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 sense the ECG signals. Smaller surface electrodes sense the EMG and EEG signals. The types of surface electrodes are as follows. Metal Plate Electrodes ECG measurement … Read more
Non-electrical parameters such as temperature, heart sound, blood pressure are measured from the human body with electronic equipment. Transducers are the devices that convert biological parameters to electrical signals. The process of conversion is Transduction. Generally, transducers convert one form of energy into another form of energy. Transducers are of two types. 1. Active Transducers: … Read more
Application of Piezoelectric Transducer Crystal microphone measures and records the Heart sounds (Phonocardiography). The microphone operates in the flat frequency range of 20 to 1000 Hz, which suppresses the breathing sounds and room noise. Sounds from heart chambers are measured with Catheter-tip piezoelectric sensors. A piezoelectric crystal detects the Korotkoff sounds during systolic and diastolic … Read more
When recording biopotentials noise and drift are the two problems encountered. Noise is due to the recording device and by the patient when they move. Drift is a shift in baseline created due to various thermal effects. A DC amplifier has a shift or sudden peak in the output when the input is zero. Therefore, … Read more
ECG Waveform This is what an ECG waveform looks like: Depolarisation When electrical activity occurs, heart muscle fibers are contracted and produces a movement. This condition is refered as Depolarisation. When blood is pumped around the body, it results in contraction. When chambers are contarcted, it is called systolic. Repolarisation The realxation of heart muscles … Read more
The electrical signals from the heart are measured with surface electrodes. The resulting electrode potential in the heart conducts to the body surface. Standardized electrode positions are used to record the ECG. The three types of electrode systems are Bipolar limb leads or standard leads Augmented unipolar limb leads Chest leads Bipolar Limb leads – … Read more
What are Electrodes? Electrodes are defined as a solid electric conductor through which an electric current enters or leaves an electrolytic cell. It converts ionic potentials to electronic potentials. Different types of electrodes used for biological measurements depend on the anatomical locations, from where the bioelectric signals are measured. Bioelectric electrodes acquire signals like ECG, … Read more
EEG Lead System International Federation of EEG society has suggested 10 – 20 electrode placement system for EEG recording. Silver / silver chloride electrodes are used as surface electrodes in this setup. On the scalp, distances between two electrodes are given as 10% and 20% of the distance between specified points. Nasion and Inion are … Read more
What is Biomedical Instrumentation? Biomedical instrumentation and engineering is the application of knowledge and technologies to solve problems related to living biological systems. It involves diagnosis, treatment and prevention of disease in human. As the medical field is emerging, the area of Biomedical Engineering is an expanding field. We use the term “bio” to denote … Read more
