Biomedical Instrumentation Systems

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  • Polarizable vs. Non-Polarizable Electrodes

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    John Mulindi
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    We may categorize electrodes into two possible types albeit theoretically: those that are perfectly polarizable and those that are perfectly non-polarizable. This categorization is based on what happens to an electrode when a current passes between it and the electrolyte. Perfectly polarizable electrodes are those in which no actual charge crosses the electrode-electrolyte interface when…

  • Commonly used EEG Electrodes

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    John Mulindi
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    The most commonly employed electrodes for recording electroencephalographic signals from the brain (EEG) are cup electrodes and subdermal needle electrodes. Cup electrodes are fabricated from platinum or tin approximately 5-10 mm in diameter. These cup electrodes are filled with a conducting electrolyte gel and can be attached to the scalp with adhesive tape. Recording of…

  • Key Properties of Bioelectrodes

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    John Mulindi
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    To record biopotentials, an interface is required between the electron-conducting copper wires connected to signal conditioning amplifiers and the ion-conducting environment of living organisms. Electrodes form this interface. Some of the several kinds of electrodes are better than others in terms of low noise and ease of use. Initial ECG electrodes were non-disposable, nickel-silver plated…

  • What is a Biosensor?

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    John Mulindi
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    This is a biological sensor that has the following features: Biosensors are typically miniature and include monitoring of blood gas and biochemical concentrations additionally, physical quantities such as force, shear, potential, etc. Biosensors can be divided into those that measure electrical properties e.g. pH meters, CO2 electrodes, O2 electrodes, field-effect transistor-based biosensors, etc. and those…

  • Types of EMG Electrodes Commonly Used in Medical Measurements

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    John Mulindi
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    We have different types of biopotential electrodes that are used in recording electromyographic (EMG) signals from different muscles in the body. The shape and size of the recorded EMG signals depend on the electrical property of these electrodes and the recording location. For non-invasive recordings, proper skin preparation, which normally involves cleansing the skin with…

  • ECG Electrodes

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    John Mulindi
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    A typical flexible ECG electrode is composed of certain types of polymers or elastomers that are made electrically conductive by the addition of fine carbon or metal powder. These electrodes are available with pre-pasted AgCl gel for quick and easy application on the skin using double-sided peel off adhesive type. Related: Electrocardiogram (ECG) The common…

  • Features of Floating Type Biopotential Electrodes

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    John Mulindi
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    One key source of motion artifact in biopotential electrodes is the disturbance of the double layer of charge at the electrode-electrolyte interface. Employing non-polarizable electrodes like Ag/AgCl electrode can greatly reduce this artifact but it still can be present, and efforts to stabilize the interface mechanically can help to reduce the artifact further. Floating electrodes…

  • Biomedical Instrumentation Questions & Answers

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    John Mulindi
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    Q1. What are the problems encountered in biomedical measurements? The problems encountered in biomedical measurements are: Q2. What are the key requirements for specifying biomedical instrumentation systems? They key specifications to consider when specifying biomedical instruments include: Q3. What are the diagnoses made from Electroencephalogram (EEG)? The brain cells are referred to as neurons. The…

  • Bioelectric Potentials and Electrodes Questions & Answers

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    John Mulindi
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    Q1. What do you understand by bioelectric potentials? List the different types of biopotentials. Bioelectric potentials are ionic voltages produced when special types of cells perform electrochemical activities. These bioelectric potentials can be measured and the measurement results provide meaningful information to physician to diagnose and treat the patient. The devices that convert ionic potentials…

  • Types of Bioelectrodes

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    John Mulindi
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    Introduction Bioelectric events have to be picked up from the surface of the body before they can be put to the amplifier for subsequent record or display. This is done by use of electrodes. The potentials produced at different points are measured by placing electrodes at various points on the body. They carry the currents…