**Author details**

is being monitored. Power line noise is a very difficult problem in biological monitoring because the 50-or-60-Hz frequency is usually at the range of biological signal which could be monitored. Band-stop filters are commonly used to reduce the power line noise. The notch frequency in the band-stop filters is set to the power line frequency of 50 or 60Hz with the

The second type of noise is called inherent noise. Inherent noise arises from random processes that are fundamental to the operation of circuit's elements and thus is reduced by a good circuit design practice. While inherent noise is reduced, it can be never eliminated. Low-pass filters are used to reduce high-frequency components. However, noise signals within the frequency range of biological signals being amplified cannot be eliminated by this filtering approach.

Computer is a main device which is used to display the biological signals being monitored. However some low or high level languages such as machine language, FORTRAN, visual C+ +, MATLAB or LabView, have to be used to realize the operation on the acquisition data from biological body. When computers are used to acquire physiological data, programming instruction tell computer when acquisition data should begin, how often samples should be taken from how many sensors, how long acquisition data should continue, and where the digitized data should be stored. The rate at which a system acquires sample depends on the speed of computer clock's frequency and the number of computer instruction that could be completed in order to realize a sample. Of course, some computers are utilized to control the gain on the input amplifiers so that biological signals could be adjusted during data acquisition.

In this chapter, main biomedical sensors, devices and biological measurement systems are introduced to make readers understand present bioinstrumentation in market. The common biomedical sensors are narrated here to make readers grasp their basic sensing principle such as heart sound sensor, blood flow sensor and enzyme sensor. Furthermore, basic charge, current, voltage, power and energy used in biomedical engineering are explained to design some detecting circuits. Besides above, signal filters and operational amplifiers are also described and some advice or opinions are given out to give readers some available references. The basic detecting blocks of biomeasurement system are provided to quickly design relative bioinstrumentations. Readers need to carefully learn the content of biomedical sensors, signal

[1] Wang Baohua. Biomedical measurement and instrument [M]. China Fudan press, shanghai,

cutoff frequency located a few Hertz to either side.

In other systems, the gain of data acquisition has to be adjusted.

filters, operational amplifiers for bioinstrumentation.

**•** Computer

226 Advances in Bioengineering

**7. Chapter summary**

**Suggested reading**

January, 2009.

Gaofeng Zhou1\*, Yannian Wang2 and Lujun Cui1

\*Address all correspondence to: yaofabiaolunwen@163.com

1 School of Mechatronic Engineering, Zhongyuan University of Technology, Zhengzhou, China

2 School of Information Engineering, Zhengzhou University, Zhengzhou, China
