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Chapter 7
Biomedical Sensor, Device and Measurement Systems
Gaofeng Zhou, Yannian Wang and Lujun Cui
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/59941
1. Introduction
1.1. Sensor definition and classification
Sensors are very critical components in all devices and measurement systems. They have been
widely used in a lot of fields such as science, medicine, automated manufacturing, environ‐
mental monitoring, and so on. Some cheap sensors are finding their ways applying into all
sorts of consumer products, from children’s toys, dishwashers to automobiles. To some extent,
sensors are multidisciplinary and interdisciplinary field of endeavor. This chapter introduces
sensor’s basic definition and features, biomedical sensors, equivalent components in circuit,
signal filters and amplifiers, biomeasurement systems and design.
There are a lot of terms which are often used for sensors including transducer, meter, detector,
and gage. Defining the term sensor is a very difficult task. At present, there is not a uniform
definition which is agreed by all of us. The most widely used definition is that which has been
applied to electrical transducer by the Instrument Society of America(ANSI MC 1, 1975):
“Transducer —A device which provides a usable output is in response to a specified measur‐
and.” Furthermore, national standard of China points out that sensors consist of sensing
component, converting device and electronic circuit. A transducer is more generally defined
as a device which converts energy from one form to another. Output of sensor can be an optical,
electrical, chemical, or mechanical signal. In the field of electrical engineering, the measurand
is physical, chemical, or biological property or condition measured; hence output of biological
signal should be an electrical signal, too.
The words sensor and transducer are both commonly used in the context of measurement
systems, and often in an interchangeable manner. Transducer is used more in the United States,
and sensor has great popularity in Europe and China. The blurring of lines between the exact
meaning of sensors and transducers leads to a degree of confusion. Most but not all sensors
are transducers, employing one or more transduction mechanisms to produce an electrical
© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,
and eproduction in any medium, provided the original work is properly cited.

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output signal. According to the basic sensing principle, sensors are classified into mechanical
sensors, electrochemical sensors, biosensors, optical sensors, semiconductor sensors, magnetic
sensors, and thermal sensors. From different viewpoints, there are different classifying
methods. According to the physical parameters measured by sensors, sensors are classified
into resistance displacement sensor, inductive displacement sensor, capacitive displacement
sensor, piezoelectric pressure sensor, laser interferometer displacement sensor, bore gagging
displacement sensor, ultrasonic displacement sensor, optical encoder displacement sensor,
optical fiber displacement sensor, optical beam deformation sensor, flow sensor, imaging
sensor, temperature sensor, intelligent sensor and chemical ingredient sensor. Biomedical
sensors are used to gain the information on body and pathology, which is a branch of bio‐
medical engineering. Biomedical sensors are classified into physical sensor, chemical sensor
and biosensor. Physical sensor could be employed to measure blood pressure, body temper‐
ature, blood flux, blood viscosity, biological magnetic field, etc. Chemical sensor is utilized to
detect the ingredient and concentration of body liquid such as PH value, Ca
+
concentration,
glucose concentration, etc. Biosensor is used to sense enzyme, antigen, antibody, hormone,
DNA, RNA and microbe. In nature, biosensor is a kind of chemical sensor, which is mainly
used to detect biological signals.