Vidya Muthukrishnan 
What is a Surface Electrode? Surface electrode measures the potential available from the surface of the skin. It senses the signal from heart, brain and nerves. Larger surface electrodes are commonly used for ECG. Smaller surface electrodes are commonly used for EMG and EEG. The types of surface electrodes are as follows. Metal Plate Electrodes … Read more
Non-electrical parameters such as temperature, heart sound and blood pressure are measured from the human body with electronic equipment. Biomedical Transducers are the devices that convert those biological parameters to electrical signals. The process of conversion is transduction. Generally, transducers convert one form of energy into another form of energy.Two common transducer classes are active … Read more
Application of Piezoelectric Transducer In biomedical instrumentation, piezoelectric transducers convert pressure and vibration into electrical signals. A crystal microphone measures and records heart sounds (phonocardiography). That microphone is often specified for a flat band of 20 to 1000 Hz so breathing and room noise sit outside the passband more than the heart sounds. Sounds from … Read more
When recording biopotentials, noise and drift are two problems. Noise can come from the recording device and from the patient when they move. Drift is a shift in baseline created due to various thermal effects. A DC amplifier can show a shift or sudden peak in the output when the input is zero. A chopper … Read more
ECG Waveform An ECG recording setup measures the heart’s electrical activity and draws the ECG waveform below. The same chain of protection, lead selection, amplification and display is what produces that trace. Depolarisation When electrical activity spreads through the heart, muscle fibers then contract and move blood. That electrical change is depolarisation. When the ventricles … Read more
An ECG lead system measures heart electrical signals using surface electrodes at standardized positions. Those electrodes sense the surface potential produced by the heart; they do not carry the heart’s internal voltage out of the chest. Standardized positions are used so ECG recordings can be compared. The usual 12-lead set groups electrodes into three systems: … Read more
What are Electrodes? Electrodes are solid electric conductors that let electric current enter or leave an electrolytic cell, converting ionic potentials to electronic potentials. In biomedical work the same idea is used to pick up body signals. Different electrode designs are used depending on where the bioelectric signals are taken from. These electrodes can acquire … Read more
EEG Lead System EEG measurement uses a lead system on the scalp. The International Federation of Clinical Neurophysiology (the EEG societies’ successor) recommends the 10-20 electrode placement system for EEG recording. This system uses silver/silver chloride electrodes as surface electrodes. The distances between electrodes on the scalp are set at 10% and 20% of the … Read more
What is Biomedical Instrumentation? Biomedical instrumentation applies engineering and technology to medical diagnosis, treatment and disease prevention. The field uses biophysics and biochemistry, then applies that overlap of physics and chemistry with biology in medical work. Biomedical instrumentation measures biological signals such as ECG and EMG so a physician can diagnose and treat a patient. … Read more