Module Overview

Medical Measurements 2

The aim of this module is to provide the student with knowledge and understanding of the physical principles of electrophysiological measurement systems as applied to the measurement of ECG signals. Signal measurement theory, sources of electrical noise and interference, and the physical principles and design of biomedical electrodes.

This module provides an introduction to the principles of physics and physical instrumentation as they are applied to the measurement and recording of human physiological signals. The module is inextricably linked to its other two co-requisite partners in this course.

Module Code

PHYS 2812

ECTS Credits


*Curricular information is subject to change

Electrodes   (4 hours)

Electrode electrolyte reactions at interface and formation of half-cell potential. Electrode polarisation. Polarisable and non-polarisable electrodes. Electrode circuit models and frequency response. Electrode-skin circuit and contact impedance. Minimisation of contact impedance. Electrode noise and motion artefact.

ECG Instrumentation   (6 hours)

The Forward and Inverse problems. Concept of the cardiac vector. Movement of the cardiac vector during the cardiac cycle. Einthoven’s triangle and frontal lead vectors. Wilson’s Central Terminal and augmented leads. ECG lead redundancy. Block diagram of ECG lead system. Vectorcardiography. Example of ECG circuit using operational amplifiers.


Signal Measurement Theory   (4 hours)

Accuracy and precision. Analogue to digital conversion and quantisation error. Sampling and the Nyquist Criterion. The law of faithful reproduction for biomedical signals. Linearity of amplitude, phase and frequency response. Bandwidth matching. Frequency spectra and Fourier series. Measurement specificity and predictive value.


Amplifiers   (6 hours)

Description of the operation of the PN-junction diode and the bipolar transistor amplifier. Description of the operational amplifier. Ideal op-amp characteristics. Common-mode rejection ratio. Positive and negative feedback. Inverting, non-inverting and differential op-amps. Control of amplification. Measuring gain in decibels. Op-Amp frequency response. Impedance matching and loading of circuits. Pre-amplification.


Noise and Interference   (4 hours)

Shot and Nyquist Noise. Generation of Electric Field coupling. Body coupling. Generation of magnetic field interference and methods of noise elimination.                                                                           

A typical laboratory programme may include experiments taken from the list below or equivalent experiments may be used:

  • Operation of CRO and Fourier Synthesis of Time-Varying periodic Waveforms;
  • Investigation of the characteristics of the Silicon pn-junction diode;
  • Half-wave and full-wave voltage rectification;
  • Investigation of bipolar transistor characteristics;
  • Operational Amplifier Characteristics;
  • Design and Implementation of Differential Amplifiers;
  • ECG Measurement and Extensions.

Lectures, laboratory sessions, student-directed learning, computer-based learning, catheterization, plethysmography and electromagnetic flow measurement.

24 hours lectures, 18 hours laboratory.

Module Content & Assessment
Assessment Breakdown %
Formal Examination40
Other Assessment(s)60