Biomedical Engineering Reference
In-Depth Information
different types of computers to exchange information. When word processing files are
saved as text files, they are saved in ASCII format. Ordinarily, word processing files are
saved in special program-specific binary formats, but almost all data analysis programs
can import and export data in ASCII files.
The lowest level of computer languages is machine language and consists of the 0s and
1s that the computer interprets. Machine language represents the natural language of a
particular computer. At the next level, assembly languages use English-like abbreviations
for binary equivalents. Programs written in assembly language can manipulate memory
locations directly. These programs run very quickly and are often used in data acquisition
systems that must rapidly acquire a large number of samples, perhaps from an array of
sensors, at a very high sampling rate.
Higher-level languages such as FORTRAN, PERL, and C
contain statements that
accomplish tasks that require many machine or assembly language statements. Instructions
in these languages often resemble English and contain commonly used mathematical nota-
tions. Higher-level languages are easier to learn than machine and assembly languages. Pro-
gram instructions are designed to tell computers when and how to use various hardware
components to solve specific problems. These instructions must be delivered to the CPU of
a computer in the correct sequence in order to give the desired result. Newer programing
languages such as MATLAB and LabView are easier to use and more user friendly.
When computers are used to acquire physiological data, programming instructions tell
the computer when data acquisition should begin, how often samples should be taken from
how many sensors, how long data acquisition should continue, and where the digitized
data should be stored. The rate at which a system can acquire samples depends on the
speed of the computer's clock—233 MHz—and the number of computer instructions that
must be completed in order to take a sample. Some computers can also control the gain
on the input amplifiers so signals can be adjusted during data acquisition. In other systems,
the gain of the input amplifiers must be manually adjusted.
þþ
9.15 EXERCISES
1.
Find the power absorbed for the circuit element in Figure 9.7 if
(a)
v
(V)
2
i
(A)
1
1
t
t
(s)
0
(s)
0
1
2
1
2
(a)
Continued
