hz interference.
The level of interference depends on the load on the used household network (there is almost no interference at night and day). After 0.5-1 minute after installing the sensor on the body, the interference is significantly reduced.
4. The signal when connecting the sensor to a PC through galvanic isolation. The power to the PC is turned off, but the power cable is connected to the PC.
Fig. 10: EMG signal does not contain 50Hz interference.
5. Touching the body of wires and devices connected to the power supply network.
Fig. 11: In this case, the EMG signal contains noticeable 50 Hz mains interference.
Fig. 12: EMG signal with 50 Hz interference.
6. The signal when the sensor is connected to a PC with the power off (the power comes from the battery), but:
a) the power cord is not disconnected from the PC,
b) the power cord is on the side of the PC (for example, it is placed on the same table with the PC).
Fig. 13: EMG signal with 50 Hz interference.
7. The output of the signal to a predetermined value with a strong interference of 50 Hz.
Fig. 14: Sensor signal in the first seconds after installation on the body in the presence of strong interference of 50 Hz.
14 FEBRUARY / 2020
copyright: Elemyo